Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS11 KWNS 301631
SWOMCD
SPC MCD 301631
NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-301900-

MESOSCALE DISCUSSION 1240
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CDT TUE JUN 30 2015

AREAS AFFECTED...PORTIONS OF ERN PA...WRN NJ...SERN NY...MD...NRN
DE...NRN VA...AND WASHINGTON DC

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 301631Z - 301900Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TSTMS WILL INCREASE IN NUMBER AND INTENSITY THROUGH THE
AFTERNOON AND POSE AN INCREASING RISK FOR DMGG WIND GUSTS AND
POSSIBLY A COUPLE OF TORNADOES. WW ISSUANCE WILL BE POSSIBLE.

DISCUSSION...VISIBLE SATELLITE IMAGERY DEPICTS AREAS OF INSOLATION
FROM THE NRN VA PIEDMONT TO S-CNTRL PA AMIDST A BROAD...MERIDIONALLY
ORIENTED WARM/MOIST CONVEYOR ON THE PERIPHERY OF AN ERN-CONUS
TROUGH. STEEPENING LAPSE RATES IN THOSE AREAS HAVE CONTRIBUTED TO AN
UPTICK IN CONVECTION ACROSS PARTS OF S-CNTRL/SERN PA PER RECENT 7-KM
CAPPI RADAR DATA. AS LOW-LEVEL STRATUS CONTINUES TO ERODE ACROSS
PARTS OF E-CNTRL/NERN PA AND POINTS FARTHER N/E...THE ENTIRE AREA
WILL BE SUBJECTED TO CONTINUED DIURNAL DESTABILIZATION AMIDST RICH
PBL MOISTURE CHARACTERIZED BY DEWPOINTS FROM THE MIDDLE 60S TO THE
LOWER 70S. THIS WILL FOSTER A CONTINUED INCREASE IN THE
COVERAGE/INTENSITY OF CONVECTION INTO THE AFTERNOON IN THE
LOW-MLCINH ENVIRONMENT... ESPECIALLY AS A LOW-AMPLITUDE MID-LEVEL
PERTURBATION ACROSS PA GRAZES THE AREA.

THE PRESENCE OF 30-40 KT OF EFFECTIVE BULK SHEAR WILL SUPPORT SOME
POTENTIAL FOR ORGANIZED/SUSTAINED CONVECTION AND POSSIBLE
SUPERCELLS...WITH ISOLATED TO WIDELY SCATTERED DMGG WIND GUSTS AND
PERHAPS MARGINALLY SVR HAIL. WHERE SFC WINDS REMAIN BACKED --
ESPECIALLY IN AREAS WHERE VERTICAL MIXING IS MORE SUPPRESSED --
LOW-LEVEL DIRECTIONAL SHEAR WILL CONTRIBUTE TO SOME RISK FOR A
COUPLE OF TORNADOES. THIS WOULD PARTICULARLY BE THE CASE IN ERN PA
AND VICINITY WHERE INTERPOLATION BETWEEN REGIONAL VWPS IMPLY THE
STRONGEST FLOW WITH THE LLJ. THE MODEST NATURE OF MID-LEVEL LAPSE
RATES AND UNCERTAINTY IN ANTECEDENT CLOUD/BUOYANCY EVOLUTION YIELD
SOME LIMITATIONS TO EXACT CONVECTIVE INTENSITY CONFIDENCE...THOUGH
THE AREA WILL CONTINUE TO BE MONITORED FOR POSSIBLE WW ISSUANCE.

..COHEN/HART.. 06/30/2015

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

ATTN...WFO...OKX...PHI...BGM...CTP...LWX...

LAT...LON   39647785 41167731 41667687 42007625 42057503 41367424
            39987489 39007609 38737739 39647785



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