Alert archive / Pennsylvania / Mesoscale Discussions in 2011
Mesoscale Discussion 1817
The Storm Prediction Center issued this mesoscale discussion at Aug 1, 2011, 2:15 PM EDT for 7 states. It was in force for 90 min.
The area
The outline as issued.
The facts
- Issued
- Aug 1, 2011, 2:15 PM EDT (18:15 UTC)
- Expired
- Aug 1, 2011, 3:45 PM EDT
- In force
- 90 min
- Issued by
- the Storm Prediction Center
All 49 counties
Berkshire County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Norfolk County, MA, Worcester County, MA, Androscoggin County, ME, Cumberland County, ME, Franklin County, ME, Kennebec County, ME, Oxford County, ME, Piscataquis County, ME, Somerset County, ME, Belknap County, NH, Carroll County, NH, Cheshire County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH, Bergen County, NJ, Morris County, NJ, Passaic County, NJ, Sussex County, NJ, Warren County, NJ, Dutchess County, NY, Orange County, NY, Putnam County, NY, Rockland County, NY, Sullivan County, NY, Ulster County, NY, Westchester County, NY, Carbon County, PA, Columbia County, PA, Lackawanna County, PA, Lehigh County, PA, Luzerne County, PA, Monroe County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Union County, PA, Wayne County, PA, Kent County, RI, Providence County, RI
The radar
The Portland,ME radar (KGYX), 114 km from the middle of the area, began a volume at 18:15 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
Gray, ME (KGYX), launched 12:00Z, 6.3 hours before the alert went out and 114 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
- 55 J/kg
- Mixed-layer CIN
- -256 J/kg
- Mixed-layer LCL
- 1509 m above ground
- 0-6 km bulk shear
- 16 kt
- 0-1 km storm-relative helicity
- 45 m²/s²
- 0-3 km storm-relative helicity
- 88 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
303
ACUS11 KWNS 011816
SWOMCD
SPC MCD 011815
MEZ000-MAZ000-NHZ000-RIZ000-CTZ000-VTZ000-NYZ000-NJZ000-PAZ000-011945-
MESOSCALE DISCUSSION 1817
NWS STORM PREDICTION CENTER NORMAN OK
0115 PM CDT MON AUG 01 2011
AREAS AFFECTED...PORTIONS OF ME...NH...MA...RI...CT...SERN NY...ERN
PA...NRN NJ
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 011815Z - 011945Z
DAMAGING WIND GUSTS AND LARGE HAIL WILL BE POSSIBLE DURING THE
AFTERNOON HOURS ACROSS PORTIONS OF ME...NH...MA...RI...CT...SERN
NY...ERN PA AND NRN NJ. HOWEVER...UNLESS AN ORGANIZED SVR WEATHER
THREAT BECOMES APPARENT...A WW WILL PROBABLY NOT BE NEEDED.
AT 18Z...SCATTERED THUNDERSTORMS CONTINUED TO DEVELOP ALONG A ZONE
OF LOW-LEVEL CONVERGENCE AND AHEAD OF A SERIES OF MINOR UPPER-LEVEL
IMPULSES. SURFACE AIRMASS IS CHARACTERIZED BY TEMPERATURES IN THE
80S TO LOW 90S OVER MOST OF NEW ENGLAND AND THE MID ATLANTIC
REGION...WITH DEWPOINTS RANGING FROM 70F OVER PA/SERN NY/NRN NJ TO
AROUND 60F IN ME. A ZONE OF STEEP LOW-LEVEL LAPSE RATES HAS
DEVELOPED ACROSS THE AREA...WITH MLCAPE VALUES INCREASING TO
1000-3000 J/KG. THE FAVORABLE THERMODYNAMIC ENVIRONMENT WILL AID IN
SOME POTENTIAL FOR SVR MULTICELL THUNDERSTORMS POSING A DAMAGING
WIND AND LARGE HAIL THREAT. HOWEVER...AREA VWP/S AND RUC FORECAST
SOUNDINGS INDICATE FAIRLY WEAK VERTICAL WIND SHEAR PROFILES RESIDE
OVER THE REGION...WHICH WILL LIKELY PRECLUDE ORGANIZED SVR STORM
DEVELOPMENT. DESPITE THE WEAK SHEAR...IF STORM CLUSTERS CAN ORGANIZE
A COLD POOL AT THE MESOSCALE...THEN A WW MAY BECOME NECESSARY.
CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED.
..GARNER.. 08/01/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...CAR...GYX...BOX...OKX...ALY...PHI...BGM...CTP...
LAT...LON 46707000 46976970 46966874 44396955 43337094 41797113
40527531 40817788 42327332 43477188 46707000SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 1, 2:34 PM EDT | Severe Thunderstorm Watch | SPC | Greater Bridgeport Planning Region, Capitol Planning Region, Lower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region, Southeastern Connecticut Planning Region, Northeastern Connecticut Planning Region | 6 hr |
| Aug 1, 6:18 PM EDT | Mesoscale Discussion | SPC | 57 min | |
| Aug 1, 12:07 PM EDT | Mesoscale Discussion | SPC | Berkshire | 53 min |
| Aug 1, 3:22 PM EDT | Mesoscale Discussion | SPC | Burlington, Camden, Cumberland, Gloucester, Hunterdon, Mercer and 5 more | 83 min |
| Aug 1, 3:47 AM EDT | Mesoscale Discussion | SPC | Cattaraugus, Chautauqua, Erie, Genesee, Livingston, Monroe and 5 more | 58 min |
| Aug 1, 8:01 AM EDT | Mesoscale Discussion | SPC | Allegany, Cattaraugus, Chautauqua, Chemung, Erie, Genesee and 10 more | 89 min |
| Aug 1, 1:06 PM EDT | Mesoscale Discussion | SPC | Beaver, Lawrence | 24 min |
Nearby
Mesoscale Discussions in Pennsylvania, 2011Mesoscale Discussions in Connecticut, 2011Mesoscale Discussions in Maine, 2011Every mesoscale discussion in 2011
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.