Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/12/20

See below for an aviation forecast discussion for the 00Z TAFs.

&& .SHORT TERM...(This Evening through Wednesday Night) Issued at 339 PM CST Tue Feb 11 2020 Powerful Arctic boundary is on its way early Wednesday with very strong winds along and behind it. The ops models along with hi-res models show that there should be some light snowfall from upper level lift with the upper level low pressure trough axis moving through early Wednesday. The Arctic front will then follow quickly with a big pressure surge (up to 10mb+) along with rapidly falling temperatures. We should see snow squall type/blizzard conditions along the front as the hi-res models have depicted this with the enhanced radar reflectivity output. Snowfall amounts should be around an inch or less. With the existing snow cover combined with the new snowfall and strong north winds gusting to 40 to 50 mph, issued a blizzard warning for the eastern cwa for Wednesday. With less snow to blow around with the strong winds, went with a Winter Weather Advisory from Brown county and west to the Missouri River for Wednesday. The snow will end quickly by noon with the winds continuing through the afternoon. Otherwise, wind chills will fall quickly through the day and evening to 25 below to 45 below zero. Clearing skies Wednesday night with enough winds, temperatures will fall to the teens to around 20 below zero. Therefore, dangerous wind chills will continue into Thursday. Issued a Wind Chill Advisory/Warning for much of the region Wednesday afternoon into Thursday morning. .LONG TERM...(Thursday through Tuesday) Issued at 339 PM CST Tue Feb 11 2020 Arctic high pressure will be in place over the region on Thursday, with high temperatures likely remaining below zero from the James valley and points eastward. Winds will be light on Thursday with the surface high in place, but will still be dealing with possible wind chill headlines through the day Thursday and more so Thursday night into Friday as the return flow sets up again and southerly winds increase. Quick warm up Friday and through the weekend as 925/850 mb temps rebound. 20s, 30s, and even 40s across the southwest counties are in the forecast for this time period. As for precipitation, the start of the period looks quiet, with just a weak shortwave crossing the region Friday night into Saturday morning. This wave may bring some light snow to parts of the CWA, but moisture looks to be lacking. Models show potential for perhaps a stronger storm system early next week. But obviously, way too early to concern ourselves with specifics - will just continue to monitor model trends over the next few days. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) Issued at 644 PM CST Tue Feb 11 2020 VFR conditions are expected through 06Z. Beyond that, in the late night hours and on into Wednesday morning, an arctic front is expected to push through the region bringing light snow and very strong north winds and blowing snow. Sub-VFR vis/cigs are expected at all terminals through, at least, the first half of Wednesday. KABR/KMBG/KATY may experience a short window of IFR conditions with KATY reaching short lived blizzard conditions and KMBG/KABR reaching near blizzard conditions for a brief time Wednesday morning. Falling snow should be over by 18Z Wednesday, and by 00Z Thursday, VFR cigs/visbies should be returning as wind speeds back down and blowing snow diminishes. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory from 4 AM to noon CST Wednesday for SDZ004>006-009-010. Wind Chill Advisory from noon Wednesday to noon CST Thursday for SDZ004>006-009-010-016>018-034-036-037. Wind Chill Warning from noon Wednesday to noon CST Thursday for SDZ007-008-011-019>023. Blizzard Warning from 4 AM to 6 PM CST Wednesday for SDZ007-008- 011. Winter Weather Advisory from 6 AM to 6 PM CST Wednesday for SDZ016-017-034-036-037-051. Blizzard Warning from 9 AM to 6 PM CST Wednesday for SDZ018>023. MN...Wind Chill Warning from noon Wednesday to noon CST Thursday for MNZ039-046. Blizzard Warning from 4 AM to 6 PM CST Wednesday for MNZ039-046. && $$ UPDATE...Dorn SHORT TERM...Mohr LONG TERM...TMT AVIATION...Dorn
Area Forecast Discussion
National Weather Service Bismarck ND
952 PM CST Tue Feb 11 2020 .UPDATE... Issued at 941 PM CST Tue Feb 11 2020 Light snow has spread across a good portion of western and central North Dakota. Surface low pressure was located over far northwest North Dakota, with the Arctic cold front just pushing into the northern tier counties. No significant changes with the overall pattern and still looks like a general 1-3 inches of snow across the forecast area. However, the latest mesoscale models and new NAM have trended a little farther west with the area of heavier snow, tracking from western into south central ND, and have also trended a little lighter with snow amounts over the Turtle Mountains area. Overall though, nothing to warrant any changes to the current hazards. Updated text products will be sent shortly. UPDATE Issued at 537 PM CST Tue Feb 11 2020 The main adjustment to the forecast late this afternoon was to delay the start time of the advisory over the north central until 9 PM this evening. Previous start time was 00 UTC and the Arctic front remains a ways away from the border. Latest RAP shows the front moving into the area around 03-04 UTC. Otherwise for the update we made some minor adjustments to the timing of the arrival of precipitation, slowing it down a little. We also bumped up sky cover. && .SHORT TERM...(This evening through Wednesday) Issued at 313 PM CST Tue Feb 11 2020 The main concern for the short term period is the powerful Arctic cold front sweeping through the region tonight into Wednesday. Hazards include light snow accumulations, blowing snow with near whiteout conditions in open areas, and eventually, very cold wind chills. Currently, a surface arctic cold front extended west-east across central Alberta to central Manitoba. Southwest surface winds to its south allowed a mild February day across the northern tier states, with temperatures this afternoon in the 20s and 30s. At upper levels, a large Hudson Bay Low was well established with northwesterly flow across western Canada and the northwestern and north central US. A significant shortwave in the upper flow was over southern Alberta, with its coincident surface low along the western side of the arctic front. The upper level shortwave and its attendant clipper-type low will dive southeast into Montana/the Dakotas tonight. This arctic cold front associated with the clipper system will plunge south, arriving in northern North Dakota during the evening hours and continuing south into the central Plains states on Wednesday. Light snow will accompany the front, and will begin early this evening in the far north and far west. Latest model guidance continued to result in 1-3 inches of snow for much of the area. Simulated reflectivity, negative EPV, and strong frontogenesis suggest the potential for enhanced snow rates, but think it would be a transient threat and not significantly add to the big picture accumulation forecast. The dendritic growth zone is deep, but only lasting a few hours within the arctic frontal zone. The greatest concern with the Arctic frontal passage is strong winds resulting in impactful blowing and drifting snow. Not much has changed in the model data over the past 24 hours. Very strong pressure rises (over 10 mb/3 hr) and cold air advection accompany the front, but still struggling to find boundary layer winds exceeding 40 kts. The timing of the frontal passage on the 12z models is similar to that of the 00z runs from last night. This will mean that the arctic front moves through the state during the nighttime hours before any diurnal effects on mixing can be realized. We are expecting peak wind gusts around 45 mph, which will likely not be strong enough to break the crust of the existing snowpack. However, the forecast snow amounts create a greater potential for blowing snow significantly reducing visibility, and for at least a few hours in duration. For this reason, we will continue the Winter Weather Advisory for blowing snow, generally along and east of Highway 83. The winter weather advisory lines up with where the strongest winds are expected. Near blizzard conditions are possible in rural areas across the James River Valley. Given the current forecast, confidence is not high enough in blizzard criteria being reached over a geographically significant area to warrant a warning or even a short-fused watch. For areas of western North Dakota, we issued a Special Weather Statement earlier today for the rest of western/central North Dakota. This Special Weather Statement will be re-issued for tonight and Wednesday...addressing the sub-advisory snow/blowing and drifting snow, etc. Travel impacts are possible even though advisory criteria may not be met. Temperatures are expected to fall through the day Wednesday, with daily maximums occurring very early Wednesday morning ahead of the frontal passage. Winds will slowly diminish Wednesday afternoon. Advisory criteria wind chills appear likely north and east of the Missouri River Wednesday morning through Thursday morning. As the winter weather advisories end on Wednesday, they may need to be replaced/extended because of wind chills. .LONG TERM...(Wednesday night through Tuesday) Issued at 313 PM CST Tue Feb 11 2020 Arctic high pressure will reside over the Northern Plains Wednesday night into Thursday. Widespread low temperatures in the 10 to 20 below zero range are expected. Wind chills will remain a concern north and east of the Missouri River Wednesday through Thursday morning. Daytime highs for Thursday will be mainly in the single digits above zero with a chance at getting into the teens in far western North Dakota. Mild Pacific air under an upper level ridge will quickly push into the region Thursday night into Friday, bringing temperatures back to near to perhaps even above average, with highs above freezing across the western third of the state on Friday. A shortwave trough will move across the area late Friday into Saturday. Timing differences and small precip amounts in the models resulted in no chances or very slight chances of light precip Friday/Saturday. The synoptic pattern continues to look progressive into early next week, with near to above normal temperatures remaining favored. The deterministic GFS/ECMWF and several GEFS members now show a chance of very light snow accumulations around the late Sunday/Monday timeframe. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 941 PM CST Tue Feb 11 2020 VFR conditions to begin the 00Z TAF period. An arctic cold front and a clipper system will combine to produce a period snow (generally 1-3 inches) along with strong winds, producing areas of blowing and drifting snow. Snow will move into the west this evening. The Arctic cold front will drop north to south late this evening and overnight. Expect a period of MVFR to occasionally IFR ceilings and visibilities in snow and blowing and drifting snow at all TAF sites. The worst conditions will be late tonight through mid morning on Wednesday. Expect VFR conditions to return to southern areas by early afternoon Wednesday with North to northwest winds diminishing through the afternoon. && .BIS WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until noon CST Wednesday for NDZ004-005- 012-013-022-023. Winter Weather Advisory until 6 PM CST Wednesday for NDZ025- 035>037-046>048-050-051. && $$ UPDATE...TWH SHORT TERM...JV LONG TERM...JV AVIATION...TWH
Area Forecast Discussion
National Weather Service Caribou ME
1047 PM EST Tue Feb 11 2020 .SYNOPSIS... Low pressure will exit well south of Nova Scotia this evening, followed by high pressure building over the area through Wednesday. Another Low pressure approaches from the southwest Wednesday night, then tracks over the Gulf of Maine Thursday. An arctic front pushes through later on Thursday followed by Canadian high pressure building in through Saturday. The high will then slowly move east of the area Saturday night and Sunday. && .NEAR TERM /THROUGH WEDNESDAY/... 1035 PM Update...Still some reports of patchy freezing drizzle, but there things are improving. RAP and CAR 00Z sounding supported potential for some freezing fog overnight. Radar showed enhanced returns pulling across eastern Washington County attm as low pres passes s of Nova Scotia. Temps have cooled down AOB 32F as far s as Bangor w/light rain changing to snow. Temps were still in the mid 30s along the coast w/light rain. Temps will continue to cool down and light rain along the coast could change to a brief period of snow before ending. A weak cold front or trof across western Maine this evening is expected to slide across the region overnight into Wednesday. Flurries/isolated snow showers are expected along the northern and western border. No accumulation is expected. Adjustments were made to the temps. Previous Discussion... Sfc high pres well SW of the FA will ridge into the Rgn on Wed, providing partly to msly sunny skies and mild temps. However, a stronger sfc pres grad and winds alf in the 925 to 850 mb layer will result in much breezier conditions by midday contg into the aftn hrs. By late in the aftn, clds will begin to increase ovr the far N in advc of a strong arctic cold front movg E of QB. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... Main concern is a system for late Wednesday night into Thursday with advisory level snow possible mainly southern half of the area. This system is relatively weak with a shortwave upper trough moving in from the Great Lakes and a weak surface low forming in the northern Gulf of Maine. With this system not having a whole lot of amplitude, it won`t be able to tap into much warm air ahead from the south, and precip type looks like mostly snow except perhaps rain mixing in along the coast. One interesting aspect of this system is an Arctic front moving through from north to south on the tail end of the system. This could provide some local enhancement of the snow before it tapers off, plus allow for plummeting temperatures Thursday afternoon and night after the snow tapers off. Winds don`t look terribly strong behind the Arctic front, but it could possibly be enough for a bit of blowing snow. Something to keep an eye on. Do not expect any freezing rain or sleet with this system. Models are in pretty good agreement. Much colder for Friday and breezy with highs around 0 in the north and 10 to 15 Downeast. May need a wind chill advisory Northern Maine late Thursday night into early Friday. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Friday night has the potential to be bitterly cold as Arctic high pressure moves in late in the night. Undercut most temperature guidance and went for lows below zero virtually everywhere, and as cold as about -30 in some of the usual coldest spots in the North Woods. Still cold on Saturday but not quite as bad since the high moves east with some moderation of the airmass in the afternoon. Weak system for Sunday and milder with a chance of snow showers, perhaps followed by another shot of Arctic air Sunday night into Monday, though models disagree on how far south the Arctic front makes it. For example, 12z ECMWF has it stalling over the area. Next potential system is Tuesday/Tuesday night. Models actually are in pretty good agreement on there being a system around this time...above average agreement for being so far out. Went with likely PoPs. This system has the potential to be fairly strong and appears likely to tap into deep moisture from the south. Way too early to determine precip type, but this is the type of system where all precip types could be on the table. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... NEAR TERM: Tonight...IFR to low MVFR clgs with ocnl MVFR vsbys in any lgt sn or sn shwrs Nrn TAF sites this eve, then MVFR clgs ovrngt. IFR to low IFR clgs Downeast with MVFR/IFR vsbys in lgt rn and sn, becmg MVFR clgs late tngt. Lgt winds all sites. Wed...VFR all sites. Mdt NW winds. SHORT TERM: Wednesday night...VFR early, perhaps becoming MVFR late with snow developing. Fairly light winds. Thursday...MVFR and IFR with widespread snow, possibly mixed with rain from KBGR south. Fairly light winds until late Thursday when an Arctic front moves through and brings a decent N breeze. Thursday night and Friday...Mostly VFR except possible MVFR ceilings north. North breeze. Friday night and Saturday...VFR with light winds. Saturday night and Sunday...Mostly VFR Downeast, with MVFR possible north. SW breeze. && .MARINE... NEAR TERM: No chgs to the SCA issued for very erly morn til erly aftn Wed. Until then winds and seas below SCA thresholds. Winds and seas should again subside below SCA thresholds mid to late aftn Wed. Kept close to blended model wv guidance. SHORT TERM: Conditions improving below small craft by Thursday morning. Conditions back to small craft Thursday night and Friday with an offshore wind and seas over 5 feet. Good chance of moderate freezing spray in this period as well. Back below small craft Saturday, then another shot at small craft seas and winds Sunday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory from 3 AM to 1 PM EST Wednesday for Anz050>052. && $$ Near Term...Hewitt
Area Forecast Discussion
National Weather Service Nashville TN
828 PM CST Tue Feb 11 2020 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Some light showers are moving through the area with MRMS QPE showing less than one tenth of an inch in the last 3 hours along the southern tier of counties. Elsewhere, any rainfall has been just a hundredth or two. HRRR shows more light showers overnight with no significant rain amounts. With the blanket of cloud cover, temperatures will not move much the rest of the night. The current forecast is on track. Only made minor adjustments to hourly temperatures and PoPs. && .AVIATION... 00Z TAF DISCUSSION. A couple of spots are still MVFR but it looks like KBNA/KMQY/KCKV should improve to VFR for several hours overnight as the warm front takes its time moving northward. Conditions should start to deteriorate again by 10-11Z with IFR and more showers settling in by mid-morning Wednesday. TS will be possible near the end of this TAF cycle, but for better timing, will wait until 06Z issuance to prevail. Winds will remain light tonight and most of tomorrow, but swing from the north to the east by tomorrow afternoon. && .OHX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch from Wednesday evening through Thursday morning for Cumberland-Fentress-Grundy-Overton-Pickett-Putnam- Van Buren-Warren-White. Flash Flood Watch from Wednesday afternoon through late Wednesday night for Bedford-Cannon-Cheatham-Clay-Coffee-Davidson- De Kalb-Giles-Hickman-Jackson-Lawrence-Lewis-Macon-Marshall- Maury-Perry-Robertson-Rutherford-Smith-Sumner-Trousdale-Wayne- Williamson-Wilson. Flash Flood Watch from Wednesday afternoon through late Wednesday night for Dickson-Houston-Humphreys-Montgomery-Stewart. && $$ DISCUSSION......Reagan AVIATION........Unger
Area Forecast Discussion
National Weather Service Pocatello ID
105 PM MST Tue Feb 11 2020 .SHORT TERM...Tonight through Thursday. Northwest flow will continue around the ridge currently centered near the coast. There is a chance of light snow that will remain through this period across portions of the central mountains, Centennials/Island Park, and south through the eastern and southeast highlands. Snow amounts will be light, although we could see on occasion like Monday where a band or burst of snow could create slick roads. We will also be watching for expanding stratus and possible fog the next 2 mornings as inversion strengthen. A couple of other areas we COULD see light snow will be 1) tomorrow morning across the South Hills/Albion Mountains as the next storm drops down the Divide, and 2) under any stratus deck. This would be courtesy of the "seeder feeder" process. Under the inversion, expect much colder temperatures. Lows will likely be in teens to single digits below zero at night, and 10s-20s during the day. Where we can get some mixing, especially across the Lower Snake Plain, Magic Valley and lower elevations south of I-84 & 86...highs will jump above freezing and some cases above 40 degrees! Keyes .LONG TERM...Thursday Night through next Tuesday. The next storm moves in Thursday night and Friday. The normal runs of the GFS and ECMWF are slowing this down by a good 6-12 hours, while the Blend of Models is still on the faster side. This storm won`t dump a lot of precipitation, maybe 1-3" in favored upslope areas like the Sawtooths and eastern highlands. Other places will see little snow and/or a mix of rain and snow depending on the time of day. Winds kick up so there could easily be some blowing and drifting up in the high country. This trend of normal model runs slower vs the Blend continues with the next storm over the weekend. Whenever the storm does arrive, this one should a lot more moisture and warm up to work with. Rain, snow and some decent wind will occur, with a mix likely from Pocatello to Burley and points south...and snow likely everywhere else. With this storm have more moisture and "wet" snow, blowing and drifting conditions might be a little less of an issue...but certainly not a "zero issue" either. Another storm will quickly follow on its heels and be here on Tuesday. Keyes && .AVIATION...A weak shortwave disturbance diving SE across MT tonight will deal a very minor, glancing blow to our region, with increased clouds and some snow showers possible in some of our highlands/mntns (especially as you head toward the MT/WY borders). The coarser NAM12 continues to bring this activity through KDIJ and builds showers as far SE as KIDA, but none of the higher resolution models are as aggressive at spilling snow into the Snake Plain, so we have removed VCSH from KIDA this afternoon and probably can drop it from the TAF for this evening too unless things change. SN will remain possible at KDIJ tonight and Wed AM, with snowfall rates being the main driver for vis reductions, currently forecast to MVFR but IFR is also possible and can occur easily as soon as steady snow takes hold. Otherwise, greatest forecast uncertainty revolves around potential for some low stratus/additional fog tonight, especially at KIDA. A better signature for low- to mid-level cloud decks on NAM time-heights may keep fog at bay by reducing near-surface radiational cooling, and we don`t see strong indications of fog in the MAV/MET guidance or HRRR products, so for now we maintained VFR cigs/vsbys in the TAF. However, surprise fog occurred last night despite virtually no support from model guidance, so we will need to monitor this potential hour-by-hour this evening...there may not be much lead time if it occurs. Also nudged diurnal winds down by several knots this afternoon at nearly all sites to better match observation trends and 12z MOS guidance. - KSmith && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$