Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/26/16


Area Forecast Discussion
National Weather Service Taunton MA
1001 PM EST Sun Dec 25 2016 .SYNOPSIS... Strong high pressure will bring clear skies and cold temperatures tonight. Light freezing rain and some sleet will make for a slick coating in some western and central sections late Monday afternoon. Any leftover freezing rain across the interior changes to plain rain showers Monday night, with rising temperatures and windy conditions developing on the coastal plain late. Turning colder late Tuesday into Wednesday. Low pressure will likely bring some snow or rain to the region Thursday into Thursday evening. Looks like colder than normal temperatures for the first half of the New Years weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 10 pm update... Temperatures have not dropped off as fast as previously thought. This is likely a symptom of the maintained pres gradient to some extent, but is more likely related to weaker dwpt mixing through the afternoon and evening. Given this fact, will be raising hourly temps and overnight mins be a few degrees. Even with this update, till expecting widespread teens and a few single digits where the snowpack remains. Other than this, the forecast remains on track late this evening, so will maintain the persistence for the time being. Previous discussion... Very strong high pressure, 1045 mb, will be working its way across southeast Canada and northern New England tonight. Winds will diminish this evening, with a weaker pressure gradient. With clear skies, expect good radiational cooling with temps dropping to the teens and low 20s around much of the region. In northwest MA, where the snowpack remains established, some locations will drop into the single digits. A few of the short-term models show low cloudiness developing along east coastal MA before daybreak in the light easterly flow. Temperature differentials between 925/850 mb and the sea surface are only marginal for ocean effect cloudiness, but this will need to be watched. For now, have kept the forecast mostly clear everywhere. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Monday... Skies will start out sunny Monday morning but clouds will quickly invade the region by late morning, lowering and thickening in the afternoon. The timing of the cloud increase will be important because it will likely lock in below freezing temperatures across northern and western MA, which will have had a very cold start. It is possible that the below freezing temperatures reach as far south as northern Hartford County. Elsewhere, highs should reach the mid and upper 30s, with lower 40s on the islands. Warm air advection out ahead of a storm system well to our west will cause some scattered light precipitation to break out during the afternoon, mainly in western sections. Models differ on the eastward extent of the precipitation. The NAM and GFS have some measurable precipitation reaching eastern MA and RI while the ECMWF holds it off until nightfall, even in western areas. The temperatures aloft will be warm enough for raindrops, but with a thick cold and dry layer beneath it, we are expecting freezing rain, possibly starting as a mix with sleet in western and central areas. Because only a trace of freezing rain can coat roadways and sidewalks and become hazardous to motorists and pedestrians, we have issued a Freezing Rain Advisory, beginning at 3 PM, for Franklin, Hampden, Hampshire, Worcester, and northwest Middlesex Counties in MA. It is possible that it might need to be extended farther south into CT, or that the onset timing could change. We will be monitoring this. Monday night... A very strong low-level southwesterly jet will race across southern New England, exiting the Cape and Islands by daybreak Tuesday. Any freezing rain in western MA will change to plain rain as temperatures there climb into the 40s overnight. Farther to the east, temperatures will soar to the low and mid 50s in RI and eastern MA. The K Index is forecast to reach 30 and the Showalter Index goes to -1, which means that we cannot rule out a narrow convective line of showers or an isolated rumble of thunder in southeast areas. With all that said, we are only expecting about one-quarter to one-third of an inch of rain across most areas. The main concern overnight Monday night will be the potential for strong winds along the south coast. Since this is not until late Monday night, we have not yet issued a Wind Advisory. Plus, there remains some uncertainty as to how much mixing there will be. Momentum algorithms are emphatic on confining mixing to the lowest couple hundred feet, which often is the case on southwest winds. However, we are concerned that with temperatures climbing into the 50s and some convective elements possible, the mixing could come from higher in the atmosphere. The NAM, which is the strongest of the models, has 17 knots of wind at the surface at Hyannis at 5 AM Tuesday, for example, but 75 knots at only 3800 ft! The potential is there for Advisory-level winds of 40-50 mph, especially over Cape Cod and the Islands late Monday night. It certainly will be a hazard for aircraft -- low level wind shear. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Showers move offshore Tue AM, then dry and windy * Snow or rain likely Thu into Thu evening * Cold New Year`s weekend with chance of some snow early Sunday Overview... Persistent SE upper ridge becomes suppressed to some extent during this period with northern stream flow depicting general cyclonic and fast flow during the forecast period. A more amplified upper trough in the northern stream flow draws focus to the Thu and Thu night time frame. Tue/Tue night...Front moves offshore and lingering showers end during the morning followed by dry and rather windy conditions in the NW flow with most significant gusts likely over the SE coastal plain. Temperatures start very mild Tue morning but will gradually drop during the day as the cold advection outpaces the solar insolation. A sharper drop in temperature will be noted after sunset but lows Tue night should be close to seasonal norms. Wed/Wed night...Looks to be dry with max temperatures between 35 and 40, near normal values for this time of year. Wed night lows will generally be in the 20s except upper teens in the NW. Increasing clouds later at night will prevent temperatures from fall further. Thu/Thu night...This is where most of effort for this forecast period was placed. A more pronounced short wave trough in the northern stream brings moisture and precipitation into the area but details vary among the medium range models. The ECMWF is considerably more bullish than the GFS with formation of a secondary surface low along the mid Atlantic coast which is tracked across SE MA to the Gulf of Maine. The operational GFS in contrast shows just a weakness in the surface pressure pattern with a broader upper trough. There is some support in the ensemble data for the ECMWF solution. Have gone with a blend of the ECMWF and GFS for now with a moderate QPF event of a third to half or so of precipitation. Precipitation type for Thu into Thu evening is somewhat uncertain, and this may change some in the coming days as we get closer to the event. It looks like precipitation type is likely to be snow in NW MA and rain in most of RI and SE MA. In between including Hartford, Springfield, Worcester, Boston, and Merrimack Valley the precipitation type may be snow to rain but could end up being mostly snow or mostly rain depending upon the amplitude/sharpness of the upper trough and location of surface secondary cyclogenesis. Fri through Sat...Fairly strong cold advection and brisk winds are anticipated with temperatures just a little below normal on Fri but probably somewhat more significantly below normal Fri night and Sat. Although certainly nothing extreme, temperatures may struggle to get out of the 20s for most of the area on Sat. Should be dry, however. Sat night and Sun...An upper level short wave trof and possibly weak surface trough or low center may bring a period of snow late Sat night into Sun morning. For now, any accumulation looks to be relatively light with perhaps an inch or two in some areas, but this is too far away to have much confidence one way or the other. Temperatures will probably moderate a little on Sun to near or slightly above normal. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/... Tonight...High confidence. VFR. NW winds will continue to diminish this evening. There is a low chance that areas of MVFR ceilings could develop along the east coast of MA toward daybreak. Monday...Moderate confidence. VFR into the early afternoon. Then MVFR ceilings spreading eastward late in the day. Areas of light freezing rain, mixed with sleet at the onset, in western and central MA and possibly northern CT, especially after 20Z. Monday night...Moderate confidence. MVFR-IFR conditions expected in widespread showers. Any lingering freezing rain across the interior should change to plain rain by 03-04Z. Main concern will be significant LOW LEVEL WIND SHEAR, strongest over Cape Cod and the Islands. Southwest winds could be 25-45 mph in gusts over the Cape and Islands. However, at 3000 ft, winds could be west- southwest at 60-80 mph... potentially dangerous for some aircraft. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF tonight. Moderate confidence in TAF late Monday. Outlook /Tuesday through Friday/... Tue...High confidence. Conditions becoming VFR during the morning. Gusty W or NW winds with gusts over 30 knots possibly, however. Tue night through Wed night...High confidence. VFR likely. Thur into Thu night...Moderate confidence. Conditions likely lowering to widespread MVFR and areas IFR in snow to the NW and rain and fog to the SE. Fri...High confidence. VFR expected but with gusty NW winds. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/...Moderate Confidence. NW winds will slowly subside this evening, but seas will remain near 5 ft over the outer waters through tonight. Late tonight into early Monday, high pressure will yield a brief period of quieter boating weather. A Gale Watch has been issued for all outer waters from about Midnight Monday night into early Tuesday afternoon. Strong southwest winds develop Monday evening, and gusts to 40 knots are possible. If those winds develop, seas should rise to 8 to 12 feet over the outer waters, highest over the southern and southeastern waters. Outlook /Tuesday through Friday/... Confidence...Moderate. Looks most of the waters will be under Small Craft Advisory conditions during this period with a couple of periods when gale gusts are possible. Gale Watch for most of the waters extends to early Tue afternoon in W or NW flow. Greatest uncertainty is Thu/Thu night period as to location and strength of surface low pressure center near coast. If the surface low tracks right across the waters, the winds may be relatively light for a time during this period. There is greater confidence of at least Small Craft Advisory wind gusts and possibly gale gusts in the Fri and Fri night time frame in strong NW flow. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Freezing Rain Advisory from 3 PM to 11 PM EST Monday for MAZ002>004-008>012-026. RI...None. MARINE...Gale Watch from late Monday night through Tuesday afternoon for ANZ231>235-237-250-251-254>256. Small Craft Advisory until 9 AM EST Monday for ANZ250-254. && $$ SYNOPSIS...GAF/Thompson NEAR TERM...Doody/GAF SHORT TERM...GAF LONG TERM...Thompson AVIATION...GAF/Thompson MARINE...GAF/Thompson
Area Forecast Discussion
National Weather Service Fort Worth TX
951 PM CST Sun Dec 25 2016 .UPDATE... Another quick update this evening to remove thunder wording from the gridded forecast products and to make some small tweaks to PoP trends. The vigorous mid-level cyclone continues to rapidly rotate into North Dakota late this evening, taking any dynamics of note with it. ACARS soundings reveal stout capping inversion(s) remain centered around 700 mb. Can`t rule out a clap or two of thunder, but the threat for thunderstorms appears low overnight. As expected earlier, we`re seeing some southwestward development of shower activity, but coverage south of I-20 looks to remain just isolated to perhaps scattered, with better precip chances east of I-35 and north of I-20 overnight. Might also see some very patchy visibility reductions across our far southeastern zones tonight, but any coverage appears too low to mention in the worded forecasts at this time. Carlaw && .AVIATION... /ISSUED 547 PM CST Sun Dec 25 2016/ /00Z TAFs/ Early challenges include timing of pre-frontal surface trough and cold front, along with showers/isolated tstorms and cigs overnight. Currently, a line of weak showers was associated with a slow- moving pre-frontal surface trough to the west of I-35. As expected the past several days, an upper low continued to negatively rotate northeast from the Central High Plains toward the Upper Midwest. A strong elevated mixed layer (EML) was keeping any convective activity minimal at this point. Meanwhile, both the surface trough and cold front are slowing down as the upper level energy continues moving northeast further away from the area. As such, have delayed the veering of surface winds at all airports by 3 to 6 hours, with VCSH noted through much of the night at DFW terminals, while delaying the same trend at Waco by 6 hours or more. All sites should start off with southerly winds around 15 kts, slowly veering and becoming southwesterly behind the surface trough after midnight at DFW area terminals, to after sunrise at Waco. Actual FROPA with the cold front should occur by midday Monday and after at all terminals with winds shifting northwest near 10 kts. As for tstorm potential, think the high-resolution models are struggling with the intensity of the EML (cap) and possibly overdoing convective development along the pre-frontal trough later this evening. With nightfall upon us, despite slightly better moisture and instability east of I-35, feel cooling of the boundary layer along with a residual EML(cap) should minimize tstorms and lighting to an occasional occurrence, but not widespread. As such and with lacking confidence in the models, have only introduced VCSH at all terminals until area radars and our 00Z upper-air indicates otherwise. Will be monitoring closely for lightning throughout the evening. 05/ && .UPDATE... A very narrow band of showers--barely 10 miles across--extends along a southwestward-arcing cold front from eastern Kansas into portions of Central Oklahoma, to its southern terminus in Cooke County this hour. Hardly any lightning is occurring with this line, with just a few CG strikes and in-cloud flashes noted near the Oklahoma/Kansas border, which is clearly indicative of the ongoing stout capping which is stunting vertical convective development. The 00Z FWD sounding, coupled with recent ACARS profiles, reveals the capping inversion from this morning had been lifted and weakened somewhat. RAP forecast soundings indicate a gradual lifting of the 750-650 mb layer may continue this evening, but any effects on the aformentioned inversion should wane as forcing associated with the parent mid-level cyclone races off into the Dakotas. Finally, surface winds out ahead of the cold front are slowly veering, which will further limit low-level convergence along the front tonight. High-resolution guidance suggests that some southward shower development will be possible this evening as the cold front potentially taps into a bit more buoyancy as it continues east. Based on trends, almost pulled thunder completely from the forecast, but opted to continue isolated wording given the above- mentioned potential lifting of the cap. Either way, effects from this Christmas cyclone look to remain quite limited across North and Central Texas. Made a few tweaks to the gridded forecast, mainly to adjust PoP trends based on radar and high-res guidance, and to slow the eastward progress of the front as forcing continues to leave the southern end of the front behind. Updates have been transmitted. Carlaw && .PREV DISCUSSION... /ISSUED 239 PM CST Sun Dec 25 2016/ ...DFW and Waco both tie their record high temperature for Christmas day (78 degrees) and both could break it with a little more heating left today... A weak cold front will continue to move across North and Central Texas late this afternoon and bring a few showers and isolated thunderstorms along with breezy west winds behind the front. Strong and gusty south winds will also continue ahead of the front with sustained wind speeds between 20 and 30 mph and some gusts around 40 mph. We will keep a wind advisory in place for the western two thirds of the forecast area through 6 PM. After sunset, wind speeds will quickly decrease with boundary layer decoupling and a weakening surface pressure gradient. Most areas will see little if any measurable rainfall this evening and if any location does get a thunderstorm it will only produce occasional lighting and brief moderate rainfall. The cold front will stall across the southeastern zones tonight and will continue be a source of lift for showers and isolated thunderstorms. The front will remain nearly stationary Monday through Tuesday continue to bring a chance of rain and isolated thunderstorms to the southeast half of the forecast area as moisture is lifted over the dome of slightly more dense air. Low level moisture will return beginning on Tuesday night in response to a developing lee trough across the Central High Plains. This will result in mild temperatures for late December with morning lows Wednesday in the 50s and 60s and highs Wednesday afternoon in the 70s. Another cold front will move across North and Central Texas Wednesday night through Thursday. The front will bring cooler and drier air. At this time it appears that large scale forcing and deep moisture will be absent, therefore the front should come through precipitation free. The dry and cool air will remain in place through Thursday night but low level moisture will quickly return Friday in response to an approaching low pressure system. Energy associated with this system will bring a chance of showers to the entire region Saturday with showers and some storms lingering into New Years Day. 79 && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 58 67 48 61 53 / 40 10 10 10 10 Waco 62 68 53 62 55 / 30 20 40 20 10 Paris 59 68 46 61 51 / 50 20 10 10 10 Denton 53 66 42 61 50 / 40 10 10 10 10 McKinney 58 66 44 61 52 / 50 10 10 10 10 Dallas 59 68 50 62 55 / 40 10 10 10 10 Terrell 62 68 50 62 54 / 50 20 20 10 10 Corsicana 63 68 55 63 57 / 30 30 40 20 10 Temple 63 70 54 64 56 / 30 40 40 20 10 Mineral Wells 50 66 43 62 50 / 30 10 10 10 10 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 05/90
Area Forecast Discussion
National Weather Service Grand Rapids MI
859 PM EST Sun Dec 25 2016 LATEST UPDATE... Update .SYNOPSIS... Issued at 315 PM EST Sun Dec 25 2016 Freezing rain and rain will move into Lower Michigan this evening as a blizzard moves though the Dakotas. Some icing is expected north of a line from Mount Pleasant to Ludington and roads could be hazardous there before temperatures rise early Monday morning. It will be windy and colder by Monday night and Tuesday with scattered snow showers. && .UPDATE... Issued at 853 PM EST Sun Dec 25 2016 The temperature did dip to near freezing in a few of the observation sites outside of the Advisory area. Looking upstream in Indiana...the temperature values were nearly steady. As a result...we could see a few hours of near freezing temperatures outside of the advisory area this evening. One band of rain was pushing northeast through the CWA at this time...then it looks like a lull in the steady precipitation. Thus I did go with an SPS for the region outside of the Advisory. Will monitor fog trends and may need to add this to the forecast. && .SHORT TERM...(This evening through Tuesday night) Issued at 315 PM EST Sun Dec 25 2016 We issued a winter weather advisory for freezing rain across the northern interior of the forecast area as model soundings and current obs suggest freezing rain could last several hours tonight. East flow in the low levels courtesy of 1048 mb sfc high centered near James Bay has dropped sfc dew points into the 20s across the northern forecast area and expect subfreezing dew points will continue across the northern tier through 06Z Monday. Flow eventually goes southeast then south and T and Td both go above 0C ending the icing threat up there by 10Z. The sfc low moves east on Monday and warm conveyor belt rains push through during the morning. Some instability is present but is rather marginal and thunder was left out of the forecast for now. The steadier rains clear the eastern zones in the afternoon and some mixing in the dry slot as CAA begins could bring down some gusts of 35 mph or more Tuesday afternoon and evening. Will have to watch this. Some light snow is possible across northern and central zones on Tuesday and Tuesday night as upper trough axis moves through. .LONG TERM...(Wednesday through Sunday) Issued at 315 PM EST Sun Dec 25 2016 A broad upper trough moving across the northern portion of the country may generate isolated rain/snow showers Wednesday night. This trough moves through on the heels of a cold front. We may see scattered snow showers Thursday afternoon as h8 temps fall to around -12c over the lake. Snow showers will last through Friday afternoon before warmer air arrives ahead of the next system. The gfs is more aggressive in drawing moisture north from the Gulf compared to the ecmwf, perhaps due to the upper short wave support that the gfs shows but the ecmwf doesn`t. Given the past couple of systems ability to pull moisture north toward the Great Lakes, we`ll lean toward the gfs attm. That means we`ve got scattered snow showers in the grids through next weekend. High temps will mostly be a couple of degrees above normal through the period. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 536 PM EST Sun Dec 25 2016 I did update the TAFs to reflect an increased risk for sleet. After looking at some AMDAR soundings out of KDTW late this afternoon...it looks cold in the low levels...and likely somewhat dry. One flight about an hr ago had -6.4C at 892 mb. So...it looks like a hazard exists for aviators. Thus I updated the TAFs to reflect this possibility this evening. Warmer air does eventually move in overnight...thus I limited the risk to a few hours at the onset. IFR should become widespread this evening and then persist through the night...with LIFR possible. As the wind shifts on Monday...and colder air advects in during the afternoon...conditions will likely improve. Gusts over 30 knots are likely at all TAF sites on Monday. A risk for wind shear could develop tonight. && .MARINE... Issued at 315 PM EST Sun Dec 25 2016 For simplicity sake we have replaced the SCA with a gale warning which will run from this evening through early Tuesday. Winds will be borderline gales tonight but probably be solid gales by Monday afternoon and Monday night. && .HYDROLOGY... Issued at 1158 AM EST Sun Dec 25 2016 Flood advisories have been posted in anticipation of above-bankfull rises on Sycamore Creek at Holt and Looking Glass River at Eagle. Others may follow... Maple Rapids, Ionia, and Hastings being the usual suspects. Water contained in the existing snowpack is around 1 inch in Muskegon, 1.5 inches in Grand Rapids, and 0.6 inches in Lansing. Dewpoint temperatures will climb above 32 degrees for a 12 to 18 hour period on Monday, peaking around 50 degrees amidst gusty winds. This will promote rapid snowmelt in concert with a third of an inch of rainfall. Insulated by the thick snow cover, soil remains mostly unfrozen around the area, but is quite waterlogged. Runoff from a melting snowpack plus rainfall will cause rivers to rise this week, some of them above bankfull. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 5 AM EST Monday for MIZ038>040. LM...Gale Warning until 4 AM EST Tuesday for LMZ844>849. && $$ UPDATE...MJS SYNOPSIS...Ostuno SHORT TERM...Ostuno LONG TERM...04 AVIATION...MJS HYDROLOGY...CAS MARINE...Ostuno