Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/03/21

Area Forecast Discussion
National Weather Service Bismarck ND
1004 PM CST Thu Dec 2 2021 .UPDATE... Issued at 1002 PM CST Thu Dec 2 2021 Snow has ended across the Turtle Mountains region. An area of very low clouds has now settled in across parts of Burke, Mountrail, Renville, Bottineau, and Rolette Counties. Tioga, which is near the edge of the low cloud deck, recently reported 2 mile visibility. Think that patchy fog may also be possible along higher terrain areas underneath the low clouds. The clouds and patchy fog will likely persist until the cold front moves through later tonight. Gusty winds have been observed upstream along the cold front. The 90th percentile of NBM membership along with the HRRR were utilized to increase forecast winds and gusts as the front moves across western and central North Dakota overnight. Peak gusts should be limited to around 35 mph. Periods of light rain continue along the South Dakota border, and will likely diminish or drift out of the state after midnight. UPDATE Issued at 636 PM CST Thu Dec 2 2021 A band of moderate snow has developed across Bottineau, Rolette, northern Pierce, and far northern McHenry Counties in response to mid level frontogenesis and isentropic ascent. Area webcams are showing snow-covered roads across Bottineau County, where the snow will soon be winding down. Areas along and north of Highway 2 and east of a line from near Bottineau to Towner can expect deteriorating conditions through 730 PM CST. A separate area of frontogenesis further to the south continues to promote areas of light rain along and south of Interstate 94. This rain is likely not as intense as some radar returns are making it out to be due to a low level layer of dry air, but at least sprinkles are reaching the ground. The chance for light rain will drift off to the south and east through the evening. A cold front will move from northwest to southeast across the state later tonight. The forcing from the frontal passage through a more saturated low level layer in north central North Dakota may provide enough lift to generate some light freezing drizzle and/or fog, but this is not a high probability outcome at this time. There is also a potential for gusty winds with the frontal passage, perhaps stronger than we are currently advertising. This potential will be examined closer for the next update. && .SHORT TERM...(This evening through Friday night) Issued at 251 PM CST Thu Dec 2 2021 We continue to watch two areas of precipitation this afternoon across western and central North Dakota. One area of light rain was located over the south, parked under enhanced 700 mb frontogenesis per the SPC mesoanalysis page. This light rain should continue through the afternoon, slowly diminishing from west to east as frontogenesis starts to wash out by this evening. Another area of light snow will continue to develop across the north central and northeast this afternoon through early evening. As a weak wave continues to ride down the broad ridge to our west, it will interact with a backdoor cold front as the drifts from the northeast into the north central. When all is said and done, we could end up seeing anywhere from a trace of snowfall to a half inch or so, mainly in and around the Turtle Mountains. It will be a bit cooler tonight with lows in the 20s and diminishing clouds. Surface high pressure moves in on Friday, leading to cooler high temperatures (but still normal to slightly above normal for this time of year) in the lower 30s to lower 40s. Clouds will be on the increase again Friday night in advance of the next shortwave trough with lows in the mid teens to lower 20s. .LONG TERM...(Saturday through Thursday) Issued at 251 PM CST Thu Dec 2 2021 Accumulating snowfall from Saturday morning through Sunday morning will be the big story for the long term forecast period. The upper ridge to our west will continue to flatten on Saturday as the aforementioned shortwave trough approaches. As this wave passes over the Northern Rockies, we will see a low develop under the influence of the right entrance region of one upper level jet streak and the left exit region of another. Precipitation will enter the west Saturday morning and spread north and east through the day and night as the low approaches the Montana/North Dakota border towards Saturday evening. Models are in good agreement on the dynamics: strong frontogenesis to the north and northwest of the low overlapping strong upper level Q-vector divergence and steep midlevel lapse rates. All of this points to a classic heavy banded snowfall setup somewhere across northern or central North Dakota. Along and south of this frontogenetical band, some negative EPV is also likely so a convective element may present itself as well. The big question and main source of uncertainty remains the track/location of the low/band as the band could be relatively narrow. In previous days, models had been settling on areas along and north of Highway 2 but there has been a trend in the ensembles to nudge the band a bit more south. While the northern third of the state is still most favored for the heaviest snowfall, a further south solution cannot be ruled out. The best bet for accumulations will be north of Interstate 94. Expect moderate to heavy snowfall to develop wherever the band does setup. Several inches of snow are possible under this band and areas under the heaviest part are likely to see 6 or more inches before the low moves out. We did discuss the potential for a Winter Storm Watch but chose to hold off given the exact placement of the band will likely change multiple times between now and the event. For now, will communicate the potential in the Hazardous Weather Outlook, a Special Weather Statement, and social media messaging. But, headlines will likely be needed at some point as confidence grows. Behind the low, winds will increase out of the northwest and become gusty Saturday night and Sunday. Some lingering light wrap around snow will be possible Sunday. Any fresh snow that has fallen or is still falling will blow around, causing visibility reductions and drifting snow. A Wind Advisory will also likely be needed at some point Sunday for at least the south where the models are showing the strongest pressure rises and steepest lapse rates. Another weak wave will move through Sunday night, possibly bringing with it some more light snow, before high pressure moves in on Monday. Monday morning lows will be chilly with double digits below zero possible across the north. Wind chills could dip as low as 25 below here. Afternoon highs will struggle to rise much above zero northeast, and up into the mid 20s southwest. Another frigid night is on tap Monday night. We will likely see our typical baroclinic zone in place across the region with northwest mean flow aloft through the rest of the period (cold northeast and milder southwest), and the NBM depicts this well with large high and low temperature spreads of its members through Thursday. The next best chance for some more light snow will be Monday night into Tuesday morning. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 1002 PM CST Thu Dec 2 2021 A cold front moving from northwest to southeast across North Dakota later tonight could bring a period of MVFR ceilings and gusty northwest winds. The probability of MVFR ceilings is highest at KMOT. Clearing skies and northwest winds around 10-15 kts are expected for Friday. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Hollan SHORT TERM...ZH LONG TERM...ZH AVIATION...Hollan
Area Forecast Discussion
National Weather Service Caribou ME
922 PM EST Thu Dec 2 2021 .SYNOPSIS... The low will track north of the area tonight into Friday bringing a strong cold front across the region. Canadian high pressure will build later Saturday into Sunday. Another low will approach and track north of the state on Monday. A cold front will push through Monday night with high pressure returning on Tuesday. && .NEAR TERM /THROUGH FRIDAY/... 9:20 PM Update...Forecast remains on track with bands of rain moving east across the area. A closer look at mesoscale forecast models is revealing a small but shortwave trough coming through in the early morning as much colder air begins to surge in. This could bring a burst of snow around sunrise Friday morning. Added a brief period of numerous snow showers to the early morning. Tonight...Warm/occluded front will lift n of the region tonight w/the warmer air streaming all the way to the northern border w/snow or mixed precip going to rain. Not expecting heavy rain as precip has been generally light under-performing the expected amounts. Radar had the first batch of precip lifting across northern and eastern areas this afternoon w/another set of precip apchg western areas lifting ne w/the warm front. That batch of precip in the form of rain will lift up across thew region. Adjustments were made to rainfall amounts to go a bit lower than previously expected for early evening. However, there is a llvl jet moving into NYS, which could enhance rainfall amounts w/that second batch at it lifts ne into the late evening. This in turn could enhance rainfall as it moves through the region into late evening. Given the latest setup w/the cold front still well back across Ontario and NYS, warmer air looks like it will hang in longer into daybreak as shown by 12Z GEM The GEM has been consistent over the last 3 runs w/hanging the colder air back, which is now backed up by the HRRR and RAP. The bulk of the precip will lift into Canada by the wee hrs of Friday morning. The low temp tonight will be around 7 PM as temps will rise overnight. There will be some melting of the snow, which will lead to some fog formation into the late evening. For Friday, the vigorous cold front is set to move across the region during the morning hrs w/nw areas seeing temps falling off quickly by daybreak w/some snow showers and streamer action setting up. High temps will be hit early, most likely before 12 PM for most of the region, w/the coast being the last to see the sharp drop off in temps. That cold air will sweep across the region during the rest of the day w/temps falling back. Upper trof, NW flow and steep llvl lapse rates will allow for some shower and streamer activity to continue right into mid afternoon before the column starts to dry out. The GEM depicts the streamer action quite well as does the 12Z NAMNEST. Another item to point out is those steep lapse rates combined w/the dropping temps, and strong pres gradient will lead to some wind gusts closing in around 40 mph, especially across the higher terrain. This will lead to some lower vsbys, blowing snow at times and sporadic power outages. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... Fri night expect strong gusty winds to slowly dissipate during the night but with the pressure gradient still tight expect gusts 20-25mph through much of the night. Despite the winds the air mass is very cold with 925-850mb temps -13C to -16C advecting into the area on northwest flow aloft. NOAA Hysplit backward trajectories show this air mass originating from the Arctic region of far northern Canada. So despite the winds expect low temperatures Sat AM to be around 0F in the North Woods, Single Digits to low teens across the northern 1/2 of the FA with Teens to near 20F from Bangor region to the coast. Wind chills Fri night into Sat AM will be running -15F to -5F across the northern zones, +5F to +10F in southern zones. Saturday will feature a weak disturbance approaching from the west with a weak cold front. Sunny start to the day with increasing clouds with a weak front but a coastal system well offshore may squeeze out a few snow showers back across the Downeast coast. The weak front will spread snow showers into the North Woods during the evening then spread south and east through the night. Not expecting much in the way of accumulations with perhaps a Dusting in spots. Another cold night with a reinforced shot of cold air originating from the Arctic region of Canada. Lows 0-10F north with 10-15F from Bangor to interior Downeast with around 20F right at the shore. Sunday will feature high pressure setting up over southern New England which is in very good agreement with latest GFS/ECMWF and Canadian ops runs. Highs running 5-10 degrees below average area wide partly sunny skies resulting in highs mid to upper 30s in southern zones and low to mid 20s across the north. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Sun night the high pressure will slowly drift east of the Gulf of Maine waters. A warm front will lift northward through the night across the state. As precip develop after midnight expect cold air damming intially so light snow will develop from the Bangor region northward into the Crown. It is likely the warm air shoots inland across coastal areas by the time precip starts. The warm front will push well north of the St. John Valley by afternoon with warm air surging north and all areas turn to rain. Models are in very good agreement with the low pressure tracking north well into Quebec. A large slug of high PWATs surge north so expecting gusty southerly flow and moderate to perhaps brief heavy rain. Given the cold ground and highs in the low 50s across the south and mid to upper 40s north expect patchy fog to develop. Precip will slowly taper but colder air will push east as a strong cold front clears the state. Rainfall totals generally 0.5-0.75" possible and perhaps some snow accumulations on the backside. High pressure settles over the Mid Atlantic and the pressure gradient tightens up so expect breezy westerly winds on Tuesday. Partly to mostly sunny skies but expecting upslope clouds across the North Woods. Highs will be 20-25F cooler than Monday back into the 20s to low 30s. High pressure looks to shift east Tue night and another system develops over the Mid Atlantic states. There is significant differences in the operational runs and ensemble members where this storm tracks. For now opted to take a blend resulting in a chance to likely snow with the best shot of precip in the southern 2/3rd. This could produce a decent accumulating snow if the track remains over the Gulf of Maine but the upper level phasing will be the key. As the system departs east expect a chance of snow showers but temperatures remain below average. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... NEAR TERM: IFR/LIFR into late evening w/rain becoming MVFR LATER tonight w/rain going to a period snow by daybreak for KFVE. S winds 10-20 dropping back to around 10 kt later in the evening, and becoming SW. LLWS tonight as winds around 1500 ft could reach 40 kt. For Friday, W wind 10-20 kt in the morning becoming NW 15-25 kt w/gusts to 35 kt, especially across the higher terrain such as KFVE and KCAR. MVFR cigs at times w/vsbys dropping down to IFR times in snow showers and gusty winds. SHORT TERM: Fri night...VFR. W winds 15-25kts. Sat...VFR. W winds 5-15kts. Sun...VFR/MVFR. SW winds 5-10kts. Mon...MVFR/IFR cigs/vsby w/ LIFR possible in the afternoon. Snow changing to Rain at all sites. S winds 15-25kts. LLWS possible. Tue...MVFR cigs early becoming VFR. W winds 15-25kts. && .MARINE... NEAR TERM: Gales in place including the intra-coastal zones through Fri evening. S wind 20-25 tonight becoming SW late and increasing to 25-30 kt w/higher gusts. Seas climbing to 8-9 ft. For Fri, SW winds become WNW and increase to 30-35 kt w/gusts hitting 40+ kt due to the strong pres gradient. Seas could hit near 10 ft before dropping back to 7-8 ft late in the day. SHORT TERM: Gales weaken to SCA level gusts through Sat daybreak. Wind gusts fall below SCA levels through the morning and remain below SCA through early Mon AM. By Mon late morning southerly Gales likely return with another strong storm system. Seas subside to between 2 and 4 feet through Sat. Seas become 1-3ft for Sun with seas building to 6-10ft by Mon afternoon. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Gale Warning until 10 PM EST Friday for ANZ050>052. && $$ Near Term...Hewitt/MCB Short Term...Sinko Long Term...Sinko Aviation...Hewitt/Sinko Marine...Hewitt/Sinko
Area Forecast Discussion
National Weather Service Cleveland OH
906 PM EST Thu Dec 2 2021 .SYNOPSIS... A cold front will cross the area this evening ushering in a much colder airmass. High pressure will briefly build across the Ohio Valley and lower Great Lakes by Saturday before a strong low pressure system and associated cold front progresses into the region Sunday into Monday bringing gusty winds. && .NEAR TERM /THROUGH FRIDAY NIGHT/... 900 pm update... We made some minor adjustments to the hourly POP forecast from this evening through Friday morning. We increased POPs slightly for the primary Snowbelt areas of far NE OH and NW PA overnight for some lake effect snow showers overnight into early in the morning. Some light accumulations up to localized inch of snowfall could be possible. Otherwise, the rest of the near term forecast is in good shape at this time. Previous discussion... A secondary cold front that will be responsible for bringing the true airmass change is currently dropping southward onto Lake Erie. Current surface analysis depicts this boundary well showing strong 3 hour pressure rises behind the front and winds veering from WSW to WNW. Expect the boundary to progress across the region quickly this evening with temps falling through the 40`s. Moisture along the front is limited with NAM and RAP forecast soundings showing significant mid-level dry air, but kept slight chance PoPs for a few light showers in NW PA this evening where moisture is a bit better. The flow will become increasingly NW in the cold air advection overnight with 850 mb temps falling to -6 to -9 C through Friday morning with the coldest being over the eastern basin of Lake Erie. This will set up a minimal lake response with about a 14 C lake to 850 mb deltaT and 19 C lake to 700 mb delta T. However, the aforementioned shallow moisture and weak instability will keep lake-effect precip light. HREF guidance suggests a Lake Huron fetch into eastern Erie County PA for a few hours in the 05 to 12Z timeframe, so kept chance PoPs for light rain and snow in that area through the night. On Friday, a fast moving mid-level vort max and associated 150 knot 300 mb jet streak will slide across the lower Great Lakes and Upper Ohio Valley. The resultant upper divergence and PVA and isentropic upglide will squeeze out a band of light precipitation starting over NW Ohio during the mid morning hours expanding through NE Ohio and NW PA during the afternoon and evening. Moisture is once again limited, so QPF will only be a few hundredths of an inch. The main impact with this feature will be to create overcast skies and scattered light rain/snow or drizzle leading to a cold, damp day. Behind this feature, renewed NW flow returns Friday night. Soundings show a lot of boundary layer shear, so think any lake response will be very limited, but HREF guidance suggests a little lake enhancement over NW PA. Kept slight chances of light rain/snow, but we could very well end up dry. Went a degree or two colder then NBM/CONSSHORT for temps Friday given the clouds and precipitation. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A few lingering lake effect snow showers may continue for NW PA into the beginning of the near term, but should diminish through Saturday as high pressure and a much drier airmass move southeast across the area. Little to no accumulation with these remaining showers is expected for Saturday. The high pressure and dry conditions will persist through Saturday night before moving off the New England Coast ahead of an approaching low pressure system. High temperatures on Saturday will be in the low to mid 40s with overnight lows in the mid to upper 20s. On Sunday, a low pressure centered over the northern Plains will continue to strengthen with strong upper level support as it approaches the Great Lakes region. South-southwest winds will increase WAA and moisture over the area as a warm front moves north. Winds are expected to steadily increase across the area beginning Sunday afternoon/evening into the long term period as a result of the pressure gradient becoming stronger with the deepening low. The track of the surface low continues to look very favorable to sustained winds near 20 mph, with elevated wind gusts of 40 mph or greater Sunday night into Monday. This will need to continue to be monitored for the potential of a wind advisory. During the day on Sunday, most areas should remain dry, although areas of NW OH may start to see rain showers late afternoon. These rain showers will develop along and ahead of a strong cold front, moving west to east Sunday night. Current thinking is that much of the precipitation should remain primarily as rain as 850 mb temperatures remain above freezing. Only areas that may see some snow mix in would be the higher elevations in NW PA and NE OH. High temperatures will be above average, reaching the low to mid 50s. Overnight lows will be in the low to mid 30s. && .LONG TERM /MONDAY THROUGH THURSDAY/... A few lingering showers may persist across the eastern counties as the cold front departs to the east near day break on Monday. The low is forecast to be centered north of the Great Lakes, allowing for primarily west winds to persist into Tuesday. Strong winds remain a concern through Monday evening as much colder air surges southeast across the area. 850-mb temperatures are expected to decrease to -8 to -12C. This pushing across Lake Erie will likely allow for lake effect snow to develop and impact the snowbelt, which will persist until the winds shift to become southwesterly on Tuesday. The biggest challenge with this lake effect set-up is how far inland the wind will push snow showers. In conjunction with much colder air aloft, high temperatures at the surface on Monday will be in the 40s, dropping into the 30s on Tuesday. An active pattern persists over the area, with numerous shortwave troughs modeled to move over the Great Lakes region through Thursday. A low pressure system moving north from the Gulf Coast could bring widespread synoptic snow Tuesday night into Wednesday as the area will lie on the northern side of the low, but any change in track of the low will adjust precipitation chances and type. This will need to continue to be monitored. Temperatures Wednesday and Thursday will return to near normal. && .AVIATION /00Z Friday THROUGH Tuesday/... VFR to MVFR conditions are expected for the next 24 hours. Mainly VFR is expected tonight. An area of light rain/snow will develop across western Ohio by 12z Friday with MVFR ceilings and visibilities. Have this area of MVFR impacting TOL and FDY and moving close to CLE and MFD during Friday morning. This precip should decrease by midday and not really impact terminals in NE OH or NW PA. West to northwest winds will slowly decrease this evening and overnight to around 5 to 8 knots. Winds will become light and variable by Friday morning and stay on the light side during the day. Outlook...Non-VFR possible across NE OH/NW PA with lake clouds on Saturday. Non-VFR likely again Sunday into Monday with rain and low ceilings. Non-VFR possible for the Snowbelt region with lake effect snow showers Monday into Tuesday. && .MARINE... A very active weather pattern across the Great Lakes will keep hazardous marine conditions around for the bulk of the forecast period. Currently, low pressure centered over Quebec has resulted in gale force winds from the northwest over the eastern basin of Lake Erie, with waves of 6 to 8 feet. As a result, a Gale Warning remains in effect until 7 PM this evening. The central and eastern basins have sustained winds of 15-20 knots, building waves along the shore to 2-5 feet, locally higher, maintaining Small Craft Advisory criteria. The major change in headlines with this update is the cancellation of the Low Water Advisory for the western basin. With onshore flow and gradually weakening of winds into the evening, waters levels are currently 35 inches above low water datum and are expected to continue to rise, not reaching the critical mark of 18 inches above low water datum. Conditions will gradually improve through the evening and overnight hours as high pressure builds across the area for Friday. Another low pressure moves across the region on Saturday, which will bring marginal Small Craft conditions to the central and eastern basin. Another weak high pressure will move in on Sunday before a much stronger system impacts the Great Lakes on Sunday night into Monday. The strongest impacts will be on Monday, with increasing confidence in gales across all basins of Lake Erie. This system will need to continue to be closely monitored. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...Small Craft Advisory until 7 AM EST Friday for LEZ145>149. Small Craft Advisory until 10 PM EST this evening for LEZ142>144. && $$ SYNOPSIS...Garuckas NEAR TERM...Garuckas/Griffin SHORT TERM...Campbell LONG TERM...Campbell AVIATION...Griffin MARINE...Campbell
Area Forecast Discussion
National Weather Service Goodland KS
850 PM MST Thu Dec 2 2021 .SHORT TERM...(This evening through Sunday Morning) Issued at 127 PM MST Thu Dec 2 2021 To begin the short term period, the northwest flow that has been present has flattened out. A strong inversion was present this morning with RAP soundings indicating that it was as strong as 20 degrees C while the surface was just above 0 degrees C. As of mid day the inversion has been slowly eroding allowing the warmer air to make it to the surface. As of 12p MT all of our AWOS/ASOS stations were above 70 degrees Fahrenheit; also interesting to note that Hill City had broken their record high temperature at 11am CT. The temperature forecast still shows most if not all of the area warming into the mid to upper 70s with perhaps a few locales making it into the 80s as there is till another roughly 3 good hours of diurnal heating remaining. Into tonight, low level flow becomes more SW in the vicinity of a trough. A cold front moves N to S over the area overnight into Friday morning in association with the eastward propagation of the trough. Winds will shift to the NNW with the passage with winds picking up to around 10-15 knots. Overnight lows look to fall into the mid 30s to low 40s over the area. Friday, winds will increase to 10-20 knots throughout the morning with gusts of 25-35 knots possible, with the strongest winds mid to late morning when the surface pressure change looks to be the strongest. The stronger echelon of the wind gusts will be dependent on if sufficient CAA will be available to help mix the stronger winds to the surface. Temperatures look to be cooler, but still above normal in the upper 50s to mid 60s over the area. Overnight lows will be cooler in part to radiational cooling as widespread 20s are expected over the area. Saturday, cooler temperatures than Friday are expected with the entire area seeing 50s. Winds will remain breezy as well as pressure gradients tighten ahead of a developing surface trough over the northern Rockies. Sustained southerly winds of 10-20 knots with gusts up to 30 knots are currently expected. Winds begin to turn towards the north overnight Saturday as another cold front begins to move into the area. Saturday night lows look to fall into the lower 30s with clouds on the increase. .LONG TERM...(Sunday through Thursday) Issued at 143 PM MST Thu Dec 2 2021 This part of the forecast will be dry for the most part, except for low chances for precipitation Tuesday as a cold front moves through. Due to the upper level northwest flow shifting more over the forecast area, the light wind days will be fewer than what has happened recently. With the ridge shifting to our west, cooler air will be allowed into the forecast area, bringing temperatures closer to normal. Sunday a cold front will move through. Behind the front north winds will increase and temperatures will fall through the day. The strongest winds will likely be in the morning, then gradually decline through the day as the stronger winds shift east. Due to the majority of the lift with this front being over the Midwest with the trough, am not expecting any precipitation with the frontal passage. Sunday night will be the coldest temperatures that have been seen in a while. A surface high will move through, leading to favorable radiational cooling (as long as clouds are few and far between). This will cause lows to fall well into the teens. With dew points in the single digits, wouldn`t be surprised if lows end up being closer to ten degrees for most of the area. The next cold front to move through will be Tuesday. Like Sunday, temperatures will fall through the day behind the front. The upper level pattern looks favorable for precipitation potential with the passage, except for the potential split flow setup. The GFS clearly shows the flow splitting over the forecast area, while the ECMWF is much less suggestive but still evident. This is the only day for precipitation chances for this week, but am doubtful anything more than a few hundredths of an inch of precipitation will occur due to the split flow potential. A reinforcing round of cold air will move in Tuesday night. With dew points in the mid teens, the current low forecast should see little change. Toward the end of the week another trough moves onshore, then deepens over the Desert Southwest. This will cause a ridge to form over the Plains. This will lead to precipitation for the Plains, the question is where at this point. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 850 PM MST Thu Dec 2 2021 KGLD...VFR conditions through the period. A west wind near 10kts at taf issuance will veer to the northwest at similar speeds through sunrise as a cold front moves through. During the day Friday north winds gusting around 25kts are expected. For the evening hours winds subside and steadily veer to the east at speeds around 5kts. KMCK...VFR conditions through the period. A west wind up to 10kts at taf issuance will veer to the north at 11kts through sunrise as a cold front moves through. During the day Friday north winds gusting around 25kts are expected. For the evening hours winds decrease below 11kts while veering to the east. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...TT LONG TERM...JTL AVIATION...99
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
807 PM CST Thu Dec 2 2021 .UPDATE... Issued at 807 PM CST Thu Dec 2 2021 The forecast appears to be on track. As expected, a band of showers is developing from southern South Dakota to central Minnesota associated with increasing mid-level frontogenetical forcing and upper-level diffluence in the right entrance region of an elongated jet streak over the northern Great Lakes. Light radar returns have also started to appear in northeastern Iowa in response to increasing low-level frontogenetical forcing ahead of an approaching but subtle mid-level wave, which leverages confidence in the forecast scenario outlined in the short term discussion below. A quick look at the incoming 00Z guidance does not provide any additional insight into how the low-level thermal profile may look about 6 to 12 hours from now, with forecast hrrr profiles literally right on the line between rain/snow at Waukegan. Perhaps one factor that may tip the scales toward rain will be modest low-level advection off the warm and moist waters of Lake Michigan, which may anchor wet bulb temperatures above freezing. However, it`ll still be way too close for comfort and we would not be surprised at all if a narrow band of slushy/wet snow accumulates from Sharon, WI to Lake Forest, IL. Strong frontogenetical bands of precipitation often have a sharp southern edge, and indeed areas along and south of a line from Rockford to Chicago look to remain dry through the next 12 hours. Updated products will be sent shortly. Borchardt && .SHORT TERM... Issued at 252 PM CST Thu Dec 2 2021 Through Friday night... The primary forecast note for the short term is the low probability of a short burst of snow late tonight/very early Friday morning for mainly far northeast Illinois. Otherwise, the main message is cooler Friday but still above normal. Sunny, breezy, dry, and mild conditions prevail this second day of Meteorological Winter, as a couple 60 degrees highs have shown up south of I-80. Winds will drop off quickly after sundown as a 1017 mb surface high pressure ridge shifts over the area this evening. In general, this will favor a good radiational cooling evening, especially as cooler 925 mb temperatures have oozed into the area from the north. However, mid-level clouds that have their front edge pushing across southern Minnesota this afternoon will spread over locations north of I-80 this evening. This should slow the diurnal drop there and that does become somewhat key as the best chance for late night precipitation is near the Wisconsin state line. Have lows fading into the mid 30s in this area, with dew points recovering some from current mid 20s to the upper 20s by late tonight. A 135+ kt jet stream extends from southern British Columbia all the way through the Great Lakes, with a 150+ kt maximum moving from the North Dakota/Canada border to Lower Michigan by Friday morning. As that jet max translates, it will send a very low amplitude mid-level wave toward southern Wisconsin and, more noteworthy, increase a lower to mid tropospheric frontogenetic (f-gen) circulation. Guidance today has continued the trend of an increasing signal of enough saturation with this for QPF clipping at least the far northern Chicago metro. While the overlapping signal in guidance remains better for north of the state line and still fairly large spatial uncertainty on the southern periphery, there was enough of a high-resolution signal to further increase PoPs for Lake and McHenry Counties and a slight boost in adjacent areas. The main timing looks to be ~2-7 A.M. Deterministic soundings from the NAM, GFS, RAP, and HRRR (irregardless of whether they show precipitation) do show marginally warm enough profiles for melting aloft. Further below, the profiles in the boundary layer are also marginal, and some dependency on evening trends as noted earlier. So rates of any precipitation will likely be key in changeover and impacts, and that will be tied to enough well-aligned, negative saturated EPV (instability) on the warm side of the circulation above the f-gen. In general the models do show that, so feel that if there is an established f-gen band into far northern Illinois, it likely will turn precipitation type over to snow. Given the time of day, some minor accumulations would be possible with this including on roads. The potential for this to occur to impacting levels still remains on the less likely side of the spectrum of outcomes. The evening shift will keep a close eye on it though to see if trends support an increasing chance of impacts. Any early morning precipitation will be shifting out fairly quickly. Clouds though will probably linger into the afternoon in northeast Illinois and far northwest Indiana, keeping highs south of 50. But elsewhere, should be able to top that again on Friday. MTF && .LONG TERM... Issued at 224 PM CST Thu Dec 2 2021 Saturday through Thursday... A more active pattern is on the horizon with a couple storm systems requiring close monitoring late this weekend and again during the middle of next week. Strong WNW aloft will remain over the Great Lakes region on Saturday as surface high pressure rapidly advances from southern MN to southern Lower MI through the day. Seasonable temps in the low 40s under mostly sunny skies are expected. Modest mixing into an exceptionally dry airmass aloft should allow dew points to fall into the teens to possibly locally single digits above zero across northern Illinois. Extensive low-level WAA will commence Saturday evening and continue well into Sunday ahead of broad low pressure shifting east from the central Great Plains. Initial low-level trajectories from the southeast will not be ideal for moisture advection into the area until significant veering occurs toward daybreak Sunday. Therefore, there remains low confidence that sufficient moisture will advect into the area to support precip by daybreak Sunday. However, the substantially dry low-levels will result in surface wet-bulb temps remaining below freezing across much of the area potentially into mid-morning. Given an increasingly warmer profile aloft, initial precip will be primarily liquid, indicating at least a low risk of light freezing rain around daybreak Sunday. Air and wetbulb temps will quickly rise through the morning, supporting all rain beyond mid-morning. An expanding rain shield will then affect much of the area through the day and across the southeast half into the evening. Precip will end late Sunday evening as a mid-level dry slot advects into the area, but scattered snow showers will likely affect northern Illinois late Sunday night into Monday morning as the upper- trough brushes the area to the northeast. Strong winds NW winds gusting to 30 mph combined with modest low-level lapse rates support the potential for some briefly heavier snow bursts. Dry conditions should prevail Monday afternoon and night before low pressure developing across the central CONUS brings unsettled weather to the region Tuesday into Wednesday. Phasing issues with a split trough exiting the western CONUS on Tuesday support a varying range of solutions, from the potential for some accumulating snow in the CWA to a N/S split of most precip around much of Illinois. Kluber && .AVIATION... For the 00Z TAFs... Forecast concerns for the terminals... *Increasing cloud cover with VFR ceilings tonight. *Chance for a mix of light rain/snow showers late tonight through Friday morning. *Light and variable winds Friday. High pressure resides over the area this evening which is keeping the terminals under mostly cloud-free conditions with the exception of a few cirrus clouds overhead. However, a weak frontal boundary is advancing towards the area which will bring in more cloud cover overnight tonight with VFR ceilings that will linger through the day on Friday. Along with the clouds, the frontal boundary will also bring the chance for light rain/snow showers across northeastern Illinois with the best chances for precipitation being along the Illinois-Wisconsin border. However, sufficient forcing with the boundary may allow showers to move as far south as the terminals after midnight and lingering through daybreak. Guidance suggests that rain showers are likely to be the dominant precipitation type as forecast soundings look to remain just above freezing in the lower levels, but a slight shift in temperatures due to evaporative cooling would favor a few snow flakes mixing in. Winds will remain light and turn generally northeast overnight before shifting southeasterly after daybreak. Winds will remain less than 10 kts throughout the day on Friday with winds backing towards the east and northeast in the evening. Yack && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
National Weather Service Morristown TN
1022 PM EST Thu Dec 2 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... Passing high clouds across the northern valley and portions of southwest VA have kept diurnal cooling at bay over the last few hours, while in the southern valley temperatures are cooling nicely. Thus blended in a little HRRR tonight for temperatures which favored those trends the best. On that, am expecting some patchy fog in the river valleys tonight given cooling, thus such was added. No other changes needed/made with this update. CDG && .AVIATION... 00Z TAF DISCUSSION. VFR through the period at all sites with the possible exception of light patchy MVFR fog at TRI around daybreak per xover temp analysis and HREF probs, thus such was included via tempo. Otherwise, swly winds will gradually weaken through the evening/overnight as PGFs relax favoring light swly flow on Friday amidst SKC or high cirrus with some moisture advection late in the period from the southwest favoring increased sky cover after periods end. CDG && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 44 70 48 68 48 / 0 0 0 10 10 Knoxville McGhee Tyson Airport, TN 44 68 47 63 45 / 0 0 0 10 10 Oak Ridge, TN 42 66 46 62 45 / 0 0 0 10 10 Tri Cities Airport, TN 41 64 43 59 41 / 0 0 0 10 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$
Area Forecast Discussion
National Weather Service Pocatello ID
149 PM MST Thu Dec 2 2021 .SHORT TERM...Tonight through Sunday. Flat upper ridge remains in place with upper jet centered along the Canadian border, keeping East Idaho on the northern extent of high pressure across the Great Basin. Patchy fog is still possible overnight tonight into early Friday, and then again Friday night into Saturday morning. At this time, do not expect widespread visibility issues for the Snake Plain and surrounding lower elevation areas, especially those along waterways. Temperatures remain mild/above normal into Saturday, ahead of cold front that drops across the region during the day. This system may produce a few light showers across higher elevations to the north and along the Divide late Saturday into Saturday night, but accumulations look to remain minor. Of more concern is the winds associated with the front as the surface low steeps significantly as it moves through Montana into Wyoming. 700mb winds >50kts combined with strong mixing look supportive of winds approaching Wind Advisory late in the day, and continuing past sunset, and possibly past midnight as well. Higher elevations across the central mountains could take the brunt of the wind, but the amount of blowable snowpack even at higher elevations is a question. Winds should weaken after midnight, with cooler temperatures headed into Sunday. This frontal system looks like the prelude into a more unsettled work week, and some much needed precipitation. The Long Term discussion below has more details on the next system to arrive early in the work week. DMH .LONG TERM...Sunday night through Thursday. A fairly robust upper trough will work its way in from the northwest on Monday. The trough should cover the vast majority of the forecast area in rain and/or snow. Snow levels are coming in a bit lower than previous forecast, coming to valley floors early Tuesday morning. GFS is back to a split system as it passes through Idaho with the ECMWF keeping a more consolidated trough. As a result, ECMWF is a tad more progressive than the GFS; however, the end result from both solutions is similar. Snow amounts Monday and Tuesday will add up to an inch or less in the Snake Plain. Eastern Highlands should see about 7 to 10 inches with over 12 inches at the highest peaks along the WY border. Central Mountains will likely see 7 to 10 inches, and about 2 to 5 inches around pass levels. Another similar-looking weather system will drop in from the northwest on Wednesday, though model consensus is lacking right now. GFS again proposes a split system while the ECMWF again is more progressive and consolidated with the trough. Day 6 and 7 have chance to likely PoPs though with temperatures and snow levels supporting snow. Accumulations will be difficult to predict at this point as ensembles are vastly spread. Hinsberger && .AVIATION...TAF sites are mostly clear today as high pressure remains in control. Satellite imagery shows some fog/stratus in the Upper Snake Plain that the HRRR and HREF expand down the valley early tomorrow morning. HRRR visibility progs blanket IDA and PIH in dense fog in the morning, though NBM highly favors VFR conditions at both sites. Tough decision to make, as PIH/IDA could either stay VFR or be below airfield minimums for the morning. Keeping other sites VFR, but taking PIH and IDA to minimums. Hinsberger && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$