Alert archive / Pennsylvania / Mesoscale Discussions in 2026
Mesoscale Discussion 21
The Storm Prediction Center issued this mesoscale discussion at Jan 11, 2026, 10:19 AM EST for 4 states. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Jan 11, 2026, 10:19 AM EST (15:19 UTC)
- Expired
- Jan 11, 2026, 3:15 PM EST
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Snow squall
All 41 counties
Allegany County, MD, Garrett County, MD, Allegany County, NY, Cattaraugus County, NY, Cayuga County, NY, Chemung County, NY, Cortland County, NY, Livingston County, NY, Ontario County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Tioga County, NY, Tompkins County, NY, Wyoming County, NY, Yates County, NY, Armstrong County, PA, Bedford County, PA, Blair County, PA, Bradford County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Elk County, PA, Fayette County, PA, Forest County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Lycoming County, PA, McKean County, PA, Potter County, PA, Somerset County, PA, Sullivan County, PA, Tioga County, PA, Westmoreland County, PA, Mineral County, WV, Preston County, WV
The radar
The State College radar (KCCX), 53 km from the middle of the area, began a volume at 15:18 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.
The nearest sounding before it
Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 3.3 hours before the alert went out and 181 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 878 m above ground
- 0-6 km bulk shear
- 95 kt
- 0-1 km storm-relative helicity
- 2 m²/s²
- 0-3 km storm-relative helicity
- -26 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
004
ACUS11 KWNS 111519
SWOMCD
SPC MCD 111519
NYZ000-PAZ000-MDZ000-WVZ000-112015-
Mesoscale Discussion 0021
NWS Storm Prediction Center Norman OK
0919 AM CST Sun Jan 11 2026
Areas affected...Parts of southwestern/south-central
NY...western/central PA...and far northern WV and western MD
Concerning...Snow Squall
Valid 111519Z - 112015Z
SUMMARY...Periodic snow squalls with bursts of heavy snow and
visibility reductions to 1/4 to 1/2 mile will be possible into this
afternoon.
DISCUSSION...Preceding a robust midlevel trough and within the
left-exit region of a 90-100-kt midlevel jet, a secondary cold front
is tracking eastward across parts of western NY, western PA, and far
northern WV. Mosaic radar data indicates a few loosely organized
snow squalls along the wind shift -- some of which have been
associated with visibility reductions to 1/4 mile and gusty winds.
Through the afternoon, cold midlevel temperatures accompanying the
trough will steepen low-level lapse rates (generating weak low-level
instability) amid 30-40 kt of unidirectional west-southwesterly flow
in the lowest 2 km (per regional VWP). This will support the
development of periodic snow-squall conditions spreading eastward
into the afternoon.
Given the lack of a stronger cold front/low-level frontogenesis,
these squalls may tend to be transient and generally be associated
with visibility reductions of 1/2. However, 1/4 mile visibility and
strong gusts will be possible with the stronger squalls that evolve,
as seen by the Delevan NY State mesonet web cam in northeast
Cattaraugus County NY at 1500-1515Z.
..Weinman.. 01/11/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BGM...BUF...CTP...LWX...PBZ...
LAT...LON 40847957 41447933 42217883 42807830 43147773 43177729
43067649 42787614 42277584 41707596 41407639 41237689
40837756 39407859 39147924 39297985 39627990 40847957Nearby
Mesoscale Discussions in Pennsylvania, 2026Mesoscale Discussions in New York, 2026Mesoscale Discussions in Maryland, 2026Every mesoscale discussion in 2026
Sources
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.