Mesoscale Discussion 1489

Issued

Jul 18, 2012, 10:25 AM EDT (14:25 UTC)

Expired

Jul 18, 2012, 12:30 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

95%

The Binghamton radar (KBGM), 143 km from the middle of the area, began a volume at 14:25 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.

• Severe Thunderstorm Watch 490Jul 18, 12:20 PM EDT
• Severe Thunderstorm Watch 491Jul 18, 12:45 PM EDT
• Severe Thunderstorm Watch 492Jul 18, 1:15 PM EDT

608 
ACUS11 KWNS 181426
SWOMCD
SPC MCD 181425
MAZ000-RIZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-181630-

MESOSCALE DISCUSSION 1489
NWS STORM PREDICTION CENTER NORMAN OK
0925 AM CDT WED JUL 18 2012

AREAS AFFECTED...MUCH OF PA/NJ TO SOUTHERN NY/SOUTHERN NEW ENGLAND

CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY

VALID 181425Z - 181630Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...WITH INCREASING POTENTIAL FOR DAMAGING WINDS/SEVERE HAIL
THIS AFTERNOON...A SEVERE TSTM WATCH WILL LIKELY BE NEEDED FOR ALL
OR MUCH OF PA/NJ AND SOUTHERN PORTIONS OF NY/NEW ENGLAND BY 15Z-16Z.

DISCUSSION...A FRONTAL BOUNDARY IS ANALYZED THIS MORNING FROM LAKE
ERIE VICINITY EAST-NORTHEASTWARD TO EAST-CENTRAL NY/CENTRAL NEW
ENGLAND. THE AIRMASS TO THE SOUTH OF THIS BOUNDARY IS STEADILY
WARMING AMID RELATIVELY CLOUD-FREE SKIES PER VISIBLE SATELLITE
IMAGERY...WITH DEWPOINTS GENERALLY IN THE UPPER 60S/LOWER 70S F.
INCIPIENT TSTM DEVELOPMENT IS ALREADY OCCURRING ACROSS WEST-CENTRAL
PA AS OF 14Z. ALONG/SOUTH OF THE COLD FRONT...WITH ADDITIONAL AIDE
OF NEAR-COASTAL/PRE-FRONTAL SURFACE TROUGH DEVELOPMENT...IT SEEMS
VERY LIKELY THAT SCATTERED TSTMS WILL CONTINUE TO DEVELOP/INCREASE
INTO EARLY/MID AFTERNOON ACROSS MUCH OF THE REST OF PA/NJ AND
SOUTHERN NY/SOUTHERN NEW ENGLAND.

BASED ON 12Z OBSERVED SOUNDINGS SUCH AS BUF/ALB/OKX...MUCH OF THE
REGION RESIDES ON THE SOUTHERN FRINGE OF MODERATE WESTERLIES ALOFT
/30-50 KT 3-6 KM/ AND COINCIDES WITH A PLUME OF RELATIVELY STEEP MID
LEVEL LAPSE RATES /ESPECIALLY SOUTHEAST NY AND SOUTHERN NEW
ENGLAND/. WITH STEEPENING LOW LEVEL LAPSE RATES AND A LIKELIHOOD OF
2000-3500 J/KG SBCAPE SOUTH OF THE COLD FRONT...STRONG/SEVERE TSTM
DEVELOPMENT AND INTENSIFICATION IS LIKELY THROUGH EARLY/MID
AFTERNOON. SUFFICIENT VERTICAL SHEAR EXISTS FOR ORGANIZED/SUSTAINED
MULTICELLS...AND THIS WILL ESPECIALLY BE THE CASE FOR AREAS SUCH AS
NORTHEAST PA/NORTHERN NJ INTO FAR SOUTHEAST NY/SOUTHERN NEW ENGLAND.
HERE...SOMEWHAT STRONGER VERTICAL SHEAR WILL SUPPORT BOWING
STRUCTURES/SOME SUPERCELLS...WITH DAMAGING WINDS/SEVERE HAIL AND
PERHAPS A TORNADO BEING POSSIBLE.

..GUYER/MEAD.. 07/18/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...BOX...OKX...ALY...PHI...BGM...CTP...PBZ...

LAT...LON   39907668 40067864 40937942 41677867 42107704 42377440
            42697266 42577146 42207103 41607103 41327181 40587347
            39437479 39907668

Mesoscale Discussions in Pennsylvania, 2012Mesoscale Discussions in New York, 2012Mesoscale Discussions in New Jersey, 2012Every mesoscale discussion in 2012

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.