SWODY2
SPC AC 121730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT SAT SEP 12 2009
VALID 131200Z - 141200Z
...NO SVR TSTM AREAS FORECAST...
...NRN HIGH PLAINS...
A COMPACT CLOSED UPPER LOW MIGRATING WWD INTO WY TODAY IS EXPECTED
TO DEEPEN SOME LATE TONIGHT WITH THE LOW CENTERED ALONG THE NRN WY/
MT BORDER BY 12Z SUNDAY. THIS SYSTEM WILL BECOME ENTRAINED WITHIN
WRN PERIPHERY OF NRN AMERICAN UPPER RIDGE AS AN UPPER TROUGH MOVES
INTO THE WEST COAST...WITH CLOSED LOW TRACKING NWD ACROSS ERN MT.
MODELS ARE CONSISTENT INDICATING A VORT LOBE ATTENDANT TO COMPACT
UPPER LOW WILL TRANSLATE NWD THROUGH THE NRN HIGH PLAINS SUNDAY...
REACHING SRN SASKATCHEWAN BY 12Z MONDAY. STRONGEST MID LEVEL WINDS
/40-50 KT/ ARE EXPECTED TO BE LOCATED OVER ERN PERIPHERY OF UPPER
LOW. A SURFACE LOW WILL DEVELOP OVER WY AND MOVE INTO ERN MT SUNDAY
EVENING. SSELY LOW LEVEL WINDS DEVELOPING INTO THE NRN HIGH PLAINS
BY 12Z SUNDAY WILL ADVECT LOW LEVEL MOISTURE INTO THIS REGION.
ALTHOUGH STEEP LAPSE RATES WILL SPREAD NWD ACROSS NRN HIGH PLAINS
ALONG TRACK OF COMPACT UPPER LOW...MODELS DIFFER WITH DEGREE OF LOW
LEVEL MOISTURE RETURN WHICH RESULTS IN AN UNCERTAINTY IN AMOUNT OF
AIR MASS DESTABILIZATION. TSTMS ARE EXPECTED TO DEVELOP SUNDAY
AFTERNOON OVER THE HIGHER TERRAIN AND THEN NWD INTO ERN MT BY SUNDAY
EVENING AS LOW LEVEL WAA INCREASES BENEATH FORCING FOR ASCENT
SPREADING NWD WITH VORT LOBE. EFFECTIVE BULK SHEAR WILL BE MORE
THAN SUFFICIENT FOR ORGANIZED STORMS/SUPERCELLS...BUT THE POTENTIAL
FOR LIMITED DESTABILIZATION /MLCAPE AOB 1000 J/G/...PRECLUDES THE
INTRODUCTION OF HIGHER SEVERE PROBABILITIES AT THIS TIME.
...SERN TX TO THE LOWER MS VALLEY/CENTRAL GULF COAST REGION...
WEAK CLOSED UPPER LOW LOCATED OVER TX DAY 1 PERIOD WILL MOVE SLOWLY
NWD ON SUNDAY...WITH ATTENDANT SURFACE LOW INITIALLY JUST OFFSHORE
SRN LA AT 12Z SUNDAY TRACKING NWD INTO LA. A WARM FRONT SHOULD
EXTEND EWD ALONG THE NRN GULF COAST...WITH THE WRN EXTENT OF THIS
BOUNDARY EXPECTED TO MOVE NWD THROUGH THE LOWER MS VALLEY.
EXTENSIVE CLOUD COVER/PRECIPITATION ALREADY LOCATED OVER THIS REGION
WILL PERSIST INTO DAY 2. THIS COMBINED WITH WEAK LAPSE RATES WILL
LIMIT AIR MASS DESTABILIZATION. ALTHOUGH EFFECTIVE BULK SHEAR WILL
BE SUPPORTIVE FOR MULTICELLS AND SOME SUPERCELLS...THE OVERALL WEAK
INSTABILITY WILL PRECLUDE THE INTRODUCTION OF HIGHER SEVERE
PROBABILITIES. LOCATIONS OVER SERN LA INTO SRN MS MAY HAVE SLIGHTLY
GREATER INSTABILITY SUPPORTING A FEW STRONGER TO ISOLATED SEVERE
STORMS.
..PETERS.. 09/12/2009
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