Subj : HVYSNOW: Probabilistic Heavy Snow And Icing Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Mar 12 2024 20:19:47 FOUS11 KWBC 122019 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 419 PM EDT Tue Mar 12 2024 Valid 00Z Wed Mar 13 2024 - 00Z Sat Mar 16 2024 ....Northwest... Day 1... Shortwave trough energy currently moving through the Intermountain West will amplify as it reaches the Great Basin later tonight into Wednesday before closing off Wednesday night. A final push of forcing for ascent will be driven primarily via height falls and=20 PVA associated with this shortwave, but a modest 90kt Pacific jet=20 streak is also likely to orient WNW to ESE, driving favorable LFQ=20 difluence into the area as well. This synoptic flow along with=20 upslope flow will produce heavy snowfall as moisture surges ahead=20 of the best ascent. As a result, additional snowfall for the Day 1 period (00Z Wed-00Z Thur) will be locally heavy for the higher=20 elevations of the OR/WA Cascades as well as eastward including=20 portions of the Northern Rockies, in the NW WY ranges, and south=20 to the Ruby Mountains and along the Wasatch of UT. ....Central Rockies, Southern Rockies, & Central High Plains... Days 1-3... ***Significant and long lasting winter storm to produce heavy=20 snow across much of the terrain of the Central and Southern=20 Rockies, with impactful snowfall likely into the lower elevations of the High Plains as well.*** An amplifying and digging shortwave trough will elongate as it approaches the Intermountain West and Rockies Wednesday and=20 Wednesday night in response to a rapidly strengthening eastern=20 Pacific ridge axis where height anomalies approach +4 sigma by the end of the week. The shortwave energy is then expected to close=20 off and settle southward into the Four Corners region by Thursday=20 morning. In response, an area of low pressure will develop in the=20 lee of the Rockies and a classic northeasterly upslope event will=20 begin to take shape Wednesday night through Friday. Impressive=20 dynamics, characterized by the height falls, strengthening low=20 pressure, and left exit lift from a 90-115 kt jet streak=20 positioned across NM through MO will all come together to produce=20 a longer duration precipitation event.=20 Precipitation is expected to begin more steadily during Day 1, but it's Day 2 where the greatest potential for significant upslope precipitation exists along the CO Front Range Mountains and into the lower elevations including the I-25 urban corridor. While=20 there remains some uncertainty in the placement (north/south) of=20 the greatest QPF and also the available moisture, the latest WPC=20 snow probabilities are above 50 percent for at least 1 foot for=20 much of the WY and CO mountain areas, and locally exceed 70% for 1 foot for the Big Horns south into the Laramies, across the CO=20 Front Range Mountains and south into the Palmer Divide through the Sangre de Cristos. Localized higher amounts in excess of 2 feet=20 will be possible, particularly for the Front Range Mountains. In=20 the lower elevations including the I-25 corridor, confidence is=20 increasing in a significant snowfall event and probabilities for=20 at least 8 inches are high (>70%) with a slight (20-30%) chance of totals exceeding 12 inches.=20 As the first phase of the storm winds down, a second phase begins to develop over the Four Corners region and southern CO Rockies=20 as the closed low settles southwestward over Arizona by Friday.=20 This will push a favorable fetch of moisture and lift over the=20 Four Corners northeast into the southern CO Rockies with waves of=20 precipitation likely. Snow levels will initially be high, but a=20 backdoor cold front pushing through NM will lead to a favorable=20 northeasterly flow event for significant snowfall where WPC snow=20 probabilities for 6 inches during Day 3 are high (>70%) across=20 along/north of the Mogollon Rim, the White Mountains of AZ,=20 southern Wasatch and into the San Juans and localized totals in=20 excess of a foot are possible (30-50% probability).=20 The probability of receiving at least 0.1" ice is less than 10% across the CONUS through Day 3. Weiss/Taylor **Key Messages for March 13-16 Winter Storm have been started and can be found on our website at https://urldefense.com/v3/__https://www.wpc= ..ncep.noaa.gov**A__;Kio!!DZ3fjg!7N5xeGBPH2Ni2PARulimLIcWkC4elhkcJKMLqxOoJX7= jOUf90hwxbhTFaKKa98pRtdGLHh_KYF2OGwQCYpdlMkGYlOo$=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .