DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 311245
SWODY1
SPC AC 311244

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0744 AM CDT THU MAY 31 2012

VALID 311300Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING FROM
PORTIONS OF THE OH VALLEY SWWD INTO THE LOWER MS VALLEY AND WWD INTO
CNTRL/SRN TX...

...SYNOPSIS...

THE SEWD PROGRESSION OF A MID LEVEL JET STREAK FROM THE CNTRL HIGH
PLAINS INTO OZARK PLATEAU/MID-SOUTH WILL CONTRIBUTE TO THE
AMPLIFICATION OF LARGE-SCALE TROUGH OVER THE MS VALLEY WITH
SUBSEQUENT UPPER LOW FORMATION FORECAST OVER THE UPPER MIDWEST BY
01/12Z. WITHIN THIS BROADER-SCALE PATTERN...A NUMBER OF
PERTURBATIONS --SOME OF CONVECTIVE ORIGIN-- WILL SHIFT EWD FROM THE
OZARKS AND SRN PLAINS THROUGH THE MID/LOWER MS VALLEY.

AT THE SURFACE...LOW PRESSURE OVER CNTRL MO WILL DEVELOP ENEWD
ACROSS THE OH VALLEY WHILE TRAILING COLD FRONT...INITIALLY FROM THE
OZARKS TO SRN HIGH PLAINS...ADVANCES SEWD TOWARD THE NWRN GULF
COAST. A WARM FRONT WILL PRECEDE THE MIGRATORY SURFACE
LOW...GRADUALLY LIFTING NWD THROUGH THE OH VALLEY.

...OH/TN/LOWER MS VALLEYS...

RADAR MOSAIC SHOWS A COUPLE OF MCVS THIS MORNING WITHIN PRE-FRONTAL
WARM SECTOR...ONE OVER S-CNTRL MO...AND THE OTHER NEAR THE ARKLATEX.
CONVECTION ASSOCIATED WITH BOTH OF THESE FEATURES HAS WEAKENED
DIURNALLY...THOUGH RESIDUAL COLD POOLS AND DEEPER-LAYER FORCING
ATTENDANT TO THESE VORTICITY MAXIMA WILL LIKELY PROMOTE AN INCREASE
IN STORM COVERAGE AND VIGOR BY LATE MORNING/EARLY AFTERNOON OVER THE
LOWER OH/LOWER MS VALLEYS.

12Z JAN SOUNDING SHOWED THE PRESENCE OF A VERY MOIST LOW-LEVEL AIR
MASS WHICH WILL ALLOW MLCAPE VALUES TO INCREASE TO 2000-2500 J/KG BY
AFTERNOON ACROSS THE LOWER MS VALLEY. INSTABILITY WILL DECREASE
WITH NWD EXTENT INTO THE OH VALLEY /I.E. AFTERNOON MLCAPE OF
1000-1500 J PER KG/ OWING TO A COMPARATIVELY DRIER BOUNDARY LAYER
AND THE EWD SPREAD OF HIGH CLOUDS WHICH WILL TEMPER DAYTIME HEATING.
LATEST CONVECTION-ALLOWING MODELS SUGGEST THE POTENTIAL
ORGANIZATION OF STORMS INTO MULTIPLE LINEAR CONVECTIVE SYSTEMS WITH
THE PRIMARY HAZARDS BEING SOME HAIL AND DAMAGING WINDS INTO MID-LATE
EVENING. THE THREAT FOR A TORNADO OR TWO WILL BE HIGHEST ALONG
SURFACE LOW TRACK WHERE LOCALLY BACKED NEAR-SURFACE FLOW WILL
ENHANCE LOW-LEVEL SHEAR.

...TX...

MCS CURRENTLY NE OF CLL APPEARS TO BE WELL-RESOLVED BY A NUMBER OF
CONVECTION-ALLOWING MODELS WHICH SUGGEST THAT THE SYSTEM SHOULD
CONTINUE TO WEAKEN AS IT PROGRESSES SEWD TOWARD THE UPPER TX
COAST/SWRN LA. LOW-LEVEL UPLIFT ALONG LEADING EDGE OF RESIDUAL GUST
FRONT MAY ALLOW FOR RENEWED DEVELOPMENT BY LATE MORNING/EARLY
AFTERNOON NEAR THE COAST WITHIN A MOIST AND MODERATELY UNSTABLE AIR
MASS WITH MLCAPE OF 1500-2500 J/KG. VERTICAL SHEAR WILL BE SOMEWHAT
MARGINAL FOR STORM ORGANIZATION/LONGEVITY...THOUGH THE PRESENCE OF
STEEP MIDLEVEL LAPSE RATES AND WATER-LOADING EFFECTS MAY ENHANCE
DAMAGING WIND AND HAIL POTENTIAL.

FARTHER W...12Z DRT/CRP/BRO SOUNDINGS ALL SHOWED THE PRESENCE OF A
VERY MOIST BOUNDARY LAYER /I.E. LOWEST 100-MB MEAN-MIXING RATIOS OF
AROUND 16 G PER KG/ AND STEEP MIDLEVEL LAPSE RATES...RESULTING IN AN
ALREADY MODERATE-STRONGLY UNSTABLE ENVIRONMENT. HOWEVER...A STRONG
CAP OBSERVED AT THE BASE OF THE EML CASTS CONSIDERABLE UNCERTAINTY
ON EVENTUAL STORM COVERAGE LATER TODAY. CURRENT THINKING IS THAT AN
OUTFLOW BOUNDARY NOW SETTLING SWD THROUGH NRN PARTS OF THE EDWARDS
PLATEAU...THE ARRIVAL OF THE SYNOPTIC COLD FRONT LATER
TODAY...AND/OR ENHANCED LOW-LEVEL UPSLOPE INTO THE HIGH TERRAIN OF
SWRN TX/NRN MEXICO MAY PROVIDE THE FOCUS FOR ISOLATED-WIDELY
SCATTERED TSTM DEVELOPMENT BY LATE AFTERNOON/EARLY EVENING. ANY
STORMS THAT INITIATE WILL LIKELY BECOME SUPERCELLS OWING TO MLCAPE
OF 2000-3000 J/KG...VERTICALLY VEERING WIND PROFILES...AND THE
CO-LOCATION OF THE SUBTROPICAL JET WHICH WILL ENHANCE DEEP-LAYER
SHEAR/UPDRAFT VENTING. VERY LARGE HAIL WILL BE THE MAIN THREAT WITH
THESE STORMS.

...SRN CO/NRN NM...

STEEP LAPSE RATES AND POST-FRONTAL DEWPOINTS IN THE 40S WILL YIELD A
MARGINALLY UNSTABLE ENVIRONMENT BY LATE AFTERNOON/EARLY EVENING
WITHIN THE LEE OF THE HIGHER TERRAIN. LOW-LEVEL UPSLOPE FLOW MAY BE
AUGMENTED BY THE SEWD PROGRESSION OF A WEAK MIDLEVEL
IMPULSE...GIVING RISE TO ISOLATED STORM DEVELOPMENT LATER TODAY.
GIVEN THE PRESENCE OF THE STEEP LAPSE RATES AND 30-35 KT OF DEEP
NWLY SHEAR...SETUP MAY SUPPORT A MARGINAL WIND/HAIL THREAT THROUGH
THIS EVENING.

..MEAD/ROGERS.. 05/31/2012

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