Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 449 AM EDT Mon Apr 08 2019 Valid 12Z Mon Apr 08 2019 - 12Z Thu Apr 11 2019 ...Northeast... Days 1-2... Low pressure developing along a stationary front draped over the Northeast will track east across northern New England this evening. A wintry mix will develop over northern VT/NH and east over central Maine this morning with all snow farther north over northern Maine until the low passes this evening. A swath of 8 or more inches has a high probability over northern Maine and there are moderate probabilities for a quarter inch of ice in the White Mountains and northern VT. An upper trough will track east from the Great Lakes tonight through Tuesday with a surface low tracking across central New England late Tuesday allowing a second wave of wintry weather with effects reaching farther south than the Day 1 system. Moderate probabilities for four inches extend north from the White Mountains to north-central Maine while low probabilities for an inch extend to the Catskills and higher elevations of MA. ...The West across the northern Plains to the Great Lakes... Days 1-3... A broad trough currently allowing an atmospheric river to push into the Pac NW with particularly high snow elevations digs and amplifies as it reaches the West Coast tonight. Snow elevations decrease with the trough as does the influx of Pacific moisture into the Pac NW, so heavy snow on Day 1 is limited to the highest Cascades and northern Rockies. Favorable upper jet forcing in addition to low to mid level convergence/frontogenesis and ample moisture inland are expected to support increasing probabilities for locally heavy accumulations across the central Idaho to southwestern Montana and northwestern Wyoming ranges on Day 2. Moderate probabilities for one foot are across higher elevations (though snow will occur at least 3000ft lower than Day 1) of ID/MT/WY. The trough digs into the Desert SW Tuesday and allows the next powerful storm to impact the northern and central Rockies and northern Plains to develop. The 00Z consensus is for an upper low closing off over the Intermountain West Tuesday night with a powerful surface cyclone developing in the lee of the CO Rockies around that time. This surface low deepens into the 980mb range as it tracks from eastern CO across KS on Wednesday. Strong upslope flow along with deep forcing will support moderate to heavy snow accumulations developing across the northern into the central Rockies by early Wednesday. Rain changing to snow is expected farther east across the Plains late Tuesday night through Wednesday, with heavy accumulations expected in a broad TROWAL extending east from eastern WY across SD/NE and IA/MN to Lake Michigan by Wednesday night. By the end of the period, expect accumulating snow to stretch as far east as the lower peninsula of MI. Moderate probabilities for one foot or more on Day 3 are across southeastern SD and south-central MN. Furthermore, intense frontogenesis should allow a narrow swath of freezing rain over MN/IA where moderate probabilities for a tenth inch are there for Day 3. Jackson