MESO: Mesoscale Discussion 1950

ACUS11 KWNS 071211
SWOMCD
SPC MCD 071210
NYZ000-PAZ000-NJZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-071415-

MESOSCALE DISCUSSION 1950
NWS STORM PREDICTION CENTER NORMAN OK
0710 AM CDT MON OCT 07 2013

AREAS AFFECTED...ERN VIRGINIA...CNTRL AND ERN MARYLAND...ERN
PENNSYLVANIA...SRN NEW YORK STATE

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 071210Z - 071415Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...SEVERE THUNDERSTORM POTENTIAL MAY INCREASE SUFFICIENTLY TO
REQUIRE ONE OR MORE WATCHES...PERHAPS AS EARLY AS THE 13-14Z TIME
FRAME.

DISCUSSION...A NARROW ENHANCED CONVECTIVE BAND APPEARS TO GRADUALLY
BE IN THE PROCESS OF EVOLVING ALONG A SIGNIFICANT SURFACE FRONT NOW
CROSSING THE LOWER GREAT LAKES/UPPER OHIO VALLEY AND CENTRAL
APPALACHIANS REGION. FURTHER DEVELOPMENT AND INTENSIFICATION
APPEARS LIKELY WHILE ACTIVITY SLOWLY PROGRESSES EASTWARD THROUGH THE
REMAINDER OF THE MORNING...AS FRONTOGENETIC FORCING CONTINUES TO
STRENGTHEN WITH THE APPROACH OF THE VIGOROUS UPSTREAM SHORT WAVE
TROUGH. THIS IS ALSO EXPECTED TO COINCIDE WITH SUBSTANTIVE
STRENGTHENING OF SOUTHERLY PRE-FRONTAL LOW-LEVEL FLOW...WITH THE
HIGH RESOLUTION RAPID REFRESH INDICATING 850 MB WINDS IN EXCESS OF
50 KT IN A CORRIDOR ACROSS NORTH CENTRAL VIRGINIA THROUGH
CENTRAL/EASTERN PENNSYLVANIA AND THE SOUTHERN TIER OF NEW YORK STATE
BY THE 15-17Z TIME FRAME.

INSTABILITY APPEARS THE PRIMARY LIMITING FACTOR CONCERNING THE
SEVERE WEATHER POTENTIAL. WITH CONSIDERABLE CLOUD COVER LIKELY TO
INHIBIT SURFACE HEATING...AND COLDER AIR ALOFT CONTINUING TO LAG THE
SURFACE FRONT...LOWER/MID TROPOSPHERIC LAPSE RATES WILL REMAIN WEAK.
BUT MOISTURE CONTENT IS SEASONABLY HIGH...AND CONTRIBUTING TO
SUFFICIENT CAPE THROUGH FAVORABLY COLD MID-LAYERS TO SUPPORT ONGOING
THUNDERSTORM ACTIVITY ALONG AND TO THE LEE OF THE BLUE RIDGE
MOUNTAINS. THIS LIKELY WILL CONTINUE DEVELOPING NORTHWARD WHILE
GRADUALLY SHIFTING EASTWARD DURING THE NEXT FEW HOURS. IT MAY NOT
TAKE MUCH CONVECTIVE INTENSIFICATION TO SUPPORT TO SUPPORT AT LEAST
LOW PROBABILITIES FOR SEVERE WIND GUSTS ASSOCIATED WITH DOWNWARD
MOMENTUM TRANSFER. AS PRECIPITATION LOADING INCREASES...THE
POTENTIAL FOR SEVERE WIND GUSTS PROBABLY WILL INCREASE THROUGH MID
TO LATE MORNING.

GIVEN THE HIGH BOUNDARY LAYER MOISTURE CONTENT...AND THE ANTICIPATED
EVOLUTION OF RATHER LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS IN
THE PRE-FRONTAL ENVIRONMENT...THE RISK FOR TORNADOES MAY NOT BE
COMPLETELY NEGLIGIBLE. HOWEVER...THIS THREAT SEEMS LIMITED BY THE
LOW POTENTIAL FOR VIGOROUS DISCRETE STORM DEVELOPMENT.

..KERR/EDWARDS.. 10/07/2013

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

ATTN...WFO...PHI...BGM...AKQ...CTP...LWX...RNK...

LAT...LON 39957748 41487743 42637660 42227526 39567538 37547684
36877792 36987908 37997828 39957748

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