Thursday, April 19, 2012

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 190600
SWODY1
SPC AC 190559

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT THU APR 19 2012

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NWRN TX...OK..ERN KS INTO
THE MID MS VALLEY REGION...

...SYNOPSIS...

PROGRESSIVE QUASI-ZONAL UPPER PATTERN WILL BEGIN A TRANSITION ON
THURSDAY AS A SYNOPTIC TROUGH AMPLIFIES OVER THE PLAINS AND MS
VALLEY. SEVERAL IMPULSES EMBEDDED WITHIN THIS FEATURE WILL AFFECT
PORTIONS OF THE PLAINS DURING THE DAY. A SHORTWAVE TROUGH NOW OVER
THE NRN ROCKIES WILL MOVE THROUGH THE NRN PLAINS...UPPER MS VALLEY
AND GREAT LAKES...WHILE FARTHER SOUTH ANOTHER IMPULSE WILL AFFECT
THE SRN AND CNTRL PLAINS. SFC LOW WILL TRACK ENEWD THROUGH UPPER MS
VALLEY INTO THE GREAT LAKES ALONG STALLED BOUNDARY IN ASSOCIATION
WITH THE NRN STREAM FEATURE. A COLD FRONT EXTENDING SWWD FROM THIS
LOW WILL ADVANCE THROUGH THE CNTRL AND SRN PLAINS. BY LATE AFTERNOON
THIS FRONT WILL LIKELY EXTEND FROM ERN KS SWWD TO A WEAK SFC LOW IN
NWRN TX. A DRYLINE WILL EXIST SWD FROM THE LOW THROUGH WRN TX. THE
COLD FRONT WILL CONTINUE SEWD OVERNIGHT.

...NWRN TX THROUGH OK...ERN KS AND THE MID MS VALLEY AREA...

WITH DEWPOINTS OVER THE WRN GULF ONLY IN THE MID 50S...BOUNDARY
LAYER MOISTURE WILL NOT INCREASE MUCH ABOVE WHAT IS ALREADY IN PLACE
OVER THE CNTRL AND SRN PLAINS. HOWEVER...INCREASINGLY WLY FLOW
ACCOMPANYING THE UPPER TROUGH WILL TRANSPORT PLUME OF STEEPER LAPSE
RATES EWD ABOVE AXIS OF LOW-MID 50S DEWPOINTS. THIS PROCESS IN
CONJUNCTION WITH BOUNDARY LAYER WARMING AND COOLING TEMPERATURES
ALOFT ACCOMPANYING THE UPPER TROUGH SHOULD YIELD 1000-1500 J/KG
MLCAPE FROM NWRN-NCNTRL TX INTO OK AND ERN KS WITH HIGHER CAPE
LIKELY RESIDING OVER THE SRN PLAINS. THE EWD TRANSPORT OF THE EML
WILL CONTRIBUTE TO A CAP. HOWEVER...FRONTAL FORCING WILL LIKELY
RESULT IN STORMS DEVELOPING FROM IA SWWD THROUGH ERN KS INTO NWRN OK
BY LATE AFTERNOON. LARGELY UNIDIRECTIONAL SHEAR OF 35-40 KT WILL
SUPPORT BOTH MULTICELL AND POSSIBLY SOME SUPERCELL STRUCTURES...BUT
TENDENCY MAY BE FOR SOME OF THIS ACTIVITY TO GROW UPSCALE INTO LINE
SEGMENTS WITH A THREAT OF DAMAGING WIND AND LARGE HAIL.

OTHER STORMS WILL LIKELY DEVELOP IN VICINITY OF THE DRYLINE/COLD
FRONT INTERSECTION AND NEAR WEAK SFC LOW OVER NWRN TX OR SWRN OK.
DEEP VERTICAL SHEAR IN THIS REGION WILL INCREASE TO 45-50 KT BY
EVENING AS MID LEVEL JET ROTATES THROUGH BASE OF AMPLIFYING UPPER
TROUGH. THESE STORMS WILL LIKELY BE DISCRETE SUPERCELLS CAPABLE OF
VERY LARGE HAIL AND ISOLATED DAMAGING WIND. A TORNADO OR TWO CANNOT
BE RULED OUT INTO EARLY EVENING...BUT LIMITING FACTORS WILL BE WEAK
INITIAL LOW LEVEL SHEAR AND RELATIVELY HIGH BOUNDARY LAYER
TEMPERATURE-DEWPOINTS SPREADS. NEVERTHELESS...A SMALL WINDOW MAY
EXIST FOR A TORNADO AS THE LLJ STRENGTHENS AND BEFORE THE BOUNDARY
LAYER DECOUPLES.

..DIAL/SMITH.. 04/19/2012

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