ACUS01 KWNS 132018
SWODY1
SPC AC 132016
DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
0316 PM CDT THU OCT 13 2011
VALID 132008Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS FOR ERN AND NRN VA INTO THE
DELMARVA...
AMENDED TO ADD LOW TORNADO PROBS
ADDED 5% TORNADO PROBABILITIES FOR A SMALL PORTION OF VA...MD AND
DE. A FEW STRONGER STORMS WILL MOVE NEAR THE BAROCLINIC
ZONE/BOUNDARY MENTIONED IN THE PREVIOUS OUTLOOK. LOCALIZED SHEAR IN
THIS VICINITY MAY RESULT IN A WEAK AND BRIEF TORNADO OR TWO.
------------------------------------------------------------------
...AL/GA...
SCATTERED LOW TOPPED THUNDERSTORMS EMBEDDED WITHIN A MODESTLY STRONG
WLY FLOW REGIME WILL HAVE A THREAT OF STRONG WIND GUSTS ACROSS AL
AND GA THROUGH THE AFTERNOON. FOR MORE INFORMATION SEE MESOSCALE
DISCUSSION 2253.
...MID ATLANTIC...
POCKETS OF HEATING HAVE RESULTED IN GRADUAL DESTABILIZATION FROM NC
INTO THE DELMARVA WITH DEEPENING CU FIELDS. A GRADUALLY DEEPENING
SURFACE TROUGH COMBINED WITH HEIGHT FALLS AS THE MAIN UPPER VORT
CENTER APPROACHES WILL MAINTAIN FAVORABLE WIND PROFILES FOR A FEW
SUPERCELLS AND/OR SMALL BOWS CAPABLE OF DAMAGING WINDS. A BRIEF
TORNADO CANNOT BE RULED OUT ESPECIALLY WITH STORMS AS THEY CROSS THE
WARM FRONT WHICH CURRENTLY IS ACCOMPANIED BY EFFECTIVE SRH OF
100-150 M2/S2. RELATIVELY BROAD AND WEAK FORCING ACROSS THE WARM
SECTOR IS EXPECTED TO KEEP SEVERE STORM COVERAGE DOWN...RESULTING IN
A CONTINUED SEE TEXT AREA.
ADDED A 5% HAIL AREA FROM ERN NC INTO THE DELMARVA WHERE STRONGER
INSTABILITY EXISTS AND WHERE SPORADIC MARGINAL HAIL CORES APPEAR
POSSIBLE.
..JEWELL.. 10/13/2011
.PREV DISCUSSION... /ISSUED 1135 AM CDT THU OCT 13 2011/
...CNTRL GULF STATES TO SERN ATLANTIC COAST AND NWD INTO THE MID
ATLANTIC STATES...
STRONG VORTICITY MAXIMUM ON POLEWARD SIDE OF 80-90 KT MIDLEVEL JET
STREAK OVER THE LOWER MS VALLEY WILL CONTINUE ESEWD...CONTRIBUTING
TO FURTHER AMPLIFICATION OF NEGATIVELY TILTED LARGE-SCALE TROUGH
WHICH WILL EXTEND FROM CNTRL CANADA TO SERN ATLANTIC COAST BY
14/12Z. IN THE LOW LEVELS...ASSOCIATED COLD FRONT WILL ADVANCE EWD
FROM THE TN VALLEY AND CNTRL GULF COAST STATES TO OFF THE MIDDLE AND
SERN ATLANTIC COASTS BY FRI MORNING.
12Z OBSERVED SOUNDINGS FROM THE LOWER MS VALLEY SHOWED A PRONOUNCED
MIDLEVEL INVERSION ASSOCIATED WITH A SHARP THERMAL GRADIENT
COINCIDENT WITH UPPER-LEVEL JET STREAK. AND DESPITE THE PRESENCE OF
A MOIST AND WARMING PRE-FRONTAL WARM SECTOR...FORECAST SOUNDINGS
INDICATE THAT THIS INVERSION WILL SPREAD EWD TODAY...LIMITING THE
DEPTH AND MAGNITUDE OF POTENTIAL BUOYANCY. THE COUPLING OF DCVA IN
ADVANCE OF VORTICITY MAXIMUM AND FRONTAL UPLIFT WILL PROMOTE A
GRADUAL INCREASE IN STORMS THROUGH THE DIURNAL HEATING CYCLE WITHIN
A KINEMATIC ENVIRONMENT FEATURING A STEADILY STRENGTHENING WLY
UNIDIRECTIONAL WIND FIELD. THIS SETUP WILL SUPPORT EVOLUTION OF
STORMS INTO BROKEN LINES WITH LOCALLY DAMAGING WIND GUSTS BEING THE
PRIMARY HAZARD.
A SEPARATE AREA OF SEVERE STORM POTENTIAL WILL EXIST FROM ERN NC NWD
ALONG THE MID ATLANTIC COAST THIS AFTERNOON INTO TONIGHT. WATER
VAPOR IMAGERY SHOWS A WEAK MIDLEVEL IMPULSE OVER THE CAROLINAS WHICH
WILL PROGRESS NNEWD AND COMBINE WITH A DIVERGENT UPPER-LEVEL FLOW
FIELD TO SUPPORT AN INCREASE IN STORMS ACROSS THE REGION. VISIBLE
SATELLITE IMAGERY SUGGESTS THAT FAIRLY WIDESPREAD CLOUDINESS WILL
LIMIT DAYTIME HEATING. BUT...THE PRESENCE OF A MOIST AIR MASS WILL
SUPPORT POCKETS OF MODEST DESTABILIZATION WITH AFTERNOON MLCAPE
VALUES RISING TO 1000-1500 J/KG. THIS INSTABILITY WILL ALIGN WITH A
STEADILY STRENGTHENING LOW- TO MID-TROPOSPHERIC WIND FIELD WITH THE
ENVIRONMENT BECOMING FAVORABLE FOR EMBEDDED BOWING AND SUPERCELL
STRUCTURES WITH AN ATTENDANT RISK FOR LOCALLY DAMAGING WIND GUSTS
AND PERHAPS A BRIEF TORNADO.
IT STILL APPEARS THAT THE WEAK LAPSE RATES AND MODEST LOW-LEVEL
SHEAR WILL LIMIT THE POTENTIAL FOR A MORE ROBUST SUPERCELL/TORNADO
THREAT. HOWEVER...ENVIRONMENTAL AND CONVECTIVE TRENDS WILL BE
MONITORED FOR A POSSIBLE OUTLOOK UPGRADE AT 20Z.
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