SPC AC 121254
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT SAT JUN 12 2010
VALID 121300Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS THROUGH EARLY TONIGHT FROM THE
TX PANHANDLE/SW KS TO THE MID MS VALLEY...
...TX PANHANDLE INTO SW KS THIS AFTERNOON/EVENING...
A BROAD CLOSED LOW HAS FORMED OVER THE LOWER CO RIVER VALLEY...WITH
A BELT OF 30-50 KT SSWLY MIDLEVEL FLOW EXTENDING OVER THE
SRN/CENTRAL HIGH PLAINS TO THE E OF THE LOW. AT THE SURFACE...A
COLD FRONT IS MOVING SWD ACROSS SE CO AND WRN/CENTRAL KS...AIDED BY
OUTFLOW FROM THE OVERNIGHT MCS IN NEB. THE SWD MOVEMENT OF THE
FRONT/OUTFLOW IS EXPECTED TO SLOW BY AFTERNOON ACROSS THE NRN TX
PANHANDLE INTO SW KS IN THE MERIDIONAL FLOW REGIME...AND
THUNDERSTORM DEVELOPMENT IS EXPECTED LATE THIS AFTERNOON ALONG THE
FRONT. A NARROW CORRIDOR OF SUFFICIENT DEEP-LAYER SHEAR AND
INSTABILITY FOR SUPERCELLS IS EXPECTED WHERE THE ERN FRINGE OF THE
STRONGER MID-UPPER FLOW OVERLAPS THE SURFACE FRONT AND THE NW EDGE
OF THE UNSTABLE WARM SECTOR /MLCAPE VALUES 2000-3500 J PER KG/.
THE INITIAL STORMS SHOULD BE DISCRETE SUPERCELLS WITH THE POTENTIAL
TO PRODUCE VERY LARGE HAIL AND A FEW TORNADOES. DEEP-LAYER
FLOW/SHEAR LARGELY PARALLEL TO THE FRONT WILL LEAD TO STORM
INTERACTIONS AND UPSCALE GROWTH OF CONVECTION INTO ONE OR MORE
CLUSTERS IS EXPECTED BY LATE EVENING/EARLY TONIGHT FROM THE N/NE TX
PANHANDLE INTO WRN/CENTRAL KS. THE THUNDERSTORM CLUSTERS WILL POSE
A RISK FOR DAMAGING WINDS AND LARGE HAIL.
...NE KS/IA/NRN MO/IL TODAY...
THE REMNANTS OF THE OVERNIGHT SEVERE MCS IN NEB CONTINUE TO EXPAND
EWD/NEWD INTO IA IN ADVANCE OF A LARGE NEWD-MOVING MCV OVER SE
SD...AND SEWD INTO NW MO AND N/NE KS ON CONVECTIVE OUTFLOW. FARTHER
E...A SMALLER MCS AND ASSOCIATED MCV PERSIST NEAR THE IA/IL BORDER.
NONE OF THE OPERATIONAL OR CONVECTION-ALLOWING MODELS DEPICTED THE
ACTUAL OVERNIGHT EVOLUTION OF THE NEB/IA STORMS...THOUGH THE
HIGH-RES RUNS AT LEAST MAINTAIN A REASONABLE SCENARIO WITH NEW
DEVELOPMENT TODAY ALONG THE RESIDUAL OUTFLOW BOUNDARIES.
THE REMNANTS OF THE WRN MCS SHOULD CONTINUE EWD ACROSS CENTRAL/SRN
IA TODAY...AND THE ERN MCS WILL DEVELOP EWD INTO NRN IL.
THUNDERSTORMS WILL CONTINUE THIS MORNING INTO NW MO AND NE KS WHERE
LIFT OVER THE TRAILING GUST FRONT IS FOCUSED BY THE SWLY LLJ. OTHER
SURFACE-BASED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE LATER THIS
AFTERNOON ALONG THE OUTFLOW BOUNDARIES ACROSS KS/MO/IL AS THE
BOUNDARY LAYER DESTABILIZES AND CONVECTIVE INHIBITION WEAKENS. THE
NEWD MOTION OF THE SD MCV AND SEWD MOVEMENT OF THE OUTFLOWS SUGGEST
THAT VERTICAL SHEAR WILL BE RATHER WEAK BY AFTERNOON...WITH
MULTICELL CLUSTERS THE PREFERRED CONVECTIVE MODE. GIVEN THE
MAGNITUDE OF THE INSTABILITY...THE STRONGER STORMS COULD PRODUCE A
FEW DAMAGING GUSTS AND AT LEAST MARGINALLY SEVERE HAIL.
...OH VALLEY TO VA/PA/SRN NY TODAY...
A CLUSTER OF ELEVATED THUNDERSTORMS MOVING ACROSS LAKE ONTARIO INTO
NY WILL WEAKEN SLOWLY THROUGH MID-LATE MORNING AS THE ASSOCIATED
MIDLEVEL TROUGH CRESTS THE RIDGE AND MOVES ESEWD OVER NRN NY/NEW
ENGLAND. MEANWHILE...THE WARM SECTOR WITH PW VALUES NEAR 2 INCHES
WILL SPREAD NEWD INTO PA AND SRN NY /S OF A WARM FRONT/...AND EWD
INTO VA WITH A WEAK DEVELOPING LEE TROUGH IN ADVANCE OF A WEAK
MIDLEVEL TROUGH OVER NRN KY/SW OH. ONGOING CONVECTION WITH THE OH
VALLEY SYSTEM WILL LIKELY PERSIST THROUGH THE DAY AND SPREAD EWD
OVER OH/KY/WV. ADDITIONAL THUNDERSTORM DEVELOPMENT IS EXPECTED
FARTHER E INTO PA/VA IN PROXIMITY TO THE SURFACE TROUGH...WHERE
DAYTIME HEATING WILL SUPPORT AFTERNOON MLCAPE VALUES NEAR 1000 J/KG.
RATHER POOR MIDLEVEL LAPSE RATES...WARM PROFILES ALOFT...AND WEAK
VERTICAL SHEAR WILL LIMIT THE OVERALL SEVERE STORM THREAT THIS
AFTERNOON. HOWEVER... STRONG/ISOLATED DAMAGING DOWNBURST WINDS WILL
BE POSSIBLE... PRIMARILY WITH STORMS E OF THE MOUNTAINS. VERTICAL
SHEAR WILL BE MARGINALLY FAVORABLE FOR SUPERCELLS ALONG THE WARM
FRONT INTO SRN NY...BUT WEAK INSTABILITY SUGGESTS THAT THE SEVERE
THREAT WILL REMAIN MARGINAL AT BEST.
...WRN CO AND VICINITY TODAY...
A BELT OF STRONG MID-UPPER SLY FLOW WILL PERSIST TODAY NEAR AND N OF
THE FOUR CORNERS...E OF THE LOWER CO RIVER VALLEY CLOSED LOW.
LOW-MIDLEVEL ASCENT WILL ALSO BE FOCUSED ALONG THIS SAME
BAND...WHERE WEAK INSTABILITY WILL BE PRESENT TO SUPPORT A CONTINUED
THREAT FOR SCATTERED THUNDERSTORMS. THE COMBINATION OF WEAK
INSTABILITY AND STRONG DEEP-LAYER SLY SHEAR WILL SUPPORT A FEW
EMBEDDED BOW/SUPERCELL STRUCTURES WITH AN ATTENDANT RISK FOR
ISOLATED DAMAGING WINDS.
...CENTRAL TX NNEWD TO CENTRAL/ERN OK THIS AFTERNOON...
WATER VAPOR IMAGERY SHOWS A BELT OF SOMEWHAT ENHANCED MIDLEVEL FLOW
WITH EMBEDDED SMALL VORTICITY CENTERS ALONG AN AXIS FROM DRT TO DFW
TO TUL. THE 5% WIND PROBABILITIES HAVE BEEN EXPANDED INTO THIS
CORRIDOR TO REFLECT SOME POTENTIAL FOR A FEW STORMS WITH STRONG
OUTFLOW WINDS THIS AFTERNOON...IN AN ENVIRONMENT OF MODERATE
INSTABILITY AND SLIGHTLY ENHANCED POTENTIAL FOR MOMENTUM TRANSFER TO
THE GROUND.
..THOMPSON/SMITH.. 06/12/2010
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
|
