Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 1269
The Storm Prediction Center issued this mesoscale discussion at Jul 13, 2021, 12:48 PM EDT for 29 counties in New York; 42 counties in Pennsylvania. It was in force for 87 min.
The area
The outline as issued.
The facts
- Issued
- Jul 13, 2021, 12:48 PM EDT (16:48 UTC)
- Expired
- Jul 13, 2021, 2:15 PM EDT
- In force
- 87 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 71 counties
Allegany County, NY, Broome County, NY, Cattaraugus County, NY, Cayuga County, NY, Chautauqua County, NY, Chemung County, NY, Chenango County, NY, Cortland County, NY, Erie County, NY, Genesee County, NY, Jefferson County, NY, Lewis County, NY, Livingston County, NY, Madison County, NY, Monroe County, NY, Niagara County, NY, Oneida County, NY, Onondaga County, NY, Ontario County, NY, Orleans County, NY, Oswego County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Tioga County, NY, Tompkins County, NY, Wayne County, NY, Wyoming County, NY, Yates County, NY, Armstrong County, PA, Berks County, PA, Blair County, PA, Bradford 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, Cumberland 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, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, McKean County, PA, Mifflin County, PA, Monroe County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Warren County, PA, Wayne County, PA, Wyoming County, PA
The radar
The Binghamton radar (KBGM), 95 km from the middle of the area, began a volume at 16:50 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 4.8 hours before the alert went out and 180 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
- 610 J/kg
- Mixed-layer CIN
- -36 J/kg
- Mixed-layer LCL
- 907 m above ground
- 0-6 km bulk shear
- 36 kt
- 0-1 km storm-relative helicity
- 56 m²/s²
- 0-3 km storm-relative helicity
- 90 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.9
The text
As transmitted.
543
ACUS11 KWNS 131648
SWOMCD
SPC MCD 131648
NYZ000-PAZ000-NJZ000-131815-
Mesoscale Discussion 1269
NWS Storm Prediction Center Norman OK
1148 AM CDT Tue Jul 13 2021
Areas affected...Portions of the Northeast
Concerning...Severe potential...Watch likely
Valid 131648Z - 131815Z
Probability of Watch Issuance...80 percent
SUMMARY...Scattered storms developing will pose a risk for damaging
winds and severe hail this afternoon/evening. A severe thunderstorm
watch will likely be issued in the next hour.
DISCUSSION...Visible satellite shows morning clearing has given way
to widespread cumulus development across the region. Surface
temperatures have warmed into the low to mid 80s F amid rich
low-level moisture characterized by dew point temperatures in the
low to mid 70s F. This has led to rapid destabilization, with MLCAPE
values of 1500 J/kg being analyzed across the region, and
approaching 2000-2500 J/kg across portions of south-central
Pennsylvania. Isolated storms are already beginning to develop, with
a severe/maturing convective cell noted in central New York.
This trend is expected to continue, with scattered storms expected
across the region by early to mid afternoon. With effective bulk
shear of 35-40 kt, storms should organize into a mixture of
multicells and supercells, posing a risk for mainly damaging winds
and some severe hail, and a tornado or two is possible. Given these
trends, a severe thunderstorm watch will likely be needed for the
region in the next hour or so.
..Karstens/Dial.. 07/13/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BTV...ALY...PHI...BGM...BUF...CTP...PBZ...
LAT...LON 40077851 40317946 42157955 43467877 43467709 44027622
44237541 43817479 41887524 40777511 40097610 39967680
40077851SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 13, 1:37 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Broome, Cattaraugus, Cayuga, Chautauqua, Chemung and 26 more | 10 hr |
| Jul 13, 4:07 PM EDT | Mesoscale Discussion | SPC | Allegany, Broome, Cattaraugus, Cayuga, Chautauqua, Chemung and 25 more | 113 min |
| Jul 13, 6:44 PM EDT | Mesoscale Discussion | SPC | Allegany, Broome, Cattaraugus, Cayuga, Chemung, Chenango and 20 more | 91 min |
Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New York, 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.