SWODY2
SPC AC 311742
DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1142 AM CST SAT JAN 31 2009
VALID 011200Z - 021200Z
...NO SVR TSTM AREAS FORECAST...
CORRECTED GENERAL TSTM LINE FOR NDFD GRAPHIC
...SYNOPSIS...
NRN STREAM OF SPLIT FLOW REGIME ACROSS NORTH AMERICA IS EXPECTED TO
UNDERGO AMPLIFICATION ON SUNDAY WITH A LONG WAVE TROUGH DEVELOPING
EAST OF THE ROCKIES...AS AN UPSTREAM RIDGE BUILDS EWD ACROSS MUCH OF
WRN NORTH AMERICA. MEANWHILE...SRN STREAM EXTENDING EWD ACROSS NRN
MEXICO THROUGH THE GULF OF MEXICO TO THE ATLANTIC IS FORECAST TO
STRENGTHEN ON DAY 2 AS LONG WAVE TROUGH AMPLIFIES EAST OF THE
ROCKIES. A SPEED MAX/ATTENDANT SHORT WAVE TROUGH...CURRENTLY
LOCATED OFF THE SRN CA COAST PER WATER VAPOR IMAGERY...WILL TRACK E
WITHIN SRN STREAM AND SHOULD REACH THE NWRN GULF/ADJACENT COASTAL
AREAS BY SUNDAY AFTERNOON.
IN THE LOW LEVELS...SURFACE LOWS WILL BE LOCATED OVER NW TX AND NERN
OK AT 12Z SUNDAY...ALONG THE SRN EXTENT OF A COLD FRONT WHICH IS
FORECAST TO EXTEND SWWD FROM A STRONGER SURFACE LOW CENTERED OVER
THE UPPER GREAT LAKES. THIS BOUNDARY WILL PROGRESS EWD DURING DAY 2
AND EXTEND WSWWD THROUGH THE TN VALLEY TO SERN OK AND CENTRAL TX
SUNDAY AFTERNOON...WITH THIS EXTENT OF THE FRONT REACHING THE LOWER
MS VALLEY AND SE TX/NWRN GULF BY 12Z MONDAY. THE OK LOW WILL TRACK
EWD INTO THE TN VALLEY...WHILE THE NW TX LOW SHOULD REDEVELOP SEWD
TOWARD THE UPPER TX COAST DURING THE PERIOD. GREATEST CONCENTRATION
OF TSTMS ON DAY 2 SHOULD BE LOCATED ACROSS THE NWRN GULF...WITH A
POTENTIAL FOR ACTIVITY INLAND OVER E TX TO THE LOWER MS VALLEY.
...TX/LA...
A SURFACE BOUNDARY IS EXPECTED TO RETREAT NWD ACROSS THE NWRN GULF
SUNDAY...WITH MODELS SUGGESTING THE WRN EXTENT SHOULD MOVE INLAND
ALONG THE MIDDLE/UPPER TX COAST AND INTO SE TX...WHILE THE REMAINDER
OF THE BOUNDARY STAYS S OF THE LA COAST. WLY FLOW ALOFT WILL
CONTINUE TO SUPPORT SLY LOW LEVEL WINDS AND A RETURN OF MODIFIED
MOISTURE FROM THE WRN GULF INTO THE ADJACENT PARTS OF TX/LA.
SURFACE DEWPOINTS IN THE MID-UPPER 50S ARE FORECAST TO SPREAD INLAND
BY SUNDAY AFTERNOON ACROSS THE MIDDLE/UPPER TX COAST TO SE TX/SWRN
LA...WHILE LOWER 60S DEWPOINTS WILL REACH THE SRN/MIDDLE TX COAST.
TSTMS ARE EXPECTED TO DEVELOP EARLY IN THE FORECAST PERIOD...
INITIALLY OVER THE NWRN GULF...AND THEN INLAND ALONG THE MIDDLE/
UPPER TX COAST TO SRN LA WITHIN LOW LEVEL WAA REGIME AS THE AIR MASS
UNDERGOES DESTABILIZATION. ALTHOUGH SURFACE HEATING WILL LIKELY BE
GREATER ALONG THE ADVANCING COLD FRONT...TSTMS SHOULD NOT DEVELOP
UNTIL LATE SUNDAY AFTERNOON/EARLY EVENING FROM CENTRAL/E TX TO
LA/NRN MS AS THIS BOUNDARY ENCOUNTERS NRN EXTENT OF MOISTURE RETURN.
DESPITE STEEP LAPSE RATES ACROSS THIS REGION ON SUNDAY...MODEST
MOISTURE RETURN SUGGESTS INSTABILITY /MUCAPE 500 J/KG/ SHOULD BE
GREATEST ALONG THE MIDDLE TX COAST WHERE MOISTURE WILL BE GREATER
WITH WEAKER INSTABILITY INLAND. STRONGER MID LEVEL FLOW EXPECTED TO
BE LOCATED ACROSS DEEP S TX TO THE GULF WILL ONLY RESULT IN WEAKER
EFFECTIVE BULK SHEAR /25-30 KT/ OVER SE TX. THE FORECAST
THERMODYNAMICS SUGGEST A POTENTIAL FOR MAINLY MULTICELLS WITH SOME
ORGANIZED SEVERE THREAT...BUT GENERALLY WEAK INSTABILITY/DEEP LAYER
SHEAR SHOULD PRECLUDE A CATEGORICAL SEVERE RISK AND THE NEED FOR
HIGHER SEVERE PROBABILITIES.
..PETERS.. 01/31/2009
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