DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 141723
SWODY2
SPC AC 141721

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1221 PM CDT MON SEP 14 2009

VALID 151200Z - 161200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

BLOCKING PATTERN WILL PERSIST TUESDAY WITH A MEAN RIDGE FLANKED BY
UPPER TROUGHS OVER THE ERN PACIFIC AND SERN CANADA. UNDERCUTTING THE
RIDGE WILL BE SEVERAL SMALLER SCALE UPPER LOWS. THE UPPER LOW NOW
APPROACHING THE GREAT BASIN WILL CLOSE OFF AND STALL OVER UT AS IT
BECOMES DETACHED FROM BELT OF STRONGER WLYS. WEAKER CLOSED UPPER LOW
WILL PERSIST OVER THE LOWER MS VALLEY AREA.

...UT...

STEEP LAPSE RATES WILL DEVELOP WHERE SUFFICIENT DIABATIC HEATING
OCCURS BENEATH THE COLD MID LEVEL TEMPERATURES ASSOCIATED WITH UPPER
LOW CIRCULATION. OUTSIDE OF ANY ONGOING THUNDERSTORMS AND
CLOUDS...DIABATIC WARMING OF THE BOUNDARY LAYER WILL RESULT IN
MARGINAL INSTABILITY WITH MLCAPE AOB 500 J/KG. MOST LIKELY ZONE OF
DESTABILIZATION WILL BE OVER CNTRL/SRN UT NEAR DRY SLOT REGION ALONG
SRN PERIPHERY OF UPPER TROUGH. SCATTERED STORMS WILL LIKELY
REDEVELOP DURING THE AFTERNOON. STEEP LAPSE RATES AND COLD AIR ALOFT
COULD SUPPORT A THREAT FOR HAIL. ISOLATED STRONG WIND GUSTS COULD
ALSO ACCOMPANY THE STRONGER ACTIVITY. HOWEVER...THE THERMODYNAMIC
ENVIRONMENT IS NOT EXPECTED TO BECOME SUFFICIENT FOR MORE THAN 5%
SEVERE PROBABILITIES.

...GULF COASTAL REGION...

UPPER LOW OVER THE LOWER MS VALLEY IS FORECAST TO MOVE LITTLE THIS
PERIOD. FRONTAL BOUNDARY WILL PERSIST ALONG THE GULF COASTAL REGION
AND EXTEND WWD TO A WEAK SURFACE LOW OVER THE LOWER MS VALLEY. WV
IMAGERY CURRENTLY INDICATES THAT DRY AIR ALOFT IS BEING ENTRAINED
ALONG SRN PERIPHERY OF UPPER LOW OVER THE NWRN GULF...AND THIS WILL
IMPROVE THE CHANCE FOR BOUNDARY LAYER DESTABILIZATION AS LOW CLOUDS
MIX OUT. HOWEVER...INSTABILITY WILL REMAIN MARGINAL DUE TO WARM AIR
ALOFT AND WEAK LAPSE RATES. FORECAST WIND PROFILES SHOW CONSIDERABLE
VEERING IN THE LOWEST 1 KM IN VICINITY OF THE FRONT. HOWEVER...ONLY
WEAK WIND SPEEDS ASSOCIATED WITH UPPER LOW CIRCULATION WILL LIMIT
HODOGRAPH SIZE. THIS ALONG WITH THE MARGINAL THERMODYNAMIC
ENVIRONMENT SUGGEST ANY SEVERE THREAT IN THIS REGION SHOULD REMAIN
LIMITED.

..DIAL.. 09/14/2009

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