Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
339 AM EST Sun Feb 18 2024

Valid 12Z Sun Feb 18 2024 - 12Z Wed Feb 21 2024

...Great Lakes...
Day 1...

A shortwave trough axis over northern Ontario will shift southeast
today and provide lift for continued LES into the eastern U.P. on
WNWly flow and over the eastern Great Lakes on WSWly flow. Day 1
PWPF for >6" after 12Z are around 20% near Whitefish Bay in the
U.P. and 30-60% north of the Tug Hill off Lake Ontario. All lake
effect snows will end by Monday morning as ridging builds in from
the NW.


...West and California...
...Particularly heavy snow tonight into Monday on the Sierra
Nevada above about 6500ft...

Days 1-3...

The lead wave that surged through California last evening is
weakening as it pushes inland with moderate snows expected today
over the northern Intermountain West.

Moisture surge ahead of the next upper low reaches the California
coast this afternoon on the leading edge of a 165kt jet streak
that moves into SoCal. Modest/strong PW/IVT anomalies (90-95th
percentiles) will focus into the northern/central Sierra, where
high intensity snow is likely above ~6500ft. Sharpening of the
upper trough would allow for a longer residence time of moisture
flux into the region, and several feet of snow are likely into the
crest and some of the higher passes where travel may become
difficult to impossible. 00Z HREF mean one hour snow rates top
4"/hr for most areas along the Sierra Crest starting this evening.
Day 1.5 probabilities for >18" snow are >50% above about 7000ft in
the Sierra Nevada and the Shasta/Siskiyous. There is a real risk
for >36" snow in 12 hrs from 06Z-18Z Monday.

Onshore flow then continues to bring moderate snow to the Sierra
Nevada Monday afternoon through Wednesday with slow height falls
lowering snow levels to around 5500ft by Tuesday evening. Expect
three day snow totals of 6 to 7 feet for the High Sierra and 3 to
4 feet for the terrain around Lake Tahoe (with not much snowfall
at lake level).

Some moisture periodically makes it over the Sierra Nevada with
locally heavy snow in terrain in the Great Basin to northern Utah.


The probability of receiving at least 0.1" of ice is less than 10
percent Day 1-3.


Jackson