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|  Message 40611  |
|  COD Weather Processor to wx-storm@lists.illinois.edu  |
|  HVYSNOW: Probabilistic Heavy Snow And Ic  |
|  23 Jan 26 08:58:20  |
 TZUTC: 0000 MSGID: 168814.weather@1:2320/105 2ddb01a5 PID: Synchronet 3.21a-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0 TID: SBBSecho 3.28-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0 BBSID: CAPCITY2 CHRS: ASCII 1 FORMAT: flowed FOUS11 KWBC 230858 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 358 AM EST Fri Jan 23 2026 Valid 12Z Fri Jan 23 2026 - 12Z Mon Jan 26 2026 ...Major winter storm to bring the potential for crippling icing,=20 significant sleet, and heavy snow from the Southern Plains through=20 the Southeast and up the Atlantic Coast into New England... Forecast remains largely on track with only minor changes compared to the previous cycle, with typical uncertainties surrounding the=20 depth and northern push of the mid-level warm nose. While this=20 uncertainty is rather minor from a synoptic scale, local forecasts=20 can still be drastically impacted by this feature. The event will=20 begin this morning across the Southern Plains and expand towards the MS VLY tonight. The driver of this winter storm is an=20 impressive overlap of intensifying synoptic ascent with increasing=20 subtropical moisture. The synoptic pattern becomes favorable today in response to the=20 evolution of multiple shortwaves rotating through an amplifying=20 trough across the eastern CONUS. A closed 500mb low off the Baja=20 Peninsula will begin to open and shear to the east, at the same=20 time dual shortwaves dig out of Saskatchewan/Alberta and into the=20 Northern Plains. As the northern shortwaves dive south and the Baja low ejects east, the interaction of these features will lead to=20 increasing mid-level divergence overlapping pronounced height falls to produce rich deep layer lift. The northern shortwave has=20 trended a tad slower with overnight guidance and allows for more ridging out ahead of this system, helping shift the mid-level warm nose farther north. Regardless, the impressive ascent will be on=20 top of an arctic cold front that will be sagging southward into the Southern Plains and eventually work its way southeast to the Gulf=20 and Atlantic coasts by Saturday. This overlapping ascent will=20 materialize atop a moistening column as subtropical moisture=20 downstream of the Baja low streams northeast reflected by IVT that=20 reaches above the 97th percentile according to NAEFS, in a broad=20 swath from Texas to the Carolinas, with above the record (CFSR at=20 00Z) climatology by Sunday evening in the east. This increasing moisture will result in a large swath of precipitation expanding from the Southern Plains today, to the=20 MS VLY and TN VLY Saturday, into the Carolinas and Mid- Atlantic=20 by Sunday, and finally reaching the Northeast Sunday night. This is a very large and impactful system across a huge portion of this=20 country. While impacts will be considerable in many areas (aided by extreme cold), the icing (and sleet) and snow will be most=20 impressive across two distinct areas. Freezing Rain and Sleet: Arguably the most lasting impact associated with this winter storm could be from heavy accumulating freezing rain and sleet stretching from the Southern Plains, Mid- South, Tennessee Valley, and=20 southern Mid-Atlantic. This is due to very cold low-level arctic=20 air being reinforced by the strong high over the north-central U.S. (and enhanced by pronounced mid-level confluence over the Great=20 Lakes and New England) and a warm nose aloft (at around 750mb per=20 cross section model soundings) melting snow as it falls through the column before refreezing just before or at the surface,and in some places this re-freezing layer is above the 90th percentile in=20 terms of depth, suggesting some locations will experience=20 exceptional sleet accumulations.=20 The greatest freezing rain amounts and impacts are currently=20 forecast across northeast TX through northern MS as favorable=20 thermal profiles linger for over 24 hours beginning Friday night.=20 WPC 72-hour probabilities for >0.5" of freezing rain are high >70%=20 across southern AR/northern LA into parts of northern MS. Here,=20 ice accretion could be crippling and exceed 0.75-1.00", (WPC=20 probabilities 40-50% for 1" of ice) which would almost certainly=20 lead to widespread long-lasting damage to infrastructure, including power outages and tree damage. Major sleet accumulations are also=20 likely just north of the freezing rain area stretching from=20 southern OK/north TX through central AR and into the Mid- South,=20 with more than a few inches of sleet possible. The consistency of=20 the guidance in both placement and amounts for this area are=20 resulting in high confidence in an extreme event, leading to long-=20 lasting impacts both to travel and infrastructure due to the=20 bitterly cold airmass expected to linger into next week over the=20 region. Heavy icing is also expected farther east into the southern=20 Appalachians and southern Mid-Atlantic. The setup across the=20 southern Mid- Atlantic down as far south as northern GA and areas=20 just inland from the coasts of the Carolinas is an extreme case of=20 CAD with a 1040mb high situated over the Interior Northeast on=20 Saturday night. While regional soundings indicate there may be considerable sleet in this area as well, especially across southern VA into northern NC, these CADs are notorious for their effective dry/isallobaric flow, enhanced by precipitation, leading to dry wet-bulb advection offsetting the latent heat of freezing during freezing rain. With such an impressive high in place at precipitation onset, this will likely result in considerable accumulations of sleet and freezing rain here, too, with WPC probabilities indicating a moderate-to-high risk (60-80%) of at=20 least 0.5", highest across the Piedmont and northern GA. The=20 guidance has trended just a bit colder this afternoon, but=20 significant icing is also possible as far north as Richmond, VA and towards southern MD. Heavy Snow: North of the mixed precipitation area and closely tied to both a favorable LFQ of a zonally oriented 180kt upper jet and strong 700mb fgen, snow is the primary precipitation type stretching from the southern High Plains of east-central NM and the southern Rockies through the Plains, Mid-Mississippi Valley, Ohio Valley, Mid-Atlantic, and reaching the Northeast by Sunday evening (with additional expansion beyond this forecast period).=20 Favorable upslope flow as the strong arctic high pressure noses=20 southward along the High Plains behind a strong cold front starts=20 on Friday across the southern Rockies, with light snow and even a=20 chance for freezing drizzle at onset across the central Plains=20 until the column fully saturates. Heavy snow is then forecast to=20 begin breaking out Friday night from the central/southern Plains=20 through the mid-Mississippi Valley and spanning much of the Ohio=20 Valley and parts of the Midwest on Saturday. Snowfall rates could=20 near 1"/hr as strong lift through WAA/fgen intersects with a=20 region where the DGZ is forecast to be extremely deep (SREF probabilities above 70% for >100mb of depth). This would allow for efficient formation of dendrites where ample lift can fully=20 moisture the column. While this depth is impressive, regional forecast soundings indicate that the best ascent may lie below this DGZ in many areas, and there is only modest indication of any isothermal layer beneath the DGZ to maintain aggregates. Despite this, efficient and fluffy SLRs are likely in this area, and with a long duration event expected, WPC probabilities are moderate (40-60% )for at least 12 inches from southeastern KS and northeastern OK into southern MO, with widespread 4+ inches=20 extending all the way back into the TX Panhandle and lower MS VLY. Trends have been more favorable for snow vs lately on D1 across eastern OK and central AR as guidance depicts stronger mid-level fgen and dynamic cooling aloft to keep the entire column below 0C. 00z HREF also depicts the potential for 1"/hr snowfall rates in this region. Will monitor this for potential adjustments=20 downstream. Farther east, some heavier snowfall is becoming more likely for parts of the Ohio Valley, and into the Mid-Atlantic, and especially Northeast. Here, pronounced WAA and accompanying 850-700mb fgen will drive pronounced ascent into a rapidly moistening column thanks to IVT above the 90th climatological percentile. As the upper trough (interaction of the southern and northern streams) deepens over the Plains, downstream ascent will maximize and a period of impressive WAA snow with snowfall rates >1"/hr are likely. As secondary low pressure develops offshore (in a Miller B type evolution), banded structures within the WAA are likely to translate northward from the Mid-Atlantic into New England, and then may pivot and drift eastward Sunday night into Monday. Where this occurs, the heaviest total snowfall accumulations are probable, reflected by WPC probabilities that are already above 60% for 12+ inches. While there is some uncertainty into how much=20 mixing will pivot northward, especially from Washington D.C.=20 through Long Island, the interior portions (NW of I-95 and into=20 southern New England which will remain cold as the secondary low=20 develops and tracks near the 40/70 Benchmark) will remain mostly=20 snow with above- climo SLRs leading to significant snowfall=20 accumulations. One other uncertainty that has creeped into the forecast is a pesky dry slot moving into the Mid-Atlantic and Northeast Sunday night. This could dry out the mid-level and drastically cut both precipitation and SLRs. In fact, freezing drizzle could develop early Monday morning from northern Va to northern NJ in this scenario before stronger westerly flow picks=20 up on Monday. Many areas are expected to receive more than 12=20 inches from the Ohio Valley through the Mid- Atlantic and into the=20 Northeast before this system winds down in New England on Monday=20 /D4/. Key Messages for this system are linked below (Key Message 2) ...Great Lakes...=20 Day 1... Expansive mid-level low centered over the Hudson Bay will begin to shear open and translate to the east today as a secondary=20 shortwave rotates through its base and atop the Great Lakes this evening. Behind this impulse, shortwave ridging will amplify=20 across the area, bringing an end to the persistent CAA and=20 associated lake- induced ascent on D1. The subsequent W/NW flow and accompanying CAA will lead to impressive lake effect snow (LES) in the favored W/NW snow belts D1, with some pivoting to more N/NW by early Saturday. The=20 heaviest snowfall is likely east of Lake Ontario D1 where WPC=20 probabilities indicate a moderate risk (50-70%) for at least 8 additional inches in the Tug Hill Plateau. Elsewhere, WPC=20 probabilities suggest a moderate risk (50-70%) for at least 6=20 additional inches across the northeastern U.P. Additionally, as an arctic cold front pivots into the Northeast,=20 snow squalls along and behind this front are possible. For more=20 details on the snow squall threat in the Northeast through Friday,=20 please refer to our Key Messages (Key Messages 3) below. Snell/Weiss ...Winter Storm Key Messages are in effect. Please see current=20 Key Messages below... https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!6i-JszDvIoz4IkeeFVBNKHjZJfHF0Ybqz-c67ZQcVC-f7= lPz-fsyMDtCovzI6Va6oo9mesLuh66CAbzexuk2Xq7kUJc$=20 https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!6i-JszDvIoz4IkeeFVBNKHjZJfHF0Ybqz-c67ZQcVC-f7= lPz-fsyMDtCovzI6Va6oo9mesLuh66CAbzexuk2eCfbSq8$=20 https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!6i-JszDvIoz4IkeeFVBNKHjZJfHF0Ybqz-c67ZQcVC-f7= lPz-fsyMDtCovzI6Va6oo9mesLuh66CAbzexuk2Uae-1TY$=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: Capitol City Online (1:2320/105) SEEN-BY: 1/19 100 16/0 19/10 37 104/119 105/81 106/201 114/10 120/302 SEEN-BY: 123/130 128/187 129/14 142/104 153/757 7715 154/10 30 50 SEEN-BY: 154/110 700 203/0 218/700 840 220/10 20 90 221/1 6 360 226/18 SEEN-BY: 226/30 44 50 227/114 229/110 134 206 300 307 317 400 426 SEEN-BY: 229/428 470 664 700 705 240/5832 266/512 280/5003 291/111 SEEN-BY: 301/1 320/119 219 319 2119 322/757 762 326/101 335/364 341/66 SEEN-BY: 342/200 396/45 423/81 460/58 633/280 712/848 902/26 2320/0 SEEN-BY: 2320/105 304 3634/12 5020/400 5075/35 PATH: 2320/105 154/10 221/6 1 320/219 229/426 |
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