SPC AC 201926
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0226 PM CDT WED MAY 20 2009
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CENTRAL HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE FL
PENINSULA...
...CENTRAL HIGH PLAINS...
CONVECTION IS GRADUALLY DEEPENING/EXPANDING WITHIN VERY STEEP LAPSE
RATE ENVIRONMENT ACROSS SRN WY...ALONG AND JUST SOUTH OF SHARP COLD
FRONT. AS NELY UPSLOPE FLOW INTENSIFIES ACROSS THE HIGH PLAINS THIS
ACTIVITY SHOULD GRADUALLY ORGANIZE AS IT MOVES ACROSS SERN WY INTO
THE NEB PANHANDLE. EARLIER THOUGHTS REGARDING THE POSSIBILITY FOR A
FEW LP SUPERCELLS REMAIN AS SHEAR PROFILES WILL BECOME INCREASINGLY
SUPPORTIVE OF ROTATING UPDRAFTS. LATEST SATELLITE/RADAR IMAGERY
SUGGEST CONVECTION OVER GOSHEN/LARAMIE COUNTIES WILL SOON ENCOUNTER
FRONTAL ZONE WHERE LOW LEVEL MOISTURE/BUOYANCY SHOULD ENCOURAGE MORE
ROBUST UPDRAFTS...ESPECIALLY ACROSS THE NEB PANHANDLE...THOUGH 18Z
SOUNDING AT LBF HAS YET TO MOISTEN/DESTABILIZE SIGNIFICANTLY.
...FL...
MULTIPLE BANDS OF STRONG/SEVERE CONVECTION WILL CONTINUE TO ROTATE
NWWD ALONG THE ERN PERIPHERY OF RETROGRADING UPPER LOW. THOUGH LOW
LEVEL SHEAR IS NOT THAT SIGNIFICANT...STRONG BOUNDARY LAYER HEATING
ACROSS THE SWRN PENINSULA HAS YET TO BE OVERTURNED BY THUNDERSTORM
ACTIVITY. GIVEN THE VEERING PROFILES WITH HEIGHT...MOST STRONG
UPDRAFTS SHOULD TEND TO ROTATE POSSIBLY LEADING TO A FEW TORNADOES.
..DARROW.. 05/20/2009
.PREV DISCUSSION... /ISSUED 1120 AM CDT WED MAY 20 2009/
...FL...
MORNING OBSERVATIONAL DATA AND MODEL GUIDANCE SUGGEST LITTLE CHANGE
NEEDED TO EXISTING OUTLOOK OVER THIS REGION. STRONG HEATING WILL
CONTINUE OVER SRN/CENTRAL FL SOUTH OF E-W RAINBAND PERSISTING ACROSS
NRN PARTS OF THE STATE. APPEARS SMALL AXIS OF SURFACE CONVERGENCE
WILL BECOME ESTABLISHED FROM BETWEEN MIA/PBI TOWARDS THE TBW AREA
DURING THE EARLY AFTERNOON AND LIKELY ENHANCE THUNDERSTORM
DEVELOPMENT. ALTHOUGH DEVELOPMENT HAS BEEN SLOW TO DEVELOP THUS FAR
OVER THIS REGION...POSSIBLY DUE TO SMALL AREA OF SUBSIDENCE...
TEMPERATURES IN THE MID 80S F AND FOCUSED ASCENT AHEAD OF SMALL
PERTURBATIONS ROTATING AROUND LARGER UPPER LOW OFF SW FL SHOULD
INCREASE STORMS THROUGH THE AFTERNOON. REGIONS REMAIN QUITE COLD
ALOFT...-13C AT MFL THIS MORNING...AND RESULTANT STRONG INSTABILITY
SHOULD FUEL A FEW SEVERE HAIL/WIND REPORTS WITH THE MORE ROBUST
UPDRAFTS. OVERALL STORM-SCALE ORGANIZATION SHOULD REMAIN WEAK...
ALTHOUGH ACTIVITY DEVELOPING FROM CENTRAL FL NWD TO NEAR THE MODEST
ELY LLJ OVER NRN FL WILL HAVE A GREATER CHANCE OF LOW LEVEL ROTATION
AND PERHAPS A TORNADO OR TWO. STRENGTH OF INSTABILITY MAY ALSO
SUSTAIN A FEW BRIEF SPOUTS/TORNADOES INTO SERN FL.
...CENTRAL HIGH PLAINS INTO THE NRN PLAINS...
PROGRESSIVE SHORTWAVE TROUGH WILL CONTINUE SHIFTING EWD ACROSS THE
NRN ROCKIES TODAY...WITH A PAIR OF LOW AMPLITUDE IMPULSES WEAKENING
AS THEY EJECT ACROSS THE CENTRAL ROCKIES AND NRN PLAINS. ASSOCIATED
SURFACE COLD FRONT EXTENDING FROM CENTRAL/ERN ND INTO CENTRAL WY AT
16Z WILL CONTINUE ESEWD WITH PRIMARY LOW CENTER OVER THE RED RIVER
VALLEY EXPECTED TO SHIFT NEWD ACROSS NRN MN TODAY. SHEAR WILL
STRENGTHEN FROM THE CENTRAL HIGH PLAINS INTO ND/MN THROUGH THE
PERIOD...ALTHOUGH SPARSE MOISTURE CONTINUES TO BE PRIMARY LIMITING
FACTOR FOR THUNDERSTORMS.
MODELS CONTINUE TO DEVELOP A WEAKER SURFACE LOW ALONG THE FRONT/LEE
TROUGH INTERSECTION OVER NERN CO/SWRN NEB THIS AFTERNOON.
ASSOCIATED NELY UPSLOPE FLOW JUST NORTH OF THE LOW MAY FOCUS AN AXIS
OF MARGINAL MLCAPE AND WEAK CINH INTO FAR E-CENTRAL WY/NRN NEB
PANHANDLE/FAR SWRN SD DURING THE LATE AFTERNOON. UPSLOPE FLOW AND
STRONG BOUNDARY LAYER MIXING SHOULD SUPPORT ISOLATED THUNDERSTORMS
DEVELOPMENT INTO THIS AREA WHERE SHEAR WILL REMAIN SUFFICIENT FOR
SUPERCELLS. HIGH-BASED ACTIVITY /POSSIBLY LP-SUPERCELLS/ MAY
PRODUCE LARGE HAIL/DAMAGING WIND...WITH GENERAL EVOLUTION INTO A
MARGINAL SEVERE CLUSTER EVOLVING ALONG NOSE OF NOCTURNAL LLJ
SHIFTING EWD NORTH OF THE SURFACE COLD FRONT ALONG THE NEB/SD BORDER
THROUGH THE EVENING.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
|
