SWODY1
SPC AC 281619
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CDT THU AUG 28 2008
VALID 281630Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL PLNS/LWR MO VLY
TO UPR GRT LKS...
...THERE IS A SLGT RISK OF SVR TSTMS A LARGE PART OF SRN AND WRN
AZ...
...CENTRAL PLAINS/LWR MO VLY TO UPR GREAT LAKES...
STRONG TROUGH WILL BE TRACKING EWD ACROSS UPPER MS VALLEY/GREAT
LAKES THIS FORECAST PERIOD. ASSOCIATED COLD FRONT CURRENTLY FROM LS
SWWD TO SERN NEB AND SRN CO. BY LATER THIS AFTERNOON AT THE TIME OF
EXPECTED FAVORABLE INITIATION PERIOD FOR STRONG/SEVERE CONVECTION
THE FRONT WILL EXTEND FROM NRN LM SWWD TO VICINITY MKC AND OK
PANHANDLE.
LAPSE RATES COUPLED WITH DEWPOINTS INTO THE LOWER 70S...ALONG WITH
STRONG HEATING WILL DEVELOP A VERY UNSTABLE AIR MASS BY MID
AFTERNOON WITH MLCAPES AOA 2500 J/KG ERN KS/NRN MO INTO CENTRAL IL
IN ADVANCE OF THE FRONT. THIS AREA WILL BE ON THE SRN FRINGE OF THE
STRONG FLOW TO THE N WITH DEEP LAYER SHEAR AROUND 30KT. SCATTERED
SEVERE THUNDERSTORMS WILL FORM IN RESPONSE TO FRONTAL CONVERGENCE
AND REMOVAL OF INHIBITION AS SURFACE TEMPS RISE INTO THE 90S.
STORMS EXPECTED TO BE PRIMARILY MULTICELLULAR GIVEN THE LACK OF
STRONG SHEAR...HOWEVER WITH THE AVAILABLE INSTABILITY...ISOLATED
SUPERCELLS WILL BE POSSIBLE. LARGE HAIL AND DAMAGING WINDS WITH ONLY
AN ISOLATED TORNADO THREAT ARE EXPECTED. ANY TORNADO WILL BE BRIEF
AND LIKELY ASSOCIATED WITH ANY SUPERCELL THAT CAN SPIN UP.
CLOUD COVER AND LESS FAVORABLE LAPSE RATES WILL LIMIT THE SEVERE
THREAT WITH NWD EXTENT ALONG THE FRONT. WILL CONTINUE A LOW END
DAMAGING WIND CONCERN WITH THE FRONT ACROSS THE UPPER GREAT
LAKES...BUT WITH MLCAPES GENERALLY AOB 500 J/KG...SEVERE SHOULD BE
CERTAINLY LESS OF A CONCERN THAN FURTHER S...EVEN WITH THE STRONGER
WIND PROFILES.
...AZ/SERN CA...
VERY MOIST LOW LEVEL AIR CONTINUES TO FEED INTO SRN AZ WITH PW'S
REMAINING NEAR 2 INCHES ACROSS THE SWRN DESERTS. LAPSE RATES HAVE
INCREASED ACROSS NRN AND WRN AZ RAISING THE CONCERN FOR SEVERE
STORMS. IN ADDITION THE 30KT OF ENE MID LEVEL FLOW FROM THE RIM
ACROSS THE LOWER CO VALLEY SUPPORTS EFFICIENT PROPAGATION OF STORMS
FROM THE HIGHER TERRAIN IN CENTRAL AZ INTO THE DESERTS VALLEYS.
MODEL SOUNDINGS INDICATE DCAPES INCREASE TO ABOVE 1200 J/KG BY MID
AFTERNOON WHILE MLCAPES CLIMB ABOVE 2000 J/KG.
STRONG/SEVERE THUNDERSTORMS SHOULD DEVELOP QUICKLY OVER THE RIM AND
BRADSHAW MOUNTAINS BY EARLY AFTERNOON WHERE FULL HEATING IS NOW
OCCURRING. FORWARD PROPAGATING CONVECTION SHOULD THEN MOVE W/SWWD
INTO DESERT VALLEYS WITH POTENTIAL FOR DAMAGING WINDS AND HAIL ALONG
WITH HEAVY RAIN GIVEN THE HIGH PW'S. WITH 30-35KT OF DEEP LAYER
SHEAR...POTENTIAL FOR ONE OR MORE MCS'S DEVELOPING ACROSS DESERTS
ENHANCING THE THREAT OF DAMAGING WINDS AND HEAVY RAIN BY LATER THIS
AFTERNOON/EVENING
...NRN/ERN NC INTO SE VA...
REMNANT CIRCULATION WITH T.D. FAY HAS JUST ABOUT BECOME COMPLETELY
ABSORBED WITHIN LARGER SCALE TROUGH OVER THE ERN STATES...AND THE
ASSOCIATED WIND FIELD IS NOTABLY WEAKER THAN IN RECENT DAYS.
NEVERTHELESS...CURRENT SFC OBSERVATIONS SHOW A WEAK WARM FRONT
CONTINUING TO PROGRESS SLOWLY NE ACROSS ERN NC...WHILE BACK-DOOR
BOUNDARY FARTHER N IN VA REMAINS MORE OR LESS STNRY FROM E OF DAN
TOWARD NHK. HEATING OF VERY MOIST AREA S AND E OF THESE
BOUNDARIES...AND LINGERING SELY SFC FLOW...MAY POSE A RISK FOR VERY
ISOLD TORNADOES UNTIL LATE IN THE DAY...ESPECIALLY IN SE VA/FAR NE
NC.
..HALES/IMY.. 08/28/2008
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