SWODY2
SPC AC 080555
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT WED APR 08 2009
VALID 091200Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN PARTS OF THE SRN PLNS
EWD INTO THE LWR OH/MS VLYS...
...SYNOPSIS...
UPR LOW OVER CA IS EXPECTED TO BRIEFLY BECOME AN OPEN WAVE AND
TRANSLATE ACROSS THE ROCKIES WEDNESDAY NIGHT. BY THURSDAY
AFTN...ACTIVE SRN STREAM WILL PHASE WITH SRN END OF THE TROUGH AND
CAUSE A SECONDARY CUT-OFF LOW TO EVOLVE OVER KS. THIS FEATURE WILL
TRAVEL INTO THE MID-MS VLY BY 12Z FRIDAY.
AT THE SFC...A LOW OVER NWRN OK EARLY THU WILL INTENSIFY AND TRAVEL
EWD ALONG A WRMFNT ALONG THE KS/OK BORDER DURING THE AFTN AND SRN MO
OVERNIGHT. A STRONG DRYLINE WILL MIX EWD TO THE S OF THE
LOW...REACHING THE I-35 CORRIDOR EARLY THU AFTN...AND INTO ERN
OK/ERN TX BY EVENING. A CDFNT WILL EVENTUALLY OVERTAKE THE DRYLINE
FROM NW-SE...REACHING A SCNTRL MO...CNTRL AR AND SCNTRL TX POSITION
BY DAYBREAK FRIDAY.
...SE KS/E OK/E TX EWD INTO THE MID-SOUTH/LWR OH VLY...
LLVL MOISTURE TRANSPORT WILL BEGIN IN EARNEST WEDNESDAY NIGHT AND
THURSDAY AHEAD OF THE APCHG UPR LOW. SFC DEW POINTS IN THE MID 50S
TO NEAR 60 WILL HAVE BEEN TRANSPORTED AS FAR N AS SRN MO/ERN OK/SERN
KS BY THURSDAY AFTN. STOUT EML STREAMING EWD FROM THE HIGHER SRN
PLNS WILL CAP SFC-BASED PARCELS THROUGH EARLY AFTN. BUT...AS
90-METER HEIGHT FALLS/ABRUPT COOLING ALOFT QUICKLY SPREAD EWD DURING
THE AFTN...THIS CAP WILL ERODE. DEEP DRYLINE CIRCULATION AND
WEAKENING CINH SHOULD BE VERY FAVORABLE FOR SFC-BASED TSTM
INITIATION FROM SERN KS INTO NERN OK BY MID- AFTN...WITH THE
ACTIVITY BACKBUILDING SWD INTO ERN TX.
INITIAL STORM MODE WILL LIKELY BE SUPERCELLULAR WITH THE STORMS
RAPIDLY MOVING ENE ACROSS SRN MO...WRN/CNTRL AR...ERN TX AND NWRN LA
DURING THE LATE AFTN/EARLY EVENING. MID-LVL LAPSE RATES NEAR 8 DEG
C PER KM AND BULK SHEAR IN EXCESS OF 45 KTS ACROSS THE DRYLINE WILL
FAVOR VERY LARGE HAIL. LCL/S WILL INITIALLY BE HIGH OWING TO THE
SOMEWHAT POOR QUALITY THETA-E. BUT...DURING THE EVENING... DEWPOINT
DEPRESSIONS SHOULD BECOME SMALLER AS TEMPERATURES FALL AND SURGE OF
LLVL MOISTURE OCCURS. STORM MODE MAY BECOME LINEAR AS LARGE SCALE
FORCING INCREASES DURING THE EVENING...BUT THREAT WILL EXIST FOR
MORE DISCRETE STORMS TO EXIST ALONG SRN EXTENT/STRONGER CINH.
TORNADIC THREAT WILL BE HIGHEST WITH THESE STORMS ACROSS PARTS OF AR
AND PERHAPS SRN MO DURING THE EVENING. OTHERWISE...DMGG WINDS/HAIL
WILL BE LIKELY AS THE STORMS MOVE EWD.
NRN EDGE OF ACTIVITY WILL BECOME INCREASINGLY ELEVATED ACROSS THE
MID-MS VLY AND N OF THE OH RVR OVERNIGHT THURSDAY. BUT...LARGE HAIL
COULD STILL OCCUR WITH THIS ACTIVITY. SFC-BASED STORMS COULD
MAINTAIN INTENSITY ALONG THE AXIS OF A VEERING LLJ INTO PARTS OF THE
MID-SOUTH.
MEANWHILE...SOME ENSEMBLE MEMBERS INDICATE THAT A POSSIBLE TSTM
CLUSTER...EITHER SEPARATE DEVELOPMENT OR UPSCALE EVOLUTION FROM
DAYTIME ACTIVITY...WILL OCCUR ALONG SRN FRINGES OF THE UPR TROUGH
ACROSS THE LWR MS VLY. THESE STORMS WILL BE EMBEDDED WITHIN 55+ KTS
OF MID-LVL FLOW AND STEEP LAPSE RATES. THUS...A FEW OF THESE STORMS
WILL PRODUCE LARGE HAIL AND DMGG WINDS. ALSO...AS LWR-MID 60S SFC
DEW POINTS MAKE A LATE NIGHT SURGE INTO THIS AREA... TORNADOES
CANNOT BE RULED OUT. BUT...COMPARATIVELY WEAKER LLVL FLOW THIS FAR
SOUTH MAY LESSEN THE TORNADO PROBABILITIES.
..RACY.. 04/08/2009
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