Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 1757
The Storm Prediction Center issued this mesoscale discussion at Sep 15, 2021, 4:38 PM EDT for 6 states. It was in force for 67 min.
The area
The outline as issued.
The facts
- Issued
- Sep 15, 2021, 4:38 PM EDT (20:38 UTC)
- Expired
- Sep 15, 2021, 5:45 PM EDT
- In force
- 67 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 501...502
All 55 counties
Berkshire County, MA, Franklin County, MA, Hampshire County, MA, Androscoggin County, ME, Cumberland County, ME, Kennebec County, ME, Oxford County, ME, Penobscot County, ME, Sagadahoc County, ME, Waldo County, ME, York County, ME, Belknap County, NH, Carroll County, NH, Cheshire County, NH, Grafton County, NH, Hillsborough County, NH, Merrimack County, NH, Strafford County, NH, Sullivan County, NH, Albany County, NY, Columbia County, NY, Delaware County, NY, Greene County, NY, Rensselaer County, NY, Schenectady County, NY, Schoharie County, NY, Sullivan County, NY, Ulster County, NY, Blair County, PA, Carbon County, PA, Centre County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Huntingdon County, PA, Juniata County, PA, Lackawanna County, PA, Lebanon County, PA, Luzerne County, PA, Mifflin County, PA, Monroe County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Union County, PA, Wayne County, PA, Wyoming County, PA, Bennington County, VT, Windham County, VT, Windsor County, VT
The radar
The Albany radar (KENX), 68 km from the middle of the area, began a volume at 20:38 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
Albany, NY (KALY), launched 12:00Z, 8.6 hours before the alert went out and 47 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.
834
ACUS11 KWNS 152038
SWOMCD
SPC MCD 152038
MEZ000-NHZ000-MAZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-152145-
Mesoscale Discussion 1757
NWS Storm Prediction Center Norman OK
0338 PM CDT Wed Sep 15 2021
Areas affected...eastern PA/NY into New England
Concerning...Severe Thunderstorm Watch 501...502...
Valid 152038Z - 152145Z
The severe weather threat for Severe Thunderstorm Watch 501, 502
continues.
SUMMARY...The severe threat continues across WW 501 and WW 502.
Damaging wind gusts will continue to be the primary hazard the next
few hours.
DISCUSSION...Several line segments/bows have developed ahead of the
eastward-advancing cold front from eastern PA into ME. This activity
is ongoing within a corridor of moderate instability/shear favorable
for organized convection. Damaging wind gusts will continue to be
the main hazard with this activity, though a few instances of
near-severe hail have been observed. The severe threat will
gradually diminish during the evening hours with loss of daytime
heating as the boundary-layer decouples and becomes more stable.
..Leitman.. 09/15/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CAR...GYX...BOX...BTV...OKX...ALY...PHI...BGM...
CTP...
LAT...LON 45326838 44426889 43357053 42477231 40817569 40037687
39947750 40047810 40307852 40767823 41337707 43017376
45167003 45516915 45546864 45326838SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 15, 11:59 AM EDT | Mesoscale Discussion | SPC | Androscoggin, Cumberland, Franklin, Kennebec, Lincoln, Oxford and 6 more | 2 hr |
| Sep 15, 1:15 PM EDT | Severe Thunderstorm Watch | SPC | Androscoggin, Cumberland, Franklin, Kennebec, Knox, Lincoln and 7 more | 6 hr |
| Sep 15, 10:33 AM EDT | Mesoscale Discussion | SPC | Berkshire | 2 hr |
| 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 |
Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New York, 2021Mesoscale Discussions in Maine, 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.