Mesoscale Discussion 2063

Issued

Dec 27, 2021, 6:58 AM EST (11:58 UTC)

Expired

Dec 27, 2021, 12:00 PM EST

In force

5 hr

Issued by

the Storm Prediction Center

Concerning

Freezing rain

Counties Garrett County, MD, Bedford County, PA, Blair County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Elk County, PA, Forest County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, McKean County, PA, Somerset County, PA, Venango County, PA

The State College radar (KCCX), 75 km from the middle of the area, began a volume at 12:00 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

109 
ACUS11 KWNS 271159
SWOMCD
SPC MCD 271158 
PAZ000-NYZ000-MDZ000-WVZ000-271700-

Mesoscale Discussion 2063
NWS Storm Prediction Center Norman OK
0558 AM CST Mon Dec 27 2021

Areas affected...Portions of far western MD...western/central
PA...and far southwestern NY

Concerning...Freezing rain 

Valid 271158Z - 271700Z

SUMMARY...Freezing rain rates may exceed 0.05 inch per 3 hours
through the morning, before precipitation gradually transitions to
rain from west to east this afternoon.

DISCUSSION...A fairly broad area of precipitation is moving eastward
this morning from eastern OH into western PA and vicinity. This
activity is being aided by strong warm/moist advection associated
with a 45-50 kt southwesterly low-level jet over the OH Valley. This
feature is expected to shift eastward across the central
Appalachians over the next several hours in tandem with the ongoing
precipitation shield. Dry air in the low/mid levels noted on the 00Z
sounding from PIT still exists across parts of western/central PA
and vicinity. But, gradual moistening of the low levels will occur
this morning with light to moderate precipitation continuing to
overspread this region. Surface temperatures are generally below
freezing, and wet bulb cooling will likely aid in sub-freezing
temperatures being maintained through much of the morning,
especially across higher terrain. A warm nose aloft associated with
the strong low-level warm advection will likely support partial to
total melting of hydrometeors. An initial mix of snow/sleet should
transition fairly quickly to mostly freezing rain this morning.
Freezing rain rates around 0.05 inch per 3 hours may occur, with
locally greater rates possible in higher terrain. The freezing rain
should gradually transition to rain from west to east from late
morning into the early afternoon.

..Gleason.. 12/27/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BUF...CTP...LWX...PBZ...

LAT...LON   40407916 40967918 41027941 41197970 41377987 41587958
            41777918 41947890 42147859 42157822 41757801 41257758
            40607777 39787837 39577884 39397918 39487940 40407916

Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in Maryland, 2021Every mesoscale discussion in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.