SWODY1
SPC AC 040058
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT FRI SEP 03 2010
VALID 040100Z - 041200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PROGRESSIVE NRN-STREAM PATTERN FEATURES SHARPLY DEFINED RIDGING FROM
LOWER CO RIVER VALLEY NNEWD ACROSS NRN ROCKIES TO SK...BRACKETED BY
STRONG TROUGHS OVER AK PANHANDLE AND UPPER GREAT LAKES REGION.
LATTER TROUGH IS ANCHORED BY 500 MB CYCLONE OVER NRN ONT NEAR
LS...WHICH IS PREDICTED TO MOVE SLOWLY EWD ACROSS ONT. RELATED SFC
FRONTAL ZONE -- ANALYZED AT 23Z FROM CENTRAL NY TO WRN VA...CENTRAL
MS...AND S-CENTRAL TX -- WILL MOVE EWD ACROSS REMAINDER MID-ATLANTIC
REGION AND ONTO CAROLINAS/GA PIEDMONT. TRAILING PORTION OF FRONT
WILL MOVE SWD ACROSS S TX AND LOWER MS VALLEY REGION.
...COASTAL SERN MA AND ADJACENT ISLANDS...
A FEW SHALLOW/SHORT-LIVED CELLS EMBEDDED WITHIN OUTER FRINGES OF
HURRICANE EARL...THOUGH MOSTLY DEVOID OF LIGHTNING...HAVE SHOWN
BRIEF/WEAK CYCLONIC SHEAR IN SRM IMAGERY. LOW-LEVEL SHEAR
ENVIRONMENT NNW-NE OF CENTER WILL BE FAVORABLE FOR SUPERCELLS...WITH
ENHANCED 0-1 KM AGL HODOGRAPHS. BRIEF WINDOW OF OPPORTUNITY EXISTS
DURING NEXT FEW HOURS WHERE THAT SECTOR OF EARL WILL AFFECT THIS
AREA...FOR A TRANSIENT SUPERCELL OR TWO TO DEVELOP AND MOVE ASHORE.
HOWEVER...THERMODYNAMIC CHARACTER OF AIR MASS IS IN QUESTION GIVEN
SHALLOW STABLE LAYER EVIDENT IN CHH RAOB...LOSS OF ALREADY WEAK
DIURNAL HEATING INLAND...AND CONTINUED WEAKENING OF EARL OVERALL AS
IT MOVES OVER COLDER WATER...PER NHC DISCUSSIONS. OVERALL
PROBABILITIES ARE TOO SMALL/CONDITIONAL FOR CATEGORICAL OUTLOOK.
REF NHC ADVISORIES FOR LATEST TRACK/INTENSITY GUIDANCE ON THIS
SYSTEM.
...FRONTAL ZONE FROM NERN CONUS TO CENTRAL APPALACHIANS...
POCKETS OF MARGINAL BUOYANCY LINGER ACROSS PORTIONS OF INLAND
MID-ATLANTIC REGION AND CENTRAL APPALACHIANS...SUPPORTING ISOLATED
TO WIDELY SCATTERED TSTMS INVOF COLD FRONT IN THOSE AREAS.
CONVECTIVE POTENTIAL WILL DIMINISH MARKEDLY IN NEXT 2-3
HOURS...HOWEER...AS PREFRONTAL AIR MASS EXPERIENCES DIABATIC SFC
COOLING AND AS FRONT MOVES ACROSS MOUNTAINS INTO DRIER...DOWNSLOPING
WLY FLOW REGIME.
...LOWER MS VALLEY TO S TX...
CONVECTIVE POTENTIAL MAY PERSIST OVER THIS REGION ALONG AND AHEAD OF
COLD FRONT LONGER THAN FARTHER NE...GIVEN MORE ROBUST BOUNDARY LAYER
THETAE AND SLIGHTLY STEEPER LAPSE RATES ALOFT. HOWEVER...NLY FLOW
COMPONENT ACROSS ENTIRE REGION WILL RESULT IN VERY WEAK CONVERGENCE
INVOF FRONTAL ZONE...WHILE SFC AIR MASS COOLS AFTER DARK.
THEREFORE...EXPECT CONVECTIVE COVERAGE TO DIMINISH IN THIS AREA AS
WELL. DEEP-LAYER WINDS AND SHEAR ARE TOO WEAK TO SUPPORT ORGANIZED
SVR PROBABILITIES.
...AZ/NM...
WIDELY SCATTERED TSTMS FCST TO PERSIST INTO EARLY EVENING OVER SERN
AZ AND HIGHER TERRAIN FROM NEAR MOGOLLON RIM NEWD TO WRN
NM...SUPPORTED BY POCKETS OF 250-500 J/KG MLCAPE. EXPECT CONVECTIVE
COVERAGE TO DIMINISH THROUGH EVENING...AS MLCINH INCREASES DUE TO
COMBINATION OF SFC COOLING AND SPREADING OUTFLOWS.
...INLAND NWRN CONUS...
MRGL THUNDER POTENTIAL LINGERS OVER THIS REGION...PRIMARILY TIED TO
REMAINING AREAS OF HEATING OF HIGHER TERRAIN FOR ANOTHER 1-2 HOURS.
VIS IMAGERY SHOWS TCU AND ISOLATED CB. MODIFIED RAOBS AND RUC
SOUNDINGS SUGGEST MLCAPE WILL REMAIN BELOW 300 J/KG...LIMITED BY
RELATIVELY WEAK SFC THETAE.
..EDWARDS.. 09/04/2010
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