Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 1753
The Storm Prediction Center issued this mesoscale discussion at Sep 15, 2021, 10:33 AM EDT for 5 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 15, 2021, 10:33 AM EDT (14:33 UTC)
- Expired
- Sep 15, 2021, 1:00 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 95%
All 75 counties
Berkshire County, MA, Sussex County, NJ, Warren County, NJ, Albany County, NY, Broome County, NY, Chemung County, NY, Chenango County, NY, Columbia County, NY, Cortland County, NY, Delaware County, NY, Dutchess County, NY, Essex County, NY, Fulton County, NY, Greene County, NY, Hamilton County, NY, Madison County, NY, Montgomery County, NY, Orange County, NY, Otsego County, NY, Rensselaer County, NY, Saratoga County, NY, Schenectady County, NY, Schoharie County, NY, Sullivan County, NY, Tioga County, NY, Tompkins County, NY, Ulster County, NY, Warren County, NY, Washington County, NY, Bedford County, PA, Berks County, PA, Blair County, PA, Bradford County, PA, Cambria County, PA, Carbon County, PA, Centre County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Indiana County, PA, Juniata County, PA, Lackawanna County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Monroe County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wayne County, PA, Wyoming County, PA, Addison County, VT, Bennington County, VT, Chittenden County, VT, Orange County, VT, Rutland County, VT, Washington County, VT, Windham County, VT, Windsor County, VT
The radar
The Binghamton radar (KBGM), 35 km from the middle of the area, began a volume at 14:43 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
Albany, NY (KALY), launched 12:00Z, 2.6 hours before the alert went out and 189 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
- 856 J/kg
- Mixed-layer CIN
- -92 J/kg
- Mixed-layer LCL
- 766 m above ground
- 0-6 km bulk shear
- 51 kt
- 0-1 km storm-relative helicity
- 214 m²/s²
- 0-3 km storm-relative helicity
- 248 m²/s²
- Significant tornado parameter
- 0.7
- Supercell composite
- 6.3
The text
As transmitted.
286
ACUS11 KWNS 151433
SWOMCD
SPC MCD 151433
NHZ000-VTZ000-MAZ000-CTZ000-NYZ000-NJZ000-PAZ000-151700-
Mesoscale Discussion 1753
NWS Storm Prediction Center Norman OK
0933 AM CDT Wed Sep 15 2021
Areas affected...portions of PA...NY and VT
Concerning...Severe potential...Watch likely
Valid 151433Z - 151700Z
Probability of Watch Issuance...95 percent
SUMMARY...Thunderstorms will increase in coverage and intensity
through early afternoon. Damaging wind gusts will be the main hazard
with this activity and a watch will likely be needed by 16z-17z.
DISCUSSION...Isolated showers and thunderstorms are already
developing late this morning within the pre-frontal warm sector
across parts of PA/NY. This initial activity is likely a bit
elevated and within a strong shear/weak instability environment and
not likely to produce severe wind gusts initially. However, stronger
heating is occurring ahead of this activity across central/eastern
NY/PA. As a result, low-level inhibition will rapidly erode, and
surface dewpoints around 65-70 F will aid in MLCAPE of 1000-2000
J/kg by early afternoon. Effective shear magnitudes around 35-50 kt
are already in place across the region per 12z RAOBs and 14z
mesoanalysis data. Low-level low is forecast to veer with time, and
long, relatively straight hodographs are forecast. This will support
organized clusters and line/bowing segments in bands along/ahead of
the cold front. Damaging gusts will be the main hazard as midlevel
lapse rates will remain modest (around 6-6.5 C/km). Midlevel lapse
rates will improve slightly toward eastern NY and New England (6.5-7
C/km) and any persistent, discrete activity could produce some hail
across with eastward extent.
..Leitman/Thompson.. 09/15/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GYX...BOX...BTV...OKX...ALY...PHI...BGM...CTP...
PBZ...
LAT...LON 40987893 42317680 43347524 44637294 44587246 44267215
43507235 42477302 41247418 40177628 39867759 39827864
40037915 40357934 40987893SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 15, 11:55 AM EDT | Severe Thunderstorm Watch | SPC | Berkshire | 8 hr |
| Sep 15, 3:04 PM EDT | Mesoscale Discussion | SPC | Berkshire, Essex, Franklin, Hampden, Hampshire, Middlesex and 2 more | 116 min |
| Sep 15, 3:43 PM EDT | Severe Thunderstorm Watch | SPC | Franklin, Hampden, Hampshire, Worcester | 6 hr |
| Sep 15, 4:38 PM EDT | Mesoscale Discussion | SPC | Berkshire, Franklin, Hampshire | 67 min |
| Sep 15, 11:59 AM EDT | Mesoscale Discussion | SPC | Essex | 2 hr |
Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New York, 2021Mesoscale Discussions in Vermont, 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.