DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 080558
SWODY1
SPC AC 080555

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 PM CST THU MAR 07 2013

VALID 081200Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND TONIGHT
ACROSS PARTS OF THE SOUTHERN HIGH PLAINS...

...SYNOPSIS...
AMPLIFIED DEVELOPMENTS WITHIN THE SPLIT BELTS OF MID-LATITUDE
WESTERLIES APPEAR LIKELY TO REMAIN OUT OF PHASE THROUGH THIS
FORECAST PERIOD. BUT MODELS SUGGEST AT LEAST SOME PHASING OF ONE OF
THESE PERTURBATIONS...MIGRATING INLAND ACROSS THE CALIFORNIA COAST
INTO THE FOUR CORNERS REGION LATER TODAY/TONIGHT...WITH ANOTHER
IMPULSE EMERGING FROM THE SUBTROPICAL EASTERN PACIFIC. LARGE-SCALE
FORCING DOWNSTREAM OF THESE FEATURES IS EXPECTED TO CONTRIBUTE TO
SIGNIFICANT SURFACE CYCLOGENESIS TO THE LEE OF THE CENTRAL
ROCKIES...ALONG WITH STRENGTHENING SOUTHERLY LOW-LEVEL FLOW ACROSS
THE LOWER RIO GRANDE VALLEY THROUGH THE CENTRAL PLAINS.

A MODEST MOISTURE RETURN IS ALREADY UNDERWAY FROM THE SOUTHWESTERN
GULF OF MEXICO INTO DEEP SOUTH TEXAS...AND THIS MOISTURE IS FORECAST
TO CONTINUE ADVECTING NORTHWARD...THROUGH THE CENTRAL PLAINS AND MID
MISSOURI VALLEY REGION BY 12Z SATURDAY. MUCH OF THIS MAY
OCCUR...HOWEVER...ABOVE A LINGERING COOLER/STABLE SURFACE BASED AIR
MASS...AND BELOW RELATIVELY WARM AND CAPPING ELEVATED MIXED LAYER
AIR. SUBSTANTIVE NORTHWARD BOUNDARY LAYER MOISTENING APPEARS LIKELY
TO BE MUCH SLOWER AND CONFINED TO THE VICINITY OF THE LEE SURFACE
TROUGH ACROSS THE SOUTHERN HIGH PLAINS.

IT IS POSSIBLE THAT LOWER 60S SURFACE DEW POINTS MAY ADVECT
NORTHWEST OF THE TEXAS HILL COUNTRY AND EDWARDS PLATEAU BY EARLY
THIS EVENING...OTHERWISE DEW POINTS ACROSS MUCH OF THE SOUTHERN HIGH
PLAINS DURING THE DAYTIME HOURS PROBABLY WILL BE LIMITED TO THE 40S
AND 50S. THIS IS EXPECTED TO LIMIT DESTABILIZATION...AND THE
OVERALL SEVERE WEATHER POTENTIAL...THROUGH THIS PERIOD...BUT
CONSIDERABLE CONVECTIVE DEVELOPMENT STILL SEEMS LIKELY ACROSS MUCH
OF THE CENTRAL AND SOUTHERN PLAINS TONIGHT...AS LARGE-SCALE FORCING
FOR UPWARD VERTICAL MOTION STRENGTHENS SUFFICIENTLY TO WEAKEN
INHIBITION.

...SOUTHERN HIGH PLAINS INTO CENTRAL PLAINS...
MID/HIGH-LEVEL CLOUD COVER ASSOCIATED WITH AN INITIAL IMPULSE
MIGRATING NORTHEASTWARD ACROSS THE SOUTHERN HIGH PLAINS EARLY IN THE
DAY PROVIDES ADDITIONAL UNCERTAINTY CONCERNING DESTABILIZATION ALONG
THE LEE SURFACE TROUGH ACROSS THE TEXAS PANHANDLE AND SOUTH PLAINS.
IN THE WAKE OF THIS FEATURE...GUIDANCE IS SUGGESTIVE THAT FORCING
COULD CONTRIBUTE TO ISOLATED STORM DEVELOPMENT ACROSS THE TEXAS
PANHANDLE NEAR/JUST PRIOR TO 09/00Z. BUT PRIMARY CONVECTIVE
DEVELOPMENT MAY NOT OCCUR UNTIL 09/01-03Z...GENERALLY AFTER
DARK...WHEN AN INFLUX OF BOUNDARY LAYER MOISTURE MAY COINCIDE WITH
INCREASING MID-LEVEL HEIGHT FALLS. THE MAIN UPPER IMPULSE MAY JUST
BE CROSSING THE SOUTHERN PLATEAU AT THIS TIME...BUT FORCING PROBABLY
WILL BE SUFFICIENT FOR AT LEAST SCATTERED DISCRETE STORM
DEVELOPMENT... IN THE PRESENCE OF STRONG DEEP LAYER SHEAR SUFFICIENT
FOR SUPERCELLS. TORNADIC POTENTIAL IS A BIT UNCLEAR...DUE TO THE
TIMING OF DEVELOPMENT...WHICH MAY LEAVE A RELATIVELY SMALL WINDOW OF
OPPORTUNITY BEFORE RADIATIONAL COOLING STABILIZES THE NEAR SURFACE
LAYER...AND FORECAST LOW-LEVEL HODOGRAPHS...WHICH ARE NOT
PARTICULARLY LARGE. LARGE HAIL MAY BE THE PRIMARY SEVERE THREAT
WITH THIS ACTIVITY...AND STORMS BASED IN A LOWER/MID TROPOSPHERIC
WARM ADVECTION REGIME FARTHER TO THE NORTH...ACROSS THE CENTRAL
PLAINS.

...SAN DIEGO AND ADJACENT SRN CALIFORNIA COASTAL AREAS...
DEEP LAYER SHEAR AND AMBIENT VORTICITY WILL BECOME INCREASINGLY
FAVORABLE FOR UPDRAFT ROTATION WITH CONVECTION AS THE MID-LEVEL LOW
MIGRATES INLAND ACROSS SOUTHERN CALIFORNIA TODAY. HOWEVER...EVEN
NEAR COASTAL AREAS...FORECAST SOUNDINGS INDICATE ONLY VERY WEAK
CAPE...AND RATHER WEAK LOW-LEVEL SHEAR. WHILE SOME HAIL IS NOT OUT
OF THE QUESTION WITH LOW TOPPED STORMS...POTENTIAL FOR SEVERE HAIL
STILL APPEARS NEGLIGIBLE AT THE PRESENT TIME. A WATERSPOUT OR TWO
ALSO MAY NOT BE OUT OF THE QUESTION IN COASTAL WATERS...BUT THREAT
FOR TORNADOES OVER INLAND AREAS ALSO SEEMS MINIMAL.

...PHOENIX AND ADJACENT LOWER DESERTS...
SIMILAR TO SOUTHERN CALIFORNIA COASTAL AREAS...WEAK BOUNDARY LAYER
DESTABILIZATION APPEARS POSSIBLE BY THIS AFTERNOON...WITH DEEP LAYER
SHEAR SUFFICIENT FOR UPDRAFT ROTATION. HOWEVER...LOW-LEVEL
HODOGRAPHS ARE FORECAST TO REMAIN WEAK/SMALL...AND THERMODYNAMIC
PROFILES DO NOT APPEAR SUPPORTIVE OF SEVERE HAIL...THOUGH SMALL HAIL
IS NOT OUT OF THE QUESTION IN STRONGER CONVECTION.

..KERR/ROGERS.. 03/08/2013

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