DAY1SVR: Day 1 Convective Outlook Corr 1

ACUS01 KWNS 131625
SWODY1
SPC AC 131623

DAY 1 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1123 AM CDT SAT APR 13 2013

VALID 131630Z - 141200Z

...NO SVR TSTM AREAS FORECAST...

CORRECTED MINOR GRAPHICAL ISSUE...SEE TEXT LABELS

...SYNOPSIS...
TO THE SOUTH OF A BLOCKING UPPER RIDGE OVER THE HUDSON BAY
VICINITY...THE MID-LEVEL LOW OVER THE UPPER GREAT LAKES REGION
FINALLY APPEARS LIKELY TO WEAKEN...WITH A REMNANT ASSOCIATED SPEED
MAXIMUM NOSING EASTWARD ACROSS THE UPPER OHIO VALLEY AND NORTHERN
MID ATLANTIC COAST REGION BY THE END OF THE PERIOD. THIS IS
EXPECTED TO OCCUR AS ANOTHER STRONG MID-LEVEL JET STREAK DIGS FROM
THE PACIFIC NORTHWEST COAST INTO THE GREAT BASIN...AND AN ASSOCIATED
LOW REDEVELOPS SOUTHEASTWARD FROM THE SOUTHERN CANADIAN ROCKIES
THROUGH THE NORTHERN U.S. ROCKIES REGION. THIS LATTER DEVELOPMENT
IS FORECAST TO BE ACCOMPANIED BY SIGNIFICANT SURFACE CYCLOGENESIS
FROM THE LEE OF THE CENTRAL ROCKIES INTO THE NORTH CENTRAL PLAINS BY
LATE TONIGHT.

MOST PROMINENTLY SUPPORTED BY MID-LEVEL COOLING ACROSS THE NORTHERN
ROCKIES AND ADJACENT HIGH PLAINS...AND LOWER/MID TROPOSPHERIC WARM
ADVECTION ACROSS THE LOWER NORTH CENTRAL PLAINS AND MID MISSOURI
VALLEY...SCATTERED AREAS OF THUNDERSTORM ACTIVITY APPEAR POSSIBLE
LATER TODAY AND TONIGHT. CONVECTION IS EXPECTED TO REMAIN
WEAK...HOWEVER...DUE TO WEAK INSTABILITY ASSOCIATED WITH LIMITED
MOISTURE IN THE WAKE OF THE RECENT COLD INTRUSION...WHICH HAS
ADVANCED AS FAR SOUTH AND EAST AS THE NORTHERN GULF OF MEXICO AND
SOUTH ATLANTIC COASTAL AREAS.

EVEN ACROSS PARTS OF THE SOUTHERN TIER STATES...WHERE AT LEAST
POCKETS OF BETTER LOW-LEVEL MOISTURE LINGER...CONVECTIVE POTENTIAL
SHOULD REMAIN LIMITED TODAY. BUT...THE RISK FOR ISOLATED
STRONG/SEVERE STORM ACTIVITY MAY NOT BE COMPLETELY NEGLIGIBLE.

...FLORIDA...
LOW AMPLITUDE MID-LEVEL TROUGHING IS CURRENTLY SHIFTING ACROSS THE
FLORIDA PENINSULA...AND SUPPORTING INCREASING STORM DEVELOPMENT
ALONG A WEAK PRE-FRONTAL SURFACE TROUGH/WIND SHIFT ACROSS THE FAR
SOUTHERN PENINSULA. THE BULK OF THE STRONGER MID-LEVEL FORCING FOR
UPWARD VERTICAL MOTION APPEARS TO BE SHIFTING OFFSHORE...BUT A
TRAILING AREA OF LIFT APPEARS TO BE SUPPORTING THE SMALL STORM
CLUSTER NOW PROGRESSING INTO MIAMI-DADE COUNTY. WITH THE SEA-BREEZE
PERHAPS ENHANCING LOW-LEVEL CONVERGENCE NEAR COASTAL AREAS THROUGH
EARLY AFTERNOON...ADDITIONAL STORMS AND UPSCALE GROWTH APPEAR
POSSIBLE ACROSS THE MIAMI METROPOLITAN AREA. IN THE PRESENCE OF
RELATIVELY HIGH PRECIPITABLE WATER AND MODERATELY LARGE CAPE...DEEP
LAYER SHEAR APPEARS MARGINALLY SUFFICIENT FOR UPDRAFT
ROTATION...WHICH COULD ENHANCE THE RISK FOR LOCALIZED STRONG WIND
GUSTS...PERHAPS SOME SEVERE HAIL THROUGH AT LEAST THE 18-19Z TIME
FRAME.

...SOUTHWEST TEXAS...
MODEST DESTABILIZATION APPEARS POSSIBLE BY THIS AFTERNOON IN
ASSOCIATION WITH DAYTIME HEATING AND MOISTENING SOUTHEASTERLY
UPSLOPE FLOW BENEATH STEEP MID-LEVEL LAPSE RATES. AS THIS
OCCURS...FORCING FOR UPWARD VERTICAL MOTION ASSOCIATED WITH
OROGRAPHY...COUPLED WITH THE APPROACH OF A CYCLONIC VORTICITY CENTER
WITHIN A LARGER SCALE UPPER TROUGH SHIFTING EASTWARD ACROSS THE
NORTHERN MEXICAN PLATEAU/RIO GRANDE VALLEY REGION... MAY SUPPORT AT
LEAST ISOLATED SUSTAINED STORM DEVELOPMENT ACROSS THE DAVIS
MOUNTAINS. IF THIS OCCURS...THE ENVIRONMENT APPEARS CONDUCIVE TO THE
RISK FOR A STRONG DOWNBURST OR TWO.

...CENTRAL GULF COASTAL AREAS...
THE RISK FOR THUNDERSTORM ACTIVITY WILL INCREASE LATE TONIGHT IN
ASSOCIATION WITH STRENGTHENING LOWER/MID TROPOSPHERIC WARM ADVECTION
DOWNSTREAM OF THE MEXICAN PLATEAU/RIO GRANDE VALLEY UPPER TROUGH.
HOWEVER...IT CURRENTLY APPEARS MOST PROBABLE THAT THE SURFACE WARM
FRONTAL ZONE WILL REMAIN WELL OFFSHORE...WITH AT LEAST A SHALLOW
NEAR SURFACE STABLE LAYER LINGERING OVER INLAND AREAS. WITH
MID-LEVEL LAPSE RATES ALSO NOT CURRENTLY EXPECTED TO STEEPEN
SUFFICIENTLY TO SUPPORT ANYTHING BEYOND WEAK CAPE...EVEN LOW SEVERE
PROBABILITIES MAY BE A BIT GENEROUS. HOWEVER...LOW SEVERE
PROBABILITIES WILL BE MAINTAINED FOR NOW...PRIMARILY DUE TO
LINGERING UNCERTAINTIES ASSOCIATED WITH MODEL VARIABILITY.

..KERR.. 04/13/2013

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