Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/17/16


Area Forecast Discussion
National Weather Service Louisville KY
855 PM EST Fri Dec 16 2016 ...Forecast Update... Issued at 855 PM EST Fri Dec 16 2016 The forecast is in good shape. A recent AMDAR sounding out of Louisville shows above-freezing temperatures through a deep layer of the atmosphere several thousand feet thick, with the exception of a very brief dip slightly below 0C around 1500 feet. Dual pol data are suggesting that the echoes showing up over southern Indiana are liquid drops at beam heights around two to four thousand feet. In the few spots with the best signal-to-noise ratio CC is showing strong homogeneity among the targets. This all agrees with the forecast calling for mainly rain tonight. Still, with cold surface temperatures some brief, very light freezing rain (little more than sprinkles) isn`t out of the question for about an hour at onset. The best chance of any very light freezing sprinkles is between 10pm and midnight in southern Indiana. So far, however, the bone dry air at the surface has been doing a good job of evaporating those hydrometeors before they make it to the ground. Regional mesoanalysis shows warmer dew points to our south have been steadily advecting northward for the past several hours. Dew points are already approaching 40F in western Kentucky. These higher dew points will continue to push aggressively to the north and northeast, with all of central Kentucky and central southern Indiana possessing dew points at or above freezing by 2am. So, rain will indeed eventually make it to the ground tonight. It will be light, though, with amounts less than 0.20" through daybreak. .Short Term (Now through Sunday)... Issued at 255 PM EST Fri Dec 16 2016 ...Wintry Precip Likely Late Saturday Night Into Sunday Morning... Cold and still dry air mass remains in place over the Ohio Valley as high pressure is now retreating off the mid-Atlantic coast. Enough warm advection in the SE low-level flow that temps are now just either side of freezing, even in the face of a thick cirrostratus ceiling. Surface low just about ready to pull ENE out of the OK/TX Panhandle. Low-level jet will crank up this evening, with 900mb winds expected to increase to 50 kt after sunset. Isentropic lift on the nose of this jet will develop a precip shield, but quite a bit will be lost to evaporative cooling in this very dry environment. Expect the onset of light precip late this evening, and given the evap cooling, precip type could be an issue at least initially. Have included mention of freezing rain, mainly along and north of I-64. This does not appear to be a sleet scenario given the expected lack of ice crystals. Any mixed precip will be too short-lived to have substantial impact, as temps will rise sharply through the 30s and 40s after midnight. Rain will get more patchy in the morning once the initial wave of isentropic lift pushes through. POPs for Saturday are quite high, but it does not look like a washout as hi-res models show substantial breaks, especially in the morning. Coverage and QPF will increase through the afternoon as the surface low scoots from STL to YYZ, pushing a cold front into the Ohio Valley. After the mild start, max temps will top out in the lower/mid 60s. Heaviest rainfall will be Saturday night with the strong surface cold front, and a few embedded T-storms are also possible. Instability is quite limited, but wind fields are dynamic enough that we can`t rule out a marginally severe wind gust here or there. Front pushes through after midnight Sat night, and temps will drop like a rock behind it. The cold air does come in quickly enough to undercut some decent QPF, and could present a precip type issue. Still appears that the cold air arrives around the same time that we lose ice crystals, but will be cold enough to support a period of freezing rain late Saturday night into Sunday morning. QPF is mercifully light by that point, but ice accumulations around a tenth of an inch are possible. Even without freezing rain, we could still see slick spots as any standing water freezes. Snow remains an outside chance with the loss of ice crystals, but later in the day as precip tapers off, the near-surface layer gets cold enough to allow some fine snow grains. Either way, little or no snow accumulation is expected. Temps generally in the 20s on Sunday morning will remain there for most of the day under strong cold advection. .Long Term (Sunday night through Friday)... Issued at 255 PM EST Fri Dec 16 2016 Arctic high pressure will settle in beginning Sunday night, and modify as it remains draped over the southeastern CONUS through midweek. Sunday night will be the coldest of the bunch, with lows in the teens across Kentucky, single digits in southern Indiana, and wind chills near zero. Highs on Monday will struggle to reach 30 degrees. From there expect tranquil weather and slowly moderating temps. GFS and ECMWF both show a disturbance swinging through Wed night/Thu, but have significant differences in whether it`s a northern or southern stream show. Have cut back on POPs in that time frame, but will leave it up to the next shift whether to drop completely. && .Aviation (00Z TAF Update)... Issued at 643 PM EST Fri Dec 16 2016 Lots going on during this forecast period. Low pressure will ride from END to STL tonight and on to CLE by this time on Saturday. It will pull a warm front northward in the first few hours of the period and swing a cold front through here in the SDF planning period. Winds ahead of this system tonight will increase and become somewhat gusty. With low level jetting developing plus a strong low level inversion forming, will continue to carry LLWS tonight and into Saturday morning. Precipitation will break out late this evening. There is still a possibility of about an hour of very light freezing rain at onset, but plain rain is expected to be the dominant precip type. Ceilings will lower as the atmosphere moistens, with MVFR cigs from late this evening through the rest of the forecast. Shower activity may wane a bit from late morning into early afternoon Saturday, but then coverage should increase by afternoon as the cold front approaches. Some thunder will be possible into the evening hours, especially at BWG, but is not big enough of a concern for inclusion in the TAFs quite yet. In SDF`s planning period, cold air will sweep in behind the cold front but precipitation should remain in the form of rain until the very end of this TAF package. Looking ahead to late Saturday night/early Sunday morning, beyond this forecast period, there appears to be a threat of light FZRA/FZDZ. Stay tuned. && .LMK Watches/Warnings/Advisories... KY...NONE. IN...NONE. && $$ Update.........13 Short Term.....RAS Long Term......RAS Aviation.......13
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
835 PM CST Fri Dec 16 2016 .UPDATE... 833 PM CST The main band of moderate to heavy snow, now over northeastern Illinois, will abate by late evening as the band of frontogenesis around 850 MB begins to shift out of the area. Before it ends, a good 1 to 3 inches of fresh snow are likely over far northern sections of the area. Once this band of snow ends, it appears the main accumulating snowfall will be done for much of the area until Saturday evening. However, intermittent light snow and or freezing drizzle will be possible tonight into Saturday. Freezing rain/drizzle may actually end up being the main P-type during this period as drier air aloft moves over the area, resulting in relatively warm cloud top temperatures at or above -10 C, which favors a dearth of ice nuclei. We have therefore trended the forecast for the remainder of the night in this direction. While significant ice accumulations are not expected, some glazing is likely, and this could make for hazardous travel, especially on untreated roads. Given the likelihood of freezing drizzle tonight into Saturday, followed by another period of accumulating snow Saturday night, no changes are planned to the current winter weather advisory. The next concern will be the dangerously cold conditions expected Sunday into Monday. We have opted to go ahead an issue a wind chill advisory for Sunday through Monday morning for areas generally along and north of I-80, though the entire area may end up needing to be in the advisory. At the present time, areas in the advisory are expected to have wind chills of 20 below to 30 below. There is a small potential that some areas could experience wind chills in excess of 30 below over northern Illinois Sunday night as actual air temperatures drop into the teens to low 20s below zero. If wind chill values colder than 30 below appear more likely, an upgrade to a wind chill warning may be needed for parts of the area. KJB && .SHORT TERM... 334 PM CST Through Saturday Night... After a prolonged top-down saturation process, the dry air is finally losing out to the strong forcing for ascent based off latest radar and aircraft sounding trends, with echoes indicative of moderate rates developing over far northeast Illinois as of this writing. The WAA process combined with the ascent stout mid- level wave lifting northeast (noted by impressive cold cloud tops on IR satellite) will bring the period of snow an impacts to the evening commute. Have recently received a report of moderate to heavy snow in Rockford area and snow quickly accumulating on roadways. In a nod to the slightly longer saturation time than earlier expected, did slightly lower QPF and forecast snow amounts in this first round of snow to 1 to 4 inches, highest in the Wisconsin border counties. Later this evening and overnight, the best forcing will lift northeast of the area except perhaps far north, but we will remain in broad synoptic ascent. Attention turns to the potential for freezing drizzle in roughly the I-80 to I-88 corridor area, as guidance indicates to varying degrees the loss of saturation in the snow growth zone and subsequent loss of ice crystals. Thus, freezing drizzle or a "snizzle" (snow/freezing drizzle mix) could cause a glaze of ice and additional travel issues overnight into Saturday morning. Farther south across our central Illinois counties and across northwest Indiana south of the Kankakee River, concern has greatly increased for freezing rain and ice accumulations. Guidance came into better agreement on a slightly farther south low pressure track (from STL to near/south of LAF), which will prevent much in the way of boundary layer warming as a strong warm nose surges in aloft. Overnight into Saturday morning, exit region of the upper jet and continued isentropic ascent will cause an uptick in precipitation just ahead of surface low path across area of concern. Forecast soundings are strongly supportive of freezing rain in this timeframe, with full melting of hydrometeors. Given that there is now expected to be a longer duration of temperatures at or below freezing, ice accumulation could end up slightly upwards of 1/10" in spots. With trend toward colder boundary layer in guidance, lowered high temperatures to the low-mid 30s in the far southeast CWA. If these temperatures are too warm as well, then that would prolong icing concern. Even if readings creep just above freezing, the very cold road temperatures could still result in freezing on contact of liquid precip. Thus issued the Winter Weather Advisory for Ford, Iroquois, Newton, Jasper and Benton counties, in effect starting at 9pm this evening. From mid Saturday morning through mid day, there is uncertainty on the guidance regarding whether saturation returns to the snow growth zone north of I-80. Overall lowered qpf and snow amounts during this period, so will need to closely monitor trends. Maintained mention of freezing drizzle potential in the grids, so if occurring and not a full lull, this will continue to pose a travel hazard on its own. With possibility that ice crystals will be lacking, it could be that sleet will not be much of an issue north of the heightened freezing rain concern area, but left mention in grids for now. Most recent guidance continues to be in better agreement of the synoptic pattern Saturday afternoon into Saturday evening. The mid-upper trough marking the leading edge of the incredibly cold air mass in store for Sunday will be pivoting southeast, with some sheared out short waves ahead of it. Associated large scale ascent in deformation axis will cause a solid area of precipitation to break out as thermal profiles rapidly cool with arrival of Arctic air. Most of this will be snow as it shifts from northwest to southeast across the area, except perhaps lingering mix changing to snow southeast of I-57. Up to an inch of snow is possible across far northern Illinois by sunset in this next round. As the system deformation and upper trough move across the area Saturday evening, forecast soundings show very steep lapse rates above 600 mb. Thus, with this and good lift through the snow growth zone, could see moderate to even briefly heavy snowfall rates. 1 to 3 inches of snow could fall by the late evening area wide. In addition, northwest winds will be gusting to 30-35 mph as the bitterly cold air pours in, likely resulting in blowing and drifting snow issues, particularly where the higher snow accums occur tonight through tomorrow evening. Also concerned with flash freezing of any liquid on road surfaces in southeast CWA. With temperatures falling to the single digits above and below zero after midnight, wind chill values will plunge to 15 to 30 below zero. Will need a Wind Chill Advisory after the end time of the Winter Weather Advisory (6am Sunday). Finally, favorable lake effect parameters could enhance totals a bit into Porter County, and will also need to monitor trends Sunday morning there for a possible advisory extension. Overall, made no other changes to the headlines that were already in effect, and very little change to going forecast snow amounts due to expectation of more snow Saturday evening than in previous forecast. Castro && .LONG TERM... 109 PM CST Sunday through Friday... The last big surge of cold air during this arctic outbreak will arrive on Sunday. Strong and expansive high pressure will extend through the nation`s heartland. While precipitation will be largely finished, there is still enough of a pressure gradient between the departing low to create blowing and drifting snow concerns in the morning hours. Lighter lake effect snow may still be ongoing across Porter County, IN, but the focus should shift east of the area as the high moves east on Sunday. Don`t be fooled by the sunshine on Sunday, as the 850 thermal trough will be centered over our area, it will not be a pleasant day outside. Wind chill readings which will start the day near -30 in the Rockford area to -20 in northwest Indiana only look to recover to maybe -25 to -15, and highs will range from the single digits southeast to the low to mid single digits below northwest. The ridge of high pressure will be positioned across the Mississippi Valley in the afternoon and then stretched out across the Fox River valley and into central Illinois Friday evening. With the weakening winds, very cold start point and the recent snowfall, a rapid temperature drop will ensue during this time, with some areas already reaching the double digits below zero by sunset. The biggest temperature drop will occur during the evening area with lows possibly bottoming out in the teens to lower 20s below zero. Model 2m temperatures depict -15 to -20 readings in our western outlying areas, with MEX and ECE MOS for one of our cold spots ARR of -14 and -16, impressive even for a MOS product. Model guidance does suggest some recoveries overnight and into Monday morning as lower level warm advection begins with the high departing to the east. Wind chills by daybreak will generally be -5 to -15 in the far south/southeast CWA, with -15 to -25 along and north of I-80, above -20 all areas by mid morning or so. There is some good news in that this arctic air intrusion comes to a close, and we will have several dry days with teens for highs Monday, 20s to near 30 Tuesday, and in the lower 30s (mid 30s south) Wednesday, which is more like normal for winter equinox. The next chance for precipitation will be Wednesday into Thursday as a pacific shortwave moves quickly across the country. Model guidance develops some light precip with this wave and its associated cold front which at this point appears to be snow. The wave comes through in a clipper-like fashion with current guidance favoring our northern half of our area, with some back side lighter snow showers behind it. KMD && .CLIMATE... 109 PM CST High temperatures on Sunday (Dec 18) are forecast to remain in the single digits above to single digits below zero. This will likely be the coldest day of 2016. The current coldest day of 2016 is Monday January . Chicago`s high that day: 7, Low: -4. Some records will be threatened or broken. Sunday records: Rockford: Daily Low: -17 in 1983. Forecast Low: -16. Chicago: Daily Low: -11 in 1983. Forecast Low: -13. Monday records: Rockford: Daily Low: -21 in 1983 Chicago: Daily Low: -14 in 1983. KMD && .AVIATION... For the 00Z TAFs... Steady snow is expected to persist at the Chicago terminals through mid evening with ocnl LIFR vsby expected in the heavier bursts of snow. Main axis of snow expected to shift north of the Chicago terminals late evening and through the overnight, but could continue later into the evening and perhaps overnight at RFD. In the wake of the steadier accumulating snow this evening, look for perhaps some very lift/fine snow or perhaps a little mist or freezing drizzle overnight into early Sunday morning, but it appears unlikely that this precipitation will amount to anything of significance. CIGS should steadily build down to IFR tonight and probably remain IFR or perhaps low end MVFR at times through Sunday. A second round of IFR vsby and accumulating snow is expected Sat evening with increasing northwest winds likely to eventually lead to blowing/drifting snow as well. Izzi && .MARINE... 150 PM CST Main marine concerns in the near term focus on modestly gusty south-southeast winds late this afternoon and evening across far southern Lake Michigan, in a region of surface pressure falls in association with an advancing area of low pressure lifting out of the Central Plains. Winds gusting near 25 kts at times are expected, with Small Craft Advisories already in place for the IL/IN shores through this evening. Attention then turns to the tightening gradient and strong low-level cold advection developing later Saturday as the Plains low moves south of the lake and pulls off to the east. Combined with a substantial push of bitter cold arctic air, and strong high pressure building across the Plains and into the Midwest through Sunday, north gales are expected to develop From north to south across Lake Michigan Saturday afternoon and continue through early Sunday morning. The northern periphery of the arctic high will then move across the lake late Sunday, allowing winds to diminish and back to the southwest. Southwesterly gales will then be possible on northern Lake Michigan Monday into Monday evening as an area of low pressure passes north of the Lakes, and strong high pressure remains across the Ohio Valley. With cold arctic air in place, these periods of higher winds will also produce freezing spray. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008- ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021- ILZ022-ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 6 AM Sunday. Wind Chill Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010- ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022...6 AM Sunday TO 10 AM Monday. IN...Wind Chill Advisory...INZ001-INZ002...6 AM Sunday TO 10 AM Monday. Winter Weather Advisory...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 6 AM Sunday. LM...Small Craft Advisory...NEARSHORE WATERS UNTIL 10 PM Friday. Gale Watch...LMZ743-LMZ744-LMZ745...9 PM Saturday TO 6 AM Sunday. Gale Watch...LMZ777-LMZ779...6 PM Saturday TO 6 AM Sunday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion
National Weather Service Mount Holly NJ
1012 PM EST Fri Dec 16 2016 .SYNOPSIS... High pressure will continue to move offshore tonight. Low pressure moving from the mid-Mississippi to Saint Lawrence Valley will lead to a warm frontal passage Saturday into Saturday night, followed by a cold frontal passage on Sunday. A sprawling area of high pressure will settle over the mid-Atlantic in the Monday thru Wednesday time frame, prior to another storm system approaching the region on Thursday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 10 PM: WSW and all fcst products reposted as well as updated social media and emergency manager email update. 924 PM: we sent out a sample set of zones with higher ice amounts. ice graphic has increased and should post by 930 PM. Freezing rain rates may prevent a major problem but its a little edgy for the higher terrain of se and e central PA where asos and human observed radial amounts could exceed the 1/4 ice storm warning threshold. We`ll try to have that resolved by 2 am. In the meantime... plan on a very hazardous period of travel for a few hours tomorrow morning and be very careful when stepping outside. Leaving some snow on the ground and pavement might be a good idea to allow the freezing rain to absorb into the snow instead of transfer directly to a snow cleared frozen ground. Anti ice treatments for pavement will be helpful and necessary top melt ice tomorrow morning. Cant even promise 40s temps tomorrow since the light and variable wind may turn light westerly midday off of the colder snow covered se pa. 9 PM: will discuss adjustments at 945 PM. New 00z/17 NAM slower and colder. Effectively will raise pops to near 100 pct after 09z. Will add .10 to the freezing rain ptns of se pa in the morning. This fcst deserves only a few careful changes til we see everything else from the 00z cycle. it has an 80 Kt 850 jet near FDK MD tomorrow morning. Just seems too much. Biggest dump of pcpn 11z-17z and the NCAR WRF ensembles for freezing rain look very good fm the 00z/16 cycle. No time to be sure about an ice storm warning for Berks W Chester nw Mont and Bucks, specially higher terrain but we will add ice amts in the 950 PM wsw and zones. Thats it for now. ---- Remainder discussion below from earlier today. Overrunning developing over the Mid-Atlantic region tonight as warm, increasingly moist air is driven newd on a 60 kt sw 850 jet whose center should be nosed over VA late tonight then deflects eastward across the Delmarva after sunrise Saturday. This deflection probably delays sfc subfreezing temperature erosion and we will be monitoring for trends toward the significantly colder 12z/16 GGEM solution. I prefer this colder solution though its not mode for the plethora of warmer sfc temp solutions. I kept it simple on start time. Virga loading next few hours should eventually see a scattering of snow reports in PA MD by midnight or 1 am and then a very rapid expansion in coverage around 3 or 4 am. We welcome your snow and ice amount reports..location and amount and any other significant info you wish to share on FB/Twitter/Skywarn and NWSchat accounts. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Based analysis of the 12Z guidance, we trended faster with the changeover from snow to freezing rain (with a couple hours of sleet during the transition) as an impressive 70-80 kt (NAM) low- level jet helps advance the warm nose aloft quickly northward through the area during the morning. EC and GFS are decidedly east and am concerned the NAM is too wrapped up inside. 0.25 to 1 inch qpf anticipated with max axis of rainfall probably se PA and Southern or central NJ. Basically this event is done around Noon with freezing drizzle or drizzle lagging and then dealing with fog development later Saturday. Warming at the surface will lag, especially as you get into the higher terrain N/W of the Fall Line. There is a signal in the mass fields from the models, showing an in-situ CAD ridge forming once the precip begins, with the ridge axis oriented southwestward thru NW NJ and interior portions of eastern PA. The warm front will struggle to advance this far north during the morning, especially with the potential for a weak wave of low pressure developing along the front that could enhance northeasterly flow near the surface across the northwestern third of the CWA. The dry slot is expected to quickly advance northeastward through the area during the afternoon. However, very light freezing rain or freezing drizzle could persist across the higher elevations from near I-78 northward through the late afternoon. Temperatures may rise into the 40s southeast of the I-95 corridor and even 50s toward southern DE during the afternoon. Concern is that the I95 corridor will not reach the 40s tomorrow as winds turn light west by midday. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Overview... Active period shaping up with the potential for three systems to impact the region. A long wave trough over the central conus maintains a mean southwest flow aloft into early next week. A shortwave moving this trough will lead to a cold frontal passage late Sunday, with the potential for some heavier downpours. This front will remain just to our south, due to the mid-level flow paralleling it. A rather stout shortwave moving through the Ohio Valley leads to low pressure development along the aforementioned front late Tuesday into early Wednesday, with the potential for renewed precipitation at least as far north as Delmarva. By mid- week, the flow across the conus becomes more zonal, with the next short wave progged to move across the area Thursday into Friday. At this point, we expect low pressure to move through the Great Lakes with the opportunity for secondary development off the east coast, presenting yet another chance of precipitation. Temperature-wise, after a warm Sunday with temperatures around 15F above average, we return to within a few degrees of seasonal norms through the remainder of the period. Saturday night thru Sunday... Ana-front-type cold front traverses the region Sunday afternoon. From Sunday morning into the afternoon hours, an anomalous southwesterly 850 hPa jet around 75 knots of about 3 Standard Deviations (STD DEV) above average traverses the region. Likewise, this aids in the pole ward transport of Precipitable Water (PW) values up to around 1.5 inches across the area (up to around 4 STD DEV above average). Model cross sections also indicate up to 20 micro bars (ub/s) of lift to the northwest of I-95. Thus, we have high confidence for periods of heavy rainfall over this area during the day on Sunday, with the potential for 1 to 1.5 inches of precip. Although Flash Flood Guidance values are much higher than this amount of rainfall, any leftover snow that clogs storm drains could lead to localized, urban and poor drainage flooding. Also, we are noting a low-level tongue of higher theta-e air in advance of the front, with Dew Points modeled well into the 50s moving north toward southern NJ. In addition, mid-level Lapse Rates approach 6.5 C/km, along with sub-zero Showalter values up to the I-95 corridor. Thus, a rumble of thunder south of the I-95 corridor is possible, but we kept it confined to far southern Delmarva where the potential is greatest. We also have high confidence for the formation of fog and drizzle Saturday night into Sunday morning, particularly northwest of I-95, where model sounding profiles are most favorable given the low-level inversion/ lack of mixing. In addition, the fog may be aided Sunday morning by the advection of higher Dew Points over any existing snow cover. Monday thru Tuesday... Considerable uncertainty during this time frame leads to an overall low confidence forecast. A dry Monday with increasing chances for precip Monday night and primarily Tuesday. High pressure over Atlantic Canada will ridge southward along the east coast, while cyclogensis occurs along a stalled front just south of the region. In general, the international models (EC/UKMET/Canadian) bring the low further north, while the American models (NAM/GFS) are at least 100 miles south. The primary reason for this is the more robust shortwave shown by the international models. The EC solution would bring precip to the I-95 corridor Tuesday, predominantly in the form of rain showers, although its thermal profile may be too warm. The GFS solution keeps the precip around 200 miles south (well offshore) and is much colder as a result. These setups are tricky, and tend to favor locals closer to the immediate coast for precip, given high pressure in place with a dry, offshore, low-level flow. So for this forecast, we confined PoPs to lower Delmarva, and within about 20 miles of the NJ coast. As for P-Type, an early estimate would be for precip to begin as snow showers with a changeover to rain showers. Of course, this will need further refinement in future forecast packages. Wednesday... Transitory shortwave ridging over the region will promote weak high pressure at the surface. Fair and dry weather is anticipated attm. Thursday and Friday... The next storm system is expected to traverse the region, with impacts expected primarily on Thursday, although timing at this early juncture is subject to change. The pattern would favor a progressive, inside runner with some opportunity for a secondary low formation near the coast. This would favor a snow to rain scenario, with the fast moving nature of the system limiting precipitation amounts. If the timing of the system holds, fair weather would make a return for Friday, aside for the possibility of snow flurries across the higher terrain. Overall, below average confidence during this period of the forecast. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Rest of tonight...VFR cigs lower to IFR in snow between 06z-09z. Snow quickly changes to rain KMIV and KACY with spotty icing possible for an hour or two prior to sunrise while sleet/freezing rain develops vcnty KILG around 11z. Light wind. We have fcst LLWS toward 11z in some TAFS but this is not a categorical fcst of LLWS. Saturday...IFR conds in snow, sleet and freezing rain changing to drizzle/stratus/fog in the afternoon. Please see TAFS for details. Significant travel delays expected Saturday morning, including runway and aircraft deicing treatments. Light wind. OUTLOOK... Saturday night and Sunday...Rain and fog across the terminals. Predominantly IFR. Potential LLWS sw wind 60 kt at 2000 ft Sunday morning. Otherwise, southwest surface winds becoming northwest with gusts in the afternoon of 20-30 kt knots for an hour or two with the cold frontal passage. Sunday night thru Wednesday...Predominantly VFR conditions. && .MARINE... A SCA was issued for the waters. The SCA for the coastal waters begins late tonight and continues into Saturday. For the DE Bay, the start of the SCA is delayed until mid morning. SW winds will increase over the waters during this time. There is a potential for winds to approach gale force Saturday late morning and afternoon as a strong low-level jet moves overhead. However, confidence on these higher winds aloft mixing down to the surface is low with warmer air moving atop the colder waters. Therefore, held off on a GLW but mentioned the possibility of near gale force gusts in the MWW and HWO. OUTLOOK... Saturday night...All the available 16/12Z guidance indicates the possibility of a marginal SCA (winds) across the ocean waters. A limiting factor will be the departure of the low-level jet, and formation of a weak inversion over the waters. For now, we held off on a SCA, and will let the next shift re-evaluate. Late Saturday night into Sunday...A return to SCA (winds) around 09Z Sunday, with the possibility of gales during a brief window generally in the 12Z to 15Z time frame. Monday thru Wednesday...SCA possible Mon...otherwise sub-SCA. && .CLIMATE... Checked our daily snowfall records for December 17. Long shot we can approach at KABE, the 3.0 inches in 1919. ILG would need 2.2 inches to equal the 1973 daily record and that is unlikely. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 2 PM EST Saturday for PAZ060>062- 101-103-105. Winter Weather Advisory until 11 AM EST Saturday for PAZ070- 071-102-104-106. Winter Weather Advisory until 6 PM EST Saturday for PAZ054-055. NJ...Winter Weather Advisory until 2 PM EST Saturday for NJZ007>010. Winter Weather Advisory until 9 AM EST Saturday for NJZ014- 020>027. Winter Weather Advisory until 11 AM EST Saturday for NJZ012- 013-015>019. Winter Weather Advisory until 6 PM EST Saturday for NJZ001. DE...Winter Weather Advisory until 9 AM EST Saturday for DEZ002>004. Winter Weather Advisory until 11 AM EST Saturday for DEZ001. MD...Winter Weather Advisory until 9 AM EST Saturday for MDZ012-015- 019-020. Winter Weather Advisory until 11 AM EST Saturday for MDZ008. MARINE...Small Craft Advisory from 3 AM to 6 PM EST Saturday for ANZ450>455. Small Craft Advisory from 9 AM to 6 PM EST Saturday for ANZ430- 431. && $$ Synopsis...Franck Near Term...Drag 1012P Short Term...Drag/Klein 1012P Long Term...Franck Aviation...Drag/Franck 1012P Marine...Drag/Franck/Klein 1012P Climate...