DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 211628
SWODY1
SPC AC 211627

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CDT MON MAY 21 2012

VALID 211630Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN AR...WRN TN AND NRN
MS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN NM AND WRN TX...

...ERN AR/WRN TN/NRN MS AREA...
WATER VAPOR IMAGERY INDICATES THE SRN EXTENSION OF THE UPPER TROUGH
APPROACHING THE GREAT LAKES IS BECOMING BETTER DEFINED OVER THE
OZARKS...AS MID/UPPER LEVEL SUBSIDENCE STRENGTHENS IN THE IMMEDIATE
WAKE OF A VORTICITY MAX MOVING SEWD OVER SERN MO. THIS SYSTEM IS
EXPECTED TO CONTINUE TOWARD THE MID-SOUTH/TN VALLEY AND PROVIDE
ENHANCED ASCENT FOR THUNDERSTORM DEVELOPMENT THIS AFTERNOON. COOL
MID LEVEL TEMPERATURES /-15C AT 500 MB/ ARE MAINTAINING MODERATELY
STEEP MID LEVEL LAPSE RATES /7.0-7.5 C PER KM/...AND DIABATIC
HEATING AHEAD OF THE SURFACE COLD FRONT WILL COMBINE TO PROVIDE
UNSTABLE CONDITIONS WITH MLCAPE APPROACHING 2000 J/KG THIS
AFTERNOON.

MODEL GUIDANCE IS GENERALLY CONSISTENT INDICATING THUNDERSTORMS WILL
DEVELOP OVER EXTREME ERN AR/WRN TN BY EARLY AFTERNOON WITH ACTIVITY
SPREADING SEWD WITHIN DEEP NWLY 20-30 KT UNIDIRECTIONAL FLOW ALOFT.
VERTICAL SHEAR WILL BE SUFFICIENT FOR ORGANIZED MULTICELL
STORMS...AND STEEP LOW-MID LEVEL LAPSE RATES WILL PROMOTE
DEVELOPMENT OF LARGE HAIL AND STRONG WIND GUSTS WITH STRONGER
STORMS. THE SEVERE THREAT IS EXPECTED TO DIMINISH AFTER SUNSET AS
DIURNAL COOLING BEGINS TO STABILIZE THE BOUNDARY LAYER.

...ERN NM/WRN TX...
CURRENT STORMS OVER PARTS OF NWRN TX ARE EXPECTED TO MOVE SLOWLY
SEWD THIS AFTERNOON. THIS ACTIVITY HAS GENERATED COLD OUTFLOW OVER
THE PANHANDLE WHICH HAS TEMPORARILY STABILIZED THE ENVIRONMENT OVER
THIS AREA. IT HAS ALSO HELPED TO MAINTAIN A MOIST ELY LOW LEVEL
WIND COMPONENT INTO EAST CENTRAL NM...AND SURFACE DEW POINTS IN THE
LOW/MID 50S ARE EVIDENT ATTM OVER MUCH OF ERN NM. THE MOISTURE IS
LIKELY TO MIX OUT OVER CENTRAL NM AS HEATING OCCURS THIS AFTERNOON
BUT DEW POINTS IN THE UPPER 40S-LOWER 50S WILL LIKELY REMAIN OVER
PARTS OF ERN NM WHERE MOISTURE IS DEEPER /AS EVIDENCED BY LOW CLOUDS
PER VISIBLE IMAGERY/.

12Z REGIONAL SOUNDINGS EXHIBITED STEEP MID LEVEL LAPSE RATES...AND
WHEN COMBINED WITH STRONG HEATING WILL CONTRIBUTE TO MUCAPE AROUND
1500 J/KG THIS AFTERNOON. ALTHOUGH DYNAMIC SUPPORT FOR LARGE SCALE
ASCENT APPEARS LIMITED BASED ON SATELLITE IMAGERY...HEATING OVER THE
HIGHER TERRAIN SHOULD RESULT IN NEW CONVECTIVE DEVELOPMENT LATER
THIS AFTERNOON...ESPECIALLY OVER PARTS OF NERN AND EAST CENTRAL NM.
WIND PROFILES ARE EXPECTED TO EXHIBIT CONSIDERABLE DIRECTIONAL SHEAR
AS SSELY LOW LEVEL WINDS VEER TO 30-40 KT NWLY FLOW IN THE MID
LEVELS. THIS WILL PROVIDE SUFFICIENT SHEAR TO ENHANCE STORM
ORGANIZATION AND INTENSITY INCLUDING SUPERCELL DEVELOPMENT. THE
ACTIVITY WILL SPREAD SEWD THROUGH THE EVENING HOURS WITH STRONGER
CELLS CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND
GUSTS...ALTHOUGH AN ISOLATED TORNADO MAY ALSO BE POSSIBLE.

...SERN MS/CENTRAL AND SRN AL...
VISIBLE IMAGERY SHOWS A POSSIBLE MCV MOVING SEWD OVER NWRN AL. THIS
FEATURE MAY PERSIST IN THE WEAKLY SHEARED ENVIRONMENT AND PROVIDE A
FOCUS FOR REGENERATION OF THUNDERSTORMS AS STRONG HEATING OCCURS
ACROSS THE REGION. RELATIVELY COOL MID LEVEL TEMPERATURES /-12 TO
-13C AT 500 MB/ WILL PROMOTE STEEPER MID LEVEL LAPSE RATES AND
POSSIBLE HAIL FORMATION...WHILE STEEPENING LOW LEVEL LAPSE RATES AND
ASSOCIATED LARGER SURFACE T/TD SPREADS WILL ENHANCE THREAT FOR
LOCALIZED MICROBURSTS THIS AFTERNOON.

...NRN PARTS OF INTERMOUNTAIN REGION AND ROCKIES...
SFC HEATING BENEATH RELATIVELY COOLER MID-LEVEL TEMPERATURES WILL
SUPPORT THE DEVELOPMENT OF MARGINAL INSTABILITY. ISOLATED TO
SCATTERED THUNDERSTORMS ARE FORECAST TO INCREASE FROM NERN
OREGON/SERN WA INTO W-CNTRL MT THIS AFTERNOON OWING TO OROGRAPHIC
ASCENT...ALONG WITH INCREASING LARGE-SCALE ASCENT/MID-LEVEL HEIGHT
FALLS. STORMS SHOULD MOVE EWD/ENEWD INTO CNTRL MT LATE THIS
AFTERNOON INTO THE EVENING...INCLUDING THE POSSIBILITY OF ONE TO TWO
FORWARD-PROPAGATING ORGANIZED CONVECTIVE CLUSTERS GIVEN AROUND 35-50
KT OF EFFECTIVE SHEAR. LIMITED BUOYANCY OWING TO RELATIVELY MEAGER
LOW-LEVEL MOISTURE WILL MITIGATE THE OVERALL SVR THREAT...THOUGH A
FEW INSTANCES OF SVR WIND AND PERHAPS SVR HAIL WILL BE POSSIBLE.

..WEISS/GARNER.. 05/21/2012

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