Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 503
The Storm Prediction Center issued this severe thunderstorm watch at Sep 15, 2021, 3:43 PM EDT for 5 states. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 15, 2021, 3:43 PM EDT (19:43 UTC)
- Expired
- Sep 15, 2021, 10:00 PM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 50 kt
Counties Capitol Planning Region, CT, Northwest Hills Planning Region, CT, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Worcester County, MA, Sussex County, NJ, Warren County, NJ, Dutchess County, NY, Orange County, NY, Putnam County, NY, Berks County, PA, Carbon County, PA, Lehigh County, PA, Monroe County, PA, Northampton County, PA
The radar
The Albany radar (KENX), 102 km from the middle of the area, began a volume at 19:42 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 50%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 15, 7:08 PM EDT | Severe Thunderstorm Warning | PHI | Berks | 37 min |
| Sep 15, 7:53 PM EDT | Severe Thunderstorm Warning | BOX | Hampden, Hampshire, Middlesex, Worcester | 13 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Albany, NY (KALY), launched 12:00Z, 7.7 hours before the alert went out and 103 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.
035 WWUS20 KWNS 151939 SEL3 SPC WW 151939 CTZ000-MAZ000-NJZ000-NYZ000-PAZ000-160200- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 503 NWS Storm Prediction Center Norman OK 340 PM EDT Wed Sep 15 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Connecticut Western and central Massachusetts Extreme northern New Jersey A small part of southeast New York East central Pennsylvania * Effective this Wednesday afternoon and evening from 340 PM until 1000 PM EDT. * Primary threats include... Isolated damaging wind gusts to 60 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Thunderstorms along and ahead of a cold front will continue to spread eastward through late evening. The strongest storms will be capable of producing occasional damaging outflow gusts near 60 mph and isolated large hail near 1 inch diameter, prior to the storms weakening early tonight. The severe thunderstorm watch area is approximately along and 30 statute miles north and south of a line from 35 miles east of Keene NH to 35 miles west southwest of Allentown PA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU3). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 501...WW 502... AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 50 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25030. ...Thompson
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 15, 3:04 PM EDT | Mesoscale Discussion | SPC | 116 min | |
| 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, 4:38 PM EDT | Mesoscale Discussion | SPC | Berkshire, Franklin, Hampshire | 67 min |
| Sep 15, 11:59 AM EDT | Mesoscale Discussion | SPC | Belknap, Carroll, Cheshire, Coos, Grafton, Hillsborough and 4 more | 2 hr |
| Sep 15, 1:15 PM EDT | Severe Thunderstorm Watch | SPC | Belknap, Carroll, Cheshire, Coos, Grafton, Hillsborough and 4 more | 6 hr |
Nearby
Severe Thunderstorm Watches in Pennsylvania, 2021Severe Thunderstorm Watches in Massachusetts, 2021Severe Thunderstorm Watches in Connecticut, 2021Every severe thunderstorm watch 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.