SWODY2
SPC AC 160552
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CST SUN FEB 15 2009
VALID 171200Z - 181200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PROGRESSIVE UPPER PATTERN WILL PERSIST OVER THE U.S. TUESDAY. THE
PRIMARY FEATURE OF INTEREST REMAINS A STRONG UPPER JET THAT WILL
EJECT FROM BASE OF UPPER LOW NOW SITUATED OFF THE CA COAST. THIS
FEATURE WILL REACH THE SRN PLAINS TUESDAY EVENING AND MID-LOWER MS
VALLEY TUESDAY NIGHT. CYCLOGENESIS WILL COMMENCE OVER THE CNTRL
PLAINS DURING THE DAY AS THE UPPER JET CROSSES THE ROCKIES. THE LOW
WILL DEVELOP EWD THROUGH KS WITHIN UPPER JET EXIT REGION OVERNIGHT
WHILE ATTENDANT COLD FRONT ACCELERATES SEWD THROUGH THE CNTRL AND
SRN PLAINS. FARTHER SOUTH...A WARM FRONT WILL ADVANCE NWD THROUGH
ERN TX AND THE LOWER MS VALLEY.
...ERN TX THROUGH THE LOWER MS AND TN VALLEY REGIONS...
SLY LOW LEVEL JET WILL STRENGTHEN FROM ERN TX INTO THE LOWER-MID MS
VALLEY AS LEE CYCLONE DEEPENS WITHIN UPPER JET EXIT REGION. THE LOW
LEVEL JET WILL CONTRIBUTE TO NWD TRANSPORT OF PARTIALLY MODIFIED
GULF AIR THROUGH TX...THE LOWER MS VALLEY AND WRN PARTS OF THE TN
VALLEY. STRONG WLY FLOW ALOFT WILL ADVECT STEEPER MID-LEVEL LAPSE
RATES EWD THROUGH THIS REGION ABOVE THE RETURNING MOIST AXIS. THESE
PROCESSES WILL RESULT IN MARGINAL ELEVATED INSTABILITY. ISENTROPIC
LIFT AND THETA-E ADVECTION ABOVE A STABLE SURFACE LAYER ASSOCIATED
WITH THE STRONG SWLY LOW LEVEL JET WILL LIKELY BECOME SUFFICIENT TO
SUPPORT THE DEVELOPMENT OF ELEVATED THUNDERSTORMS OVERNIGHT. STORMS
APPEAR MOST PROBABLE FROM THE LOWER MS VALLEY EWD THROUGH THE TN
VALLEY REGION WHERE DEEPER ASCENT AND COOLER MID LEVEL TEMPERATURES
WILL EXIST. THREAT OF ISOLATED HAIL MAY ACCOMPANY THE STRONGER
UPDRAFTS...ESPECIALLY ALONG ERN PERIPHERY OF THE EWD ADVANCING EML
WHERE LAPSE RATES WILL BE STEEPER.
HAVE INCLUDED A PORTION OF ERN TX IN A CATEGORICAL GENERAL
THUNDERSTORM OUTLOOK AND 5% HAIL PROBABILITIES...BUT THUNDERSTORM
PROSPECTS IN THIS REGION ARE HIGHLY CONDITIONAL. IT STILL APPEARS
MUCH OF ERN TX MIGHT REMAIN CAPPED TO DEEPER CONVECTION AS WARMER
850-700 MB TEMPERATURES ACCOMPANYING THE EML OVERSPREADS THE MOIST
AXIS.
...CA...
SCATTERED CONVECTION AND ISOLATED THUNDERSTORMS WILL REMAIN LIKELY
ACROSS PARTS OF CNTRL AND NRN CA IN ASSOCIATION WITH UPPER LOW WHERE
COLD TEMPERATURES ALOFT WILL CONTRIBUTE TO STEEP MID LEVEL LAPSE
RATES. SURFACE LOW OFFSHORE AND LOCAL TERRAIN EFFECTS WILL MAINTAIN
SELY LOW LEVEL FLOW IN THE SAN JOAQUIN AND SACRAMENTO VALLEY
AREA...WHICH WILL CONTRIBUTE TO VEERING LOW-LEVEL WIND PROFILES.
BEST CHANCE FOR SURFACE HEATING APPEARS TO BE OVER A PORTION OF THE
SAN JOAQUIN VALLEY. ISOLATED STORMS MAY BECOME CAPABLE OF PRODUCING
MAINLY SMALL TO MARGINALLY SEVERE HAIL IF SUFFICIENT INSTABILITY
DEVELOPS DURING THE DAY.
..DIAL.. 02/16/2009
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