SPC AC 261939
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0239 PM CDT TUE MAY 26 2009
VALID 262000Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN/EVE ACROSS PARTS
OF THE SRN PLAINS....
...20Z UPDATE...
ONLY MINOR CHANGES HAVE BEEN MADE TO THE 16Z CATEGORICAL AND
PROBABILISTIC OUTLOOKS...BASED ON APPARENT TRENDS IN OBSERVATIONAL
DATA AND LATEST MODEL GUIDANCE. SEVERE POTENTIAL...WHILE PROBABLY
NOT COMPLETELY NEGLIGIBLE IN MOST AREAS WITH A RISK FOR
THUNDERSTORMS...STILL GENERALLY APPEARS MARGINAL IN NATURE OR LIKELY
TO REMAIN HIGH LOCALIZED. AN EXCEPTION SEEMS TO EXIST ACROSS PARTS
OF NORTHERN/CENTRAL TEXAS...WHERE SURFACE HEATING BENEATH CAPPING
ELEVATED MIXED LAYER AIR EMANATING FROM THE PLATEAU REGION IS
CONTRIBUTING TO STRONG TO EXTREME INSTABILITY.
...NORTHERN/CENTRAL TEXAS...
BOUNDARY LAYER DESTABILIZATION APPEARS MAXIMIZED NEAR THE DALLAS/
FORT WORTH METROPLEX...NEAR OR JUST EAST OF A WEAK SURFACE LOW... ON
THE NOSE OF A PRE-FRONTAL LOW-LEVEL THERMAL RIDGE EXTENDING
NORTHEASTWARD OUT OF THE HIGH PLAINS. VERY STEEP LOW AND MID- LEVEL
LAPSE RATES...COUPLED WITH HIGH LOW-LEVEL MOISTURE CONTENT AIR ALONG
A CONVECTIVELY GENERATED/ENHANCED BOUNDARY EAST SOUTHEAST OF THE
LOW...HAS CONTRIBUTED TO MIXED LAYER CAPE IN EXCESS OF 3000
J/KG...ACCORDING TO THE LATEST RUC ANALYSIS. IT APPEARS THIS COULD
APPROACH 4000 J/KG WITH ADDITIONAL HEATING.
WHILE WEAK LOWER/MID TROPOSPHERIC COOLING IS ONGOING ACROSS THE
SOUTH CENTRAL HIGH PLAINS...WEST AND SOUTH OF A MID-LEVEL
CIRCULATION BEGINNING TO TURN EASTWARD ACROSS WESTERN KANSAS... THIS
PROBABLY WILL NOT BE OF MUCH IMPACT TO NORTH CENTRAL TEXAS.
BUT...HEATING TOWARD CONVECTIVE TEMPERATURES...COUPLED WITH
LOW-LEVEL WARM ADVECTION/CONVERGENCE...MAY BE SUFFICIENT TO INITIATE
CONVECTIVE DEVELOPMENT PRIOR TO 27/00Z. IF THIS OCCURS ...POTENTIAL
EXISTS FOR RAPID INTENSIFICATION TO SEVERE LEVELS... DESPITE THE
WEAK NATURE OF THE FLOW FIELDS AND SHEAR. LARGE HAIL AND DAMAGING
DOWNBURSTS LIKELY WILL BE THE MAIN THREATS WITH EAST SOUTHEASTWARD
ADVECTING/PROPAGATING STORMS. BUT...AN ISOLATED TORNADO IS NOT OUT
OF THE QUESTION.
THOUGH UPPER FORCING IS STILL WEAK/UNCERTAIN...IT IS POSSIBLE THAT
NOCTURNAL STRENGTHENING OF A SOUTH SOUTHWESTERLY LOW-LEVEL JET TO
AROUND 30 KT COULD SUPPORT UPSCALE CONVECTIVE GROWTH THIS EVENING.
THERMODYNAMIC PROFILES APPEAR VERY FAVORABLE FOR STRONG CONVECTIVELY
GENERATED COLD POOLS...WHICH SHOULD TEND TO CONSOLIDATE AND ADVANCE
WITH STRONGER NEW CONVECTIVE DEVELOPMENT ...SOUTHWARD INTO/ACROSS
CENTRAL TEXAS...ACCOMPANIED BY GUSTY WINDS AND HAIL.
..KERR.. 05/26/2009
.PREV DISCUSSION... /ISSUED 1127 AM CDT TUE MAY 26 2009/
...SOUTHERN PLAINS...
LATEST SURFACE ANALYSIS SHOWS A COLD FRONT DROPPING SOUTHWARD ACROSS
WESTERN KS AND THE OK/TX PANHANDLES. AHEAD OF THE FRONT...SCATTERED
OVERNIGHT THUNDERSTORMS HAVE RESULTED IN SEVERAL DIFFUSE SURFACE
BOUNDARIES OVER SOUTHERN/EASTERN OK AND NORTH TX. STRONG HEATING
AND DRYING WILL OCCUR FROM THE WEST ACROSS TX...YIELDING AFTERNOON
MLCAPE VALUES OVER 3000 J/KG ROUGHLY FROM MWL/SPS EASTWARD INTO
SOUTHWEST AR. WEAK FORCING ALOFT SUGGESTS THAT LOCALIZED
CONVERGENCE ALONG SURFACE BOUNDARIES WILL LIKELY BE THE MAIN FOCUS
FOR THUNDERSTORM INITIATION. FULL SUNSHINE SHOULD ALLOW AIRMASS TO
REACH CONVECTIVE TEMPERATURE /LOWER 90S F ON 12Z FWD RAOB/ AND LEAD
TO A FEW INTENSE MULTICELL CLUSTERS. STEEP LOW AND MID LEVEL LAPSE
RATES AND WEAK BUT SUFFICIENT DEEP LAYER VERTICAL SHEAR INDICATE A
RISK OF LARGE HAIL AND DAMAGING WINDS.
LATER THIS EVENING AND TONIGHT...A SHORTWAVE TROUGH OVER SOUTHERN NM
WILL EMERGE INTO THE SOUTHERN HIGH PLAINS AND LIKELY PROMOTE
SCATTERED HIGH-BASED THUNDERSTORMS ACROSS WESTERN AND CENTRAL TX.
THESE STORMS WILL SPREAD EASTWARD INTO CENTRAL TX OVERNIGHT WITH A
RISK OF LOCALLY DAMAGING WINDS AND HAIL.
...FL...
THE PATTERN REMAINS GENERALLY UNCHANGED OVER THE FL PENINSULA TODAY
WITH STRONG HEATING AND AMPLE MOISTURE...COUPLED WITH COOL
TEMPERATURES ALOFT...LEADING TO NUMEROUS AFTERNOON THUNDERSTORMS.
ACTIVITY WILL BE FOCUSED ON SEA BREEZES MOVING INLAND AND COLLIDING.
LOCALLY DAMAGING DOWNBURSTS AND HAIL WILL BE POSSIBLE WITH THE
STRONGEST CORES.
...IA/IL...
WEAK UPPER CIRCULATION IS LIFTING SLOWLY NORTHEASTWARD FROM NORTHERN
MO INTO IA THIS MORNING. A PLUME OF MOIST AIR AND SLIGHTLY STRONGER
WIND FIELDS OVER THE EAST HALF OF THE SYSTEM WILL CONTINUE TO POSE A
MINOR THREAT FOR SMALL ROTATING STORMS AND/OR A BRIEF TORNADO THIS
AFTERNOON AND EARLY EVENING.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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