Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/27/19

Area Forecast Discussion
National Weather Service Honolulu HI
400 PM HST Thu Dec 26 2019 .SYNOPSIS... A dissipating front will maintain wet conditions over portions of the Big Island tonight. Northerly winds will build down the rest of the island chain tonight with showers favoring north slopes of Kauai and Oahu. Showers will favor windward slopes of all islands as locally breezy trade winds develop statewide on Friday, then shift out of the east during the weekend. Trade winds will decrease on Wednesday. && .DISCUSSION... A stalled front is falling apart near the Big Island this afternoon. Moisture along the front is being pushed by southerly winds onto Kau and the south slopes of Puna, where widespread shower activity has persisted through the day. The upper level trough that was driving the front is moving off to the east, though enough instability lingers to produce a few heavy showers over South Point. A post-frontal flow is slowly veering out of the southwest over Maui and west-northwest near Kauai. The afternoon Lihue sounding and recent aircraft data show an inversion continuing to build between 5,000 and 6,500 ft, leading to rather stable and mainly dry conditions. However, though there are still pockets of moisture moving within the post-frontal flow. One such pocket is currently moving over Molokai, while another is approaching Kauai. Winds will strengthen and shift out of the north then northeast tonight as the surface high advances closer to the state. This will keep moisture along the dissipating front focused over the Big Island, initially along southeast slopes, then across north facing slopes as the winds fill in. From Maui to Kauai, showers will favor north facing slopes, with the greatest amount of shower activity expected on Kauai. Northeasterly winds will shift out of more typical trade wind direction on Friday as the surface high passes north of the state. The winds will likely be breezy and gusty over the western end of the island chain, where a shallow band of moisture will likely enhance windward rainfall. In addition, lingering moisture from the stalled front should maintain wet conditions across windward Big Island. A weak ridge aloft will produce rather stable conditions. Over the weekend, trade winds will become more easterly, perhaps even out of the east-southeast near Kauai. The surface high will move off to the northeast and settle midway between Hawaii and California, with a trailing ridge moving to within a couple hundred miles of Kauai. This will cause the trades to veer more easterly and possibly lead to brief periods of weaker winds. A weak disturbance aloft will pass overhead, but a mid level ridge should hold, allowing modest rainfall to favor windward slopes. Little change is due on Monday, though we could see trades drop off and shift southeasterly late Tuesday or Wednesday as a front approaches. && .AVIATION... Showers remain persistent in the Kau district of the Big Island this afternoon as a weakening front stalls near the state. AIRMET Sierra remains in effect from Cape Kumukahi to South Point. Behind the front, scattered showers are pushing eastward down the island chain. The movement of these showers has taken on a more easterly trajectory from this morning`s northerly direction as winds begin to shift around behind the front. There is a somewhat organized line impacting Molokai as of 3 pm moving to the east at about 10 kt. This has brought tempo MVFR conditions to PHMK, so expect brief periods of MVFR with these heavier showers. Light winds are continuing to switch around from the south to the west and will eventually become more northerly by tonight across the island chain. High pressure will continue to build to the northwest of the state, which will bring the return of the trades by Friday. && .MARINE... A dissipating front will linger around the Big Island into tonight, then fade by Friday. High pressure will build north of the state tonight and steadily move east through the weekend. This will bring the return of strong trades, gradually veering from the north towards east over the next several days. Currently, no marine warnings are in effect, however, trade winds are expected to increase to Small Craft Advisory speeds by Friday and likely continue through the weekend. Coastal flooding will remain possible over low lying areas for the next couple of mornings due to higher than normal water levels and large astronomical tides. However, subsequent high tides will gradually lower heading into the weekend, with impacts decreasing as well. A series of small northwest swells will support small surf along exposed shores through Friday. An upward trend this weekend could support moderate surf by Sunday, but still below advisory level. Guidance is still advertising a hurricane-force low developing east of Japan this weekend which could translate to a very large northwest swell arriving locally early next week. This swell will likely result in warning level surf for north and west facing shores. A tiny, long- period south swell will keep south shore surf from going flat this weekend into next week. No other significant swells are expected. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Wroe AVIATION...Dye MARINE...TS
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
531 PM CST Thu Dec 26 2019 .SHORT TERM... 145 PM CST Through Friday night... Anomalous warmth--record-breaking in fact for Boxing Day in a swath from northern Illinois into Michigan--continues across the region, although the winds of change are on the horizon here with the approach of our next cold front. Temperatures early this afternoon have soared into the low to mid 60s across much of the area, although a sharp drop-off is occurring across far northwestern Illinois with the arrival of low stratus and a northwest wind shift. Moisture remains generally lacking downstairs ahead of the front, although it does incrementally increase a tad with eastward extent into portions of NW Indiana. As a result, have continued with a precipitation-free forecast for the entire area with the main signal for any light spotty showers or drizzle looking to remain immediately off to the south and east of the CWA. Guidance continues to generally struggle with the ongoing expansive shield of low stratus in the post-frontal regime, with latest Day Snow-Fog satellite RGB imagery showing this extends back essentially across the entire state of North Dakota. Recent VAPOR aircraft soundings out of Minneapolis-St. Paul reveal this post-frontal layer remains saturated (or nearly saturated) to about 850 mb, which is much deeper than most morning model guidance had indicated for this afternoon. As a result, while the NAM has recently performed abysmally in terms of low to near-surface moisture forecasts, have generally followed it and the SREF this time around for the cloud cover and high temperatures forecast for tomorrow (Friday) based on upstream observations. In addition, an impressive subsidence inversion looks to build in overhead which would further limit our ability to vertically mix some drier air into the PBL. Could finally see some chunks getting mixed out of the stratus deck towards late Friday afternoon, but by this time it`d likely be too late for temperatures to make much of a concerted rebound. Will show highs for tomorrow mainly in the mid-upper 30s north of I-80, and in the upper 30s to near 40 south with some potential that these still are a hair too aggressive on the warm side. Our attention will then turn to the system currently spiraling across southern California at this hour which is slated to eject across the Central Great Plains late Friday night. As is typical with these anomalously deep and digging upper-lows, guidance continues to incrementally slow the system`s forward progression, such that there may be little in the way of precipitation through Friday night/very early Saturday morning. That said, profiles do appear to saturate just enough (up past 850 mb) by around daybreak Saturday across the southwestern half of the CWA which should be intercepted by a burgeoning wind of low-level warm advection. Looks more like some spotty drizzle, so will keep the PoPs fairly low. Temperatures may be flirting with the freezing mark across parts of the I-39 corridor near Rockford, so can`t entirely discount a very brief period of spotty light drizzle/freezing drizzle, but not expecting anything in the way of notable impacts given the very warm air immediately off the surface and already marginal surface temperatures before things flip over to plain rain as temperatures rise with the approach of a warm front. Carlaw && .LONG TERM... 211 PM CST Saturday through Thursday... By Saturday morning, an area of high pressure moving across the region will shift east of the CWA to the Mid-Atlantic region as a southern stream shortwave moves out of the southern Rockies with an associated sfc low develops over the South High Plains, setting the stage for the next significant chance for precipitation expected to impact the area over the weekend. The latest runs of the longer range guidance are trending toward relatively consistent solutions, lifting the sfc low through the Upper Missouri Valley Saturday afternoon/evening and then continuing to the Upper Mississippi Valley Sunday morning. While the GFS/ECMWF are trending to spreading pcpn into the wrn portions of the CWA by early Saturday morning, and this is still a possibility, the models are generally too fast in lifting southern stream shortwaves out of the southern plains, so there is still a chance that the guidance may still be a little fast, and that pcpn may not begin to overspread the CWA until later in the day on Saturday than is currently being advertised. However, as an extended period of warm, moist advection sets up in advance of the system, still expect a return of unseasonably high temps and dewpoints, with highs in the lower 50s far north and upper 50s far south and dewpoints in the lower 50s up to the I-80 corridor. With the increasing temps/dewpoints, pcpn chances should ramp up quickly through the afternoon and into the evening with the heaviest and steadiest rain occurring overnight Saturday night. The GFS/ECMWF both show a little instability, though with less favorable lapse rates, so will continue the mention of slight chance tsra, though confidence in anything more than isold/embedded ts over the wrn portions of the CWA under modest upper level diffluence and stronger mid-level flow of 60-75 kt. A mid-level dry slot should move across the region Sunday as the sfc cold front quickly pushes east and the main upper low wobbles around the Upper Mississippi Valley before finally lifting newd on Monday. Temperatures should remain unseasonably mild through Sunday following the passage of the frontal boundary given the Pacific- sourced air mass, with widespread temps in the upper 50s across the area and a chance for temps to peg 60 F over the far southern portions of the CWA. The true cold air will finally filter into the region Monday night and Tuesday as the main upper system lifts to the Upper Great Lakes, setting up deep layer cold advection. Temperatures for early to middle next week should be closer to seasonable levels with highs in the 30s and lows in the 20s. && .CLIMATE... The impressive stretch of winter warmth continues but will come to an end today with the passage of a cold front. Rockford has seen 5 consecutive days with highs at or above 50F, which is now the first time on record such a feat has occurred during the second half December. For Chicago, it would be the first time since 1971! Today`s record high temperatures have been broken at both Chicago and Rockford. && .AVIATION... For the 00Z TAFs... The concern for the aviation forecast is a likely period of IFR cigs tonight, but low confidence on the duration and specific timing. A cold front has oozed through the Chicago area airports as of 23Z. Behind this front is a large area of low clouds extending back through the Northern Plains. There is a narrow swath of IFR clouds from western Illinois through north central Illinois. These overlap with the cooling air and residual high low-level moisture, favoring saturation of lower clouds and even MVFR visibility. This regime should move into Chicago which is why we continue the period of forecast IFR, and cannot rule out LIFR ceilings either given there are several sites observing that to the west. Later into the night, the cold advection profile strengthens slightly, and this typically results in cloud bases inching upward. Given the time of day though, cannot rule out IFR lingering into the morning rush though. Confidence on the clearing time of MVFR clouds on Friday is low as well, but given the satellite trends and observed moisture profiles upstream from aircraft, we continue to favor it sticking around most of the day. Otherwise winds will generally be westerly through tonight and the day Friday. MTF && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ 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 Blacksburg VA
1035 PM EST Thu Dec 26 2019 .SYNOPSIS... High pressure will linger over the area through Saturday - maintaining dry weather with above normal temperatures. Low pressure will lift north through the central portion of the nation Saturday night into Sunday night - bringing a widespread wetting rain to the mid-Appalachian and mid-Atlantic region. Drier weather, but with a continuation of above normal temperatures will overspread the forecast area Monday into Tuesday following the passage of a weakening cool front. && .NEAR TERM /THROUGH FRIDAY/... As of 1030 PM EST Thursday... Satellite showed lower clouds across Kentucky and into Ohio which will progress over the central Appalachians by morning then across much of southwest Virginia, northwest North Carolina and southeast West Virginia during the day. Stratus was already forming in eastern Virginia and is expected to spread west, reaching Buckingham to around Danville by morning. Between the two areas with more cloud cover there may be patchy fog overnight. Have may minor adjustments to overnight lows with not much for cooling where the clouds will increase. West of the Blue Ridge, some low clouds will develop early in the morning and likely hang around for a portion Friday. This will be associated with a weak shortwave that will struggle to develop any precip at all with the dry airmass in place. Right now, western Greenbrier tomorrow is the only place with any meaningful pop were perhaps an isolated shower could occur. Clouds tomorrow will limit some of our heating, keeping us slightly cooler than what we will be this afternoon. Forecast confidence is above average for today and tomorrow, but drops to average or below for clouds/fog tonight and into tomorrow. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 245 PM EST Thursday... Weak short wave trof in northern stream will support the southeastward push of a decaying cool front into the Blacksburg forecast area on Friday night. However, passage of this front will hardly be noticable, with only some mid-level clouds and the threat of some evening sprinkles (more likely virga) most notably across the SE WV mountains before axis of trof lifts north and east of the area well before daybreak on Saturday. Passage of weak front will be followed by weak ridge of surface high pressure over New England that will wedge southwest into the mid- Appalachian and mid-Atlantic states Saturday into Saturday night as low pressure lifts northeast through the central plains into IA and MN. However, absence of any cool advection, little to no post frontal onshore flow, and a fair amount of insolation should erode any low level inversion on southwest side of weak surface high such that temperatures on Saturday should continue to be some 10-15F above seasonal normals. Next threat of widespread rain is expected later Saturday night into Sunday as isentropic lift ramps up through an increasingly saturated H8-H6 layer with approach of western system. There may even be a brief window where a rumble of thunder is heard as associated cool front sweeps east through the forecast area on Sunday night; however, mid-level atmospheric lapse rates are only barely supportive of thunder, so not included in the forecast at the present time. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 245 PM EST Thursday... Following passage of the cool front, gradual clearing is expected on/by Monday - especially in downsloping areas east of the Blue Ridge and out across the Piedmont. Clearing may be slowed somewhat across the west, most notably across the western flanks of the Appalachains where some upsloping lingering showers/sprinkles are possible through much of the day. Flow aloft behind the departing system will remain zonal or from the west-southwest, so any deeper cold air will again remain mainly northwest of the Blacksburg forecast area such that temperatures remain above seasonal normals through much of the long-term period. Post frontal weak surface high pressure system expected to maintain dry and mild weather through Tuesday night before yet another low pressure system lifts north through the Mississippi valley Wednesday through Thursday. Moist isentropic lift in advance of the system should increase the threat for another widespread rain beginning as early as Wednesday afternoon - continuing until a cool front on the backside of the system sweeps east through the region on Thursday night. As has been the case for much of the winter to date, cold air over the mid-Appalachian and mid-Atlantic region will be absent such that all precipitation will fall in the form of rain - with no threat for any wintery weather until well after the New Year. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... As of 640 PM EST Thursday... High pressure along the Atlantic coast seaboard is gradually shifting eastward, gradually setting up some return flow with moisture increasing through Friday. Expect VFR all sites early tonight with some fog/stratus developing late. Confidence in intensity and extent of fog/stratus is low with guidance of late being a bit too aggressive and not verifying with extent of low clouds currently visible on satellite. Believe the most likely scenario is fog some valley fog west of the Blue Ridge affecting both KLWB and KBCB, and low clouds/fog seeping in from the east and southeast to affect KDAN and KLYH. Will go middle of the road with cigs/vsbys and amend later as trends in satellite become evident. Any fog/stratus will dissipate Friday morning with VFR holding on most locations, but MVFR cigs may develop west of the Blue Ridge Friday afternoon at KLWB and KBLF with increasing low level moisture. Winds are expected to be light through the period with little impact to aircraft operations. Extended Aviation Discussion... VFR weather conditions are expected through early Saturday. An approaching front will bring increasing clouds and the threat for rain Saturday night through Sunday night with widespread sub- VFR likely. Monday should see return to VFR with gusty winds. Exception should be lingering moisture of MVFR variety across BLF/LWB. && .CLIMATE... As of 215 AM EST Thursday... Another mild day, but records are not expected to be reached for most of our climate sites, except possibly Blacksburg. Thursday 12/26/2019 Site Record High/Year Bluefield 68/1922 Danville 75/1982 Lynchburg 72/1922 Roanoke 70/1964 Blacksburg 64/1982 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WERT NEAR TERM...AMS/RR SHORT TERM...WERT LONG TERM...WERT AVIATION...MBS/RR CLIMATE...WP