Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/12/24


Area Forecast Discussion
National Weather Service Billings MT
639 PM MST Wed Dec 11 2024 .KEY MESSAGES... - Wintry conditions in the south and east tonight. Expect light snow accumulations and slick roads including portions of I-90, I-94, and US-212. - Breezy conditions in the western foothills tonight. - Cold air in eastern MT through Thursday. Overnight lows near zero and highs in the 20s near Baker. - Periods of strong winds along western foothills Friday night into Saturday. - Increased chance for precipitation Sunday into Monday. && .UPDATE... Light snow is dropping thru eastern MT this evening and just recently it has began snowing at Miles City. A weak shortwave will clip eastern MT tonight, with a 100kt H3 jet analyzed over western ND at 0130z. Moisture is shallow but extends into the dendritic layer, and model soundings show a shallow layer of steep mid level lapse rates around 750-700mb. All told, this is enough for occasional light snow. Have adjusted pops up to account for this confidence as well as latest radar trends. Accums will be an inch or less east of Rosebud County. A bit west of this area, a surface front is nearly stationary just east of Billings, and temps are much milder west of this boundary. The front should backdoor westward thru Billings later tonight as the wave passes, and this will need to be monitored. In the meantime, winds along the western foothills remain gusty with Livingston still flirting with 50 mph gusts. Could be localized fog (<20% chance) over central and east parts, depending somewhat on how the surface boundary evolves, and cloud cover, of course. Low temps tonight should range from the lower 30s along the western foothills to single digits in the far east. JKL && .DISCUSSION... Tonight through Thursday night... Light snow continues to move SE into the E part of the forecast area this afternoon. KBHK began reporting flurries at 19Z. Radar bands did not look as intense as they did earlier. RAP had a band of negative EPV sliding SE into the area overnight, but best moisture was during the evening. Thus had highest PoPs around 50% mainly E of Rosebud County, with lesser PoPs bordering this area on the western side. Also added low PoPs over and near the SW mountains per radar echoes and the HRRR. NAM showed QPF chances decreasing and moving E through the night, so followed suit with PoPs. Regarding winds in the W...KLVM was gusting into the 40s to lower 50s mph and K6S0 had gusts into the 30s. Ob for Harlowton was also gusting into the 30s. These winds were due to mixing and a good pressure gradient. 700 mb winds decrease tonight, and there will be a decent pressure gradient that will not be as strong as last night. Modified NBM winds for KLVM/Nye and K6S0 to gust into the 30s and 40s mph tonight. Upper ridging with dry weather will build into the area for Thursday and Thu. night. Upper trough moves into E ID and UT late Thu. night. Forecast looks dry but gusty winds return to KLVM/Nye/K6S0 as pressure gradient increases late Thu. night. Lows tonight will range from the low single digits in Fallon County to the 20s central and W. Highs will be above normal, in the 40s central and W on Thursday, with 20s and 30s in the E. It will be a tad warmer Thu. night than tonight. Arthur Friday through Tuesday... Into Friday, a shortwave will pass to the south of MT allowing for some light snow showers in the southwest mountains. The remainder of the region will be in a warm and dry ridging pattern. With this, westerly flow at 700 mb and a surface pressure gradient over the western foothills will allow for gusty gap winds for the Livingston, Nye and Big Timer areas. Best timeframe for this will be Friday night through Saturday. Precipitation chances increase Saturday night as another trough approaches. Mixed precipitation is looking likely at this time, but accumulations are low (10-30%) for at least a tenth an inch of QPF across lower elevations. Ensembles then agree on ridging coming in Monday with a weak signal for some lowering heights Tuesday. High temperatures will be in the 30s/40s Friday, 40s for the weekend, cooling to the 20s/30s for Monday and Tuesday. TS && .AVIATION... Showers and stratus will create occasional MVFR conditions at KMLS through this evening with about a 60% chance of at least MVFR with low stratus (near surface) moving in after midnight. Occasional snow showers may also deteriorate conditions at KBIL and KLVM. Gusty SW winds up to 45kts will gradually taper off this evening into overnight. TS/Archer && .PRELIMINARY POINT TEMP/POPS... Thu Fri Sat Sun Mon Tue Wed ----------------------------------------------------------- BIL 024/039 025/048 027/049 034/047 024/038 022/037 021/039 10/B 00/B 00/B 13/W 31/B 01/B 10/B LVM 028/046 028/045 030/049 032/044 023/039 022/039 019/044 10/N 00/B 00/N 25/W 31/B 12/J 10/B HDN 021/041 021/047 021/048 028/047 021/038 019/036 016/038 10/B 00/B 00/B 14/W 41/B 01/B 11/B MLS 008/027 015/033 015/039 023/041 017/031 013/028 011/031 71/B 00/B 00/U 02/W 31/B 00/B 10/B 4BQ 017/034 020/039 020/042 026/042 020/035 016/033 015/034 50/B 00/B 00/U 02/W 31/U 00/B 10/B BHK 003/023 009/032 014/041 021/039 014/028 007/025 008/029 51/M 00/B 00/U 01/B 31/B 00/B 10/B SHR 020/045 022/047 020/050 026/046 020/039 016/038 015/041 10/B 00/B 00/U 03/W 42/J 01/B 11/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings
Area Forecast Discussion
National Weather Service Caribou ME
1009 PM EST Wed Dec 11 2024 .SYNOPSIS... Intensifying low pressure will track west of the region tonight, then lift north across Eastern Canada Thursday. High pressure will build in for Friday through the weekend. Low pressure will approach from the west on Monday. && .NEAR TERM /THROUGH THURSDAY/... 10 PM Update (MS): The latest surface analysis shows a deepening 992mb low over the Saint Lawrence Valley, with a surface trough extending south through NH into southern New England. The 850mb LLJ continues to intensify and is currently analyzed over 80kt along a line extending south from just west of Bangor to Cape Cod. The jet will continue to intensify and pivot eastward, leading to widespread damaging winds, particularly across Downeast and coastal areas where gusts exceeding 70 mph are possible. The low level jet has brought in warmer air than previously anticipated, and Bangor has tied their record high temperature of 59 degrees. Rapid snowmelt north of Bangor, combined with heavy rain, areas of dense fog, and strong winds, will make travel difficult overnight. Poor drainage flooding of roads is expected. No significant changes were needed with this update, aside from raising temperatures to match observations. Previous Discussion: The large low pressure system will continue to track the center across the west this evening and bring the cold front through the region tonight. Winds: The low level jet will push in from the south, over the waters, and into the Downeast coast which will increase S flow this evening. Before midnight, winds will increase drastically with the cold front approaching the region. The main areas of concern will the the coastal and interior Downeast and the Bangor Region. This is due to the S flow and the history of S progressing through the Penobscot bay and river causing impacts in Bangor. Around midnight, the low is expected to intensify, causing the front to pick up speed and increase winds across the upsloping of the Central Highlands and along the eastern border. As the front starts to exit after midnight, high res models indicate that the pressure gradients on the backside of the front will tighten again, causing a brief increase of winds in the North Woods. Though short lived and weaker than previous runs, decided to include this wind increase for impact purposes. In addition, the HRRR has pointed to the possibility of a more stable boundary layer due to possible snow pack surviving the rain and warm temps. If the snow pack is a constant layer, there is a possibility that winds will have a hard time mixing to the surface with the latent heating. However, if the snow pack is patchy or gone, then winds will remain at forecasted values. Rain: As the cold front moves across the region tonight, bands of high rain rates will move across the region. The main area of concern will be the upsloping areas of the Central Highlands and the downsloping in the North Woods. Though these higher rain bands will move across certain areas, instability along the front will cause some convection to develop, thus localized heavier rain is possible. In addition to the rainfall, the snowpack will be melting, causing extra runoff on frozen ground. Though rivers are not as big of a concern, small streams, creeks, and urban street flooding is a concern. By Thursday, the low will exit over the Maritimes with wrap around moisture bringing snow showers across the region throughout the day. Cold air behind the front will gradually drop temps throughout the day with the majority of the region remaining in the upper 30s. Isolated snow showers are possible across far northern Maine by evening. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... High pressure will begin to build into the area through the end of the week and into the weekend. This will lead to drier weather and clearing skies. Temperatures will be mild, with highs in the 20s over most of the forecast area, and near 30 closer to the coast. Lows Thursday night may only fall into the upper teens to lower 20s, but by Friday night could fall into the lower teens across the forecast area. Light winds may linger through the short term, limiting surface decoupling chances and preventing temperatures from rapidly plummeting much further. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... High pressure will linger through this weekend. With mostly clear skies and light winds, full surface decoupling may be possible such that temperatures could fall into the lower single digits above zero Saturday night, particularly across the north. Otherwise, temperatures may remain slightly below average through the rest of the weekend. A low pressure system will approach from the west through early next week. There remains great uncertainty for when this system will enter the area, with the GFS and CMC bringing a small shortwave over the area Monday night into Tuesday and bringing the first round of light precipitation into the region. Meanwhile, the Euro hangs on to high pressure over the area. The main low may not move into the area until Tuesday night into Wednesday. Ensemble plots agree on a slower progression of this trough, though there remains the slight chance of showers ahead of the main low. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... NEAR TERM: IFR/LIFR for this evening and into tonight due to low cigs, fog, and rain. Rain will continue to be heavy at times for all terminals. Significant and unusually strong LLWS tonight for all terminals. S winds 20-25 kts with gusts around 50 kts. By Thursday, improving to VFR during the morning. SW winds 10-15 kts with gusts up to 20 kts. SHORT TERM: Thurs night - Fri night: VFR across all terminals. SW winds 5 to 10 kts, gusting 20 to 25 kts Thurs night, gradually diminishing through Fri and Fri night. Sat - Mon: VFR across all terminals. W winds around 5 kts becoming light and variable Sat night, then turning S on Sun at 5 to 10 kts. && .MARINE... NEAR TERM: The Storm Warning is in effect through tonight with seas 13-20 ft. Winds should decrease by Thursday morning to gale force throughout the day with seas 11-16 ft decreasing to 7-12 ft by the afternoon. SHORT TERM: Winds will quickly decrease back towards small craft advisory levels through Thursday night, and may continue to decrease below 25 kts by late Friday night. Seas with a long period southerly swell will gradually decrease through the end of the week, reaching 3 to 5 ft by Friday night. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Flood Watch through Thursday morning for MEZ001>006-010-011- 015>017-029>032. Dense Fog Advisory until 5 AM EST Thursday for MEZ001-002-004- 005-010-031. Wind Advisory until 6 AM EST Thursday for MEZ001-003-004. High Wind Warning until 6 AM EST Thursday for MEZ002-005-006- 010-011-015>017-029>032. MARINE...Storm Warning until 7 AM EST Thursday for ANZ050>052. && $$ Near Term...LaFlash/MStrauser Short Term...AStrauser Long Term...AStrauser Aviation...LaFlash/MStrauser/AStrauser Marine...LaFlash/AStrauser
Area Forecast Discussion
National Weather Service State College PA
926 PM EST Wed Dec 11 2024 .SYNOPSIS... *Turning windy and much colder tonight with the potential for isolated snow squalls and locally hazardous travel conditions especially in the higher elevations along the Allegheny Mtns *Brief arctic cold snap lasts into the weekend followed by mixed precipitation on Sunday *Milder pattern expected to start next week with rain most likely on Tuesday && .NEAR TERM /THROUGH THURSDAY/... Steady post-frontal precipitation associated with fgen forcing beneath the right entrance of a potent jet streak is exiting the eastern edge of the forecast area this evening. In its wake, scattered light snow showers/flurries are falling across the Alleghenies associated with the passage of the upper trough. Little if any accumulation is expected the remainder of the evening due to low inversion heights. The focus for late tonight remains on the possibility of snow squalls along a reinforcing cold front. CAMs and fcst SNSQ parameter are broadly supportive of the risk between 08Z-12Z, focused mainly over the N Mtns. A tight pressure gradient and subsidence associated with the arriving dry slot will produce strong winds this evening. Gusts between 30-45 mph could result in areas of blowing snow in those spots where an inch or so accumulated over the Allegheny Plateau. Temperatures are not expected to drop too quickly this evening. However, strong cold advection behind the reinforcing front should result in quickly falling readings very late tonight. temps at daybreak are likely to range from the upper teens across the Allegheny Plateau, to the low 30s in the Lower Susq Valley. Subsidence forced by a tropospheric-deep maximum of cold air advection should result in wind gusts ramping back up behind the front early Thu morning, resulting in wind chills 0 to +10F over the northwest half of the area. Bundle up at the bus stop! The risk of snow showers/squalls should exit the northeast part of the forecast area around 12Z, as the associated cold front pushes through. A west-southwest flow behind the front should keep lake effect snow north of the PA/NY border Thursday. The core of coldest air behind the front is progged to pass over PA Thursday with 850mb temp anomalies around 20F below climo. Mixing down 850mb temps yields expected highs ranging from the low 20s over the Alleghenies, to the mid 30s across the Lower Susq Valley. Steep low level lapse rates will enhance boundary layer mixing, resulting in occasional gusts between 30-35kts. Although model RH profiles support mostly sunny skies, the wind will likely create wind chills in the single digits/teens throughout the day across most of Central PA. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... Generally fair and cold conditions with diminishing wind is expected Thursday night, as the pressure gradient relaxes over PA. However, a weak and moisture starved clipper approaching from the Ohio Valley is likely to spread increasing clouds over Southern PA with a bit of very light snow/flurries not out of the question over the Laurel Highlands. The cloud cover should hold temps up across Southern PA. Elsewhere, boundary layer flow veering to the west may spread a few lake effect snow showers into the NW Mtns late Thu night into Friday morning. However, low inversion heights suggest any accumulation will be light and confined to the snowbelt of Northwest Warren County. Fair and cold weather is expected Friday with fading lake effect snow showers/flurries across parts of Warren/Mckean counties, as surface high pressure over the Lower Grt Lks builds into PA. Sfc high strengthens to almost 1050mb as it migrates over PA Friday night. This is a strong signal to undercut min temps Friday night especially over the eastern and northeastern portions of the CWA where skies are most likely to be mainly clear to partly cloudy. We anticipate the first single digit low temps of the season in the usual cold spots across the north central mtns into the Endless Mtns/Poconos. Max temps trend +5-10F warmer across the northern half of the area on Saturday as mean llvl flow veers to the southeast, but it will remain seasonably chilly to start the weekend. Strong WAA likely limits window for early day sun with increasing clouds by Saturday afternoon/evening. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Upper level ridging over PA at the start of the long term period should ensure dry weather through Saturday. Beyond that, medium range guidance supports a period of cloudy, wet and increasingly mild weather Sunday into early next week associated with the passage of a pair of shortwaves and a stubborn surface high over the Canadian Maritimes. Current guidance indicates the best chance of precipitation will occur with the passage of a weakening shortwave Sunday/Sunday night. A blocking high east of New England may hold in just enough cold air for a wintry mix across parts of Central PA Sunday. Ensemble mean qpf Sunday/Sunday night is currently around 0.25 to 0.33 inches. A break in the precip appears likely Monday, then a second round of rain is possible in the Monday night-Tuesday night timeframe associated with an approaching upper trough and surface occluded/cold front. Warmup next early next week: max/min temperatures trend +5 to +15 degrees above the historical average for mid December in advance of an approaching frontal system from the Great Lakes and Ohio Valley. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... Widespread MVFR conditions are being observed at all central Pennsylvania airfields as of 23Z with some deterioration possible at BFD/JST overnight with lake effect and upslope snow showers at the airfields. There remains some model spread with respect to onset of IFR ceilings with GLAMP slightly less bullish on IFR conditions compared to recent RAP guidance. Given current trends along with how model guidance is handling current conditions, have opted to put both airfields down to IFR in the 00-02Z (JST) and 06-08Z (BFD) timeframe where slightly better signals exist for these conditions to occur based on RAP model soundings and HREF probabilities in sub-MVFR conditions. The main alternative scenario will be at BFD where there remains multiple rounds of lake effect snow showers that could bring the airfield down to IFR thresholds multiple times from 00-08Z; however, generally lower (~20-30%) confidence on this occurring so have went with the most plausible solution at this time. Elsewhere, MVFR conditions seem like the most likely scenario at AOO/UNV/IPT/MDT/LNS through ~10Z with moderate (50-60%) confidence. RAP model soundings do outline drier air working into the lower levels slightly quicker than previous runs so have outlined the majority of the airfields lifting out between 08-10Z west-to-east. There remains some uncertainty on eastward extend of snow showers at AOO, with the bulk of model guidance outlining at least some potential for lower ceilings as snow showers make close approaches to the airfield between 06-08Z so have included a PROB30 due to lower confidence in a snow shower *potentially* making it into the airfield. After 10Z Thursday, generally expect all airfields to gradually lift towards VFR thresholds with BFD/JST very likely (~80-90% confidence) being the last two airfields to lift above MVFR thresholds in the 16-18Z timeframe. Breezy to gusty winds will continue throughout the entire TAF period, with gusts between 30-35kts across the higher elevations (BFD/JST/AOO) and gusting closer to 20-30kts elsewhere. Outlook... Fri...MVFR/VFR cigs with gradual clearing. Sat...VFR. LLWS possible in the west Saturday night. Sun-Mon...MVFR/IFR with rain and possible mixed precip. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Fitzgerald/Steinbugl SHORT TERM...Fitzgerald/Steinbugl LONG TERM...Fitzgerald/Gartner AVIATION...NPB
Area Forecast Discussion
National Weather Service Goodland KS
343 PM MST Wed Dec 11 2024 .KEY MESSAGES... - 20% chance of freezing fog along the leading edge of a westward moving cold front tonight. 5% chance of dense freezing fog. - 10-15% chance of a light wintry mix across Norton and Graham counties late Friday afternoon through the evening. - Mild and dry conditions return for the weekend. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 124 PM MST Wed Dec 11 2024 A fairly tranquil day across the region as northwest flow continues across the area along with dry mid and upper levels which is leading to clear skies along with warmer temperatures as highs are forecast to reach at least the low 50s by this afternoon. Enjoy the day as a backdoor cold front works east to west into the area overnight which will shift winds that are mainly westerly through the day to more easterly. Some guidance is hinting that there may be a period of fog/stratus along the front starting around 2-3am MT that would push to the west towards the Highway 25 corridor by 8-9am MT before dissipating. The ENE nature of the winds due to the cold front would support it climatologically. Overall confidence is highest in low stratus developing, however over the past couple hours it seems as if guidance is starting to get on board with the more aggressive HRRR on the fog potential. There are still some doubts about fog due to dew point depressions not being low enough for fog but the increasing signal is giving me enough confidence to introduce patchy fog into the forecast for Thursday morning. Dense fog may also be on the table as well as the HRRR has been consistently showing that potential for the past 6+ runs, it is also safe to assume that any fog would be freezing fog which may lead to some ice accumulation on elevated surfaces if it can persist long enough. Again the lack of dewpoint depressions makes me think dense fog isn`t as likely with my current confidence around 5% for that. Thursday, continued cold air advection will be in place throughout the day thanks in part to the continued easterly winds. Have trended a little colder due to current temperatures across NC Kansas and SC Nebraska where temperatures remain in the upper 20s to low 30s as some of that air mass will spill into the region so have nudged temperatures down a bit for that along with increasing clouds through the day. Cold air advection will continue to spill into the area Thursday night and into Friday morning. Cloud cover looks to limit how cold it will get as a very dry air mass with dew points in the single digits moves into eastern portions of the area; low temperatures are currently forecasted in the teens area wide. Friday, continues to look chilly for most as highs may struggle to get out of the mid 30s for the majority of the area. Some guidance continues to go with an even colder route with sub freezing highs completely in the realm of possibility especially if cloud cover is slow moving out. The focus will be on a quickly developing low pressure system right over the forecast area as this will lead to some moisture advection into eastern portions of the area (Graham/Norton counties). Mid level lift will support the potential for some light rain/snow to occur across each county from the late afternoon and through the evening. Cross section analysis does show dry mid level air and more saturated at the surface which overall does lessen my concern for precipitation. There may be a brief window for some freezing drizzle to occur from around 5pm CT through 11pm CT however. Some ingredients that support the freezing drizzle is that there is a saturated layer from the surface to around 1km AGL along with the minimum temperature in the saturated layer being warmer than 8C. Furthermore there is the low RH above the saturated layer due to the drier air aloft along with ESE winds being present. The part that doesn`t completely support it is omega (source of lift) being less than negative 5 micro bar (preferred amount of lift) as NAM cross sections only show negative 3 micro bar; there does appear however to be a weak surfer frontogenesis boundary in the area that may help increase the lift in the saturated layer some. The NAM also does support isentropic lift in the 285K layer as well which may help overcome the lack of omega in place. NAM forecast sounding also show a warm nose from about 2000-3000 feet AGL as well. With all of this in mind there does appear to be enough ingredient to support at least a slight chance of freezing drizzle during that time frame. All of this may be for not however as the overall position of the low will dictate precipitation chances as well; a further east track (more likely) would decrease chances but a further south or west track (less likely) would increase precipitation chances. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Issued at 124 PM MST Wed Dec 11 2024 Friday`s low pressure system will move off to the east and will begin an overall pattern shift to a more progressive pattern. Overall within the pattern there will be the potential for more systems along with ridging between the systems. The ridging looks to be in place for the weekend across the Tri-State area with high temperatures in the 50s and mainly clear skies especially Saturday. Clouds will then begin to increase throughout the day Sunday as the next system moves towards the area. The timing of the systems as we remain in this progressive pattern will be key to any precipitation chances as moisture will need a chance to return after the previous system shunts it out. As of right now the early week system looks to remain dry. Another system then may impact the area mid to late week which some ensembles suggest looks to be more compact which would give the area a relatively better potential for precipitation. At this time I`m giving that a 10-15% chance as the majority of ensemble members keeps it as an open wave. As for temperatures, a combination of mild days and cooler days are forecasted due to the progressive nature of the pattern. As mentioned above temperatures currently forecast in the 50s for this weekend will then lead to a cool down to start the week. There are also some suggestions that colder air may infiltrate the area with the mid week system but the overall timing of this is still in question but then looks to return to mild conditions towards the latter portion of next week. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 342 PM MST Wed Dec 11 2024 VFR conditions are currently forecasted for this TAF period for each terminal (KGLD/KMCK). Will be monitoring for the potential for fog/low stratus to impact mainly KMCK as a frontal boundary pushes in from the east. Guidance continues to show potential for either/or to occur by 06z. Will adjust the next forecast issuance as needed, but for now will only have a transition from SCT040 to SCT025 from 05z onward for KMCK. WindS for KGLD, southwest around 10kts through 06z Thursday, then light/variable. By 15z, east/southeast around 10kts. Winds for KMCK, light/variable through 05z Thursday, then east- southeast 5-10kts. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...None. CO...None. NE...None. && $$ SHORT TERM...Trigg LONG TERM...Trigg AVIATION...JN
Area Forecast Discussion
National Weather Service Indianapolis IN
930 PM EST Wed Dec 11 2024 .KEY MESSAGES... - Mostly Clear and Colder Overnight - Sub-zero wind chills tonight into Thursday morning - Light snow possible Thursday afternoon and evening along and north of I-70 - Rain chances and near normal temperatures return for this weekend && .FORECAST UPDATE... Issued at 929 PM EST Wed Dec 11 2024 Surface analysis this evening shows deep low pressure in place over Quebec. Arctic high pressure was found over the northern plains stretching south toward the lower Mississippi Valley. A sharp, cyclonic pressure gradient was found across Central Indiana. Radar shows the wave associated with the arrival of the arctic air and afternoon snow showers has exited east of Central Indiana. GOES16 shows limited cloud cover across Central Indiana in the wake of the wave. Mostly clear skies were found upstream across Illinois, and had already worked into the Wabash Valley. Much colder air, in the 20s, has arrived across Central Indiana. Upstream, dew points in the single digits were found amid arriving subsidence. Overnight, the cold air advection is expected to continue as high pressure builds across Central Indiana from the west. Forecast soundings and time heights both show a dry column through the night, suggesting mostly clear skies. Models suggest the moderate pressure gradient in place across the area causing the gusty winds will lessen overnight. This will lead to gradually decreasing winds. HRRR suggests low falling to the lower teens and single digits in the northwest parts of Central Indiana. Given the dew points upstream, this seems quite reasonable. && .SHORT TERM (This evening through Thursday)... Issued at 306 PM EST Wed Dec 11 2024 Two rounds of snow are expected through the short term, with one arriving this afternoon and another arriving Thursday afternoon. The two rounds of snow will be quite different from one another as well. Today`s snowfall looks to be more scattered in nature with a few squalls possible. Thursday`s snow looks to be more stratiform in nature with a light but steady area of snowfall. Each will be discussed below. Today As mentioned above, today`s snow will be scattered in nature due to an environment characterized by steep low-level lapse rates and instability. An approaching arctic front will provide the lift necessary for widespread snow showers, some of which may be heavy leading to snow squall conditions. ACARS soundings out of IND already show increasing low-level lapse rates, despite widespread stratus, and some areas of clearing are filling in with cumulus indicative of the rapidly destabilizing air mass. Further upstream, radar shows snow showers already entering into Indiana. Deeper into Illinois, radar echoes take on a more cellular appearance hinting at further destabilization upstream. As the increasingly unstable air mass advects east-southeastward into Indiana, these heavier snow showers are expected to spread into the area as well. Snow showers may retain this cellular appearance and not that of a typical linear snow squall, mainly due to the lack of a sharp front and PV anomaly aloft. Temperatures across the region are generally in the low to mid 30s. Dew point temperatures are in the low 20s with wetbulb temperatures below freezing. This sets the stage for potential "flash-freezes" where initial snow melts on contact with the road but then quickly refreezes as temperatures wetbulb down to below freezing. Combined with reduced visibility in heavy snow, treacherous driving conditions are possible this afternoon and evening. Additionally, winds along and behind the front will increase substantially. Gusts up to 40mph are possible which could further impact driving conditions within heavy snow showers or squalls. Tonight Snow showers and squalls should diminish by midnight, leaving us with clearing skies and bitterly cold temperatures. Lows are expected to drop quickly into the teens, and combined with the gusty winds, could lead to wind chills below zero in portions of our CWA. Thursday The day should start off mostly sunny with dry cold advection ongoing behind tonight`s front. Clouds quickly increase after sunrise as a mid-level wave approaches from the west. Guidance is coming into better agreement on an area of steady light snow on the northern edge of this system, which could track west to east across central Indiana. There remains some model uncertainty regarding the exact placement of where this corridor of snow may fall, but the overall consensus is generally along or just to the north of I-70. There has been a slight shift southward within guidance over the past 12 to 18 hours. Timing looks to be mid to late afternoon continuing into the overnight hours. In terms of amounts, guidance only has a couple hundredths of an inch liquid, on average, with at most an inch of snow in the more robust model solutions. Model soundings show deep saturation around the -10C isotherm, hinting at the potential for optimal dendritic growth. This could lead to an "over-achiever" scenario should forcing be a bit more than initially modeled. One particular HRRR run had upwards of 2-3 inches of snow in a narrow band across the area. This would represent a good reasonable worse case scenario. && .LONG TERM (Thursday night through Wednesday)... Issued at 306 PM EST Wed Dec 11 2024 In a very similar fashion to last week, after a brief period of winter weather, a warming trend arrives just in time for the weekend! In addition to warmer temperatures comes multiple chances for rainfall this weekend and into next week. A warmer, wetter, and more progressive weather pattern sets up for the next week or so across the Great Lakes region as the persistent trough overhead is kicked out and numerous smaller systems pass through the region. With the jet stream lifting northward, the main P-type in the extended range should be mainly rain through early next week, limiting the overall impacts expected. Long range signals for indicate a return of cooler, more winter-like conditions mid to late next week. The systems to focus on arrive Saturday into Sunday, Monday into Tuesday, then again mid to late next week. .This weekend... An upper low approaches the Great Lakes region from the west this weekend with ridging building out ahead of it. This should lead to drier and relatively "warmer" conditions Friday. Surface low tracks from Northern MO to near Chicago Saturday into Sunday morning spreading rainfall across all of Indiana midday Saturday. Latest guidance has slowed down the onset of the precipitation some; however Saturday still looks mostly wet for the second half of the day. Brief ridging builds in Sunday as the region will be in between the departing low to the northeast and the next incoming system to the southwest. Expect widespread clouds to persist; however southerly flow and weak warm air advection aloft will keep temperatures above average in the 40s and low 50s. .Next week... The next system follows a slightly more northerly track from the previous one, keeping Central Indiana within the "warm" sector of the system. Above average temperatures persist into the beginning of next week with rain likely much of the day on Monday. Tuesday will likely be colder and dreary on the backside of that system as cyclonic flow through the region will support a low chance for showers within the cold air advection regime. There is a little more discrepancy in the overall pattern for mid to late next week; however confidence is high that the active pattern will continue. Ensembles to indicate a switch back to a colder weather pattern with more chances for snow. && .AVIATION (00Z TAF Issuance)... Issued at 607 PM EST Wed Dec 11 2024 Impacts: - Snow showers with sudden visibility reductions to sub-IFR levels ending by 02Z - West winds gusting to around 30 knots late this afternoon and evening - A second round of snow possible Thursday afternoon and evening. Discussion: Radar this evening shows a band of snow showers pushing across Indianapolis and Bloomington. Low Visibilities were found as this quick moving band passes. Upstream, little in the way of cloud cover is found. Strong cold air advection will persist overnight as an arctic air mass arrives across the area. A moderate pressure gradient will allow for some gusty winds overnight, but mainly clear skies, resulting in cold, but VFR conditions after the current wave of snow passes. Another round of snow is possible Thursday afternoon and evening, especially from IND northward. Some impacts that are possible are brief MVFR or lower conditions. Confidence too low at this time to warrant a prevailing mention. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Puma SHORT TERM...Eckhoff LONG TERM...CM AVIATION...Puma
Area Forecast Discussion
National Weather Service Marquette MI
701 PM EST Wed Dec 11 2024 .KEY MESSAGES... - Moderate to heavy snowfall persists up over the northwest snow belts through tonight. In addition, areas of blowing snow are expected along the lakeshores. A Winter Storm Warning is in effect from Gogebic to Luce Counties but excluding Marquette County, where expected snowfall totals have trended lower. - Confidence is high (80%) that a band of heavy snow will stretch into the eastern UP this afternoon/evening, persisting tonight. This band will make travel very difficult. 1 to 2 inches per hour or higher snowfall rates and visibilities below half a mile should be expected in this band. - The coldest airmass of the season will continue to move into the UP, with minimum wind chills Thursday morning ranging from -10 in the east to -25 in the west. A Cold Weather Advisory is in effect for Gogebic County tonight into Thursday morning. The frigid temperatures continue Thursday and Thursday night, when lows could reach -10 in the interior west. - Lake effect snow and blowing snow continue for the northwest snow belts Thursday, with locally heavy accumulations continuing for the eastern UP. - Above normal temperatures with highs above freezing expected over the weekend into early next week && .SHORT TERM /THROUGH THURSDAY/... Issued at 335 PM EST Wed Dec 11 2024 Early afternoon water vapor imagery and RAP analysis shows closed 500 mb low near 505 dam in southwest Ontario. At the surface, an Arctic high is stretched out from the Canadian Prairies into the northern Plains. Meanwhile low pressure is analyzed over the Northeast US and southeastern Canada, with inverted troughing extending westward toward eastern Lake Superior. Vorticity associated with the trough, combined with moderate overlake instability (surface to 850 mb delta-T of 20C) is resulting in several mesolows evident on KMQT radar imagery. Colder air associated with the incoming upper low is already filtering into the area, with the Ironwood area in the single digits (and wind chills below minus 10). Lake effect snow and blowing snow continue over the western UP as overlake instability reaches the extreme category (sfc to 850 mb delta T values of 25-30C). This will be too cold for the best lift and moisture to reside within the DGZ, as the column will be colder than the DGZ. However, we will continue to expect lake effect snow and blowing snow to continue to result in hazardous travel conditions, with rates of 0.5-1 inch per hour at times through the first part of tonight. Totals will be maximized along the higher terrain between Ironwood and Houghton (Porkies and Mass City to Twin Lakes area) where another 6-12" could fall by the end of the day Thursday. More complicated picture to the east as the aforementioned mesolows continue to cause havoc in forecast model projections. As mentioned earlier today, the distinct trend has been to shift one or more heavier bands associated with convergence along the westerly flank of the composite surface trough further east, necessitating a snowfall forecast and headline downgrade for Marquette and Delta Counties. The convergent band could be quite impressive for Alger, Schoolcraft, and eventually Luce Counties, especially with potential for some smaller-scale mesolows to feed into a larger/dominant band. Forecast soundings at Munising and Grand Marais are prime for heavy LES with high snow to liquid ratios, with inversion heights at 3 km or higher, and plenty of lift in a saturated DGZ near the surface. This will likely result in hourly snowfall rates of 1-2" or higher in the heaviest band. The prime time for these bands are basically later this afternoon through the overnight hours, with HREF guidance honing in on eastern Alger and northern Schoolcraft with the highest totals. Strong winds off the lake will further add to the hazards, especially tonight, and travel will become very difficult to impossible. Luce County has been upgraded to a Winter Storm Warning, and the warning for Alger and northern Schoolcraft has been extended into Thursday. By Thursday, the LES should have transitioned to more multi-band NW flow LES, but additional moderate to locally heavy rates will be expected over the NW belts of the eastern UP, as there is still a decent signal for a saturated DGZ within the convective layer near the surface. The other story is the cold weather, with the coldest airmass of the year associated with the 850 mb temps falling to -20 to -25C, a standardized anomaly of -1 to -2. Wind chill-wise, tonight into Thursday morning will be the coldest, with minimum wind chills ranging from -10 in the east to -25 in the interior west. A Cold Weather Advisory is in effect for Gogebic County tonight into Thursday morning. The frigid temperatures continue Thursday and Thursday night. Highs Thursday just reach a couple degrees above zero in the interior west to near 20 in the east. Better radiational cooling for Thursday night which should send lows to around -15 in the interior west, and near zero in the east. LES should transition to the westerly belts Thursday night, but some additional light accumulation is expected near the lakeshores. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Issued at 302 PM EST Wed Dec 11 2024 Surface ridge axis will extend from northeast MN into northeast WI will set the stage for ideal cooling conditions with light winds, clear skies, and a snowpack across the interior west Thursday night. Expect the coldest night of the season for most with typical cold spots well into the teens below zero. Temperatures will be warmer near the lakeshores and across the Keweenaw where light westerly winds will maintain mixing. As surface ridging slides eastward on Friday, light southerly return flow will allow temperatures to climb to more seasonable levels. The next weather system to have some impact on the area will begin to take shape on Friday into Saturday as low pressure over the central plains begins to lift towards the Upper Mississippi Valley. As he low runs into upper ridging over the Great Lakes it will weaken with time. Scattered precipitation associated with it will be light and will take on multiple forms as the airmass warms. After a brief lull on Sunday, the next weather system will develop over the mid-Mississippi Valley as next shortwave and upper trough eject out into the Plains. Extended models begin to diverge at this time with regards to the track and strength as the system lifts into the Great Lakes on Tuesday. The one consistency amongst the models is the lack of cold air for the system to work with. All precipitation types are still on the table at least until the low moves east of the area and remaining precipitation transitions back to all snow. Even after the low moves east, temperatures will continue to average on the positive side of normal. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 700 PM EST Wed Dec 11 2024 Reduced visiblity due to lake effect snow and blowing snow continues to be the main aviation hazard through the TAF period, particulary for KCMX and KIWD. IFR conditions will persist overnight, with temporary reductions to LIFR at times as when heavier snow showers move overhead. KIWD will see improvement to MVFR late in the TAF period. KSAW will be further removed from the main lake effect snow bands with mostly MVFR conditions expected tonight, although brief reductions to IFR are possible (around a 20% chance). IFR conditions are expected at KSAW during the day on Thursday. West to northwest winds will continue to gust to 20-30 kt through the TAF period at all three terminals. && .MARINE... Issued at 302 PM EST Wed Dec 11 2024 Westerly winds will slowly diminish below 20 knots Thursday night but very cold airmass and 5-10 foot waves over the east half of the Lake will maintain the freezing spray threat through the first half of the night. Ridging moving across Lake Superior on Friday will keep winds below 15 knots through the day. A weakening area of low pressure moving through the lower lakes on Saturday will produce southeasterly winds up to 25 knots over the eastern Lake. Expect more tranquil conditions on Sunday with light southerly winds. Extended models are offering differing solutions as the next system approaches the Upper Lakes next Monday and Tuesday. A gale event is possible in the late Monday to early Wednesday window next week but confidence is low on any specific details at this time. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Storm Warning until 7 AM EST /6 AM CST/ Thursday for MIZ001>004-009-014-084. Winter Weather Advisory until 7 AM EST Thursday for MIZ005. Winter Storm Warning until 7 PM EST Thursday for MIZ006-007- 085. Cold Weather Advisory from 10 PM this evening to 9 AM CST Thursday for MIZ009. Lake Superior... Heavy Freezing Spray Warning until 10 AM EST /9 AM CST/ Thursday for LSZ162-240>242-248-249-263>265. Gale Warning from 1 AM to 1 PM EST Thursday for LSZ248>250-265- 266. Heavy Freezing Spray Warning until 7 PM EST Thursday for LSZ250-266. Heavy Freezing Spray Warning from 1 AM to 7 PM EST Thursday for LSZ251-267. Gale Warning from 7 AM to 7 PM EST Thursday for LSZ251-267. Lake Michigan... Gale Warning until 10 AM EST Thursday for LMZ221-250. && $$ SHORT TERM...Thompson LONG TERM...MZ AVIATION...RM MARINE...MZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
723 PM EST Wed Dec 11 2024 .SYNOPSIS... Additional snow showers will continue tonight with a crossing disturbance. Colder temperatures are expected tonight and Thursday, with a gradual warmup then expected into the weekend. && .NEAR TERM /THROUGH THURSDAY/... KEY MESSAGES: - Scattered snow showers/squalls tonight, more numerous in the ridges with upsloping - Much colder with single digit wind chills late tonight into Thursday - Windy in the ridges - Winter Weather Advisory across portions of the WV higher terrain ------------------------------------------------------------- First wave of snow has ended across the area, though flurries persist in some areas. Additional snow showers are expected overnight with the cold front, along with a ramp up of gusty winds through the early morning. Previous Discussion... Strong 500 mb height falls of 200 meters in progress as rapidly deepening cyclone moves up Hudson River Valley bound for Quebec tonight. Strong cold advection starts tonight behind system with 850 mb temperatures crashing to -16 to -18C by morning. Impressive frontogenetic snow band set up briefly across center of forecast area, and this could be seen in RAP 600 mb frontogenesis field as occurring right around -15C in favored Dendritic Growth zone. Grassy surfaces picked up a quick coating of 0.5 to 1.5" of snow even in the low lands but roads remained wet for most part. Expect that snowband to push to ridges with a few inches of snow by evening per winter weather advisory. Negatively tilted upper trough crosses area around 06z, and steep low level lapse rates with relatively high snow squall parameter values suggest snow showers and perhaps snow squalls during the night. Would expect these to be progressive and would impact locations for an hour or two. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... KEY MESSAGES: - Cold and mainly dry on Thursday into Friday ------------------------------------------------------------------- Upper low pulls north across eastern Canada and heights rise over Upper Ohio River valley throughout the period, eventually rising 250-300 meters. Westerly nature of flow will keep Lake Effect snows well north of forecast area on Thursday. It will be cold with 850 mb temps remaining below -12C until Friday morning before warming really kicks in Friday and Friday night. Expecting 850 mb temps to rise to -2C by late Friday night. However, a 1040+ mb surface high crossing the Great Lakes Friday will keep boundary layer relatively cold. Readings will be about 10F below normal Thursday and Friday. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... KEY MESSAGES: - More seasonable temperatures return - Widespread precipitation chances return by Sunday ------------------------------------------------------------------- Progressive weather pattern appears likely with a series of troughs pushing through in the extended. Ensemble analysis indicates that timing of these features will be the primary uncertainty as it often is. The rising heights will result in temperatures near to above normal by the weekend, and the extent of the warming will be modulated by the speed of a ridge axis moving into Ohio River Valley. Cluster analysis indicates that the ridge by Saturday morning should be somewhere over Ohio at 500 mb with reasonable agreement of a closed low over Nebraska. The retreating polar high of about 1048 mb in combination with warm advection from approaching low should result in rain spreading over the area on Sunday. NBM 24 hour QPF 25th to 75th percentiles are roughly 0.25 to 0.75". On the heals of this system will be another one in the Monday night to Tuesday time frame. There is more spread on the details of this trough, but rain chances appear relatively high again. Without much cold air available, very little chance of winter precipitation at this point. NBM 72 hour probability of 1" or more of snow is less than 20% even in the ridges during that time frame. Highs in the 50s seem likely both Monday and Tuesday and NBM 90th percentile MaxT is in the upper 50s. The progressive pattern looks likely to continue Wednesday and beyond. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... High MVFR/LOW VFR is expected for most of the overnight period. Winds will strengthen overnight with gusts of 20 to 30kts possible. An area of scattered snow showers is expected to move through later this evening and during the overnight hours. Heavier snow showers are possible that could briefly bring high wind gusts, reduced visibility, and lower cigs. TEMPOs were included at each port, sans MGW, to cover vis restrictions. After the snow showers move through, VFR conditions and gusty westerly winds are expected throughout Thursday. Outlook... Restrictions will likely return Saturday with a new disturbance; high confidence in precip type being rain with warm trends. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...Winter Weather Advisory until 8 AM EST Thursday for WVZ512>514. && $$ SYNOPSIS...Craven NEAR TERM...Craven/Rackley SHORT TERM...Craven LONG TERM...Craven AVIATION...22
Area Forecast Discussion
National Weather Service Pocatello ID
214 PM MST Wed Dec 11 2024 .SHORT TERM...Tonight and Thursday Afternoon satellite imagery shows widespread mid/high level clouds over the region this afternoon. There`s the occasional break from time to time allowing for a bit of sunshine to peek through but for the most part, we`re stuck in clouds for a bit. A weak shortwave is forecast to move across the northern extent of the Great Basin beginning late Thursday and into the day Friday. As such, expecting continued cloud cover for the area out ahead of this feature into the day Friday. As far as precip is concerned, there have been big changes to the forecast compared to just a few hours ago. All 12Z models, both hi-res and global runs, now show basically dry conditions throughout the remainder of the short- term forecast period (into Friday AM). Recent 18Z iterations of the HRRR and NAM continue to support this trend as well. That being said, the forecast has trended PoPs downward accordingly, but not completely, for the sake of continuity as going from 50-60 PoPs in places to none at all seems a bit extreme at this juncture as models COULD flip-flop once again and show precip potential on future runs. If this trend continues, expect the next forecast (overnight tonight) to come in even drier as confidence will be increasing. As it stands now though, things are looking mostly dry with at least SOME mention of precipitation in the forecast. If we see any precipitation with the aforementioned shortwave as it moves to our south, it won`t be much or anything to be too concerned with though the way things are looking. Winds should remain mostly light into the day Friday with temperatures remaining on the warmer side of normal today and even more so tomorrow with lower 40s likely across a good chunk of the lower elevation valleys around eastern Idaho. McKaughan .LONG TERM...Friday through Wednesday Split trough works east of the state during the day Friday, with lingering light snows over higher elevation areas. Respite is short lived as next system as deeper trough brings moisture into East Idaho on southwest flow for Saturday through Sunday, exiting Sunday night. This looks to be the more potent system of the longer term with respect to moisture. The southwest flow looks to keep daytime temperatures near to above freezing for many locations, leading to rain or rain/snow mix. Exception may be the Upper Snake Plain where colder pool of air is anticipated, shifting precipitation character towards snow. Cooler night time temperatures will shift more confidently toward snow reaching valley floors. Elevations above 6000 ft look to be favored for this event, especially for the Sawtooths, mountains surrounding Sun Valley, and the Island Park region south to the Big Hole mountains. If models hold snow amounts similar to these values, a Winter Weather Advisory will likely be needed for several higher elevation zones. Transitory ridge shifts across the region Monday, with next system arriving Monday night into Tuesday. This system appears more shallow and moves through quicker than the weekend system, so qpf/snow amounts are lesser trending into the middle of next week. DMH && .AVIATION... VFR conditions expected through the period with BKN to OVC mid/high levels clouds likely to continue across the region. Winds will be light, and generally variable, through the forecast period. KSUN will continue to see upvalley/downvalley diurnal flow into the day Thursday. Introduced VCSH at KSUN for tomorrow afternoon but based on the most recent hi-res model runs, this can probably be removed for the 00Z TAFs. McKaughan && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$