Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Fri Apr 03 2020

Valid 12Z Fri Apr 03 2020 - 12Z Mon Apr 06 2020


...Central Plains to Western Great Lakes..

Day 1...
A well-defined shortwave trough rounding a deep low over Alberta
is shifting northeast over the Dakotas will continue to push a
sharp cold front southeast across the central/southern Plains and
east to Lake Michigan through tonight. Favorable upper jet forcing
along/behind the front is lifting into Manitoba with moderate snow
potential limited to northern MN today. Day 1 snow probabilities
for 4 or more inches are around 20 percent along the Rainy River.
Meanwhile, a wintry mix will continue to advance behind the
shallow cold front and spread southeast across Kansas, Iowa,
southeastern Minnesota, northwest Missouri, western Wisconsin, and
the western UP despite surface temperatures within the past 6 to
12 hrs generally in the 60s. Ice accretion in these areas will be
limited to elevated surfaces with enhanced risks to ground travel.
Day 1 ice probabilities for a tenth or more are up to 50 percent
in southeast MN (where there is also a 10 percent risk for a
quarter inch) and 10 to 20 percent from the western UP to
northeast Kansas an the KC metro area.

...Pacific Northwest and Northern California...

Days 1...
A secondary shortwave trough rounding the Alberta low pushes
southeast into eastern Washington today, swinging through
northeastern Montana and northwest North Dakota Saturday. Onshore
flow will bring Pacific Moisture across the Cascades and ahead of
this trough to the far northern Rockies. Day 1 snow probabilities
are moderate for 6 or more inches over the northern Washington
Cascades and Rockies of far northern Idaho and northwest Montana.

Days 2/3...
A pair of shortwave troughs cross the southern Gulf of Alaska and
reach the coast in succession at the CA/OR border Saturday morning
and Sunday morning. Abundant Pacific moisture streams into far
northern CA Saturday with snow levels generally around 4000ft,
dropping to around 3000ft late Saturday night. The second trough
is stronger and closes Saturday night off the OR coast and the low
tracks down the CA coast through at least midweek with snow levels
around 4000ft with the heaviest precip axis through central CA.
Day 2 snow probabilities are moderate to high for 8 or more inches
in the higher Klamath/Shasta Siskiyous, southern OR Cascades, and
northern Sierra Nevada. Day 3 snow probabilities for 8 or more
inches are nearly identical over northern CA/southern OR and are
high down the extent of the Sierra Nevada.


Jackson