Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 431 AM EDT Fri Apr 01 2022 Valid 12Z Fri Apr 01 2022 - 12Z Mon Apr 04 2022 ...Great Lakes and Northeast... Day 1... Mid-level vort max behind the surface cold front now moving off the East Coast will move through the Pennsylvania this afternoon atop a surface trough extending southwestward from the parent low. This will provide the necessary lift for isolated/scattered snow showers, some of which could be vigorous and lead to snow squalls. Steepened lapse rates, modest MUCAPEs of a few hundred J/kg, and sufficient moisture in place support their development though accumulation may be limited due to marginal surface temperatures. Areas downwind of Lakes Erie and Ontario are likely to pick up a few inches of snow (especially into the Tug Hill) with westerly to northwesterly flow during the day. Additional accumulations are expected over the Adirondacks and Green/White Mountains in VT/NH as the upper trough swings through, with probabilities of at least 4 inches confined to higher elevations. ...Corn Belt... Days 1-3... Two systems will likely affect the region over the next three days. The first will be at the very end of Day 1 into Day 2 (early Sat) as a mid-level shortwave moves through Iowa. At the surface, an area of low pressure will exit Colorado and slip eastward as a brief surge in precipitable water noses into eastern Iowa and southern Wisconsin. Temperatures at the surface will be marginal, near and maybe just above 32F, but CAM guidance suggests a focused area of frontogenesis over the area around 12Z Sat with appreciable lift into the DGZ. WPC snowband tool shows the possibility of >1"/hr rates around daybreak which could accumulate a few inches (note WPC's WSE and HREF max snow are both around 6"). Next system will be on Sunday evening into early Monday. Model spread is large with this system, so took a conservative/blended approach which yielded a light amount of snow farther north (northern WI) but only around 1-2". ...Northwest... Days 1-3... A weak system will move through the area Day 1 with snow levels around 4000ft before falling a bit on Saturday behind the front. By Day 3, strong/extended jet (160 kts) across the Pacific will aim into the WA/OR coast with the precipitable water surge focused over northern California into Oregon. Still, PW values around +1 will push into the Cascades ahead of a lead wave and then a subsequent more developed system (into Day 4). WSW flow will capitalize on upslope into the Olympics and Washington Cascades where more than a foot of snow is expected on Day 3. Lesser amounts are expected into Oregon where snow levels will be higher. ...CO Rockies... Day 3... Weak upper trough and surface cold front will lead to an increase in snow over higher elevations of Colorado Day 3, aided by upslope flow as an area of high pressure sinks southeastward over the Plains. Several inches are expected into the Sawatch Range into the Sangre de Cristos. For Days 1-3, the probability of significant icing of at least 0.25" is less than 10 percent. Fracasso ~~~ Key Messages for March 31 - April 1 Snow Squalls ~~~ -A strong cold front will push off the East Coast this morning as colder temperatures filter into the region. -Snow showers and squalls are likely today from the central Appalachians and Lower Great Lakes into the interior Northeast and Mid-Atlantic. -Intense but brief snowfall within these snow squalls can rapidly reduce visibility and lead to dangerous driving conditions, particularly on high-speed roadways. -Little to no accumulation is expected outside of the higher terrain, but slick spots may develop on bridges and overpasses.