SPC AC 181728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT MON MAY 18 2009
VALID 191200Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LARGE SCALE PATTERN WILL REMAIN UNSPRING-LIKE OVER THE NEXT FEW DAYS
AS STRONGER WLY FLOW RETREATS TO THE U.S./CANADIAN BORDER. WHILE
THIS PATTERN WOULD PROVE FAVORABLE FOR SIGNIFICANT SEVERE WEATHER
ACROSS PORTIONS OF THE NRN HIGH PLAINS INTO THE UPPER MS VALLEY THE
ABSENCE OF MEANINGFUL MOISTURE WILL LIMIT SEVERE POTENTIAL. THE
ONLY POSSIBLE EXCEPTION WILL BE WITH HIGH BASED CONVECTION THAT
EVOLVES WITHIN THE STEEP LAPSE RATE ENVIRONMENT...PRIMARILY OVER MT.
OTHERWISE...MODELS CONTINUE TO SUGGEST AN EVOLVING LOW PRESSURE
SYSTEM WILL ROTATE NWWD ACROSS SOUTH FL WHICH WILL BRING ENHANCED
PRECIPITATION/THUNDERSTORM POTENTIAL TO THAT REGION.
...NRN PLAINS...
STRONG HEIGHT FALLS...ROUGHLY 90-120M IN 12HR PERIOD...WILL
OVERSPREAD THE NRN ROCKIES BY LATE TUESDAY AFTERNOON AS MID LEVEL
SPEED MAX EJECTS ACROSS NRN ORE INTO WRN MT. THIS FEATURE WILL
FORCE A SHARP COLD FRONT/STRONG BAROCLINIC ZONE INTO WRN MT/CNTRL ID
BY 20/00Z. MOISTURE IS VERY LIMITED...PW ON THE ORDER OF .5
INCH...ACROSS THIS REGION TODAY AND WILL ONLY GRADUALLY MOISTEN BY
DAY2...PRIMARILY DUE TO LARGE SCALE ASCENT/COOLING. 12Z MODEL
GUIDANCE DOES SUGGEST H5 TEMPERATURES WILL BE QUITE COLD IN
ASSOCIATION WITH THIS PROGRESSIVE UPPER TROUGH...AS NOTED BY 500 MB
TEMPERATURES AOB MINUS 20C INTO WRN MT BY PEAK HEATING. GIVEN THE
STRENGTH OF THIS FEATURE IT APPEARS THUNDERSTORMS SHOULD EVOLVE IN
THE HEAT OF THE DAY...BOTH ALONG ADVANCING COLD FRONT AND OVER THE
HIGHER TERRAIN OF THE NRN ROCKIES. FORECAST SHEAR PROFILES ARE MORE
THAN ADEQUATE FOR ORGANIZED SEVERE THUNDERSTORMS BUT THE ABSENCE OF
MEANINGFUL BOUNDARY LAYER MOISTURE WILL LIMIT BUOYANCY FOR HIGH
BASED DEEP CONVECTION THAT EVOLVES ACROSS THIS REGION. EVEN
SO...ISOLATED SUPERCELLS SHOULD EVOLVE WHICH COULD PRODUCE GUSTY
WINDS AND HAIL.
...FL...
LATEST MODEL GUIDANCE CONTINUES TO SUGGEST AN UPPER LOW WILL DEVELOP
ALONG SRN FRINGE OF ERN U.S. TROUGH OVER THE NEXT FEW DAYS. CENTER
OF CIRCULATION WILL THEN MIGRATE SLOWLY WWD ACROSS SRN FL. DEEP ELY
FLOW...ALONG WITH A SLOWLY ORGANIZING SFC LOW NEAR THE SRN TIP OF
THE PENINSULA...SUGGESTS GREATEST CONVERGENCE WILL BE ALONG THE
ATLANTIC COAST. GIVEN THE EXTENSIVE CLOUDINESS AND
PRECIPITATION...ALONG WITH WEAK LAPSE RATES...INSTABILITY WILL BE
QUITE LIMITED ACROSS THIS REGION. HOWEVER FORECAST SHEAR PROFILES
WILL STRENGTHEN WITH TIME AND THIS COULD SUPPORT A FEW ORGANIZED
THUNDERSTORMS CAPABLE OF PRODUCING GUSTY WINDS...AND PERHAPS AN
ISOLATED TORNADO WITHIN MORE BUOYANT AIRMASS.
..DARROW.. 05/18/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
|
