Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/01/21

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
525 PM CST Thu Dec 31 2020 .UPDATE... Issued at 524 PM CST Thu Dec 31 2020 The forecast is on track this evening. No major changes are planned. && .SHORT TERM...(This Evening through Friday Night) Issued at 157 PM CST Thu Dec 31 2020 Forecast challenges revolve around downslope wind potential tonight, and temperatures. Currently, under a mostly sunny sky, temperatures are warming through the teens and 20s on a light southerly wind, east of the Missouri River valley. West of the valley, temperatures are noted warming into the 30s on west-southwesterly winds. The biggest concern right now in the short term is how strong can downslope winds become overnight tonight. Fresh snow on the ground is blowable. So if sustained winds reach 30 to 35 mph with gusts to 45 mph or higher, there will be some spots along I-29 and U.S. Highway 12 in Roberts and Grant county that experience blowing snow and potentially reduced visibility. The set-up is subtle and not really ideal for downslope winds. There is some weak low level waa happening overnight tonight and low level winds will have a west- southwesterly direction. The HRRR continues to highlight some stronger downslope winds developing (20 to 26 knots) after 7 PM CST this evening, for several hours. Have bolstered the winds in the Prairie Coteau`s downslope area and added blowing snow mention to the weather grids. By Friday morning, a weakening lee-of-the Rockies surface trof will be working south and east of the CWA, turning winds around to the west-northwest briefly on Friday. High pressure builds in during the day, causing winds to gradually subside to calm or near calm. Friday night, the next installment of lee-side surface trof begins to deepen off to the west, signaling a switch in the winds back to a southerly or southwesterly direction. Despite the ongoing weak low level waa, high and low temperatures are not expected to moderate from the most recent observed high and low temperatures all that much between tonight and Friday night. .LONG TERM...(Saturday through Thursday) Issued at 157 PM CST Thu Dec 31 2020 Not much in the extended for impressive weather systems. Late Saturday an upper trough passage will feature some cloud cover, very little lift so if any precipitation does occur, it won`t be much more then an isolated sprinkle or flurry, and blended guidance has smoothed any precipitation out with this feature. It will bring in a modified Pacific airmass, which will lead to temperatures above average for Sunday and Monday. A clipper across southern Canada Monday will draw cooler air in its wake, but really its just a glancing shot for our area with more mild 850mb temperatures to follow in its wake. The system that follows after that also appears to be influenced by the split flow pattern and will have relatively little impact on our region for the middle of next week aside from clouds and winds picking up a little. && .AVIATION...(For the 00Z TAFS through 00Z Friday Evening) Issued at 524 PM CST Thu Dec 31 2020 Terminals KABR,KATY,KPIR,KMBG VFR conditions are expected to prevail through the period. There could be a short period of restricted cigs/vsby near sunrise in stratus/fog near KATY. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Wise SHORT TERM...Dorn LONG TERM...Connelly AVIATION...Wise
Area Forecast Discussion
National Weather Service Charleston SC
1003 PM EST Thu Dec 31 2020 .SYNOPSIS... A warm front will lift north of the area late tonight. A cold front will impact the area late Friday through the weekend. High pressure will return Monday and prevail through early next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As expected, the stationary front has started to sink south late this evening. Various mass fields from both the RAP and MSAS show the front surged south across interior Southeast Georgia over the past few hours with light northeast winds now being reported at both Millen, GA (K2J5) and Metter, GA (KMHP). Surface analysis at 01/02z showed the quasi-stationary front was located roughly along a Saint Stephen-Harleyville-Hampton- Oliver-Claxton-Collins line. Dense fog has started to rapidly fill in behind the boundary with webcams out of Metter, Vidalia, Claxton, Statesboro showing pretty widespread dense fog with very low visibility. A Dense Fog Advisory has been issued for much of interior Southeast Georgia as well as Allendale County, SC, through 6 AM. The front is still expected to sink closer to the lower South Carolina coast later tonight. Dense fog should fill in behind the front, but the redevelopment of showers over the Charleston Tri-County area after midnight could keep dense fog from becoming too widespread there. The better chances for dense fog outside of the current advisory area should settle into Hampton and Walterboro south to Beaufort and Hilton Head. South of I-16, the front should not move too far south of there and only patchy fog should occur there. Late evening reports from Hilton Head (KHXD) and webcam images at sunset showed the patches of sea fog just offshore. Guidance is similar in expanding the sea fog along the far upper Georgia coast and into Hilton Head and Beaufort later tonight. This could skirt parts of the Savannah Metro Area. The fog is still expected to improve from south- north prior to sunrise as the front lifts north as a warm front so a 6 AM advisory expiration time looks reasonable, although some areas could be cancelled prior to that. The risk for isolated to scattered showers will linger through the night, gradually shifting north of the area by daybreak with the warm front. Temperatures will be some 20+ degrees above normal, with lows ranging from the upper 50s across the interior to around 60/low 60s elsewhere. These values put record high minimums for January 1 in jeopardy. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Friday (New Years Day): On Friday morning, most of the area should remain rain-free as subsidence pushes onshore from Atlantic Coastal waters. Though, a few light showers cannot be ruled out, mainly inland and in the Charleston Tri-county as a coastal trough departs the area. Lingering areas of fog is possible in the morning, mainly in SE GA and in the GA nearshore waters. Fog could be dense in areas with visibilities 1/2 mile or less. WAA over the marine waters could advect sea fog on land along the GA coast maintaining low visibilities. A surface low meandering near the ArkLaTex will finally push northeast shifting the cold front eastward closer to the region. Latest models show the cold front approaching Friday evening, before stalling just as it reaches our forecast area as the occlusion process dominates the surface low over the Midwest. SPC has kept our far inland counties in a Marginal Risk for severe thunderstorms and areas closer to the coast in general thunder. Models indicate a line of storms just ahead of the front weakening as they approach our most western counties as the front slows and weakens. An isolated strong to severe thunderstorm could occur in this high shear/low CAPE environment; however, storms should remain limited to these inland counties as sfc forcing lessens; however, showers could extend closer to the coast. Above normal temperatures are expected with highs reaching the mid 70s over most of the region and nearing 80F in southeast GA. Overnight, min temperatures will only drop to the low 60s, nearing record high min territory. Saturday: The front remains in place and weakens slightly via persistent meridional flow as a secondary upper low develops within the lingering upper trough. By the afternoon, a second H5 low propagates over the Southern Appalachians, strengthening the front as noted by strong 700 mb frontogenesis. With deep moisture in place, rainfall will be more prominent with approximately 1-3" forecast across the region, with higher amounts expected over the inland counties. Locally higher amounts are possible within stronger thunderstorms. SPC has the entire area outlooked in a Marginal Risk for severe thunderstorms. The development of discrete cells are possible due to 40-50 kt bulk shear. However, the severe potential is on the low end as higher shear could overcome updrafts and limit organization, due to minimal CAPE. Above normal temperatures are expected again with highs reaching the low/mid 70s. Overnight temps will gradually cool to the mid 50s. Sunday: The front is expected to push offshore Sunday morning with surface high pressure building into the region. The rest of Sunday should be rain-free with clearing skies and breezy conditions in the wake of the front. The strongest CAA is expected to occur late afternoon as winds shift out of the northwest. While winds do not look to exceed Lake Wind Advisory criteria, Lake Moultrie could have occasional gusts up to 20 kt. High temperatures will be cooler, yet remaining just above normal; in the 60s over the general area. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... High pressure will prevail through Wednesday and the area should remain rain-free. Monday and Tuesday will be sunny before moisture moves back into the area on Wednesday and cloud cover will increase. High temperatures will be in the 60s. Lows will be in the 30s/40s each night. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Shower activity near KCHS should largely pass north of the terminal by 00z. No impacts are expected. Fog/stratus will continue to be a concern at both KCHS and KSAV. The stationary front across the interior is expected to meander south near both terminals overnight before lifting north as a warm front prior to daybreak Friday. Fog/stratus is expected to fall in near the front, but with weak shower activity forecast to linger near KCHS for much of the night, this may be enough to keep vsbys from dropping too much. Opted to limit vsbys to MVFR 05-10z along with IFR cigs. For KSAV, some clearing this evening ahead of the front should promote a higher fog chance with chances increasing as the front settles nearby. MVFR vsbys are expected by 04z with IFR cigs/vsbys 06-09z before improving as the warm front lifts north. Lowest conditions were handled in a TEMPO Turin this time with vsbys below and cigs right at alternate minimums. Some guidance suggest several hours of dense fog, especially if winds tip northeast near the front and this will have to be watched. Gusty winds will develop by mid-morning at KSAV and early afternoon at KCHS. Finally, low-level wind shear could impact KSAV from 04-09z. Included WS020/18035kt during this time. Extended Aviation Outlook: Flight restrictions possible in showers/t- storms and early morning fog/stratus through the weekend. && .MARINE... KHXD has recently dropped to 1/4 mile and matches short term fog guidance pretty well. NARRE-TL probabilities for dense fog rapidly increase from Sapleo Sound to Edisto Beach out to roughly 10 NM over the coming hours. Given this consistent trend and the Charleston Harbor Pilot Boat recently reporting patches of dense sea fog east of the Charleston Harbor, a Marine Dense Fog Advisory has been issued for the Georgia and and far southern South Carolina nearshore waters through 6 AM. Guidance shows the best risk for dense sea fog holding south of Charleston Harbor and the Charleston nearshore waters, but this will have to be watched, especially if winds turn more south than southeast as the warm front lifts north. Tonight: Southerly winds will persist across the waters tonight. Marine conditions should remain below Small Craft Advisory criteria, with the exception being the Georgia offshore waters where 6+ foot seas persist. The main concern will be the potential for sea fog as warm, moist air moves over the cooler shelf waters. Area webcams have shown some reduced visibilities, and models indicate this trend should continue overnight. Marine Dense Fog Advisories could be needed. Friday through Tuesday: Southerly flow will prevail through early weekend ahead of a cold front. Sea fog is possible Friday morning through the afternoon over the nearshore waters with the advection of much warmer air. Winds will shift out of the northwest Sunday as the front finally pushes offshore. A Small Craft Advisory will remain in effect through the period for the offshore Georgia waters from 20nm to 60nm for seas greater than 6 ft and occasional wind gusts over 25 kt. The nearshore waters could have occasional 6 ft seas and wind gusts near 25 kt Saturday into Sunday where SCA`s could be needed. Winds in the Charleston Harbor are forecast to remain below SCA criteria. Marine conditions are expected to improve Sunday night into early next week. Seas will drop to 3 ft or less by Monday, and NW winds around 10-15 kt will prevail. && .CLIMATE... Record high minimum temperatures for Jan 1: KCHS: 61/2019 and 1973 KSAV: 62/2019 KCXM: 62/2019 Record high minimum temperatures for Jan 2: KCHS: 60/1985 KSAV: 66/2017 KCXM: 63/1985 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Dense Fog Advisory until 6 AM EST Friday for GAZ087-088-099- 100-114-115. SC...Dense Fog Advisory until 6 AM EST Friday for SCZ040. MARINE...Dense Fog Advisory until 6 AM EST Friday for AMZ352-354. Small Craft Advisory until 2 PM EST Sunday for AMZ374. && $$
National Weather Service Hastings NE
531 PM CST Thu Dec 31 2020 .DISCUSSION...(This evening through Thursday) Issued at 255 PM CST Thu Dec 31 2020 Main concern in the short term is potential for fog. Beyond that, temps and low end pcpn chances become primary forecast challenges. Not too bad out there today with full sunshine area wide, though it is a bit chilly with the southerly breeze, at times. Latest GOES WV imagery shows the area split between N stream well N of the area, and active S stream with two potent vorticity lobes noted - one over S CA, and the other over S TX. The mid level speed max associated w/ TX vort lobe is beginning to round the base of the trough, which will allow the trough to bec negatively tilted as it lifts NE tonight into Fri AM. This system will have an excellent tap to Gulf moisture, but it appears this will only aid in production of widespread convection, which will likely help "pull" the track of the trough a bit further SE than previously expected. Models have trended this way, esp short term hi-res and convective allowing models, so have pulled all PoPs from far SE for tonight and Fri AM. As far as potential for fog, HRRR and SREF continues to indicated good potential for fog development tonight and into Fri AM, esp for areas N of Hwy 6 and E of Hwy 283. This seems very reasonable given lgt winds and likely at least some snow melt from this aftn adding some moisture to the near-sfc boundary layer. Current Tds are in low to mid 20s, so low temps in the teens to upper single digits would be more than supportive from a crossover temp perspective. BUFKIT data from RAP/HRRR also shows favorable hydrolapse and MRi numbers. Have added some "dense fog" wording to the grids. The potential for high cirrus to move in from the S gives me just enough uncertainty to ramp it up more than that just yet, but it`s certainly something the eve shift will need to watch. Wouldn`t be surprised if parts of roughly N half of CWA will need a dense fog advisory by dawn. Given what happened last night, have trended temps down at least a few deg from guidance for the favored cold areas of Dawson, Valley and Greeley Counties. Shallow nature of fog and incr NW winds should allow for improving conditions by mid to late Fri AM. Nrly winds and at least some high clds will probably lead to slightly cooler high temps for New Years Day, but overall, not too bad. May have to deal with fog yet again Fri night into Sat AM as crossover temps are once again favorable and winds look to go nearly calm under clr skies. SREF probabilities are decent (50-70%) for vsbys <1sm. Debated incr from the "Patchy" mention from prev shift, but felt best to continue as is and reevaluate after we see what happens tonight. Other than fog potential, the forecast is pretty quiet through the weekend. The aforementioned CA vort lobe will probably take a similar track to tonight`s system and remain SE of the area on Sat. Models indicate a fast moving shortwave on the heels of this system in increasingly zonal flow Sat night into Sun AM. We`ll have to watch this to possibly squeeze out some flurries or sprinkles, but counting on quick hitting nature of wave and lack of deep moisture to keep forecast dry attm. Another wave looks to arrive around the middle of next week, but models are not in very good agreement as latest GFS is much further S than EC. QPF signal doesn`t look great attm, so forecast remains dry, but wouldn`t be surprised to see some low PoPs/QPF added later on. Expect a moderating temperature trend over the coming days but this will be tempered by the existing snow pack. Perhaps by early next week we`ll have lost enough snow to allow most of CWA to see highs at least in the 40s. Southern areas that remain snow free will see more substantial incr in temps into the 50s as early as Sun. Temps fall back a bit middle of next week, but overall, no significant temp fluctuations expected over the next week. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 519 PM CST Thu Dec 31 2020 Primary concern remains for the potential of fog later on tonight, especially after 06Z. With full sun and temperatures just above freezing, enough melting has occurred today to help produce fog tonight as winds will be rather light. One caveat is how soon the thick shield of cirrus will stream northward to help tamp down the widespread production of fog. If this cloud shield takes a little longer, we will almost surely have some dense fog in the area. We will hit a few degrees below crossover temperatures by as early as 03Z, and by 06Z we could be in trouble if not enough thick high- level sky cover makes its way in. I suspect that BR will develop if not FG, and that we will have a considerable stratus deck develop in response. I have forecast IFR/marginally LIFR conditions for the overnight, and hi-res models are consistently indicating the potential for this to develop. I have hit fog/stratus a bit heavier than the previous forecast and have continued this trend from the previous forecast. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Thies AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Lincoln IL
857 PM CST Thu Dec 31 2020 .SYNOPSIS... Issued at 846 PM CST Thu Dec 31 2020 Freezing rain will overspread central Illinois late tonight and continue into Friday morning, though a changeover to rain is likely in areas south of I-72 by late morning. The ice, mixed with sleet and snow at times, is expected to continue into the afternoon northwest of the Illinois River, before the storm system moves northeast in the evening and takes the precipitation with it. While much of central Illinois will reach the lower to mid 30s by afternoon, areas south of I-70 should see highs well into the 40s. && .UPDATE... Issued at 856 PM CST Thu Dec 31 2020 Plenty of dry air sampled on our evening balloon sounding, but this should moisten quickly from the top down as our storm system lifts northeast. Mid evening radar imagery shows the leading edge of the echoes across the southern third of Missouri, with surface reports showing is freezing rain. Latest HRRR shows this precip shield reaching Springfield and Decatur toward 2-3 am and the Peoria metro toward 6 am. Main concern will be with timing of any switchover to rain. HRRR keeps the freezing precip continuing past midday north of I-72, while the newly arrived 4km NAM and the ARW/NMM switch it over by midday as far north as Bloomington. Stiff low level northeast wind flow and frozen ground add some concerns that the slower solution may be the way to go, though precip rates may be heavy enough that latent heat release may compensate. Will keep a rain or freezing rain mix continuing along and west of I-55 into the afternoon with a switchover in eastern Illinois. Still looking like a widespread quarter to third inch of ice accumulation across the warning area, with a tenth or two of ice southeast of there. No changes will be made to headlines at this time. && .SHORT TERM...(This evening through Friday night) ISSUED AT 417 PM CST Thu Dec 31 2020 Lots to discuss, therefore the late products: A deep upper level trof is carrying a large Low pressure system across the far southern Plains, near the Gulf of Mexico off the se Texas coastline. This is the system that will track northeast through the overnight, impacting central Illinois and the Midwest to ring in the new year. Currently looking at sfc observations and seeing most locations throughout central and southern Illinois sitting below freezing. This is the key component to precip type for the overnight moisture. As the Low pressure system lifts through the Mississippi River Valley, the excessive moisture content will continue to lift with the core. With some precip already edging out ahead of the system, this will work through moistening up the lower atmosphere and continue leading precipitation northward. Forecast soundings indicate that although the sfc temperatures will be below freezing at the onset of precip, the mid level will be much warmer. This will melt all frozen precip in the mid levels, however as this falls, the level near the sfc will be below freezing. This depth appears to only be in excess of maybe 2kft, which would not typically be enough to provide a full refreeze of water droplets. As these still liquid droplets reach the below freezing ground (as indicated by frost depth readings from this morning), they will freeze on contact. Frost depth readings this morning, in areas where Ice Storm Warning is in effect were from 1-6 inches deep. Here at the ILX office, we reported a 4 inch depth this morning. This is sufficient enough for freezing rain development. The leading edge of this system is expected to fall as all freezing rain overnight into Friday morning. With heaviest precipitation arriving towards morning north of the I-72 corridor, this is highlighted as the best chance for ice accumulations up to 0.40 inches of ice accumulation possible. This will create dangerous and hazardous conditions throughout the region, as travel would be nearly impossible and damage to trees and power lines could create widespread power outages. As the system tracks northward, warmer air will begin to filter into the area Friday morning into the afternoon, changing freezing rainfall to rainfall...however this is only expected to occur se of the I-55 corridor. Mixed precip is expected from the I-55 corridor through the Illinois River Valley. Nw of the Illinois River Valley is forecast to remain cold enough that freezing rain will likely prevail, before a change to snowfall as the backside of the Low pressure system begins shifting to the lower Great Lakes late Friday night. This could bring up to two inches of snowfall around GBG, while decreasing to near 1 inch along a line extending from Rushville to Peoria. This system is forecast to be out of the area by 06-09z Saturday (late Friday night). && .LONG TERM...(Saturday through Thursday) ISSUED AT 417 PM CST Thu Dec 31 2020 Another Low pressure system will progress through the se US Saturday, with which another brief round of precipitation could bring mixed precip to the area. This would be due to excessive moisture lingering from tonight`s system. High pressure then returns across much of the eastern US during the first part of next week, however this is pushed off the Atlantic coast by the middle portion of the week, as another upper level trof and split Low pressure system traverse through the central CONUS. Current model trajectory indicates a general path north and south of the local area in the upper level, as the sfc Low`s both track along the same idea. This will drape a frontal boundary through the region Wednesday night into early Thursday, however the current moisture availability does not support much precipitation. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 518 PM CST Thu Dec 31 2020 MVFR conditions have overspread much of central Illinois early this evening. HRRR and NBM guidance suggests there may be a period between 08-12Z that may come back up, but confidence on this lowers the further north you go, so will only include a TEMPO period for the KSPI-KCMI area. IFR/LIFR conditions will be widespread by mid morning Friday. Large area of freezing rain will overspread central Illinois early Friday morning from south to north, with northeast winds gusting from 20-25 knots. The question will be whether any conversion to straight rain will take place in the afternoon, as temperatures rise. Most uncertainty for this will be at KPIA/KBMI, and will keep the FZRA mention there through the end of the period, with a switch to rain is more likely further south between 18-21Z. && .ILX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from midnight tonight to noon CST Friday for ILZ044>046-052>057-061>063-066>068-071>073. Ice Storm Warning from 3 AM to 6 PM CST Friday for ILZ031-037- 038-041>043-047>051. Ice Storm Warning from 6 AM Friday to midnight CST Friday night for ILZ029-030-036-040. Winter Weather Advisory from 6 AM Friday to midnight CST Friday night for ILZ027-028. && $$ UPDATE...Geelhart SYNOPSIS...Geelhart SHORT TERM...Baker LONG TERM...Baker AVIATION...Geelhart
National Weather Service Jackson KY
757 PM EST Thu Dec 31 2020 .UPDATE... Issued at 757 PM EST THU DEC 31 2020 Forecast is on track this evening. Evening update entailed only minor adjustments to the hourly grids, mainly temperatures and dew points. Also freshened up the zones to remove afternoon wording. No other changes at this time. Frontal boundary has stalled out just to the south of our forecast area. With the loss of upper level support steady rains have exited the area with only low stratus left behind. Low pressure over ARKLATX is winding up and will be poised Friday morning to shoot rapidly into the Great Lakes Region by late in the day. This action will lift the surface front to our south back northward during the day Friday. Consequently rain will redevelop across the area late tonight. Current forecast has all this handled well. && .SHORT TERM...(This evening through Friday night) Issued at 431 PM EST THU DEC 31 2020 Late this afternoon an upper level ridge extended from the Caribbean into portions of the western Atlantic with a ridge over portions of the eastern Pacific. A split flow pattern was observed over much of the Conus with the northern stream displaced well to the north and a broad trough in the southern stream. Moving within the southern stream was an upper level low moving across TX. A shortwave trough is moving across the Great Lakes and mid OH Valley. At the sfc, high pressure was centered over the Great Lakes region while a sfc frontal zone extended from the Atlantic into VA and then into the TN valley. Surface low pressure is organizing over southeastern TX with a warm front developing to its east across the Gulf Coast states. Patchy light rain and drizzle lingers across portions of the CWA at this point. The upper level low is expected to track to the north northeast to the mid MS Valley on Friday, New Years Day, and then into the Great Lakes Friday night. Meanwhile, the sfc low should track into southeast OK tonight and then into the mid MS valley on Friday with a triple point low developing over western KY with the sfc low tracking northwest of East KY on Friday night. As the mid level shortwave passes east of the area over the next couple of hours, the patchy light rain and drizzle should tend to decrease in coverage with a relative lull in the precipitation anticipated during the evening into the first portion of the overnight. However, warm air advection and isentropic lift ahead of the warm front lifting north toward the Commonwealth is expected to lead to showers spreading into the area toward dawn from the TN Valley. This warm front should lift into the region on Friday afternoon and lead to the steadier precipitation departing to the northeast. Showers are still anticipated on Friday afternoon to Friday evening as the cold front approaches. Enough instability may exist near the cold front for isolated thunderstorms over central KY and middle TN that try to move into the area later in the afternoon or early evening. If thunderstorms were to materialize they may be able to mix down some of the higher momentum from stronger winds aloft. Outside of thunderstorms, the higher momentum from stronger winds aloft should mix down to some of the higher terrain over southeastern KY. At this point, we opted to increase the wind gusts across the higher terrain. The 12Z HREF and hi resolution models such as the 12Z and 18Z HRRR suggest advisory level wind gusts are possible in the higher terrain particularly in Harlan and Letcher counties near Pine and Black Mountains for a few hours either side of 18Z. That pattern is also somewhat conducive to mountain wave development potential downwind of Black and or Pine Mountain as well. With this in mind, opted to go with an SPS for some of the southeastern counties though trends may need to be monitored for the need of an advisory for some of the VA border counties. As the cold front moves east and the associated upper level low/mid level wave depart to the northeast, deeper moisture will depart and chances for precipitation will diminish on Friday night. Plenty of low level clouds are expected to linger, however. Lows and temperatures tonight should not be far from current readings with a north to south gradient anticipated. Temperatures will be much milder on Friday in the warm advection pattern. Highs should reach the 60s in many areas with temperatures remaining mild behind the front on Friday night. .LONG TERM...(Saturday through Thursday) Issued at 440 PM EST THU DEC 31 2020 12Z Saturday - 12Z Monday... By 12z Saturday, eastern Kentucky will be in between systems. Aloft, upper level ridging will reside across the Southeast US with an axis extending NWward to over Illinois. To our north, upper level troughing, associated with the remnants of Friday`s storm system, will be weakening over Lake Ontario and a new coastal low will be taking shape along the New England coast. The cold front associated with this transitioning system will be to our southeast over the Piedmont while another weak surface trough trails SWward to along the Ohio River. Between the front and this surface trough, a narrow, anemic surface ridge will likely reside along the western slopes of the Appalachians. To our southwest, another upper level low will be deepening over TX/OK. Model agreement is fairly good showing this next low lifting toward the Ohio Valley Saturday and crossing the region Saturday night into Sunday morning. As the low pulls away toward New England Sunday night, another shortwave pivots around the southern periphery of the low. At the surface, a weak surface low develops over the mid-Mississippi Valley Saturday. This system quickly occludes as it rides NEward along the Ohio River Saturday night and a new low develops along the triple point over the GA or SC. This new coastal low quickly strengthens and pulls away on Sunday as the upper low`s trailing cold pool moves in from the southwest. In sensible terms, lingering low-level moisture under a subsidence inversion should lead to mostly to partly cloudy skies on Saturday. The more widespread cloud cover will likely be found closer to the surface trough along the Ohio River while nearly full sun develops over far southeast KY. With that in mind, highs are expected to remain suppressed in upper 40s north of I-64, but should rebound into the upper 50s in the warmest valleys near the TN and VA borders. Increasing clouds will yield to a period of widespread rain showers Saturday night. Temperatures aloft will become borderline cold enough to support ice crystals and possibly a few flakes above 3,000 feet on Sunday before the precip tapers off. Low clouds, weak CAA, and precipitation should hold Sunday`s highs in the 40s. The trailing shortwave will likely keep plenty of clouds around Sunday night with even a flurry or two possible. 12z Monday - Thursday... Model agreement worsens Monday into Tuesday before improving slightly for Wednesday. Initially, heights will rise on Monday with surface high pressure expanding northeastward from the Southern Plains and Gulf Coast. However by late Monday and Monday night, another shortwave trough drops through the Great Lakes. The ECMWF and Canadian feature a more amplified trough relative to the GFS. The Canadian even hints at some light precipitation. Retained the NBM guidance for now, which kept forecast dry but increased sky cover to account for the increasing moisture and raised surface winds to cover the tightening pressure gradient. Once the trough exits, a stronger ridge, aloft and at the surface, passes Wednesday. Yet another trough or upper level low ejects eastward from the Rockies and brings renewed precip chances for Thursday, but the poor model agreement obscures many of the details for now. Mostly clear to partly cloudy skies should prevail for most of the Monday through Wednesday timeframe except for early Tuesday when the trough could bring a period of mostly cloudy skies. Thicker cloud cover will likely arrive by Thursday as the next system approaches. Temperatures will remain mild for early January with highs of 45 to 50 on Monday moderating to between 50 and 55 on Wednesday. Lows are expected to range from the mid 20s to mid 30s. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 757 PM EST THU DEC 31 2020 A surface frontal boundary has stalled out just to our south this evening. With the loss of upper level support, steady rains have exited the region, leaving only low stratus behind and LIFR CIGS. Low pressure over ARKLATX is winding up and Friday morning will be poised to shoot rapidly into the Great Lakes Region by late in the day. This action will lift the surface front to our south back northward during the day Friday. Consequently, rain will be redeveloping late tonight and for a good portion of the day Friday. The boundary to our south will lift north as a warm front tomorrow as well, helping to scour out the low LIFR CIGS and putting the area within the warm sector of this storm system by late in the day. Wind fields are quite strong with this storm. Thus non-convective LLWS will become an increasing threat towards dawn and through much of the day Friday. Otherwise, surface winds will be generally light, around 5 kts or less and variable, but becoming southeasterly late and increasing in strength to around 10 kts (and gusty). Eventually will will continue to veer to the south after the warm front lifts to our north. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...JP LONG TERM...GEERTSON AVIATION...RAY
Area Forecast Discussion
National Weather Service Lubbock TX
710 PM CST Thu Dec 31 2020 .UPDATE... The major winter storm was over central Texas and spreading snow further west to along and even west of US 87 in Lynn County south of Lubbock, and through Slaton and Ransom Canyon just east of Lubbock in Lubbock County. We have added both Lynn and eastern Lubbock Counties to the Winter Weather Advisory. But the situation remains highly dynamic and fluid this evening. RADAR was showing reflectivity developing over the western South Plains that may indicate the back edge of the Deformation Axis. Latest HRRR indicates a spoke of reflectivity also rotating back west to very near Lubbock by mid evening. But we still have a dewpoint depression of over 20 degrees needing to be mostly overcome in order for snow rates to have a significant impact. None-the-less, this is a very close call for the more populated I-27 corridor from Lubbock through Plainview this evening into early Friday and we will update as needed. RMcQueen && .PREV DISCUSSION... /issued 610 PM CST Thu Dec 31 2020/ AVIATION... A major winter storm system was rotating northeast over central Texas. Snow and sleet bands were spreading north through the Rolling Plains and eastern South Plains and best estimate is they will remain just to the east of both KLBB and KPVW. Precipitation has lifted north to near KCDS and will lead to increasing snow through the evening. Appears the best chance for LIFR conditions at KCDS will occur late this evening into early Friday morning once full moistening and cooling occurs at the surface. Snow chances at KCDS are expected to diminish near daybreak Friday with gradual improving in ceiling thereafter. Cool northerly flow will continue over KLBB and KPVW with VFR expected to dominate, even with a possibility of light snow this evening. RMcQueen PREV DISCUSSION... /issued 224 PM CST Thu Dec 31 2020/ SHORT TERM... The afternoon short term forecast continues to revolve around the snow potential this evening into the first day of 2021. While some uncertainties still remain, the potential for accumulating snowfall across the eastern half of the forecast area seems likely with the greatest confidence in accumulating snowfall across the last two columns of the Rolling Plains where the better moisture and forcing will reside. That being said, late afternoon observations show a moistening of the lower atmosphere from Lubbock southeastward with snow being reported at Lake Alan Henry and a few flurries across the City of Lubbock. This activity is tied to energy moving northward into the FA from the south. CAMs continue to show the upper low tracking northeastward, digging and reforming a new deformation zone over Oklahoma after sunset shifting the precipitation shield more to the east putting areas from Garza County northward to Briscoe County on the fringe of the snowfall by late this evening. This biggest uncertainty continues to be the dry air near the surface and in the mid-layers and how it will affect our accumulations due to sublimation as top down moistening occurs. Have trimmed snowfall amounts and QPFs back a tad to take this into account, but the winter weather advisory still stands. It does appear from AMA and MAF 12Z soundings and from 12Z NAM that the colder solution for mid-level temperatures will win out with snow the dominant, if not sole, precipitation phase for the event. LONG TERM... The long term portion is quiet relative the storm in the short term. Another, albeit weaker, upper level low will track across the region Friday night. This one will also be much more limited in the moisture it can tap. Add in a fast motion and a quick burst of light snow across the northern zones still looks like the best this one will do. Afterwards, northwest flow aloft will back toward zonal as a low-amplitude ridge moves across the region early next week. As a result quiet and mild weather is expected for Saturday through Tuesday. The next upper low to potentially affect the region is progged for the middle of next week, however there is a large variance in the models regarding the handling of this system. That will be something to watch as we head through the first week of 2021. Happy New Year, y`all. && .LUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 AM CST Friday for TXZ024>026- 030>032-035>038-041>044. && $$ 05/99
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
601 PM CST Thu Dec 31 2020 .SHORT TERM...(This evening through Friday night) Issued at 256 PM CST Thu Dec 31 2020 Surface analysis this afternoon shows extensive high pressure centered over IL/IN, expanding westward into the mid-upper Mississippi River Valley. A weak surface low pressure sits over far southern Saskatchewan province, with a warm front sagging south southeast over the central Dakotas. Aloft, generally zonal flow is in place over the northern Tier states from the Great Lakes well west into the northern Rockies, with several minor perturbations in the flow. As alluded to above, one such perturbation is slow to move out of the region and has shown up on RAP guidance atop satellite imagery. Though the morning KMPX RAOB showed the saturated layer at around 1000ft and it is very shallow (only several hundred feet), it has sustained low stratus over much of eastern MN into western WI into this afternoon. Weak PVA well in advance of the warm front has been just enough to keep the low stratus in place. It has shown a very slow erosion eastward and this slow trend looks to continue into tonight, trying to show this progression in the gridded forecast. Another weak wave aloft will move across the region tomorrow in conjunction with a southern stream system ejecting from the Deep South into the Ohio Valley. With little impetus to kick the shallow moisture out of the region, the low stratus is expected to advect back to the west and encompass much of the area once again on Friday. Thus, diurnal temperatures from today to tonight to tomorrow will be fairly small (only about a 10-14 degree from today`s highs to tonight`s lows) and highs on Friday will be very similar today, reaching the mid 20s for much of the area. The return southerly flow expected for Friday and Friday night will also keep Friday night temperatures from dropping off much, again in the 10-15 degree range which is what will be experienced tonight. .LONG TERM...(Saturday through Thursday) Issued at 256 PM CST Thu Dec 31 2020 An expected quiet pattern continues to be the case for the first week of the new year. The upper level flow will remain split between the fairly inactive northern stream and more noticeably active southern stream, as evidenced by the potent storm system coming out of the Deep South and into the northeast over the next couple days and low pressure centers remaining north in Canada. Other than increased clouds, potentially more than what is currently advertised through the weekend per the NBM, impacts will be next to none. A slight uptick in temperatures is expected with a generalized south to southwest flow across the region going into early next week but any systems to the north will stay to the north. There are some indications Wednesday of a system developing in the lee of the Rockies and spreading east northeast Tuesday-Wednesday, but NBM continues to show very low PoPs (less than 20%) across the region with conflicting ideas on what the P-type may be. Conventional thinking looks for it to be snow, if anything at all, and best timing with this model run confines any precip potential for only Wednesday morning so have only advertised precipitation (slight chance -SN) for that period. Otherwise, temperatures will rise into the low-mid 30s for early next week. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 601 PM CST Thu Dec 31 2020 A swath of MVFR ceilings continues to dominate eastern MN and western WI. There have been some broken and even scattered clouds along the edges of this swath, but the trend has been to remain mostly in place, and there are signs of it already expanding this evening. In fact, some IFR stratus has been expanding over southeastern MN and was heading northward, and this has not been picked up in many of the latest short term models. Thus, any breaks of broken or scattered clouds in eastern MN will be short lived. With decent moisture advection from the south, and a gradient that will become weaker overnight and Friday, it seems rather likely that MVFR/IFR ceilings will be common, even expanding westward to Alexandria and Willmar, and continuing most of Friday. There will also be some visibility reductions to MVFR. KMSP...Some brief breaks are expected this evening, but a broad area of IFR stratus is making its way northward from southeast MN, so have indicated IFR ceilings later this evening and for much of the night. Short term models suggest improvement Friday midday, but only to MVFR, then ceilings going back down Friday evening as the gradient becomes very weak and low level moisture remains trapped under the inversion. /OUTLOOK FOR KMSP/ Sat...Mainly VFR. MVFR possible. Wind SW 5 kts. Sun...VFR. Wind SW 5-10 kts. Mon...VFR. Wind W 10-15 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ SHORT TERM...JPC LONG TERM...JPC AVIATION...TDK
Area Forecast Discussion
National Weather Service Blacksburg VA
953 PM EST Thu Dec 31 2020 .SYNOPSIS... Front will stall to our south tonight while high pressure wedges southwest into our region. Strong low pressure moving from the southern Plains to the Ohio Valley will lift the front north across the area Friday, withe main cold front pushing across Friday night. Another low will track across the southeast by Sunday. && .NEAR TERM /THROUGH FRIDAY/... As of 950 PM EST Thursday... Fog beginning to increase across parts of NC and timing of light rain from the south may be even slower. Back door wedge front has moved into central NC and is still try to push into the foothills of wrn NC. Some gusts of 13-20mph from the NE behind it. Lowering vsbys and ceilings ahead of the boundary in foothills and Piedmont of NC, and this trend should continue mainly NC foothills and into the mountains as well overnight. Will likely issue an SPS for the fog but unsure of how dense or widespread it may get. Certainly appears worse south of the CWA. Made a few minor adjustments to account for milder then expected temps this evening ahead of the back door front and so far temps not falling behind the wind shift boundary quite as quickly as anticipated. Also continued to slow down timing of arrival of light rain from the south by a couple more hours as most hi-res guidance and trends on national radar mosaic seem to agree it will likely be 4 or 5am or even later before beginning in NW NC. Prev discussion as of 630 PM EST Thursday... Cloudy much of tonight with patchy fog and isolated drizzle, then light rain moving north across the area from pre-dawn south to just after dawn north of I-64. Some light freezing rain along ridges Friday morning mainly north of US 460. Made some minor adjustments for mild temperatures early this evening and lack of precip most places with only a few light sprinkle extreme southeast corner from Yanceyville to Charlotte Court House, and also in the far west. As back door front moves down from northeast, already pushing through LYH area, will begin to see ceilings drop, more patchy fog and even some isolated drizzle form. Most 18Z and even more recent high res models such as HRRR are a little slower with arrival of more steady light rain late tonight and into Friday morning so made some adjustments to that timing, but at this point not adjustments to early morning and Friday daytime temperatures, but with precip arriving with a few temps, mainly on ridges, still at or below freezing, this added just a tiny amount of additional ice accum in a few spots. All after 12Z though given timing of precip arrival. Not enough to warrant any changes to advisory area, but a few higher ridges down to Poor Mtn on Roanoke/Floyd border, and some of the ridges in Giles and even wrn Montgomery Co could see a very light glaze during the morning. Can likely cover these with statements since these will be small areas. No other changes at this time. Prev discussion as of 140 PM EST Thursday... A messy New Years Day - Light ice accumulation late tonight into Friday morning north of Roanoke...rain for most of the area, but nothing substantial. Not much on radar early this afternoon, as moisture convergence is limited to the eastern Carolinas. Nonetheless, a shortwave moving across the mid-Atlantic this afternoon/evening should touch of showers across the Wv mountains but overall most of the forecast area will be dry yet damp/drizzly through this evening with spotty rain along/east of the Blue Ridge. Overnight insentropic lift increases and warm advection overtop the frontal boundary will set up rain moving from south to north late. At the same time high pressure wedge extends southwest to the NC mountains. Models having tough time with wedge and how cold air will be in the lowest 2kft. Leaning toward cooler temps but not very confident as warm nose looks pretty strong. Thinking is that any ice will be on elevated objects (tree/powerlines), but only takes a trace of ice on roads to cause headaches, so will hoist a winter wx advisory from Greenbrier to Amherst, south to Craig County for late tonight through Friday morning. Best threat will be in the 7am-11am time frame. Ensemble plumes overall have best threat of ice north of HSP-Lexington, VA Friday afternoon, therefore ending advisory at noon. Patchy icing on elevated objects may occur as far south as Mountain Lake to Floyd/Meadows of Dan, but too isolated for advisory. As far as the rainfall, excessive amounts are not looking as likely as line of convection moves across the southeast states, which could rob inflow of deeper moisture up our way as the front moves across late Friday. Thunder is not out of the question but wedge overall looks strong enough to preclude it in the forecast. Best threat of thunder would be in far SW VA into the NC mountains/foothills around dusk Friday. Lows tonight will be in the 30s, coldest along the eastern slopes of the Alleghanys/Blue Ridge north of Roanoke, with lower 40s across portions of far SW VA. Wedge in place with increasing rain will keep it chilly New Years Day for most of the area, with mid to upper 30s from the Roanoke and Greenbrier Valleys east to southside Virginia/Lynchburg, but warmer south and west with mid 40s to lower 50s expected. Potential for bust on temps based on strength of wedge. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 209 PM EST Thursday... No headlines at this time for Saturday and Sunday. As upper low shears out over the southern Great Lakes Friday evening, the front exits the CWA with showers ending from west to east overnight. Wedge slow to erode Friday night, but models have cold front moving through which clears a wedge out, so temperatures could actually rise for some as the wedge erodes. Lows will be in the mid 30s to lower 40s, coolest across the Alleghanys, warmest in the Clinch and Holston River Valley. A cold front along the coastal plain Saturday morning will move east into the Atlantic ocean Saturday afternoon as the low center lifts northeast into the New England coast. High temperatures Saturday will be mild with readings from the mid 40s in the northwest mountains to the mid 60s in the piedmont. Another closed low tracks across the Red River Valley Saturday into Saturday night, heading into the Ohio River Valley Sunday. This low will tap the Gulf and bring a wave of low pressure into the Carolinas Saturday evening into Sunday. Rain on the northern edge of this low will spread northward into our area. At this time, this low is expected to track south of the area, but may clip Southside with an half inch to an inch of rain. If the track of this low is further to the west, heavy rain and the potential for flooding increases for areas along and east of the Blue Ridge. Low temperatures Saturday night will vary from the mid 30s in the mountains to the mid 40s in the piedmont. Mostly cloudy conditions with scattered showers especially in the west expected Sunday. High temperatures Sunday will range from the lower 40s in the mountains to the mid to upper 50s in the piedmont. A few snow flurries may linger in the northwest mountains of Greenbrier county in southeast West Virginia Sunday night. Otherwise, dry and cold weather is expected. Low temperatures Sunday night into Monday morning will be cold with values from the mid 20s in the mountains to the mid 30s in the piedmont. Moderate confidence in the Short term forecast. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 209 PM EST Thursday... A progressive flow pattern aloft will continue through the middle of next week. The upper trough axis across the mountains Monday morning will pivot east into the Atlantic ocean by Monday evening. High pressure and ridging will build north into the central Appalachians Monday night into Tuesday. High pressure will be centered over the region Tuesday night and slide east Wednesday into Wednesday night. Low pressure and its associated cold front will approach from the west on Thursday. A cold front will move across our area Thursday night into Friday. Temperatures will be near normal during the long term period. Moderate confidence in the Long Term Forecast. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... As of 700 PM EST Thursday... Poor flying conditions will set in tonight as wedge sets up moving down from the northeast, with patchy rain/fog reducing vsbys to under 3-5sm at times later tonight and especially Friday. Look for conditions, mainly ceilings, to drop to IFR at all locations overnight, with light rain moving in by 12Z-14Z, and some patchy drizzle even before that. Some icing appear possible mainly north of a BLF-ROA line Friday morning, with LWB-HSP showing best threat for freezing rain for a few hours between 12-16z. BCB may also see very light icing for a couple of hours after 12Z, but temps will be hovering very close to freezing so may or may not be much of a factor at BCB. More so farther north. Higher ridges north of BCB-ROA will certainly experience some light ice accretions. By 16-18Z rain may increase to moderate for much of Friday afternoon with continued IFR conditions. Winds will be light/variable for most location, with a couple of exceptions. In the Piedmont northeast winds may gust from 10-15mph tonight at times behind back door wedge front, and then Friday afternoon south to southeast winds may begin to pick up at BLF as deep low pressure moves up into the Ohio Valley, increasing ridge top winds especially. Forecast confidence is above average for all elements, except low confidence on how low cigs/vsbys may drop overnight at most sites. Extended Aviation Discussion... MVFR/IFR conditions are expected into Friday night, but with some partial clearing later Friday night in the central part of the forecast area, with best chances for ceilings lifting at ROA and maybe BCB. Brief return to VFR on Saturday for most locations with exception of BLF and maybe LWB, before next system with rain and sub-VFR conditions moves in for Saturday night into Sunday. High pressure should bring a return to VFR by Monday-Tuesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Winter Weather Advisory from 4 AM to noon EST Friday for VAZ018>020-023-024-035. NC...None. WV...Winter Weather Advisory from 4 AM to noon EST Friday for WVZ507-508. && $$ SYNOPSIS...AMS/WP NEAR TERM...SK/WP SHORT TERM...KK/WP LONG TERM...KK AVIATION...AMS/SK/WP