Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 AM EST Sat Feb 17 2024

Valid 12Z Sat Feb 17 2024 - 12Z Tue Feb 20 2024

...Great Lakes...
Days 1-2...

Lake Effect Snow (LES) on WNWly flow continues today in the wake
of low pressure moving off the Mid-Atlantic coast. Day 1 PWPF are
10-40% for >4"  in portions of the U.P. northern L.P., and east of
lakes Erie and Ontario. Flow shifts Wly tonight and single band
LES is likely on Lake Ontario late tonight into Sunday with Day
1.5 snow probs for >4" 70-90% north of the Tug Hill Plateau. A
shortwave trough crosses the lakes Sunday with the main trough
lifting north of the Great Lakes, ending LES Sunday night.


...Northern Mid-Atlantic into southern New England...
Day 1...

Moderate to locally heavy snow bands push off the Mid-Atlantic
coast early this morning as the parent low zips ENE off the
southern Delmarva on a 175kt + jet. Trailing upper troughing
shifting over the eastern Great Lakes makes for scattered snow
bands/showers over the Northeast today with 40% probs for >2" over
the Mass Cape and Islands and eastern Long Island.


...West...
Days 1-3...

Interior ridge axis continues to weaken today as the next Pacific
trough reaches the Pacific Northwest later today and directs an
Atmospheric River into California. Strong southerly flow will
raise snow levels to 6000-7000ft as precip moves inland today
before diminishing into the ridge with a weakening mid-level
shortwave carrying light snow into the Intermountain West. Day 1
PWPF for >8" are 40-80% along the Sierra Nevada crest, the
Shasta/Siskiyou, and the highest OR Cascades.

The next low then approaches northern California late Sunday with
even more moisture and snow levels upwards of 7000-8000ft. Day 2
PWPF for >8" remain 40-80% for the Sierra Nevada crest and the
Shasta/Siskiyou. Even heavier precip pushes across CA on Monday
with height falls allowing snow levels of 5500-7000ft. Day 3 PWPF
are 50-90% for >8" again for the length of the Sierra Nevada and
the Shasta/Siskiyou.

Resident cold air over the Columbia Basin/Gorge does allow for
some risk for light freezing rain in the surrounding Cascades and
perhaps the northern Oregon Coast Ranges into tonight where Day 1
PWPF for >0.1" ice remain 10-20%.


Jackson