Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/05/21


Area Forecast Discussion
National Weather Service Denver/Boulder CO
849 PM MST Sat Dec 4 2021 .UPDATE... Issued at 823 PM MST Sat Dec 4 2021 Satellite imagery shows areas of high clouds moving into northeast Colorado this evening. Very minor adjustments were made to cloud cover to reflect latest observations. A High Wind Warning is in effect from 11pm tonight through 11am Sunday for the mountains/foothills and the latest model/ensemble data continues to support this. RAP analysis shows increasing NW flow aloft this evening. Model cross-sections indicate a mountain top stable layer and strong cross-barrier flow (50-70kts). Some solutions show better indications of mountain wave amplification with a stable layer coupled with weakening winds above 600mb. HREF ensemble shows mean gusts to 70 mph and max gusts 75+ mph. This is similarly reflected in the HRRR showing potential for gusts above 85 mph. The plains will also experience gusty winds although likely below high wind criteria. && .SHORT TERM...(This evening through Sunday) Issued at 245 PM MST Sat Dec 4 2021 Currently, weak flow aloft and at the surface prevail across the forecast area with some thin Cirrus cloudiness overhead. Current temperatures are 10-20 degrees F above normal highs, at least over the plains and foothills. Tonight, models show increasing northwesterly flow aloft. Cross sections indicated a decent mountain wave set up developing by 06Z tonight. The low level pressure gradient tightens up significantly as well. High wind speeds seem to be a good bet along the divide and into the foothills a ways from midnight through about 18Z on Sunday. Will go with a high wind warning for zones 33, 34, 35 & 36. It appears the strongest winds should stay above 7,000 feet MSL. Out on the plains, the downsloping winds should stay below high wind criteria. However, a pretty strong cold front, with is expected to upslope flow behind is expected to move across the plains, into the foothills from 20Z onward during the later afternoon hours. Some of the models hints at some, potential, low level cloudiness with this by 00Z, but precipitation is not expected. There could be a bit of elevated fire danger over the southern plains and Palmer Ridge of the forecast area by Sunday afternoon with RH values getting into the teens for a short period of time. For temperatures on Sunday, readings should be about 5-8 C cooler than today`s highs, except about 12 C colder over the far northeast corner. .LONG TERM...(Sunday night through Saturday) Issued at 243 PM MST Sat Dec 4 2021 Cold advection behind the front will bring temperatures on the plains down to near or slightly below normal by Sunday night, and breezy northerly winds should gradually decrease through the night. Strong winds in the high country will also gradually decrease as the mountain wave relaxes, but breezy conditions will persist. Expect lows in the teens to low 20s across the area. Monday, temperatures will remain slightly below normal across the plains with highs in the mid 30s to low 40s. Continued breezy conditions across the higher elevations will moderate the cooldown there, where temps will stay closer to or slightly above normal especially in the mountain. Monday, a weak shortwave will bring an increase in moisture and cloud cover and some light snow showers in the mountains late Monday through Tuesday. Accumulations should be light. A few showers may make it over the Front Range to the adjacent plains but would only bring flurries. Isolated to scattered, light orographic snow showers may continue late Tuesday and early Wednesday as the nose of a northerly jet moves over. Models disagree on the synoptic situation Wednesday. The GFS has some quick ridging ahead of another shortwave, while the ECMWF and Canadian models have a persistent northwesterly flow aloft with the nose of another jet pushing into Colorado. In general, expect some brief ridging, subsidence and warming with gradually increasing winds. By Thursday, models come back into agreement with a more zonal flow and around 120 knot jet streak over the area. Breezy westerly winds are likely in the high country. A trough will be deepening as it moves over the western states. There is good model consensus about this next system especially given the time range. It should be a much colder airmass with better moisture and increasing potential for widespread snowfall. Snowfall should begin to impact our mountain zones on Thursday, though the greatest impacts look to occur Friday into Saturday. Models are showing light snowfall for the lower elevations as well though details are more uncertain east of the mountains. Ensembles still favor at least some measurable snow across the urban corridor and much of the plains, but with varying degrees of impact. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 440 PM MST Sat Dec 4 2021 VFR conditions expected tonight and Sunday. Light SE and E winds early this evening will return to drainage (SSW) after 00z. Main concern for impacts will be gusty winds after 15z Sunday. Confidence is high for breezy conditions to extend eastward from the foothills tomorrow. Gusts up to 30kts out of the west to northwest are possible in the afternoon. Additionally, a front will bring a surge of gusty northeast winds likely in the 22-00z timeframe. Winds decrease after 02z. No precipitation expected. && .BOU WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 11 AM MST Sunday for COZ033>036. && $$ UPDATE...Mensch SHORT TERM...RJK LONG TERM....EJD AVIATION...Mensch
Area Forecast Discussion
National Weather Service Boston/Norton MA
956 PM EST Sat Dec 4 2021 .SYNOPSIS... A weak frontal system passes from the Great Lakes into the waters tonight, with high pressure returning for Sunday. Generally dry and seasonably chilly weather is expected through the remainder of the weekend. Potential for strong to damaging wind gusts on Monday along with showers and thunderstorms. Will be unseasonably mild with highs in the low to mid 60s. Dry and cooler than seasonable air works into the region late Monday night and Tuesday. Accumulating snow likely for parts of the region on Wednesday, but the rain/snow line and the axis of the heaviest precipitation remains uncertain. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Latest few runs of the HRRR and RAP were doing the best at acknowledging the clouds and scattered light showers shown on radar. Not a large risk for accumulating precipitation, but did tweak precipitation chances this evening. Once the clouds depart, most of southern New England should remain clear the rest of tonight. Areas north of Route 2 in MA may flirt with a few more clouds associated with a lake effect band extending east from Lake Ontario. Minor tweaks to temperatures and dew point to reflect observed trends. 745 PM Update... Have increased precipitation chances across the interior per latest observations. Have some flurries/light snow showers moving across the region. Given the temp/dew point spread do not think much of this reaching ground, but folks could see some flakes falling over the next few hours. Leaned toward the latest HRRR guidance. 630 PM Update... Have adjusted the forecast to lower overnight low temperatures. We are just a bit clearer than the previous forecast indicated and with the relatively light winds there should be fairly strong radiational cooling in place. Lowered temps to the 5th percentile of guidance to more accurately capture the current falling temps. Lows bottom out in the 20s across much of the interior and the low-mid 30s along the coastal plain. Winds have also decoupled a bit faster than previously indicated, so adjusted wind speeds/gusts down across the interior. Offshore winds still looking good. Rest of the forecast remains on track. 215 PM Update... Generally scattered to overcast mid level clouds prevail across most of Southern New England this afternoon, with lower cloud cover around the Berkshires. Fast belt of WNW flow governs conditions across Southern New England, stuck between two weak frontal systems: one near the mid-Atlantic coast leading to a shield of clouds affecting our far southern offshore waters, and the more prominent if still weak frontal system over western Quebec. This latter feature moving in from western Quebec and the Great Lakes will still contribute to areas of mid-level clouds through early this evening, although the moisture layer is rather shallow between 900 and 700 mb. Thus, this frontal passage should be a dry one with a wind shift from SW to W/WNW with associated brief period of gusts between 25-30 mph between mid- evening to midnight, driven by onset of moderate cold advection coupled rising sea-level pressure tendencies. As pressure rises become less pronounced overnight, cooling PBL to then be offset by gradually falling temperatures, with model soundings for the after- midnight period becoming inverted with a tendency for gusts to abate for most. The exception is near the coasts/shorelines and over the waters where somewhat milder air temps/water temps may maintain WNW gusts to 25 mph into the overnight. With at least some sustained WNW winds overnight, kept lows on the milder side of available guidance, generally in the upper 20s for a large part of the interior, with lower 30s for the southern/eastern coastlines, and mid to upper 30s for most of Cape Cod and the Islands. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... 215 PM Update: Sunday: An approximate 1030 mb high pressure over the western Allegheny Plateau in PA to progress eastward over Southern New England by the early to mid afternoon hours. Still rather dry columnar moisture with PWATs around 0.25 to 0.30 inches, but as high pressure shifts offshore later in the day and winds become more onshore, expect PWAT values to improve to around 0.35 to 0.50 inches. Overall a seasonably chilly day but with light south to southeast winds and generally more sun than today, though high to mid-level clouds approach late in the day. Highs should be fairly similar today as more sun offsets the cooler thermal profiles expected (925 temps -4 to -7C). Sunday Night: High pressure moves offshore early Sunday night, with tightening pressure gradient allowing for stronger S/SE surface winds. Will see clouds lower and thicken as lead shortwave disturbance comes up from the mid-Atlantic region, spreading a warm front northward during the latter half of the night and especially for the early Monday morning period. Fairly strong warm and moist advection and increase in cloud cover toward OVC favored a non-diurnal temperature curve for many locations with expectation of temperatures rising into the overnight. 925 mb temps rise to around +5 to +9C by daybreak! Warm front should bring mainly light showers northward as temperatures by daybreak for most locations in the 40s to perhaps near 50F towards the South Coast. However there is some level of uncertainty as to how quickly will any shallow sub- freezing air be scoured out across part of the northern hills in Worcester County, the Route 2 corridor into the Berkshires. Given the warm profiles aloft with wet-bulb temps running between 30-32F in this corridor, some light freezing rain or ice pellets could be possible at onset. While trace amounts are anticipated, as roads or sidewalks here still may not be treated/salted, slippery spots possible. Given that some models show above- freezing surface temps in this area when precip begins, hence the uncertainty in predominant p-type, have refrained from winter weather headlines at this point. A statement or possible winter advisory could be needed for these far northern and northwestern locations if colder solutions become more apparent or surface temps are slower to rise then presently envisioned. && .LONG TERM /MONDAY THROUGH SATURDAY/... Highlights... * Unseasonably warm Monday into Monday night with the potential for strong to damaging wind gusts, showers and thunderstorms. * Near to slightly cooler than seasonable temperatures for the rest of the work week. * Appears that we will see the first widespread accumulating snowfall Wednesday into Wednesday night, but the specific amounts and details are uncertain at this time. Monday into Monday night... Trough lifts from the Upper Midwest early on Monday into the eastern Great Lakes/Quebec by late Monday. Will also initially have a subtle leading shortwave trough lift into the region early on Monday ahead of the deeper wave. At the surface a warm front lifts into and through southern New England early on Monday. A weak low lifts across the Mid Atlantic through the CT River Valley. There may be a bit of a lull in the precip late in the AM into the early afternoon before the cold front swings in for later in the day. Main concern during this period is the potential for strong to damaging wind gusts. Will have a roughly 45-65+ kt low S/SW low level jet crossing the region. This really picks up during the afternoon and into the evening immediately ahead of the incoming cold front. Did back off slightly from the previous shift on how strong gusts get as there is quite an inversion to overcome. If we can break out in enough sunshine and deepen the mixed layer then these higher end gusts could be realized, but it will be dependent on how warm we get. For now started off with the NBM90th and bumped up speeds around 5 kts, which is roughly 80 percent of the 925 hPa low level jet. Risk of the strongest wind gusts is highest across SE MA, which includes Cape Cod and the Islands. Not out of the question that Wind Advisories will be needed in future updates, but confidence too low at this point in time. On top of the wind risk there is the potential for some convection. There is a lot of deep layer shear in place with 40-70+ kts in place with those values really increasing as that cold front slides in. The big question is how much instability can we get, which appears meager and elevated at this point in time per BUFKIT soundings. As previous shift mentioned, there is the potential for rotating storms given the helicity in place, so there is a non-zero risk of a few strong to severe thunderstorms. Have kept the isolated thunder mention in the forecast, but really would like to see more convective allowing guidance other than just the NAM/NAMNest to really dive into the details. Will also mention there are decent mid level lapse rates/an EML in place, 6-8 degree Celsius lapse rates, as the warm front is lifting through earlier in the day. The big question at this point is how much instability will be in place. The latest SPC Day 3 general thunder outlook highlights the risk area well. Will need to hone in more on the convective allowing guidance in future updates. Expect it to be anomalously warm with 925 hPa temps of 8-13 degrees Celsius. Went with the 75th percentile of guidance given am not completely certain how much sunshine we will get in the break between the warm front lifting through and the cold front moving in. The result are highs in the mid/upper 50s across the higher terrain of the interior and the low 60s elsewhere. If we can clear out a bit more then temps will need to be increased further in future updates. Tuesday... Weak mid level ridge builds into the region bringing drier and cooler than seasonable temperatures. A surface high builds in from the eastern Great Lakes/Quebec. Will have blustery conditions especially earlier in the day before the high can really relax the pressure gradient. High temps topping out in the mid 30s to low 40s. Wednesday into early Thursday... Next shot for potentially impactful weather for southern New England. Does appear that there is a risk for widespread accumulating snowfall, especially across the interior. The specific amounts/details are uncertain at this point in time however. The reason for the uncertainty is that there are differences in the intensity of the trough lifting through the region. On top of this the exact track of the surface low associated with the trough is widely spread at this point in time. Will really need to hone in on the details to determine the exact totals and where the rain/snow line sets up. Given the uncertainty at this point in time have really just stuck with the NBM guidance as there is a lot of spread amongst guidance. Will point out that the EPS has roughly a 30-60 percent chance of snowfall amounts AOA 3 inches with SLR of 10-1. The GEFS is much more keen on these chances in the roughly 40-80 percent range, but will point out that both pieces of ensemble guidance have backed off a bit in the probabilities when comparing run to run. Luckily, the storm is fairly progressive in nature so would be moving through fairly quickly. Much too early to dive in the specific details given the uncertainty, but folks who are traveling will want to keep an eye on the forecast for future updates. Mid Thursday through Friday... Drier on Thursday with any lingering precipitation ending earlier in the day as low pressure exits. Behind the low, high pressure builds in briefly bringing dry weather for much of the day. Will have another shot for isolated to scattered snow showers late Thursday into Friday as a shortwave swings through. However, away from the highest elevations across the interior precip may change over to rain during the day time. Again given the uncertainty in the Wednesday-Thursday window have mainly stuck with the NBM. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight...High confidence VFR with W winds around 5-10 kts. Could have some 10-15 kt speeds across the Cape/Islands with gusts of 20-25 kts possible at ACK. Sunday...High confidence VFR with W to WNW winds around 5-10 kts becoming light and variable as high pressure builds in overhead. The high moves offshore during the afternoon shifting winds to the S/SE. Sunday Night...High confidence in trends, moderate on timing. VFR with lowering ceilings; deterioration to MVFR-IFR more likely after 06Z across the interior. Eastern locations could see MVFR conditions and spotty IFR toward daybreak. Light rain for most as temperatures warm overnight, though a period of light frozen precip (mainly light ZR/IP) may be possible across northern MA, Route 2 corridor and the Berkshires (e.g. away from any TAFs). SE winds increase to 5-10 kt in the interior, and around 10-15 kt eastern/southeast MA and southern RI. Southerly LLJ of 40 kt associated with warm front may lead to areas of low-level wind shear and local turbulence from BDL-BED north and west. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Monday through Thursday/... Tuesday: VFR. Breezy. Tuesday Night: VFR. Chance SN. Wednesday: MVFR/IFR conditions possible. Breezy. SN likely, RA likely. Wednesday Night: MVFR/IFR conditions possible. Breezy. Chance SN, chance RA. Thursday: Mainly VFR, with local MVFR possible. Breezy. Thursday Night: VFR. Breezy. Slight chance SN. Friday: Mainly VFR, with local MVFR possible. Slight chance RA, slight chance SN. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 4 PM Update... Have hoisted a Gale Watch on Monday into early Tuesday for the waters. Will have a strong south/southwesterly jet bring a period of gale force gusts. Not completely out of the question there could be some brief storm force gusts late in the day, but will not be as widespread as the gales. High confidence. Small craft advisories continue for tonight into Sunday morning with a period of 25-30 kt westerly gusts as colder air surges across the waters. Seas briefly build to 3-5 ft on most offshore waters. Winds then begin a decreasing trend and become east to southeast into Sunday afternoon as high pressure moves offshore. Seas decrease to 3 ft or less all waters. For Sunday night, gradient strengthens and leads to SE winds becoming around 15-20 kt, perhaps near small craft levels by daybreak. Seas will be building toward the 4-6 ft range offshore and around 2-4 ft on nearshore waters. Light rains approach southern waters late Sunday night into early Monday morning. Outlook /Monday through Thursday/... Tuesday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain. Wednesday: Winds less than 25 kt. Seas up to 5 ft. Rain likely. Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Rain likely. Thursday: Low risk for Small Craft Advisory winds with gusts up to 20 kt. Rough seas up to 10 ft. Slight chance of rain, slight chance of snow. Thursday Night: Winds less than 25 kt. Areas of rough seas. Slight chance of rain, slight chance of snow. Friday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain. && .TIDES/COASTAL FLOODING... Tide heights are rising to their December monthly highs over the weekend. The following are the astronomical heights and do not include surge values from local wind/weather conditions. Pockets of splash over and minor coastal flooding are possible on Monday with the best chance along the south coast given southerly winds. However, significant coastal flooding is not expected. Boston Saturday 12.1 feet 1029 AM Sunday 12.2 feet 1120 AM Monday 12.0 feet 1214 PM Nantucket Saturday 4.3 feet 1129 AM Sunday 4.4 feet 1224 PM Monday 4.4 feet 120 PM Providence Saturday 5.9 feet 732 AM Sunday 5.9 feet 824 AM Monday 5.8 feet 917 AM && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Watch from Monday morning through Tuesday morning for ANZ230>237-250-251-254>256. Small Craft Advisory until 5 AM EST Sunday for ANZ232. Small Craft Advisory until 3 AM EST Sunday for ANZ233-234-255- 256. Small Craft Advisory until 4 AM EST Sunday for ANZ230. Small Craft Advisory until 7 AM EST Sunday for ANZ231-251. Small Craft Advisory until 2 AM EST Sunday for ANZ237. Small Craft Advisory until 3 AM EST Sunday for ANZ235. Small Craft Advisory until 8 AM EST Sunday for ANZ250. Small Craft Advisory until 9 AM EST Sunday for ANZ254. && $$ SYNOPSIS...BL/Loconto NEAR TERM...Belk/BL/Loconto SHORT TERM...Loconto LONG TERM...BL AVIATION...Belk/BL/Loconto MARINE...Belk/BL/Loconto TIDES/COASTAL FLOODING...Staff
Area Forecast Discussion
National Weather Service Grand Forks ND
850 PM CST Sat Dec 4 2021 .UPDATE... Issued at 850 PM CST Sat Dec 4 2021 Heavy snow potential on track. Looking like some sort of lull in impacts by later Sunday morning. Confidence continues to increase toward significant blowing snow impacts within the Red River Valley Sunday afternoon and evening. The pattern is a classic hybrid blizzard event. Majority of hi- res guidance indicate a strong secondary cold front will propagate through the region, bringing strong cold air advection. Temperatures will rapidly drop, making it easier for freshly fallen snow to blow around. RAP guidance indicates 925mb winds ~40 knots (and unidirectional through that layer), with due northerly winds increasing the valley component. Winds will be strong enough for at least near blizzard conditions, and blizzard conditions if winds materialize as expected. Using NBM wind probabilities and the Canadian blowing snow model, there is ~70% chance for winds to be strong enough to lead to consistent whiteout conditions (where enough fresh snow exists). Will keep current headlines as is since they mainly deal with the falling snow, and plan to transition headlines toward blowing snow impacts once the falling snow comes to an end or is nearly done. UPDATE Issued at 700 PM CST Sat Dec 4 2021 Radar imagery indicates band of 700mb warm air advection snowfall across much of North Dakota, propagating north/northeast. Current snowfall forecast in good shape, as this initial slow moving area of snow should lead to 3-5 inches of snow. Then, the upper wave seen on water vapor imagery provides additional synoptic forcing across the area where the heaviest snowfall is forecast thus adding another 3-5 inches of snow by Sunday morning within that corridor. Planning on taking a closer look at winds and potential blowing snow impacts Sunday afternoon/evening with the next update. && .SHORT TERM...(This evening through Sunday night) Issued at 338 PM CST Sat Dec 4 2021 Low pressure continues to deepen from southeastern MT into northwest SD as a nascent winter storm system intensifies. The elevated warm frontal band which has formed ahead of this system continues to slowly lift northward now from northern SD into south central and far southeastern ND attm, with light snow showing from the Sisseton Hills along an arc toward Bismarck and points west. The deterministic model suite has come into fair agreement on the overall evolution of this storm system through the remainder of today through Sunday, with both the GFS and ECMWF operational runs having slowed just a tad from previous runs. The consensus favors a slight southerly expansion of the heavier snow, so that the Fargo-Moorhead area and points eastward have been added into the Winter Storm Warning area, with expected highest snowfall amounts still running along and either side of the Hwy 2 corridor. The Winter Storm Watch area across the far southern Red River Basin is now in a Winter Weather Advisory. Heavier snow fall is still expected to develop into eastcentral and southeastern ND through early evening, and expand across the remainder of the area during the late evening and over night period tonight. On Sunday... The surface low center is expected to pass across central MN through midday, with a very strong wraparound wind developing in its wake. Though snowfall amounts will drop off appreciably as the low center passes, there will like be residual light snow and appreciable blowing and drifting snow developing across eastern ND by midday and then across northwest through west central during the afternoon. The more exposed areas of eastern ND, the Red River corridor, and western MN will likely experience near blizzard conditions Sunday afternoon into the evening. Forested areas in northcentral MN will see pockets of significant blowing and drifting snow in more exposed areas. Temperatures tonight through Sunday afternoon will range though the teens north to upper 20s south, then dropping off throughout the afternoon on Sunday. Overnight lows on Sunday night will plummet down to and below zero across most of eastern ND and northwest MN.. with winds chills ranging from minus 15F to minus 25F by Monday morning. .LONG TERM...(Monday through Saturday) Issued at 524 PM CST Sat Dec 4 2021 Not much risk for impactful weather coming up for the week ahead, in the wake of the prior weekend event. A much colder airmass moves in as the winds gradually diminish from near 20 mph around sunrise to a more zephyr-like 5 to 10 mph by sunset on Monday. High temps will only be in the single integers above zero before dipping to between 5 and 15 below at night as a result wind chills will be in the 15 to 30 below range. The new snow pack will aid in the redux, the degree of which will naturally be determined by cloud coverage. Ensembles and clustered products don`t really show much of consequence for Tue through Fri; a few short waves moving through NW flow could trigger some light snow over the southern valley later Tue, with another chance coming on Thu. Temps will rebound on Wed/Thu, maybe getting above freezing over the far south on Thu. That time frame should offer more robust winds, out of the SW approaching 20 mph. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 524 PM CST Sat Dec 4 2021 Snow will lift northward this evening across the region as it does VSBYs and CIGs will erode. Expecting mostly MVFR and IFR conditions to develop within the heaviest snowband overnight and some gusty southeasterly winds. Tomorrow snow wanes but north winds will increase with BLSN concerns and gusts of 30 to 40 kts. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Winter Weather Advisory until midnight CST Sunday night for NDZ038-049-052-053. Winter Storm Warning until midnight CST Sunday night for NDZ006>008-014>016-024-026>030-039-054. MN...Winter Weather Advisory until midnight CST Sunday night for MNZ029>031-040. Winter Storm Warning until midnight CST Sunday night for MNZ001>004-007-022-027-028. Winter Storm Warning until midnight CST Sunday night for MNZ005- 006-008-009-013>017-023-024-032. $$ UPDATE...TG SHORT TERM...Gust LONG TERM...JK AVIATION...WJB/JK
Area Forecast Discussion
National Weather Service Green Bay WI
911 PM CST Sat Dec 4 2021 New Information added to update section .UPDATE... Issued at 910 PM CST Sat Dec 4 2021 Decided to issue a Winter Weather Advisory for Door, Southern Oconto, Menominee, Shawano and Marathon counties for Sunday. Forecast soundings suggest that 2 to 5 inches of snow should fall in most of that area along with winds gusting to 35 mph at times. && .SHORT TERM...Tonight and Sunday Issued at 335 PM CST Sat Dec 4 2021 The main concern for today will be the snow arriving late tonight and continuing into Monday morning. There was a slight shift to the south with the heavier snow. A northwest to southeast band of snow is expected to break out ahead of the main system. Still a good deal of uncertainty in where the band will set up as some of the models are farther south than yesterday. However, the latest HRRR model has trended slightly to the north on the latest run. Decided to go with a winter storm warning for Vilas, Oneida, Forest and Florence counties where some locations could see 6 inches within 12 hours on Sunday if the band sets up over the same area for a period of time. Have winter weather advisories for the tier of counties to the south. To the south, there will be a wintry mix as boundary layer temperatures should climb into the middle to upper 30s. There will be a lull in the heavier precipitation at some point Sunday evening with the heavier precipitation moving back into the north after midnight. Some of the worst conditions across the north will be late Sunday night into Monday as the snow ratios lower, thus providing a powdery snow will blow around with wind gusts of 30 to 40 mph creating considerable blowing and drifting of the snow. Snowfall accumulations of 7 to 11 inches are expected across Vilas County while totals less than an inch are are expected south of a Wisconsin Rapids to Green Bay to Sturgeon Bay line. Gusty northwest winds late Sunday night could result in some power outages across the north as well. .LONG TERM...Sunday Night Through Saturday Issued at 335 PM CST Sat Dec 4 2021 The mix of drizzle, freezing drizzle, and snow on Sunday will transition to all snow Sunday night as the storm system moves northeast into Canada and cold air pushes in on the back side of the system. Lake-effect snow across the far northern counties of WI will be the primary source of precipitation Sunday night thru Monday afternoon. However, winds will gust to 30-40 mph out of the west-northwest Monday morning, causing blowing snow and poor visibility across many areas from Highway 29 north. Low temperatures will tank Monday night as Canadian air moves in and winds slacken. Lows in the Fox Valley will drop to near zero while central and northern WI should see temperatures as low as 10-15 degrees below zero. The progressive pattern aloft will remain in place, and there will be chance for snow on Tuesday as a mid-level shortwave rotates through the region. With cold air and weak northerly winds still in place, high temperatures on Tuesday will only struggle into the teens. After that, winds should switch around to the south again as the high pressure ridge shifts east of us. Temperatures should moderate on Wednesday with the wind shift and as another shortwave possibly approaches on Thursday. && .AVIATION...for 00Z TAF Issuance Issued at 549 PM CST Sat Dec 4 2021 Middle clouds will increase this evening as low pressure approaches from the Northern Plains. Light snow will arrive from west to east after midnight, with MVFR conditions conditions by daybreak west of an IMT to CWA line. Snow and IFR conditions are expected north of a CWA to SUE line Sunday, with snow and rain showers to the south and mostly MVFR conditions. Snow will continue north of a AUW to IMT line Sunday night, with areas of drizzle or friezing drizzle elsewhere. A cold front will move across the area late Sunday night and bring an end to the precipitation, with the exception of lake effect snow showers north of a RHI to IMT line. Winds will become westerly and gust to 35 knots or more through midday Monday. && .GRB WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 3 AM Sunday to noon CST Monday for WIZ005-010>012. Winter Weather Advisory from 6 AM to 9 PM CST Sunday for WIZ022- 074. Winter Weather Advisory from 3 AM Sunday to noon CST Monday for WIZ013-018-019-021-073. Winter Weather Advisory from 3 AM to 6 PM CST Sunday for WIZ020- 030-031. && $$ UPDATE.........RDM SHORT TERM.....Eckberg LONG TERM......ML AVIATION.......RDM
Area Forecast Discussion
National Weather Service Lincoln IL
739 PM CST Sat Dec 4 2021 .SYNOPSIS... Issued at 255 PM CST Sat Dec 4 2021 Cool high pressure will slide east-southeast through the area tonight. Rain is in the forecast for Sunday with mainly scattered showers expected, but there could be some thunderstorms south of I-70 Sunday night. Central Illinois will see an active pattern through next weekend, with a chance of snow on Tuesday night followed by chances for mainly rain for the latter part of the week and into the weekend. && .UPDATE... Issued at 739 PM CST Sat Dec 4 2021 Mid and high level clouds have gradually been spreading southeast early this evening, with the thicker clouds still north of I-74. Most places are still in the mid 30s to lower 40s at 7 pm. Exception was the Decatur airport at 29 degrees, but after an investigation of nearby mesonet stations, this appears to be an anomaly as other stations around Decatur are in the mid 30s. The clouds will continue to expand across the forecast area overnight, though areas south of I-70 should remain fairly clear until closer to daybreak. Not expecting a huge dropoff in temperatures, as winds are expected to pick up some toward midnight. Latest HRRR suggests some light rain making it as far as Springfield by 6 am, but soundings show a decent amount of dry air lingering below 850 mb at that point, so will leave the forecast dry there at this time. && .SHORT TERM...(This evening through Sunday night) ISSUED AT 255 PM CST Sat Dec 4 2021 Currently, the region is under the influence of a ridge of high pressure at the surface, with the high centered over southern MN and IA. The high will slide ESE across northern IL to PA tonight in order to make way for a strong low pressure system developing in the Northern Plains. This low will move east across the Great Lakes region Sunday night into Monday. With the warm, moist air pushing northward ahead of this system, expect enough instability and lift to produce some showers on Sunday and Sunday night across much of Illinois. The latest suite of near-term convective allowing models indicate there should be MUCAPEs of perhaps up to 500 J/kg generally south of I-70 Sunday night. So, have included a chance of thunderstorms in this area. Not expecting severe weather this far north, but it will be possible south of Lawrenceville. A cold front will sweep through the area Sunday night as well, ushering in considerably colder air for Monday. && .LONG TERM...(Monday through Saturday) ISSUED AT 255 PM CST Sat Dec 4 2021 By Monday, the cold front will have pushed through the area and an upper trough will exist aloft over the region. Skies will be clearing and temps will struggle to rise during the day, leaving highs only in the 30s in most areas. Cold high pressure will settle in over the region on Monday night, with lows in the teens to low 20s expected. With west-northwest flow aloft across the region on Tuesday, an upper level wave will begin to deepen across the central U.S...and push ESE from the Northern Plains. Isentropic lift, and eventually a band of frontogenesis, will set the stage for some snow development Tuesday night. The latest forecast supports light snow accumulations in the region. Expect the region to stay active with yet another system possible late in the week. However, temperatures support a mostly rain forecast at this time as we transition to a warmer southwest flow aloft. Models have trended wetter with this system, but uncertainty remains high. Another weather system is expected for the weekend and currently looks like one of the stronger systems. There`s plenty of uncertainty with the details of this system also. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 535 PM CST Sat Dec 4 2021 The pre-12Z period will be fairly quiet, with winds gradually shifting southeast and increasing to about 8-10 knots. After that, a steady lowering of ceilings is expected as rain showers move in from the southwest, with MVFR conditions likely at all sites between 15-18Z. Ceilings linger below 2,000 feet through the afternoon. Southeast winds will continue to pick up and gust around 20 knots most of the day. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SYNOPSIS...Knutsvig SHORT TERM...Knutsvig LONG TERM...Knutsvig AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Melbourne FL
924 PM EST Sat Dec 4 2021 .DISCUSSION... Skies will be mostly clear to partly cloudy into tonight with ridge axis of high pressure over the west Atlantic remaining extended across the area. This will generate a light southerly flow in the low levels, which will again be conducive for fog development overnight. Greatest potential and coverage of any dense fog, producing visibilities of a quarter mile or less, will continue to be toward and N/NW of the I-4 corridor after midnight through early morning Sunday. However, patchy dense fog will be possible across much of the area as favorable radiational cooling conditions drop temperatures into the 50s over much of the region. Dense Fog Advisories may again be needed over portions of the area should fog become widespread enough late tonight. HRRR is showing some isolated showers approaching the Treasure Coast late tonight, but not moving onshore until after daybreak. Will therefore keep rain chances out of the forecast for land areas tonight. && .AVIATION...Fog development possible again tonight, with light winds and mostly clear to partly cloudy skies prevailing overnight. Greatest chance for areas of dense fog still looks to be toward and N/NW of I-4, with visibilities less than a mile. Model guidance has not been in the best agreement with coverage, but should begin to see fog form after 06Z and increase in coverage through daybreak and then gradually lift and dissipate into late morning Sunday. VFR conditions then expected to largely prevail during the day, with only brief reductions in cig/vis in isolated onshore moving showers along the Treasure Coast. && .MARINE...Ridge of high pressure over the west Atlantic will remain extended across the waters into tonight, with S/SE winds around 5-10 knots. Seas will linger around 1-2 feet. && .PRELIMINARY POINT TEMPS/POPS... DAB 52 77 61 80 / 0 10 10 0 MCO 54 81 63 83 / 0 0 0 0 MLB 57 78 63 81 / 0 10 10 10 VRB 59 81 65 85 / 10 20 10 10 LEE 53 81 62 83 / 0 0 0 0 SFB 54 80 62 83 / 0 0 10 0 ORL 55 80 63 82 / 0 0 10 0 FPR 58 79 63 83 / 10 20 10 10 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Weitlich/Cristaldi
Area Forecast Discussion
National Weather Service Springfield MO
525 PM CST Sat Dec 4 2021 ...00Z AVIATION UPDATE... Key Messages: 1. Drizzle or light rain showers possible tonight-Sunday. 2. Strong to severe storms possible Sunday Night south of I-44. 3. Cooler and drier weather early next week. 4. Additional precip chances next weekend. .SHORT TERM...(This evening through Sunday) Issued at 130 PM CST Sat Dec 4 2021 A stationary front across Oklahoma and Arkansas was in the process of slowly lifting north this afternoon. Dewpoints to the north of the front, across our area, were in the 30s, with areas south of the front experiencing dewpoints in the 60s. Low to mid level clouds will continue to lift north into the area tonight. As we head later into the night, a low level jet will increase across the area. A weak 700mb wave approaches and should provide additional lift for some isolated to scattered precip to form. Forecast soundings show plentiful low level moisture, however an absence of cloud ice will likely lead to areas of drizzle or very light showers. Temperatures will likely level off or slowly rise across the western half of the area overnight. While some patchy drizzle or showers could last through the morning, HREF cloud cover data and forecast soundings suggest that the area may see some clearing during the afternoon Sunday ahead of the next cold front. Stayed with NBM highs for now (middle 60s), however if clouds clear sooner, then highs could go up a few more degrees. Gusty winds up to 30mph are possible during the day. .LONG TERM...(Sunday Night through Saturday) Issued at 130 PM CST Sat Dec 4 2021 Sunday Night Storms: Models are in excellent agreement that a cold front will drop southeast into Missouri Sunday Evening. The area will be located in a favorable position to the subtropical jet to the south of the area, and a digging polar jet to the north. This is a classic clash of airmasses. Forecast soundings show that the area will likely be capped until late evening. The cold front looks to enter the far NW counties by 7-8pm. HREF updraft probabilities increase markedly once the front gets to Interstate 44 by 9-10pm. This is where storm initiation appears possible. Storms look to then form quickly as the front moves through areas south of Interstate 44. Updraft helicity values from the HREF are maximized just south of the Missouri/Arkansas state line. Forecast soundings from Branson to West Plains off the RAP and NAM both have about 500-750j/kg of ML cape, and about 40kts of 0-6km shear. Hodographs generally show a unidirectional flow, with west to southwest winds. Mid level lapse rates look to be in the 7-7.5 C/KM range. Therefore the ingredients are there for a few strong to severe storms with large hail and damaging winds south of Interstate 44. The tornado potential looks very low at this time, especially with the forecast hodographs. The band of storms will likely be southeast of the area by 3-5am early Monday morning. Early Next Week: The airmass behind this front will be much cooler and drier, with surface dewpoints in the teens by Monday morning. Gusty northwest winds and a dry airmass will likely lead to a elevated fire weather threat Monday afternoon. NBM spread of temps are small, with highs in the lower 40s likely. Model ensemble clusters are in decent agreement that a zonal upper level pattern will develop during the week, with a few weak waves moving through at times. One such wave, as shown more pronounced by the GFS ensembles, moves through the area Tuesday night into Wednesday morning. There may be enough lift for some light precip during this time, however other model clusters are much lighter, or even dry. Given the colder environment, if any precip were to fall, it would likely be flurries/light snow. Current NBM probabilities for light snow are less than 50 percent, with slightly higher probabilities just northeast of the area. Warm ground temps would negate any impacts. The pattern then looks to become zonal to slightly southwesterly for the rest of the week, with NBM temperatures slowly climbing a few degrees each day. A 10 degree spread exists for Friday, however the range is all above average, either in the upper 50s to upper 60s, therefore the warmest day of the week will likely be Friday. Next Weekend Storm System? We will be monitoring the ensemble data as we look to next weekend. Ensembles are in decent agreement that a large upper level trough will develop out west, however timing differences exist on when it will eject out into the plains. This has large implications on temps and precip chances and for now have not strayed from the NBM which has precip chances in the 30 to 50 percent range for next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 511 PM CST Sat Dec 4 2021 Current VFR conditions will begin to change to MVFR status likely after 03Z as ceilings begin to lower. Winds will shift and take a more southwesterly direction, and some gusts over 20 kts will be likely for KSGF overnight into tomorrow. Low level wind shear can be expected between 10Z-16Z Sunday, mainly for KSGF and KBBG. Tomorrow afternoon, winds will take a southerly direction, and gusts over 20 kts will be likely again for all sites. Cannot rule out light rain showers or drizzle late tonight into Sunday morning. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ SHORT TERM...Burchfield LONG TERM...Burchfield AVIATION...Schwartz