SPC AC 051950
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0250 PM CDT MON MAY 05 2008
VALID 052000Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ERN SC AND SRN NC...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS AND SRN
HIGH PLAINS TO LOWER PECOS VALLEY...
...SYNOPSIS...
PROGRESSIVE UPPER AIR PATTERN IS FCST THROUGH REMAINDER
PERIOD...WITH MEAN TROUGHING EXTENDING FROM HUDSON BAY CYCLONE SSEWD
OFFSHORE SRN ATLANTIC COAST. CLOSED AND NEARLY CUT OFF LOW ALOFT --
EVIDENT IN MOISTURE CHANNEL IMAGERY OFFSHORE NRN BAJA -- HAS BEGUN
ITS EWD TURN AND SHOULD MOVE INLAND AROUND 6/00Z. THIS LOW THEN
SHOULD MOVE ENEWD ACROSS CO RIVER DELTA REGION TO SWRN AZ BY END OF
PERIOD.
DOWNSTREAM...WEAK UPPER PERTURBATION NOW OVER NWRN/N-CENTRAL MEX IS
EXPECTED TO LIFT NEWD TOWARD DEEP S TX. WEAK SHORTWAVE TROUGH IS
EMBEDDED IN NWLY FLOW ALOFT OVER CENTRAL/SRN APPALACHIANS
REGION...AND IS FCST TO MOVE OFFSHORE COASTAL CAROLINAS DURING
6/00Z-6/03Z TIME FRAME.
AT SFC...DRYLINE IS ANALYZED JUST E OF NM MOUNTAINS...WITH LITTLE
MOVEMENT EXPECTED THROUGH REMAINDER PERIOD. RESIDUAL SYNOPTIC
FRONTAL ZONE -- LEFT OVER FROM PREVIOUS NRN GULF COLD FROPA -- IS
ANALYZED FROM ABOUT 150-200 NM S OF LA COAST WNWWD ACROSS SE AND
S-CENTRAL TX...BECOMING DIFFUSE AMIDST GEN SELY FLOW FARTHER NWWD
OVER LOWER PECOS VALLEY AND PERMIAN BASIN REGIONS. WEAK LOW IS
ANALYZED OVER ERN SC...AND SHOULD REMAIN ILL-DEFINED AS UPPER LEVEL
TROUGH MOVES PAST. CONVECTIVE PROCESSES IN THAT AREA WILL BE
DOMINATED MORE BY LOCALIZED/BOUNDARY EFFECTS.
...CENTRAL/SRN HIGH PLAINS...
TSTMS SHOULD CONTINUE TO DEVELOP AND INCREASE IN COVERAGE OVER
HIGHER TERRAIN OF ERN NM...MOVING NEWD ONTO ADJACENT HIGH PLAINS
THROUGH REMAINDER AFTERNOON. SOME OF THIS ACTIVITY ALREADY HAS
EVOLVED SUPERCELL STRUCTURES...WITH MORE TO COME. LARGE HAIL IS
PRIMARY THREAT...AS FOREGOING AIR MASS HEATS/DESTABILIZES FOLLOWING
BREAKUP OF EARLIER LOW LEVEL CLOUD COVER. ISOLATED HAIL EXCEEDING
TWO INCHES DIAMETER IS POSSIBLE...GIVEN STEEP LAPSE
RATES...INCREASING INFLOW-LAYER WATER CONTENT...AND LIKELIHOOD OF
SUSTAINED STORM-SCALE ROTATION. A FEW TORNADOES ALSO MAY OCCUR. REF
WW 261 AND SUBSEQUENT MESOSCALE DISCUSSION FOR THAT AREA...FOR
LATEST SHORT-TERM GUIDANCE REGARDING THIS SITUATION. SIGNIFICANT
HAIL THREAT ALSO EXTENDS SSEWD FROM ERN NM ACROSS FAR W TX AND LOWER
PECOS VALLEY REGIONS...SHIFTING EWD TOWARD PORTIONS PERMIAN
BASIN...PER MESOSCALE DISCUSSION 789.
REF MESOSCALE DISCUSSION 788 FOR NOWCAST GUIDANCE REGARDING SVR
POTENTIAL INCREASING ATTM OVER S-CENTRAL HIGH PLAINS FROM WRN KS SWD
INTO TX PANHANDLE. MOISTURE LIKEWISE IS FCST TO INCREASE ACROSS
THIS REGION THROUGHOUT REMAINDER PERIOD...LEADING TO POTENTIAL FOR
SUPERCELL DEVELOPMENT THIS AFTERNOON AND EARLY EVENING...AND
POSSIBLE UPSCALE GROWTH INTO MCS OVERNIGHT. SVR HAIL AND GUSTS ARE
MAIN THREATS WITH BOTH MODES OF CONVECTION.
...ERN CAROLINAS...
SCATTERED TSTMS ARE UNDERWAY ACROSS THIS REGION IN WEAKLY CAPPED AND
FAVORABLY HEATED/UNSTABLE AIR MASS...PERTURBED AND DESTABILIZED
ALOFT BY WEAK SHORTWAVE TROUGH NOW EVIDENT OVER REGION. DAMAGING
DOWNDRAFT WINDS AND SCTD REPORTS OF MRGL SEVERE HAIL ARE EXPECTED.
ALTHOUGH LOW LEV LEVEL FLOW IS FCST TO REMAIN RATHER WEAK IN MOST
AREAS...LIMITING HODOGRAPH SIZE...RELATIVELY STG UPPER LEVEL WINDS
-- E.G. 60-70 KT AT ANVIL LEVEL -- SHOULD AID IN STORM ORGANIZATION.
PREDOMINANT STORM MODE SHOULD BE MULTICELLULAR...ALTHOUGH
BRIEF/MESSY SUPERCELL MODES MAY DEVELOP LOCALLY AS STORMS INTERACT
WITH OUTFLOW/SEA BREEZE BOUNDARIES AND WITH OTHER STORMS. REF WW
260 AND RELATED MESOSCALE DISCUSSIONS FOR LATEST NOWCAST INFO. SVR
THREAT IS EXPECTED TO DIMINISH AFTER DARK...AS AIR MASS BECOMES MORE
STABLE FROM COMBINATION OF DIABATIC SFC COOLING...INCREASING
COVERAGE OF OUTFLOW-COOLED AIR...AND DEPARTURE OF MID-UPPER WAVE AND
OF ASSOCIATED LARGE SCALE ASCENT.
...NWRN THROUGH CENTRAL/S TX...E-SE OF HIGH PLAINS...
ERN PORTION OF RETURNING WARM/MARINE FRONT HAS MERGED WITH -- AND
BECOME REINFORCED BY -- QUASISTATIONARY DIFFERENTIAL HEATING
BOUNDARY THAT EXTENDS FROM MIDDLE TX COAST NEAR MATAGORDA BAY...NWWD
ACROSS NRN HILL COUNTRY AND LOW ROLLING PLAINS REGIONS OF CENTRAL-NW
TX. ADDITIONAL/ELEVATED TSTM DEVELOPMENT SHOULD CONTINUE IN ZONE OF
ELEVATED ISENTROPIC LIFT TO LFC...JUST NE OF THIS BOUNDARY.
ISOLATED HAIL NEAR SVR LEVELS CANNOT BE RULED OUT...HOWEVER
ORGANIZED SVR POTENTIAL APPEARS MINIMAL ATTM.
FARTHER W...CONDITIONAL POTENTIAL EXISTS FOR TSTMS TO DEVELOP OVER
SERRANIAS DEL BURRO RANGE AND ADJACENT PIEDMONT SLOPE OF NRN
COAHUILA...THEN MOVE EWD-NEWD ACROSS RIO GRANDE INTO S TX. CINH
SHOULD CONTINUE TO WEAKEN OVER HIGHER TERRAIN THROUGH REMAINDER
AFTERNOON...ESPECIALLY AS REMAINING LOW CLOUDS BREAK UP AND ALLOW
STRONGER SFC DIABATIC HEATING. ANY SUCH ACTIVITY MAY PRODUCE LARGE
HAIL AND STG-SVR GUSTS LATE AFTERNOON INTO EARLY EVENING BEFORE
WEAKENING.
..EDWARDS.. 05/05/2008
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