SWODY1
SPC AC 140557
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT THU AUG 14 2008
VALID 141200Z - 151200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN/EVE ACROSS PARTS OF
THE SOUTH CENTRAL PLAINS....
...SYNOPSIS...
MODELS INDICATE THAT...AS A STRONG UPPER JET STREAK TOPS THE CREST
OF A SHARP RIDGING EXTENDING NORTHWARD FROM THE GREAT BASIN THROUGH
THE CANADIAN ROCKIES...AN UPPER LOW WILL SHIFT SOUTH/SOUTHWESTWARD
FROM SOUTHERN SASKATCHEWAN INTO THE NORTH CENTRAL ROCKIES BY 12Z
FRIDAY. AS THIS OCCURS...LINGERING RIDGING ACROSS THE SOUTHERN
PLAINS WILL FINALLY BREAK DOWN...WHILE LARGE-SCALE UPPER TROUGHING
PERSISTS ACROSS MUCH OF THE EASTERN UNITED STATES.
IN RESPONSE TO THE EVOLVING UPPER PATTERN...SEASONABLY HIGH MOISTURE
CONTENT AIR WILL BECOME CONFINED TO PARTS OF SOUTHEAST TEXAS...THE
FLORIDA PENINSULA AND IMMEDIATE GULF/SOUTH ATLANTIC COASTAL AREAS.
BUT...RELATIVELY COOL MID-LEVEL TEMPERATURES WILL PROBABLY
COMPENSATE FOR LOWER MOISTURE LEVELS TO THE LEE OF THE
ROCKIES...ALLOWING FOR SUFFICIENT DESTABILIZATION TO SUPPORT
SCATTERED AREAS OF CONVECTIVE DEVELOPMENT. THIS WILL BE AIDED BY
FORCING ASSOCIATED WITH NUMEROUS PERTURBATIONS EMBEDDED WITHIN THE
BROADER SCALE PATTERN.
...SOUTH CENTRAL PLAINS INTO THE UPPER MISSISSIPPI VALLEY...
SOUTHEAST OF THE DIGGING/RETROGRADING CLOSED LOW...A SHORT WAVE
TROUGH APPEARS LIKELY TO DIG FROM THE NORTH CENTRAL ROCKIES INTO THE
CENTRAL PLAINS DURING THE DAY. POSSIBLE CLOUD COVER/ CONVECTION
LINGERING THROUGH THE MORNING HOURS IN ASSOCIATION WITH THIS FEATURE
PROVIDES SOME UNCERTAINTY WITH REGARD TO CONVECTIVE POTENTIAL FOR
LATER THIS AFTERNOON EVENING. BUT...IT APPEARS PROBABLE THAT
MODERATE INSTABILITY WILL BE ABLE TO MATERIALIZE ON THE
SOUTHERN/WESTERN FRINGE OF THE IMPULSE...FROM PARTS OF NORTHEAST NEW
MEXICO AND THE TX/OK PANHANDLE REGION THROUGH WESTERN/CENTRAL
KANSAS.
MIXED LAYER CAPE MAY EXCEED 2000 J/KG WITH DAYTIME HEATING. IN
CONJUNCTION WITH WEAKENING INHIBITION ASSOCIATED WITH LOWER/MID
TROPOSPHERIC COOLING...AT LEAST BROADLY DIFLUENT HIGH-LEVEL
FLOW...AND FOCUSED LOW-LEVEL CONVERGENCE ASSOCIATED WITH A MODEST
SOUTHERLY LOW-LEVEL JET...POTENTIAL EXISTS FOR SCATTERED LATE
AFTERNOON STORMS TO CONGEAL INTO AN EXPANDING STORM CLUSTER BY EARLY
THIS EVENING. IF THIS OCCURS...THE PRESENCE OF AT LEAST MODERATE
DEEP LAYER SHEAR BENEATH NORTHWESTERLY MID-LEVEL FLOW WILL
CONTRIBUTE TO THE RISK FOR DAMAGING WIND GUSTS...IN ADDITION TO
LARGE HAIL...BEFORE CONVECTION WEAKENS LATER TONIGHT.
...FLORIDA...
ANOTHER LOW AMPLITUDE IMPULSE IN THE BASE OF THE EASTERN TROUGH IS
PROGGED TO CONTRIBUTE TO STRENGTHENING WESTERLY LOW-LEVEL FLOW
FIELDS /UP TO 30-40 KTS AT 850 MB/ ACROSS THE CENTRAL PENINSULA
EARLY TODAY. COUPLED WITH UNSATURATED LOWER/MID TROPOSPHERIC
THERMAL PROFILES...THIS MAY CONTRIBUTE TO AT LEAST LOW SEVERE
POTENTIAL...MAINLY IN THE FORM OF STRONG GUSTY WINDS...WITH
SCATTERED THUNDERSTORM ACTIVITY DEVELOPING ACROSS THE CENTRAL
PENINSULA. TIMING OF STRONGER FORCING ACROSS THIS REGION IS STILL
UNCERTAIN. IT CURRENTLY APPEARS MOST PROBABLE BY EARLY
AFTERNOON...BUT IF IT IS A BIT LATER...THE SEVERE THREAT MAY BE
HIGHER THAN CURRENTLY INDICATED.
...NORTHERN MID ATLANTIC STATES...
DAYTIME HEATING TO THE LEE OF THE NORTH CENTRAL APPALACHIANS COUPLED
WITH LINGERING LOW-LEVEL MOISTURE IS EXPECTED TO CONTRIBUTE TO WEAK
TO MODERATE INSTABILITY SUPPORTIVE OF FAIRLY VIGOROUS CONVECTIVE
DEVELOPMENT. GIVEN WEAK INHIBITION...THIS SHOULD OCCUR...AIDED BY
AT LEAST WEAKLY DIFLUENT/DIVERGENT UPPER FLOW. LOW/MID-LEVEL FLOW
FIELDS/SHEAR WILL REMAIN WEAK...BUT MODERATE TO STRONG HIGH LEVEL
FLOW IN PROXIMITY TO A SOUTHWESTERLY UPPER JET STREAK NOSING ACROSS
THE MID ATLANTIC COAST COULD ENHANCE ACTIVITY...CONTRIBUTING TO A
FEW STORMS CAPABLE OF PRODUCING GUSTY WINDS AND HAIL.
...UPPER MISSISSIPPI VALLEY...
ANOTHER IMPULSE DIGGING AROUND THE NORTHWESTERN PERIPHERY OF THE
MAIN UPPER TROUGH AXIS ACROSS THE LOWER GREAT LAKES MAY CONTRIBUTE
TO A DEFORMATION ZONE WHICH COULD ACT AS A FOCUS FOR CONVECTIVE
DEVELOPMENT ACROSS THE REGION DURING THE LATE AFTERNOON HOURS. DEEP
LAYER FLOW/SHEAR WILL BE GENERALLY WEAK...BUT RELATIVELY COOL MID
LEVEL TEMPERATURES COULD PROMOTE THE RISK FOR SOME HAIL/ LOCALLY
GUSTY WINDS IN ISOLATED STRONGER CELLS BEFORE ACTIVITY DIMINISHES
THIS EVENING WITH LOSS OF DAYTIME HEATING.
...SOUTHERN PLATEAU...
MODELS SUGGEST AN INCREASING NORTHEASTERLY COMPONENT TO THE
MID-LEVEL FLOW ACROSS THE REGION TODAY. THOUGH THE SPEEDS PROBABLY
WILL REMAIN GENERALLY LIGHT...IF THIS OCCURS...IT WILL AID STORM
PROPAGATION OFF THE HIGHER TERRAIN INTO THE LOWER DESERTS...WHERE
THERMODYNAMIC PROFILES SHOULD BECOME SUPPORTIVE OF AT LEAST
LOCALIZED DOWNBURSTS...PERHAPS SOME HAIL..
..KERR/CROSBIE.. 08/14/2008
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