SWODY2
SPC AC 221719
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1219 PM CDT FRI MAY 22 2009
VALID 231200Z - 241200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LARGE SCALE PATTERN WILL ALLOW FOR GRADUAL MOISTENING ACROSS THE
CONUS OVER THE NEXT FEW DAYS...ALTHOUGH DEEP LAYER SHEAR WILL REMAIN
QUITE WEAK FOR THE SRN TWO THIRDS OF THE COUNTRY. THIS GRADUAL
MOISTENING WILL CONTRIBUTE TO AN EXPANSION OF DEEP CONVECTION ACROSS
A GOOD PORTION OF THE U.S. FROM THE INTERIOR WEST...ACROSS THE
CNTRL/SRN PLAINS INTO THE OH VALLEY...NOT TO MENTION THE WIDESPREAD
STORMS EXPECTED ACROSS THE GULF STATES IN ASSOCIATION WITH NWD
MOVING UPPER LOW.
...NRN ROCKIES...
UPPER RIDGING WILL GRADUALLY FLATTEN DURING THE DAY2 PERIOD AS
SEVERAL WEAK SHORTWAVE TROUGHS EJECT ACROSS THE NRN ROCKIES. EVEN
SO...MID LEVEL FLOW IS EXPECTED TO REMAIN SOMEWHAT MARGINAL WITH H5
FLOW EXPECTED TO BE ON THE ORDER OF 20-30KT. LATEST THINKING IS
PW/S WILL APPROACH .75 INCHES ACROSS PORTIONS OF MT INTO ID BY LATE
AFTERNOON WHICH SHOULD CONTRIBUTE TO MODEST INSTABILITY AND
THUNDERSTORM DEVELOPMENT BY MID AFTERNOON. FORECAST SOUNDINGS
SUGGEST STRONG HEATING WILL ENHANCE BUOYANCY AND CONVECTIVE
INITIATION ACROSS MUCH OF THE HIGHER TERRAIN FROM ID INTO SWRN MT
ALONG SRN FRINGE OF STRONGER FLOW ALOFT. IN FACT 24/02Z SOUNDING AT
BIL APPEARS SUPPORTIVE OF WEAK SUPERCELL DEVELOPMENT WITH ELY LOW
LEVEL FLOW VEERING INTO THE WEST AT MID LEVELS. ANY STORMS THAT
EVOLVE ACROSS THIS REGION MAY ROTATE WHICH COULD ENHANCE THE
PROSPECT FOR HAIL AND PERHAPS GUSTY WINDS. AT THIS TIME SHEAR
PROFILES AND MOISTURE APPEAR A BIT TOO WEAK TO WARRANT A SLIGHT
RISK.
...CNTRL PLAINS...
STRONG HEATING ACROSS THE CNTRL PLAINS WILL ALLOW SFC PARCELS TO
REACH THEIR CONVECTIVE TEMPERATURES ALONG THE KS/NEB BORDER INTO
NERN CO BY LATE AFTERNOON. ALTHOUGH LOW LEVEL MOISTURE/INSTABILITY
IS EXPECTED TO ONLY BE SOMEWHAT MODEST...STEEP LAPSE RATES AND WEAK
FLOW ALOFT SUGGEST A FEW STORMS COULD PRODUCE DOWNBURSTS OR PERHAPS
MARGINALLY SEVERE HAIL AS LLJ IMPINGES ON FRONTAL ZONE.
...NY/PA...
STRONGER MID LEVEL FLOW WILL GLANCE UPSTATE NY AS PRIMARY SPEED MAX
ROTATES ACROSS QUEBEC SATURDAY. ALTHOUGH LARGE SCALE FORCING WILL
BE SOMEWHAT LIMITED ACROSS PA/NY IT APPEARS SUFFICIENT HEATING WILL
DEVELOP BY 18Z FOR SCATTERED THUNDERSTORM DEVELOPMENT ALONG WEAKLY
CONVERGENT SFC BOUNDARY WHICH SHOULD REMAIN ORIENTED FROM CNTRL
NY...SWWD INTO WRN PA UNTIL LATE EVENING. INSTABILITY IS NOT
EXPECTED TO BE THAT STRONG BUT WLY DEEP LAYER SHEAR VECTORS SUGGEST
ANY STORMS THAT EVOLVE ACROSS THIS REGION WILL PROPAGATE SEWD AT
ROUGHLY 20-25KT. HAIL AND GUSTY WINDS MAY ACCOMPANY STRONGER
UPDRAFTS.
...GULF STATES...
PERSISTENT...BUT SLOW MOVING UPPER LOW WILL GRADUALLY LIFT NWD ALONG
THE CNTRL GULF COAST WITH MODEST LLJ EXPECTED TO DEVELOP ACROSS
AL/MS. THIS INCREASE IN LOW LEVEL SHEAR MAY ENHANCE THE POTENTIAL
FOR ROTATION IN THE LOWEST LEVELS WITH ANY PERSISTENT
UPDRAFT...HOWEVER VERY WEAK LAPSE RATES AND EXTREMELY LIMITED
BUOYANCY DOES NOT APPEAR PARTICULARLY FAVORABLE FOR ORGANIZED SEVERE
STORMS CAPABLE OF PRODUCING TORNADOES.
..DARROW.. 05/22/2009
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