DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191624
SWODY1
SPC AC 191622

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1122 AM CDT SUN AUG 19 2012

VALID 191630Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM FAR SERN VA TO THE LOWER
SAVANNAH RIVER VALLEY...

...SYNOPSIS...

LONGWAVE TROUGH --ANCHORED BY UPPER LOW JUST E OF JAMES BAY-- WILL
BE MAINTAINED E OF THE ROCKIES THROUGH THE D1 PERIOD. WITHIN THIS
BROAD-SCALE PATTERN...CONSIDERABLE STRENGTHENING OF MID AND
HIGH-LEVEL WIND FIELD IS FORECAST ALONG THE ATLANTIC SEABOARD IN
CONJUNCTION WITH A SERIES OF VORTICITY MAXIMA TRANSLATING NEWD FROM
BASE OF LONGWAVE TROUGH. ON THE UPSTREAM SIDE OF BASAL PORTION OF
LARGE-SCALE TROUGH...A VORTICITY MAXIMUM WILL MOVE SEWD THROUGH THE
OZARK PLATEAU REGION TODAY BEFORE WEAKENING ACROSS THE LOWER MS
VALLEY OVERNIGHT.

IN THE LOW LEVELS...16Z SURFACE ANALYSIS SHOWS AN AREA OF LOW
PRESSURE OVER NERN TN/FAR WRN VA WITH A COUPLE OF SEPARATE SURFACE
WAVES PRESENT IN ERN NC AND N-CNTRL SC. LATEST MODEL GUIDANCE
SUGGESTS THAT A CONSOLIDATION OF THESE FEATURES WILL OCCUR TODAY
WITH A DEEPENING SURFACE LOW MOVING OFF THE SERN VA COAST LATE
TONIGHT INTO MONDAY MORNING. MEANWHILE...A TRAILING COLD FRONT WILL
ADVANCE EWD THROUGH THE APPALACHIANS AND PIEDMONT WITH WRN EXTENSION
OF BOUNDARY SETTLING SWD ACROSS THE GULF COAST STATES AND CNTRL/SRN
TX.

...SERN AND SRN MID-ATLANTIC COASTAL AREAS THROUGH THIS AFTERNOON...

A BROKEN BAND OF STRONG-SEVERE STORMS IS IN PROGRESS THIS MORNING
FROM SERN VA TO THE LOWER SAVANNAH RIVER VALLEY...FORCED BY GLANCING
INFLUENCE OF A VORTICITY MAXIMUM PROGRESSING NEWD THROUGH THE CNTRL
APPALACHIANS. MODIFICATION OF 12Z MHX AND CHS SOUNDINGS FOR CURRENT
SURFACE CONDITIONS SUGGESTS THAT AMBIENT INFLOW AIR MASS HAS BECOME
UNCAPPED AND IS MODERATELY UNSTABLE WITH MLCAPE OF 1500-2500 J/KG.
MOREOVER...AREA VAD DATA SHOW THE PRESENCE OF A 40-50 KT MIDLEVEL
JET DEVELOPING EWD FROM THE APPALACHIANS INTO PIEDMONT WHICH IS
YIELDING VERTICALLY VEERING WIND PROFILES WITH 35-45 KT OF
DEEP-LAYER SHEAR. THE GIVEN ENVIRONMENT WILL REMAIN SUPPORTIVE OF
EMBEDDED SUPERCELL AND BOWING STRUCTURES THIS AFTERNOON WITH THE
PRIMARY HAZARD BEING DAMAGING WINDS ASSOCIATED WITH WET MICROBURSTS.
A WEAK TORNADO OR TWO IS ALSO POSSIBLE...NAMELY OVER SERN VA/NERN
NC...WHERE NEAR-GROUND SHEAR IS BEING ENHANCED BY LOCALLY BACKED
SURFACE WINDS INVOF WARM FRONT.

...NRN FL...

W-E ORIENTED BAND OF TSTMS ALONG THE SHELF WATERS OF THE GOM IS
EXPECTED TO MOVE/DEVELOP EWD ACROSS AREA TODAY WITHIN WLY FLOW
REGIME SAMPLED BY 12Z TLH SOUNDING. MODEL GUIDANCE INDICATES SOME
STRENGTHENING OF WIND FIELD TODAY...WHICH WHEN COUPLED WITH THE
MOIST...MODERATELY UNSTABLE AIR MASS /I.E. MLCAPE OF 1500-2500 J PER
KG/...SETUP WILL SUPPORT EMBEDDED...FORWARD-PROPAGATING STORM
CLUSTERS CAPABLE OF ISOLATED DAMAGING WIND GUSTS.

...ERN OK/WRN AR...

FORCING FOR ASCENT/DCVA ASSOCIATED WITH VORTICITY MAXIMUM MENTIONED
IN SYNOPSIS WILL COMBINE WITH LOW-LEVEL UPLIFT ALONG WEAK COLD
FRONT/WIND SHIFT MOVING EWD/SEWD ACROSS THE AREA TO FOSTER WIDELY
SCATTERED TSTMS THIS AFTERNOON AND EVENING. DESPITE SOME MIDLEVEL
COOLING...POOR LAPSE RATES WILL LIMIT THE POTENTIAL FOR MORE ROBUST
INSTABILITY TO DEVELOP. STILL...SOME POTENTIAL WILL EXIST FOR
LOCALLY STRONG WIND GUSTS OWING TO THE PRESENCE OF MODESTLY STRONG
DEEP...NWLY SHEAR.

...ERN NM/WRN TX...

A CLUSTER OF TSTMS IS ONGOING AS OF LATE MORNING W OF LBB ALONG WEAK
FRONT SAGGING SWD THROUGH WRN TX. MODIFYING 12Z MAF SOUNDING FOR
ANTICIPATED AFTERNOON CONDITIONS SUGGESTS THAT ENVIRONMENT SHOULD
SUSTAIN THE SWD PROGRESSION OF THESE STORMS AS MLCAPE INCREASES TO
1500-2500 J/KG. ADDITIONAL...ISOLATED-WIDELY SCATTERED TSTMS WILL
BE POSSIBLE LATER THIS AFTERNOON INTO EVENING WITHIN POST-FRONTAL
UPSLOPE REGIME DEVELOPING OVER NERN NM. THOUGH VERTICAL SHEAR WILL
REMAIN RELATIVELY WEAK...THE MODERATE INSTABILITY AND STEEP LAPSE
RATES WILL PROMOTE VIGOROUS UP/DOWNDRAFTS WITH A RISK FOR LOCALLY
DAMAGING WINDS AND SOME HAIL IN BOTH REGIMES.

..MEAD/SMITH.. 08/19/2012

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