Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
345 PM EST Wed Jan 23 2019

Valid 00Z Thu Jan 24 2019 - 00Z Sun Jan 27 2019

...Great Lakes...
Days 1-3...

An active period of lake enhanced and lake effect snow under
persistent low pressure has begun across the Great Lakes and looks
to continue into February. Much below normal temperatures should
lead to greatly increased ice coverage on the lakes over the
coming days, but for now ice coverage is low enough to warrant
full lake effect potential through the next three day forecast
period.

The surface low will eject northeast from MI by this evening with
the associated cold front shifting east of the eastern Great Lakes
by late tonight. Wrap around snow will end over MI early this
evening.

A weak shortwave trough associated with an Arctic cold front
pushing down the Great Plains will slowly shift east across the
Lakes late tonight into Thursday night. Expect light snow along
this slow moving front from the Arrowhead of MN tonight across the
Lakes through Thursday night. North then northwest winds behind
the front will begin lake effect snow that persist through
Saturday.


...Central Appalachians to Upstate New York...
Day 1...

Low pressure develops along the cold front and lifts north up the
east side of the Appalachians tonight. This will slow progression
of the back side of the precip over the the western slopes of the
Appalachians and allow a changeover to snow tonight into Thursday
despite current 2m temps in the mid to upper 40s over the eastern
half of OH and western PA with 50s and 60s over WV. Moderately
high Day 1 WPC probabilities for two inches stretch across eastern
OH/western PA and WV and down the KY/VA line and even into the
Cumberland Plateau of TN.

Northwesterly flow behind the cold front then allows a period of
upslope snow into the crest of the central Appalachians Thursday
afternoon. Moderate Day 1 four inch probabilities are in typical
upslope snow areas of WV.


...Northern and Central Rockies...
Day 1...

Arctic surface high pressure will shift southeast from Alberta and
across the Dakotas into Thursday. Upslope flow west of this high
center along with mid-level support from a shortwave trough will
allow locally heavy snow across the CO/WY/UT Rockies and high
plains of MT. Moderate Day 1 WPC probabilities for six inches of
snow are across these areas. Continued high pressure over the
Plains will continue to bring chances for four inches to higher
terrain of the north and central Rockies and Black Hills for Days
2 and 3.

Jackson