DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 301237
SWODY1
SPC AC 301234

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0734 AM CDT WED MAY 30 2012

VALID 301300Z - 311200Z

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
ACROSS PART OF SWRN KS...WRN/CNTRL OK... AND FAR NRN TX...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL HIGH PLAINS INTO
THE OZARK PLATEAU AND SRN PLAINS...

--POTENTIALLY SIGNIFICANT SEVERE WEATHER EPISODE ACROSS PARTS OF THE
CNTRL/SRN PLAINS THIS AFTERNOON INTO TONIGHT--

...SYNOPSIS...

POLAR BRANCH SHORT-WAVE TROUGH OVER THE NRN HIGH PLAINS WILL
PROGRESS SEWD AND PHASE WITH LOWER-LATITUDE IMPULSES EMERGING FROM
THE CNTRL/SRN PLAINS TO SUPPORT BROADER-SCALE TROUGH AMPLIFICATION
FROM THE UPPER MS VALLEY INTO OZARK PLATEAU AND SRN PLAINS BY
31/12Z. THIS UPPER-AIR PATTERN EVOLUTION WILL RESULT IN THE EWD
DEVELOPMENT AND/OR RE-FORMATION OF A SURFACE LOW FROM NWRN TX INTO
THE OZARKS BY LATE TONIGHT/EARLY THU. AS THIS OCCURS...A COLD FRONT
MOVING SEWD THROUGH THE NRN/CNTRL PLAINS WILL MERGE WITH A
STATIONARY FRONT SITUATED OVER SRN KS/NRN OK INTO THE OZARK PLATEAU
WITH THE COMPOSITE BOUNDARY --LIKELY AIDED BY CONVECTIVE OUTFLOW--
SURGING SEWD INTO THE SRN PLAINS.

...CNTRL/SRN PLAINS...

12Z SURFACE OBSERVATIONS SHOW THAT A CONVECTIVE OUTFLOW ASSOCIATED
WITH DECAYING MCS OVER N-CNTRL/NERN TX EXTENDS FROM NEAR LFK NWWD
THROUGH ACT TO A SURFACE LOW N OF LBB. VAD DATA FROM FREDRICK OK
AND OK MESONET OBSERVATIONS INDICATE THAT THIS BOUNDARY IS QUITE
SHALLOW OVER SWRN OK/NWRN TX WHERE SURFACE WINDS HAVE ALREADY VEERED
TO A SELY DIRECTION. AND WHILE DEWPOINTS HAVE DROPPED INTO THE
UPPER 50S AT MANY LOCATIONS ACROSS THE WRN HALF OF OK...INCREASED
BOUNDARY LAYER MIXING WILL LIKELY RESULT IN VALUES INCREASING INTO
THE LOW/MID 60S LATER TODAY. AT THE SAME TIME...A PLUME OF VERY
STEEP MIDLEVEL LAPSE RATES /I.E. 8.5-9.5 C PER KM/ WILL OVERSPREAD
WARM SECTOR AND CONTRIBUTE TO A MODERATE-STRONGLY UNSTABLE AIR MASS
BY AFTERNOON WITH MLCAPE RANGING FROM 1000-1500 J/KG IN SWRN NEB TO
AS HIGH AS 3000-4000 J/KG ACROSS PARTS OF WRN OK.

CONSIDERABLE VARIABILITY EXISTS AMONGST MESOSCALE AND
CONVECTION-ALLOWING MODEL GUIDANCE WITH REGARD TO SPECIFIC DETAILS
OF CONVECTIVE EVOLUTION THIS AFTERNOON INTO EVENING. CURRENT
THINKING IS THAT THE PREFERRED CORRIDOR FOR STORM INITIATION WILL BE
ACROSS WRN PARTS OF KS/OK BY MID AFTERNOON WHERE LARGE-SCALE FORCING
FOR ASCENT PROGRESSIVELY OVERSPREADS WRN/NWRN EXTENSION OF WARM
SECTOR. FORECAST HODOGRAPHS INDICATE VERTICALLY VEERING WIND
PROFILES /MOST NOTABLY ACROSS WRN KS/ WITH 45-55 KT OF EFFECTIVE
BULK SHEAR WHICH WILL SUPPORT RAPID SUPERCELL EVOLUTION.

VERY LARGE HAIL AND A FEW TORNADOES WILL BE POSSIBLE WITH THE
INITIAL STORMS BEFORE ACTIVITY GROWS UPSCALE INTO ONE OR MORE
FORWARD-PROPAGATING MCSS. LARGE-SCALE PATTERN IS ANALOGOUS TO PAST
CNTRL/SRN PLAINS DERECHO EVENTS...AND A SIMILAR TYPE SCENARIO MAY
UNFOLD THIS EVENING INTO TONIGHT WITH THE POTENTIAL FOR WIDESPREAD
DAMAGING WINDS FROM PARTS OF SRN KS THROUGH WRN/CNTRL OK INTO NRN
TX.

...SERN TX/LA TO THE CNTRL GULF COAST...

OUTFLOW BOUNDARY ASSOCIATED WITH DECAYING N-CNTRL/NERN TX MCS WILL
LIKE FOCUS RENEWED TSTM DEVELOPMENT THIS AFTERNOON WITHIN A MOIST
AND MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF 1000-2000 J/KG.
DEEP-LAYER FLOW FIELD WOULD SUPPORT THE SEWD MOTION OF TSTM CLUSTERS
WITH A RISK FOR SOME HAIL AND DAMAGING WINDS SPREADING TOWARD THE
CNTRL GULF COAST THROUGH THIS EVENING.

..MEAD/ROGERS.. 05/30/2012

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