BBS: TELESC.NET.BR Assunto: HVYSNOW: Probabilistic Heavy Snow And Icing Discussion De: COD Weather Processor Data: Sat, 14 Mar 2026 07:28:40 +0000 ----------------------------------------------------------- FOUS11 KWBC 140728 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 328 AM EDT Sat Mar 14 2026 Valid 12Z Sat Mar 14 2026 - 12Z Tue Mar 17 2026 ...Northern High Plains through the Great Lakes...=20 Days 1-3... ...Blizzard likely this weekend with widespread major impacts and record-breaking snowfall for portions of the Upper Midwest and=20 Great Lakes... Confidence continues to be high in a widespread major winter storm from the Northern Plains through the Upper Midwest and Great Lakes as a lee surface low lifts northeast and rapidly deepens into an increasingly moist column. While it is this lee cyclone that will be responsible for the most significant impacts, this event is really two-pronged with the first event already ongoing across the Northern High Plains. Across the High Plains of Montana, moisture continues to stream onshore within an impressive IVT plume (atmospheric river)=20 pushing well inland leading to a surge in PW/column moisture=20 across the northern Plains. The accompanying upper jet streak=20 arcing zonally across the region working in tandem with a surface=20 stationary front will cause snowfall to continue to spread ESE-=20 ward. Overall ascent during D1 across this area appears modest as=20 noted by omega fields and regional soundings, but the impressive PW anomalies (nearing +2 sigma) will support periods of moderate=20 snowfall from MT through parts of SD. The heaviest accumulations=20 are likely in the higher terrain, with lower accumulations expected elsewhere across the High Plains today. Where the heaviest snow=20 occurs, generally just east of the Continental Divide, WPC probabilities are high (>70%) for at least an additional 4" of snowfall through tonight, with more than 8" possible in the higher elevations around the Little Belts. The more significant portion of this event begins this afternoon=20 as lee cyclogenesis begins in more impressive fashion east of=20 CO/WY. A shortwave digging onshore the British Columbia coast=20 tonight will begin to amplify as it digs into the Central Rockies=20 Saturday night. The rapid amplification of this shortwave will=20 drive impressive height falls downstream, with impressive jet=20 streak intensification occurring as a result. The overlap of height falls with this jet development will lead to a rapidly deepening=20 surface low tracking from CO to IA before 12Z Sunday.=20 After 00Z Sunday is when this event truly becomes a major winter event with widespread considerable impacts. As the surface low continues east from the Central Plains it will encounter dual=20 moisture streams, one from the decaying AR pushing east, and a=20 second as the theta-e ridge begins to arc northward on intensifying WAA/southerly flow out of the Gulf. The overlap of robust deep=20 layer ascent with maximizing moisture return will deepen the low=20 substantially, and help expand a considerable precipitation shield, with heavy snow arcing from SD through the Great Lakes by Sunday morning, and then slowly pivoting northeast while continuing=20 through D3 as the surface low moves into Ontario by 00Z/Tuesday. The synoptic setup is extremely favorable for a classic Midwest winter storm with widespread intense snowfall. Embedded bands=20 with snowfall rates of 1-3"/hr are expected as reflected by high=20 potential for CSI and even CI in model cross-sections Sunday aftn=20 into Monday which drives intense omega into the TROWAL. Although=20 guidance has continued to trend north, there is high confidence in a laterally translating band of heavy snow from SD into MN Sunday=20 morning, with the environment transiting into one that matches the=20 conceptual model for a pivoting band over eastern MN and WI Sunday=20 evening into Monday, It is in this area where the heaviest snowfall is expected, and potentially record, or near-record 2-day snowfall is possible from eastern MN through WI and northern MI. Elsewhere, snowfall rates of 1"/hr or more are still likely at times, just=20 with lesser duration. These snowfall rates combined with gusty=20 winds reaching up to 60 mph will create blizzard and near-blizzard conditions and whiteouts, with major to extreme impacts progged by the recent WSSI-P. Even in areas that get lower snow totals, the=20 blowing snow potential will still result in difficult travel, and=20 it is likely that most forms of transportation will be treacherous=20 at best, and impossible at worst, through the event across a large=20 area from Montana to Michigan, and everywhere in between. Event-total snowfall is likely to be extreme in some areas. This is reflected by 72-hr WPC probabilities (ending 12Z Tuesday) that are high (>70%) for at least 12" from the Coteau des Prairies of SD eastward through the Twin Cities, across much of north-central WI, and the entirety of the U.P. of MI. Where snowfall is most prolific, likely in northern WI and the U.P of MI, WPC probabilities indicate a 70-90+% chance of at least 24", and localized totals of 3-4 feet are possible before this event ends.=20 This could result in record snowfall in some places, and with SLRs being slightly below climo, combined with the strong winds, power=20 outages and long-lasting impacts are expected. For these reasons,=20 Winter storm key messages are in effect, and are linked below (Key=20 Message 1). On the S/SE side of this snowfall swath, an axis of mixed=20 precipitation is likely, leading to icing accretion from central IA through southeast WI and into lower MI. The most significant icing is expected for lower MI where WPC probabilities for at least=20 0.25" of ice have climbed to over 50%, and the axis of higher probabilities for at least 0.10" of ice have extended back into SE WI. As this system finally departs late D3, pronounced CAA on NW flow in its wake could result in some lake effect snow in the favored NW snow belts downstream of all the Great Lakes. WPC probabilities are moderate (50%) for at least 4" of snow from LES in SW MI, as well as along the Chautauqua Ridge and into the Tug Hill Plateau. Additional heavy snow will occur near Marquette, MI as well, adding onto the extreme snowfall event there the next few days. ...Cascades, Northern & Central Rockies...=20 Day 1... The persistent atmospheric river (AR) which has plagued the Pacific and Interior Northwest the past several days will finally come to=20 an end Saturday as the IVT plume weakens and sinks southward into CA. This will be the result of the intensifying shortwave diving out of British Columbia and pushing a surface low pressure east, which will then trail its accompanying cold front southward into the Great Basin. Much of of the available moisture will be focused ahead of this front, so as the front digs south, the moisture will follow, bringing a slow end to this impressive event. Strong ascent will continue, at least the first half of the period, into the Northern Rockies, with ascent expanding into the Central Rockies as well, and this is where the heaviest snowfall is expected before everything shifts into the middle of the country by D2. Additional snowfall in the Cascades is expected to be minimal, but WPC probabilities are high (>70%) for at least 6 additional inches in the Absarokas, Tetons, and Wind Rivers, with locally more than 12 inches possible in the higher elevations. ...Northeast...=20 Day 1... The intense and compact low pressure over the Great Lakes tonight will eject eastward with secondary cyclogenesis expected along the coast of Maine Saturday morning. Although this low will become=20 dominant as it pivots into the Canadian Maritimes, an elongated=20 inverted trough extending west from this low will maintain ascent=20 across the Northeast much of Saturday. Continued impressive WAA/theta-e advection into ME will manifest as periods of heavy snow across that state, especially just northeast of the surface low and up along the eastern half of the state.=20 This is where the heaviest snow rates are expected, and may exceed=20 1"/hr as suggested by HREF probabilities surpassing 70% across=20 eastern Maine. Here, WPC probabilities indicate a 50-90% chance of 4+ inches of snow today. =20 Farther west, NW flow along and behind the residual inverted trough will leave periods of light to moderate snow across the interior=20 northeast, with local snowfall maxima occurring in favored upslope=20 terrain and across the Tug Hill Plateau where some lake enhancement off Lake Ontario is expected. Snowfall inland may be less than along the coast, but WPC probabilities indicate around a 70% chance of 4+" of snow, highest across the Tug Hill Plateau and Green Mountains of VT, before the system exits and snow ends by Sunday=20 morning. 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!7M5ro4GT31sY3zKNuesvKLtIgiKZkjMEGn_kmMJwtIprZ= a6Uy7J48cciO8XAeFRYymT66kYFHU9djMdFC8k1wQNJfvE$=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 (1:2320/107) ----------------------------------------------------------- [Voltar]