DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 260534
SWODY1
SPC AC 260532

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 AM CDT FRI APR 26 2013

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS WRN TX/OK BORDER
REGION TO EXTREME WRN AR AND EXTREME NRN TX...

...SYNOPSIS...
SPLIT-FLOW PATTERN FCST ACROSS CONUS...WITH NRN STREAM JET CORE
REMAINING OVER OR EVEN N OF CANADIAN BORDER...EXCEPT OVER PAC NW.
MEANWHILE...PRIMARY PERTURBATION FOR CONVECTIVE POTENTIAL IS APCHG
CENTRAL/SRN ROCKIES ATTM. THIS FEATURE WILL MAINTAIN DECIDEDLY
POSITIVE TILT AS IT MOVES TO NERN/CENTRAL KS...SRN TX PANHANDLE AND
SERN NM BY 27/00Z. ASSOCIATED HEIGHT GRADIENTS...250-500 MB FLOW
MAXIMA AND 500-MB VORTICITY FIELD EACH WILL CONTINUE TO WEAKEN IN
SYSTEM-RELATIVE SENSE THROUGHOUT REMAINDER PERIOD. DESPITE
THAT...HEIGHT RISES AND FLATTENING OF PATTERN TO ITS N COULD RESULT
IN THIS PERTURBATION DEVELOPING WEAK/NEARLY CLOSED 500-MB LOW BY
DEFAULT OVER NRN MO/SRN IA BY 24/12Z...WITH TROUGH TRAILING SWWD
ACROSS OK AND NW TX.

AT SFC...RESIDUAL/QUASISTATIONARY FRONTAL ZONE WAS ANALYZED AT 04Z
FROM OFFSHORE CAROLINAS SWWD ACROSS SRN GA TO NERN/N-CENTRAL
GULF...BECOMING WARM FRONT OVER NWRN GULF OFFSHORE TX.
WRN/WARM-FRONTAL SEGMENT WILL PROGRESS INLAND DURING DAY...BECOMING
MORE ILL-DEFINED WITH WWD EXTENT AMIDST STG LOW-LEVEL WAA AND
DIABATICALLY DRIVEN VERTICAL MIXING ON BOTH SIDES OF BOUNDARY. WARM
FRONT SHOULD REACH SERN OK AND SRN AR BY
27/00Z...DECLERATING/STALLING AS IT ENCOUNTERS SWATH OF PERSISTENT
CLOUD COVER/PRECIP-ALTERED BOUNDARY LAYER OVER ERN OK. INCREASING
BOUNDARY-LAYER MOISTURE TO ITS S WILL RESULT IN PROGRESSIVELY
BETTER-DEFINED DRYLINE THROUGHOUT DAY...EXTENDING AT 27/00Z ROUGHLY
FROM CDS AREA SWD TO SSWWD ACROSS EDWARDS PLATEAU INTO COAHUILA.
FRONT/DRYLINE INTERSECTION...IF ANY...SHOULD BE POORLY DEFINED NEAR
SFC LOW LOCATED AROUND CDS/LTS AREA...WITH INVERTED TROUGH EXTENDING
NNEWD OVER WRN OK. LOW SHOULD MOVE/REDEVELOP NEWD THROUGH REMAINDER
PERIOD...REACHING ERN OK/WRN AR BY 27/12Z WITH COLD FRONT SWWD
ACROSS N-CENTRAL/W-CENTRAL TX.

...SRN PLAINS TO ARKLATEX/OZARKS...
ISOLATED TO WIDELY SCATTERED TSTMS ARE POSSIBLE LATE AFTN INVOF
DRYLINE...WARM FRONT AND SFC TROUGH. COVERAGE INITIALLY WILL BE
LIMITED BY CAP...BUT A FEW SUPERCELLS ARE POSSIBLE WITH LARGE
HAIL...DAMAGING GUSTS AND LOW/CONDITIONAL TORNADO RISK. EVENTUAL
CLUSTERED TO LINEAR EVOLUTION IS POSSIBLE WITH CONVECTIVE UPSCALE
GROWTH SHIFTING EWD ACROSS OK AND AR DURING EVENING AND OVERNIGHT.

MOST PROBABLE AREA FOR AFTN DEVELOPMENT MAY BE INVOF DRYLINE AND SFC
TROUGH OVER WRN OK AND PERHAPS SMALL PART OF NW TX...DESPITE GREATER
LOW-LEVEL THETAE BEING FARTHER S AND SE. BY THAT TIME...SFC
DIABATIC HEATING SHOULD BE MOST PERSISTENT S AND W OF CLOUD COVER IN
ACTING TO ERODE MLCINH. THIS AREA SHOULD RESIDE JUST WITHIN NRN
FRINGES OF STRONGEST DIURNAL HEATING...NARROW NWRN TONGUE OF
FAVORABLE LOW-LEVEL MOISTURE...AND SERN RIM OF LARGE-SCALE
ASCENT/DCVA PRECEDING MID-UPPER TROUGH. BACKED FLOW N OF
WARM-FRONTAL REMNANTS WILL AID IN LOW-LEVEL AND DEEP-LAYER
SHEAR...RESULTING IN WIND PROFILES FAVORABLE FOR SUPERCELLS WITH
LARGE HAIL AND SVR GUSTS. GEOMETRY OF WIND PROFILES INFLUENCED BY
POSITIVE TILT OF MID-UPPER TROUGH SHOULD LEAD TO SOME PRONOUNCED
WEAKNESSES IN 1-4 KM AGL HODOGRAPHS...WHICH COULD LEAD TO
STORM-SCALE PROCESSES MAKING TORNADO RISK CONDITIONAL BUT NOT
PRECLUDING IT.

ANY ACTIVITY DEVELOPING OR QUICKLY MOVING INTO LARGER-HODOGRAPH
ENVIRONMENT OF NE TX OR SE OK DURING LATE AFTERNOON...ESPECIALLY
ALONG WARM FRONT...MAY RESIDE IN BAROCLINIC ZONE LONG ENOUGH TO POSE
TORNADO RISK...GIVEN FRONTAL ENHANCEMENT TO LOW-LEVEL VORTICITY AND
STORM-RELATIVE INFLOW...AS WELL AS FORECAST SOUNDINGS SHOWING
300-400 J/KG EFFECTIVE SRH. HOWEVER...COVERAGE OF SFC-BASED TSTMS
ALONG/S OF FRONT IS IN QUESTION...MAKING THIS POTENTIAL IS TOO
CONDITIONAL FOR MORE THAN MRGL TORNADO OUTLOOK ATTM.

..EDWARDS/ROGERS.. 04/26/2013

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.