Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 99
The Storm Prediction Center issued this mesoscale discussion at Feb 15, 2021, 9:16 PM EST for Sussex County, New Jersey; Orange County, Sullivan County, New York; 40 counties in Pennsylvania. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 15, 2021, 9:16 PM EST (02:16 UTC)
- Expired
- Feb 16, 2021, 2:15 AM EST
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Freezing rain
All 43 counties
Sussex County, NJ, Orange County, NY, Sullivan County, NY, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Blair County, PA, Bradford County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Carbon County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Dauphin County, PA, Elk County, PA, Forest County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lackawanna County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Monroe County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Pike County, PA, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wayne County, PA, Westmoreland County, PA, Wyoming County, PA
The radar
The State College radar (KCCX), 6 km from the middle of the area, began a volume at 02:19 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
Pittsburgh, PA (KPIT), launched 00:00Z, 2.3 hours before the alert went out and 187 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
- 557 m above ground
- 0-6 km bulk shear
- 76 kt
- 0-1 km storm-relative helicity
- 368 m²/s²
- 0-3 km storm-relative helicity
- 599 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
797
ACUS11 KWNS 160216
SWOMCD
SPC MCD 160216
NYZ000-NJZ000-PAZ000-160715-
Mesoscale Discussion 0099
NWS Storm Prediction Center Norman OK
0816 PM CST Mon Feb 15 2021
Areas affected...Portions of central and northern Pennsylvania into
southern New York
Concerning...Freezing rain
Valid 160216Z - 160715Z
SUMMARY...Moderate to occasionally heavy freezing rain is possible
across central/northern Pennsylvania into the overnight.
North-central and northeastern portions of the state will see the
longest duration of freezing rain. Heavier rainfall rates will
likely cease by 3-4 AM EST.
DISCUSSION...An increase in precipitation is expected to occur over
Pennsylvania this evening where light to moderate freezing rain has
already been observed in western and central portions of the state.
A strong shortwave trough is expected to move northeastward into the
region, deepening a surface low in the process. As this occurs, 850
hPa flow and warm air advection will increase from west to east. Any
lingering mixed precipitation should change to freezing rain as the
warm nose aloft strengthens and the cold near-surface layer becomes
more shallow. Pockets of moderate to perhaps heavy freezing rain are
possible. The areas that should see the longest duration of freezing
rain are north-central into northeastern Pennsylvania. Precipitation
should begin to diminish from west to east as the shortwave trough
passes. Furthermore, the strong low-level warm advection should also
allow a gradual changeover to rain from south to north, generally.
The heaviest freezing rain should cease by 3-4 AM EST.
..Wendt.. 02/16/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...ALY...PHI...BGM...CTP...PBZ...
LAT...LON 40178001 40388043 40718035 41107981 41557939 41877803
41957547 41757418 41267386 40717556 40457659 40087836
40177955 40178001SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 15, 8:06 PM EST | Mesoscale Discussion | SPC | Allegany, Cattaraugus, Cayuga, Chautauqua, Erie, Franklin and 18 more | 5 hr |
| Feb 16, 2:51 AM EST | Mesoscale Discussion | SPC | Albany, Columbia, Greene, Montgomery, Rensselaer, Schenectady and 1 more | 4 hr |
Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New York, 2021Mesoscale Discussions in New Jersey, 2021Every mesoscale discussion in 2021
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.