Aikyam-Lab/Synoptic-Bench huggingface dataset:
Specifically where the snow-sleet-freezing rain transition zone develops will dictate where greatest resultant p-type accumulations occur. As mentioned above, the greatest freezing rain impact is expected near the KS border where flat-ice accretion could approach three- tenths of an inch. It still appears that a mid-level dry slot will overspread the area from the west this afternoon, signaling a transition from snow to freezing rain or freezing drizzle.
Snow will develop over mainly northwest Indiana and southwest Lower Michigan and then change to sleet and freezing rain overnight. The precipitation will become just rain before Wednesday noon as surface temperatures rise above freezing. Main system precip will then arrive in the northwest after midnight where thermal profiles will feature pronounced warm nose around 900mb with sub-freezing surface layer resulting in small window of freezing rain before warm air advection brings entire column above freezing and quick change to all rain Wednesday morning. HREF means showing about a 4 hour window in NW CWA for freezing rain/ice accumulation with amounts a tenth of an inch or less.
Per several surface observation reports along with satellite imagery, updated suite of forecast products to mention patchy freezing fog through remainder of early morning hours.
The snow is expected to mix with and change to freezing rain for much of the area. North central Kansas and far southern part of Nebraska could have some sleet mixed in as well as the temperatures warm aloft this morning, but the surface temperature is still cooler. By afternoon, much of the area will have changed over to freezing rain.
A massive area of high pressure covering the entire Eastern United States, and down the Florida Peninsula and the adjacent Atlantic and Gulf waters will bridge over a disintegrating frontal boundary.
As the trof axis and associated vort max swing through SEAZ this morning and afternoon, expect additional valley rain and mountain snow showers to develop.
These areas have seen little cooling overnight with most locations currently sitting in the low to mid 20s. Cloud cover will likely stick around for much of northwest Montana and central Idaho today as high pressure keeps stagnation conditions across the area.
Currently, high pressure is centered over western Illinois. The high will move east today reaching western Pennsylvania by this evening. By tonight, a warm front will lift north across the region. Temperatures will be some 10 to 15 degrees warmer than currently with lows Wednesday morning in the 40s to lower 50s. On Wednesday, a cold front will start moving into western Arkansas and will approach the Mid-South. Temperatures will be warmer on Wednesday with highs in the upper 50s to mid 60s.
High pressure will bring mostly clear skies to most locations through this afternoon. An upper disturbance with weak surface cold front will continue moving south and east away from the area, with high pressure and drier air resulting in mostly clear skies and cooler temperatures for this afternoon. Winds begin to increase as early as this morning across the immediate Rocky Mountain Front and foothills as mid- and upper-level northwesterly winds increase aloft with upper ridging building in from the west.
At the surface, high pressure resides across the Upper Midwest with low pressure across Colorado extending north into eastern Wyoming. Behind the surface inverted trof, gusty northwest winds will develop this afternoon, blowing and drifting the freshly fallen snow across the SD plains through early evening.
315 AM CST Tue Dec 29 2020 GOES water vapor imagery showing a deep mid-level low churning through the Four-Corners area of the southwest CONUS while a fairly strong trough was pushing east through Canada. This trough will help to eject that southwest low northeastward toward the area while both phase with time. High pressure builds in Wednesday night for clearing skies and lows dipping down into the single digits above zero.
A large area of radar returns/snowfall extended from Nebraska into central/western South Dakota early this morning in advance of a short wave trough. As the lift in advance of the short wave trough moves slowly northeast through the day along with waa, these radar returns/snowfall will also expand across all of our cwa through the late morning.
As the system dives south, slight ridging builds behind the low bringing above seasonal temperatures and dry weather to the area for the weekend.
Also included a mention of freezing drizzle in far southern MN for a brief period this evening as we lose saturation in the dendritic layer.
High pressure builds into the northern plains this afternoon which will bring some gusty winds. Longwave trof remains over North America, with a ridge along the west coast.
Patchy dense fog/freezing fog has largely dissipated with the exception of a few river valleys towards southwest North Carolina. They're breaking up as the descend from the higher terrain so will keep the VFR timing, but will need to watch that. CD Chattanooga Airport, TN 52 40 55 44 61 / 0 0 0 20 60 Knoxville McGhee Tyson Airport, TN 48 33 55 44 59 / 0 0 0 20 40 Oak Ridge, TN 48 35 55 45 58 / 0 0 0 30 50 Tri Cities Airport, TN 44 29 52 38 60 / 0 0 0 20 40.
433 AM CST Tue Dec 29 2020 GOES water vapor imagery showing a deep mid-level low churning through the Four-Corners area of the southwest CONUS while a fairly strong trough was pushing east through Canada. This trough will help to eject that southwest low northeastward toward the area while both phase with time. High pressure builds in Wednesday night for clearing skies and lows dipping down into the single digits above zero.
343 AM CST Tue Dec 29 2020 A large area of radar returns/snowfall extended from Nebraska into central/western South Dakota early this morning in advance of a short wave trough. As the lift in advance of the short wave trough moves slowly northeast through the day along with waa, these radar returns/snowfall will also expand across all of our cwa through the late morning.
600 AM CST Tue Dec 29 2020 (Today and tonight) mostly cloudy and windy today as a lee trough develops in West Texas, bringing strong south winds and moisture from South Texas. A very strong cold front will move into the the Big Country late tonight, mainly after 3 AM, and should be along a Iraan. The NAM and GFS model focus most the highest chance for showers and thunderstorms in the Big Country after midnight, with the storms developing along and behind the cold front in the Concho Valley 3 to 6 AM. Temperatures will be mild overnight until the cold front pushes through, with the Big Country falling into the upper 30s around sunrise.
Can't totally rule out a few slick spots on bridges across far northwest Oklahoma, but impacts should be very limited due to marginal air temperatures, latent heat of fusion, and warm antecedent conditions. Conditions should improve with a slow rise in temperatures to above freezing by late morning. Temperatures in far northwest Oklahoma are currently at or just below freezing with wetbulb temperatures right around 30 degrees. Southeasterly surface flow should bring wetbulb temperatures above freezing in northwest Oklahoma between sunrise and mid morning, allowing precipitation to transition back to rain. A cold front will enter northwest Oklahoma late tonight as the upper level low approaches.
With a secondary wave and cold front bringing some light snow to the northern tier of the CWA, and little snow expected in the southwest. Winds behind the mentioned cold front may also be a touch breezy at times today through tonight. The general pattern looks to see weak ridging at times, with zonal flow when these weak ridges break down. This will provide for a generally dry pattern, while the weak ridging brings warming temperatures at times.
Scattered rain and snow showers will continue through early this evening, most frequent over the high terrain.
Upper trough axis lays roughly along a line from Douglas to Grand Junction this morning. Still seeing snow in downstream METARS across northern and northwestern Colorado associated with the upper trough. Ridging replacing the low pressure with increasing Craig to Casper 850/700mb height gradients.
12Z upper air analysis places an upper level ridge over Florida while southwest flow aloft is occurring over the Southern Plains and into the Lower Mississippi Valley. Meanwhile, at the surface a warm front extends from Southern Mississippi/Alabama back into the Red River Valley. Currently, high pressure is centered over western Illinois. The high will move east today reaching western Pennsylvania by this evening. By tonight, a warm front will lift north across the region. Temperatures will be some 10 to 15 degrees warmer than currently with lows Wednesday morning in the 40s to lower 50s. On Wednesday, a cold front will start moving into western Arkansas and will approach the Mid-South. Temperatures will be warmer on Wednesday with highs in the upper 50s to mid 60s.
103 PM MST Tue Dec 29 2020 Skies have cleared this afternoon in the wake of a cold front across northeast Montana.
There was a couple hours along the highway 84 corridor with areas of dense fog, but it quickly burned off.
Isentropic lift will be strong as a LLJ increases to 50 kts and becomes directed perpendicular to the low-level isotherms. Destabilization by the warmer waters of the lake may also allow some of the stronger winds to mix down, creating some blowing and drifting and lower visibility at times in lakeshore areas. Wednesday Night Through Tuesday An upper-level long wave trough extending down over the western U.
Scattered showers will linger through early this evening, most frequent over the high terrain.
Becoming Warmer than Normal through Late Week. Onshore winds will remain more notable along the coast and beaches overnight as high pressure fully extends itself across the eastern CONUS.
A long wave trough, associated with the low to the northwest, will deepen through the day and eventually develop a closed low in SWTX/NEMX.
As large scale ascent from the trough approaches the area the front will progress eastward into muggier conditions and collide with an already established warm front settled across the CWA. Heavy on the heels of the Pacific front a Canadian cold front will storm southward through the FA overnight.
1117 AM MST Tue Dec 29 2020 Line of light snow showers is currently draped across the High Plains from Chadron NE to Cheyenne WY and slowly moving towards the southeast. Upper trough axis lays roughly along a line from Douglas to Grand Junction this morning. Still seeing snow in downstream METARS across northern and northwestern Colorado associated with the upper trough. Ridging replacing the low pressure with increasing Craig to Casper 850/700mb height gradients.
High pressure will build across the region today in the wake of a departing storm system.
1026 AM CST Tue Dec 29 2020 Ceilings continue to clear rapidly along and north of a returning warm front across our airspace this morning. /issued 939 AM CST Tue Dec 29 2020/ Returning warm front very ill defined this morning but appears to be located near a Sulphur Spring, Texas to Mansfield, Louisiana to Natchez, Miss line as of 15z. Some patchy dense fog has formed just to the north of this feature across NW LA but that should quickly lift with sufficient mixing through the morning into the afternoon hours as the warm front continues to slowly lift northward.
The weak frontal boundary that sagged southward over the Gulf overnight will shift northward today as warm front. Breezy conditions will develop along the coast Wednesday as the surface gradient tightens in response to an approaching cold front. The upper level ridge axis over the area also shifts east of the area today providing for a southwesterly flow aloft and allowing more cloud cover to gradually advect into the region. Temperatures will continue to trend considerably warmer than climatological norms with overnight lows ranging from the mid 40s at cooler locations to low to mid 50s along the coast.
Ridging builds into the region for Wednesday/Wednesday night with the potential for impacts very low. A ridge sets up across much of the Northern Plains through the end of the week and into the weekend. Areas in the Southern United States and in the Midwest may see chances for more wintry precipitation as a trough moves into those regions later this week. A split pattern with a ridge in the north and a deep trough in the south tells a story of a dry Northern Plains and potential for wintry precipitation for areas in the South and Midwestern United States.
Added potential for thunderstorms to the sites late tonight into Wednesday morning as a cold front moves through the region.
Per several surface observation reports along with satellite imagery, updated suite of forecast products to mention patchy freezing fog through remainder of early morning hours. VFR will continue today as dry high pressure extends from the Ohio Valley into Middle Tennessee.
/issued 1026 AM CST Tue Dec 29 2020/ Ceilings continue to clear rapidly along and north of a returning warm front across our airspace this morning. /issued 939 AM CST Tue Dec 29 2020/ Returning warm front very ill defined this morning but appears to be located near a Sulphur Spring, Texas to Mansfield, Louisiana to Natchez, Miss line as of 15z. Some patchy dense fog has formed just to the north of this feature across NW LA but that should quickly lift with sufficient mixing through the morning into the afternoon hours as the warm front continues to slowly lift northward.
The upper trough axis continues to push east across the state and will shift east of the state tonight.
259 PM CST Tue Dec 29 2020 Sfc trof will continue to slowly move east through tonight, as upper wave drops southeast toward the northern CWA. The influence of that wave aloft should help shove the sfc trof east. Energy lifting out of the southwest upper trof will gradually shift off to the east this evening, thus ending the accumulating snows from west to east through the evening hours. Overall, the extended looks to remain dry with just a weak mid level trough passage or two, nothing definitive.
205 PM CST Tue Dec 29 2020 The warm advection pattern that was responsible for the freezing rain this morning will push off to the east, with plain rain ending over south central Kansas this evening.
Patchy dense fog/freezing fog has largely dissipated with the exception of a few river valleys towards southwest North Carolina. BW Chattanooga Airport, TN 40 55 44 61 55 / 0 0 20 60 100 Knoxville McGhee Tyson Airport, TN 33 55 44 59 51 / 0 0 20 40 90 Oak Ridge, TN 35 55 45 58 49 / 0 0 30 50 90 Tri Cities Airport, TN 29 52 38 60 48 / 0 0 20 40 90.
Dry conditions expected the remainder of the day and overnight with high pressure in control. Any lingering snow should be short- lived owing to the influence of building broad high pressure.
Strong and gusty southeast winds will persist ahead of a cold front that will through northeast Oklahoma overnight. Cold front will continue a southward progression during the day Wednesday with the heavier rain shifting into southeast Oklahoma.
This is robbing the dendritic growth zone from ice development and has lead to the transition to sleet, freezing rain, and freezing drizzle. Winds out of the WNW at 8-18mph will leave apparent temps even cooler.
Gusty winds to about 30 mph remain across the High Plains and the wind-prone areas of southeast Wyoming for areas of blowing snow, though even this looks limited across the Panhandle. May be able to drop the Winter Weather Advisories over the High Plains in the next few hours if webcams continue to reflect limited impacts from these wind gusts. This occurs in the wake of the trough now exiting east, as surface pressure gradients increase across the wind-prone corridors and subsidence increases as well.
Even the northwest zones reached the lower to mid 60's. The warming trend continues through tomorrow night as southeasterly winds and plenty of cloud cover keep the lows from dropping out of the 50s in most of the forecast area.
/issued 205 PM CST Tue Dec 29 2020/ The warm advection pattern that was responsible for the freezing rain this morning will push off to the east, with plain rain ending over south central Kansas this evening.
These warmer temperatures may also facilitate some melting of snowpack elsewhere, which could limit blowing snow potential thru the aftn.
Temperatures have warmed from south to north through the daylight hours allowing for the majority of precipitation to transition to rain, except for in far northeast Kansas where temperatures are hovering around the freezing mark. Freezing rain is expected to continue across far northeast Kansas with additional ice accumulations of one to two tenths of an inch.
Strong northern stream upper level low diving southeast into the Northern Plains tonight, and will bring an extensive area of stratus to all but my southwestern counties. The highlight tonight will be expanding stratus, seen this afternoon on visible satellite imagery pushing into the northwest from southern Saskatchewan. Under clear skies lows across the north may drop below zero, but widespread stratus will likely keep temperatures warmer. Cloud cover gradually erodes Wednesday, though with a lack of mixing under high pressure it may take its time.
A trough extends from western Colorado to Southern California this afternoon. The trough will meander eastward over the coming days with southwest flow aloft over the Tri-State area. Clearing skies overnight, fresh snowpack and a cooler airmass coming in will affect low temperatures for Wednesday morning. Wednesday, a split in the flow will bring northwest flow aloft to the region as a ridge moves over the western extent of the Rockies. Meanwhile, the southern split will be over northern Mexico with several models showing a closed low developing. Cooler air will filter into the Tri-State region through the day.
514 PM CST Tue Dec 29 2020 (This evening through Wednesday) Isentropic ascent-driven showers continue across northwest Oklahoma, and this is where the highest rainfall amounts have been so far (over 0.
This is robbing the dendritic growth zone from ice development and has lead to the transition to sleet, freezing rain, and freezing drizzle. Winds out of the WNW at 8-18 mph will leave apparent temps even cooler.
The passage of the trough will signal a transition to northwest flow at the surface, helping dry air to filter into the area. The northern stream of the upper trough also moves through tonight.
Warm and moist gulf air is moving north across the area this afternoon ahead of low pressure taking shape over the Central Plains. An upper trough that is currently digging into northern Mexico and the SW sections of the US will pinch off and upper low during Wednesday. Lift will increase through Wednesday ahead of the digging trough and newly formed upper low increasing rain chances locally.
As drier air pushes in, we are losing saturation aloft, we have seen freezing drizzle gradually develop from west to east across the area. Overnight lows may dip into the low teens, particularly in northwestern portions of the area where skies fully clear out. Even still, the cold airmass will make it tough for highs to reach freezing in portions of the area.
A North Pacific Trough approaches from the west, advecting moisture into the region. These winds will tend to evaporate and moisture that may attempt to fall to the surface of the lower elevations. An upper level ridge builds into the area, and with an upstream trough squeezing the gradient, gusty west-southwesterly winds develop. An upper level closed low develops along The British Columbia west coast. With the upper level high located over The Pacific Ocean, and the ridge, previously located over central Montana weakening and moving eastward, a strong cross-barrier flow sets up across The Rockies.
A high pressure remaining to our north tonight and Wed, will keep similar conditions through this period. For Wed, temps will be a few degrees warmer than today with no rainfall activity expected over land.
The exception could be north of I-80 as a warm front lifts across northern OH/PA overnight. Given the rather dry and cold airmass at the low levels, not expecting much measurable precipitation but a few snow showers are possible - hence the addition of very low PoPs to this area. Any lingering snow should be short- lived owing to the influence of building broad high pressure.
Earlier today we received reports of freezing drizzle in the Orofino, Idaho area and also in the vicinity of Columbia Falls. Before this system moves in, there is some concern that there could be pockets of freezing drizzle again in the areas that have low clouds in the similar areas that saw it this morning. The lower elevations including the Camas Prairie and even Orofino in Idaho should pick up enough light snow for conditions to be slick for the Wednesday morning commute. A transition to mixed precipitation is a concern along the Highway 12 corridor by mid-morning as air temperatures moderate above freezing, but ground temperatures continue to be cold. A similar concern will be found for the lower elevations across northwest Montana.
Large ridge across the eastern CONUS. with a still digging trough across the desert SW into NW Mexico. a few scattered showers may be possible during the afternoon and evening on Wednesday but likely nothing of any real significance with temps well above normal into the lower and mid 70s. Trough becomes negatively tilted by evening into the overnight hours. New Years Day the cold front should push through no later than daybreak. with cooler air.
423 PM MST Tue Dec 29 2020 The upper level trof axis is moving across central and eastern Colorado this afternoon with an expected subsident and drying airmass taking place for tonight. Have lowered temperatures in the high mountain valleys. Some mid level cloudiness with the trof axis this afternoon. A strong ridge over the southeastern US will slow the progression of troughs over the western US through the end of the work week.
259 PM MST Tue Dec 29 2020 The upper level trof axis is moving across central and eastern Colorado this afternoon with an expected subsident and drying airmass taking place for tonight. Have lowered temperatures in the high mountain valleys. Some mid level cloudiness with the trof axis this afternoon. A strong ridge over the southeastern US will slow the progression of troughs over the western US through the end of the work week.
High pressure will build across the region through Wednesday.
(This evening through Wednesday) Isentropic ascent-driven showers continue across northwest Oklahoma, and this is where the highest rainfall amounts have been so far (over 0.
VFR cigs will become MVFR/IFR overnight as a cold front approaches the region. Strong and gusty southeast winds will persist ahead of a cold front that will through northeast Oklahoma overnight. Cold front will continue a southward progression during the day Wednesday with the heavier rain shifting into southeast Oklahoma.
Sfc trof will continue to slowly move east through tonight, as upper wave drops southeast toward the northern CWA. The influence of that wave aloft should help shove the sfc trof east. Energy lifting out of the southwest upper trof will gradually shift off to the east this evening, thus ending the accumulating snows from west to east through the evening hours. Overall, the extended looks to remain dry with just a weak mid level trough passage or two, nothing definitive.
The highlight tonight will be expanding stratus, seen this afternoon on visible satellite imagery pushing into the northwest from southern Saskatchewan. Under clear skies lows across the north may drop below zero, but widespread stratus will likely keep temperatures warmer. Cloud cover gradually erodes Wednesday, though with a lack of mixing under high pressure it may take its time.
Scattered showers will linger through early this evening, primarily over the higher terrain.
The warm advection pattern that was responsible for the freezing rain this morning will push off to the east, with plain rain ending over south central Kansas this evening.