SWODY1
SPC AC 200534
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1234 AM CDT TUE OCT 20 2009
VALID 201200Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
STRONG MIDLEVEL TROUGH CURRENTLY DIGGING SEWD THROUGH CA AND THE
GREAT BASIN WILL CONTINUE SEWD THROUGH THE LOWER CO VALLEY
TODAY...EVENTUALLY TRANSITIONING INTO A CLOSED SYSTEM OVER THE
MOGOLLON RIM INTO SRN ROCKIES. THIS EVOLUTION WILL RESULT IN
SIGNIFICANT HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT SPREADING EWD
FROM THE LOWER CO VALLEY EVENTUALLY INTO THE SRN HIGH PLAINS BY
WEDNESDAY MORNING.
AT THE SURFACE...DEEPENING LEE CYCLONE NOW OVER SWRN KS IS EXPECTED
TO DEVELOP SLIGHTLY SWWD TODAY IN RESPONSE TO THE INCREASED FORCING
APPROACHING FROM THE W. AS THIS OCCURS...ATTENDANT QUASI-STATIONARY
BOUNDARY CURRENTLY FROM THE NRN HIGH PLAINS TO THE LOW PRESSURE OVER
KS AND THEN NEWD INTO THE MID MO VALLEY MAY SAG SLOWLY SWD. FARTHER
S...A LEE TROUGH WILL STRENGTHEN OVER WRN TX BEFORE BEING OVERTAKEN
TONIGHT BY PACIFIC FRONT MOVING THROUGH THE SRN ROCKIES AND
EVENTUALLY INTO THE SRN HIGH PLAINS.
...AZ/NM...
PRE-FRONTAL AIR MASS IS NOT EXPECTED TO BE PARTICULARLY MOIST WITH
PW VALUES GENERALLY LESS THAN 0.75 INCH. BUT...CONSIDERABLE DYNAMIC
COOLING /90-120 M HEIGHT FALLS PER 12 HR/ AND RESULTANT STEEPENING
OF LAPSE RATES WILL CONTRIBUTE TO A WEAKLY UNSTABLE ENVIRONMENT BY
AFTERNOON WITH MLCAPE OF LESS THAN 500 J/KG. TSTMS ARE EXPECTED TO
INCREASE IN COVERAGE AND INTENSITY BY LATE MORNING/EARLY AFTERNOON
ALONG FRONT AS THE STRONG FORCING FOR ASCENT OVERSPREADS
DESTABILIZING AIR MASS.
FORECAST HODOGRAPHS INDICATE STRENGTHENING WIND FIELD WITH
TIME...PARTICULARLY IN THE MID TO UPPER-TROPOSPHERE. RESULTANT
VERTICAL SHEAR WILL BECOME MORE THAN SUFFICIENT FOR
ORGANIZED/ROTATING STORMS CAPABLE OF MARGINALLY SEVERE HAIL AND
LOCALLY STRONG WIND GUSTS. STORMS SHOULD GROW UPSCALE INTO CLUSTERS
OR LINE SEGMENTS THIS AFTERNOON INTO TONIGHT WITH A CONTINUED THREAT
FOR ISOLATED...SEVERE WIND/HAIL EWD ACROSS NM AND FAR WRN TX. THE
LIMITED INSTABILITY PRECLUDES HIGHER WIND/HAIL PROBABILITIES AND A
CATEGORICAL SLIGHT RISK IN THIS FORECAST.
...CNTRL/SRN HIGH PLAINS...
20/00Z S TX SOUNDINGS AND CURRENT GOES SOUNDER AND GPS PW DATA
INDICATE THAT A MODIFIED CP AIR MASS IS RETURNING NWD THROUGH THE
REGION WITH DEWPOINTS LARGELY IN THE 50S. SIMILAR TO
MONDAY...CONSIDERABLE HEATING/BOUNDARY LAYER DEEPENING INVOF LEE
TROUGH WILL RESULT IN DEWPOINTS DROPPING THROUGH THE 50S OVER WRN
TX. HOWEVER...THIS MIXING WILL EFFECTIVELY ERODE CONVECTIVE
INHIBITION WITH ISOLATED/SCATTERED STORMS DEVELOPING BY MID/LATE
AFTERNOON ALONG LEE TROUGH WITHIN WEAKLY UNSTABLE ENVIRONMENT WITH
MLCAPE OF AROUND 500 J/KG.
STRONGER MID/HIGH-LEVEL WIND FIELD AND RESULTANT VERTICAL SHEAR WILL
REMAIN W OF REGION THROUGH THE DIURNAL HEATING CYCLE...WITH
ENVIRONMENT SUPPORTIVE OF MULTICELL STORM CLUSTERS CAPABLE OF GUSTY
WINDS AND PERHAPS SOME HAIL. STRENGTHENING...NOCTURNAL LLJ AND
DEEPER FORCING IN ADVANCE OF UPSTREAM TROUGH ARE EXPECTED TO SUPPORT
AN INCREASE IN STORMS TONIGHT FROM ERN NM/WRN TX INTO WRN KS/S-CNTRL
NEB WITH A CONTINUED THREAT OF MARGINALLY SEVERE HAIL AND/OR STRONG
WIND GUSTS.
..MEAD/GRAMS.. 10/20/2009
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