Monday, August 25, 2008

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 250554
SWODY1
SPC AC 250553

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1253 AM CDT MON AUG 25 2008

VALID 251200Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF AL/WESTERN GA/FL
PANHANDLE...

...SYNOPSIS...
A PROGRESSIVE YET FAIRLY AMPLIFIED LARGE SCALE FLOW REGIME WILL
REMAIN PREVALENT OVER CANADA AND THE NORTHERN HALF OF THE CONUS
THROUGH THE PERIOD. NORTH CENTRAL STATES TRANSITORY UPPER RIDGE WILL
BE FLANKED BY RELATIVELY STRONG UPPER TROUGHS /AND ASSOCIATED
SURFACE COLD FRONTS/ CROSSING BOTH THE PACIFIC NORTHWEST AND
NORTHEAST STATES/NEW ENGLAND. FARTHER SOUTH...TROPICAL DEPRESSION
FAY WILL MOVE SLOWLY OVER THE CENTRAL GULF COAST STATES /SEE HPC
TROPICAL ADVISORIES FOR LATEST DETAILS/.

...EAST-CENTRAL GULF COAST REGION...
TROPICAL DEPRESSION FAY WILL CONTINUE TO PINWHEEL OVER FAR SOUTHERN
MS...PERHAPS GRADUALLY EASTWARD TOWARD SOUTHWEST AL...THROUGH THE
PERIOD. ON THE SOUTHERN PERIPHERY OF FAY...A VORT MAX IS
CONTRIBUTING TO ACTIVE CONVECTION OVERNIGHT ALONG THE CENTRAL GULF
COAST. AS THIS FEATURE CONTINUES TO PIVOT NORTHEASTWARD ON THE
EASTERN HALF OF FAY...IT SEEMS LIKELY THAT ENHANCED/MODERATELY
STRONG LOW LEVEL WINDS WILL DEVELOP NORTHWARD ACROSS PORTIONS OF FAR
EASTERN MS/MUCH OF AL/WESTERN GA AND FL PANHANDLE DURING THE DAY.
ALONG WITH SUFFICIENT LOW LEVEL SHEAR /0-1 KM SRH LIKELY TO BE AT
LEAST 200-300 M2/S2/...DIABATIC HEATING WILL CONTRIBUTE TO WEAK
MLCAPE AND POTENTIAL FOR DIURNALLY ENHANCED ROTATING UPDRAFTS
THROUGH THE MORNING/AFTERNOON. AS SUCH...ISOLATED/BRIEF TORNADOES
WILL BE POSSIBLE.

...CENTRAL HIGH PLAINS...
ISOLATED TO SCATTERED TSTMS ARE LIKELY TO AGAIN DEVELOP OVER THE
REGION THIS AFTERNOON GIVEN AMPLE HEATING ALONG THE HIGHER TERRAIN
AND THE PERSISTENCE OF A MOIST SOUTHEASTERLY LOW LEVEL UPSLOPE
REGIME. SCENARIO WILL BE FURTHER AIDED ON THE LARGE SCALE BY A
WEAKENING UPPER RIDGE. WITH INITIAL DEVELOPMENT MOST LIKELY OVER THE
HIGHER TERRAIN/FRONT RANGES OF CO/WY THIS AFTERNOON...TSTMS SHOULD
GRADUALLY DEVELOP SOUTHEASTWARD INTO A MOIST AND UNSTABLE AIRMASS
/1000-2000 J PER KG MLCAPE/ ACROSS THE ADJACENT HIGH PLAINS THROUGH
LATE AFTERNOON/EARLY EVENING. ALTHOUGH WINDS THROUGH THE MID
TROPOSPHERE WILL BE WEAK...STRONGLY VEERING WIND PROFILES /120-150
DEGREES 0-6 KM/ WITH AROUND 30 KT OF EFFECTIVE BULK SHEAR WILL
SUPPORT SOME ORGANIZED MULTICELLS/BRIEF SUPERCELLS THROUGH EARLY
EVENING. MODEST NATURE OF THE VERTICAL SHEAR AND UNCERTAINTIES
REGARDING THE NUMBER/COVERAGE OF STRONG/SEVERE TSTMS PRECLUDES A
CATEGORICAL SLIGHT RISK AT THIS TIME.

...NEW ENGLAND STATES...
UPPER LOW IS FORECAST TO SHIFT SOUTHEASTWARD OVER QUEBEC/NEW
ENGLAND...WITH ASSOCIATED COLD FRONT CROSSING NEW ENGLAND DURING THE
DAY. ONGOING SHOWERS/TSTMS WILL CONTINUE TO SPREAD EASTWARD ACROSS
THE REGION ALONG/AHEAD OF THE COLD FRONT EARLY TODAY...WITH
ADDITIONAL TSTM DEVELOPMENT BY EARLY AFTERNOON ALONG THE NEW ENGLAND
COASTAL AREAS. SOME MARGINAL SEVERE WIND/HAIL RISK WILL EXIST WITH
THESE STORMS. ASIDE FROM THE EARLY DAY COLD FRONTAL PASSAGE/MODEST
PREFRONTAL INSTABILITY...OTHER NEGATING FACTORS FOR A MORE
APPRECIABLE SEVERE THREAT INCLUDE INITIALLY WEAK VERTICAL SHEAR AND
WEAK LOW LEVEL CONVERGENCE.

..GUYER/JEWELL.. 08/25/2008

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