National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FOUS11 KWBC 232012
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
412 PM EDT Tue Apr 23 2024

Valid 00Z Wed Apr 24 2024 - 00Z Sat Apr 27 2024

...Northern Maine...
Days 1/2...

A potent lobe of a mid-level low east of Hudson Bay is crossing
James Bay this afternoon and will take on a negative tilt as it
reaches northern Maine Wednesday afternoon. Strong ridging and cold
air quickly follows this wave which will bring a quick end to
precipitation. The question is how much precipitation can fall
Wednesday afternoon over northern Maine after the column is cold
enough for snow. As of now the most likely forecast is 1-3" over
far northern Maine, though a few ensemble members and the 12Z GFS
have heavier snow which leads to Day 1.5 PWPF for >4" of 40% over
the northern border of Maine.


...White Mountains Along California/Nevada Border...
Days 1/2....

A mid-level southern stream low in a positively-tilted trough is
currently well west of SoCal, but as it approaches/opens into a
wave on Wednesday flow will promote low level cyclogenesis over the
Great Basin which will direct Pacific moisture back to the White
Mountains and the south-central Sierra Nevada. A narrow swath of
precip over central NV back southwest through this terrain is
expected to develop Wednesday afternoon, then continue until the
trough axis passage late Wednesday night. Little movement to this
swath could lead to moderate to locally heavy snowfall above the
snow level which will be around 9000ft. High terrain of the White
Mtns snowfall of 8-12" is possible with Day 1.5 PWPF for >8" around
40% (though smoothing is likely limiting values of this narrow
mountain range).


...The West...
Day 3...

The aforementioned southern stream wave crossing the Southwest
Wednesday night will shift ENE over the southern Rockies late
Thursday with generally moderate snowfall over high terrain with
snow levels around 9000ft.

The next wave is currently a series of impulses over the northern
Pacific that will track south of a low currently over the Alaskan
Panhandle and develop into a trough into the Pacific Northwest late
Thursday that digs southeast/amplifies into a more significant
trough over the Great Basin by late Friday. As the trough develops,
broad Pacific flow into the West Coast brings moisture quickly east
to the Rockies Thursday night/Friday. Height falls under the trough
allows snow levels to drop to around 5000ft over the Northwest, to
around 6000ft over the Intermountain West/northern Rockies, and
7000-8000ft over the central/southern Rockies. The Day 3 PWPF for
>6" is 30-60% over the OR/southern WA Cascades, higher terrain over
the Great Basin ranges, especially over northeast NV and UT, and
the greater Absarokas in ID/MT/WY.

This wave further develops Friday night with continued snow
expected over the central/southern Rockies well into the weekend.


The probability of significant icing is less than 10 percent.


Jackson


$$