SWODY1
SPC AC 092000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT THU JUL 09 2009
VALID 092000Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE UPPER MIDWEST AND
LOWER/MIDDLE MO VALLEY...
...LOWER/MIDDLE MO VALLEY AND UPPER MIDWEST...
EARLY DAY SEVERE MCS HAS WEAKENED THROUGH EARLY AFTERNOON ACROSS
WESTERN IA/NORTHWEST MO...WITH MORE RECENT /INITIALLY ELEVATED/
DEVELOPMENT AT MID AFTERNOON ACROSS FAR NORTHEAST NEB/FAR SOUTHEAST
SD INTO NORTHWEST IA. SIMILAR TO THIS MORE CONTEMPORARY
DEVELOPMENT...THE MOST PROBABLE SCENARIO FOR SEVERE TSTM DEVELOPMENT
THE REMAINDER OF THE AFTERNOON INTO THIS EVENING APPEARS TO BE
CENTERED ACROSS EASTERN NEB/FAR WESTERN IA IN VICINITY OF
SOUTHWEST-NORTHEAST ORIENTED COLD FRONT AND AN EFFECTIVE WARM
FRONT/OUTFLOW INTERSECTION /WESTERN PERIPHERY OF THE EARLY DAY
MCS/...WITH ADDITIONAL SCATTERED DEVELOPMENT LIKELY ALONG THE COLD
FRONT IN MN. PERHAPS AIDED BY THE ARRIVAL OF ONE OR MORE WEAK MID
LEVEL IMPULSES LATER THIS AFTERNOON...ADDITIONAL
HEATING/DESTABILIZATION SHOULD LEAD TO AN UPSWING IN SEVERE TSTM
COVERAGE/VIGOR LATER THIS AFTERNOON AND EVENING. SEVERE TSTMS
INCLUDING SUPERCELLS ARE LIKELY TO DEVELOP AND SPREAD
EAST-SOUTHEASTWARD THROUGH THE EVENING...WITH POTENTIAL FOR LARGE
HAIL/DAMAGING WINDS AND PERHAPS A TORNADO OR TWO /MOST LIKELY IN
VICINITY IN MODIFYING OUTFLOW ACROSS EASTERN NEB AND FAR WESTERN
IA/. AIDED BY AN INCREASING LOW LEVEL JET THIS EVENING...STORMS
SHOULD CONSOLIDATE/GROW UPSCALE INTO ONE OR MORE MCS/S TONIGHT WITH
A CONTINUED DAMAGING WIND/HAIL THREAT ACROSS THE LOWER/MIDDLE MO
VALLEY. FOR ADDITIONAL INFORMATION ON THE SHORT TERM THREAT...PLEASE
SEE MESOSCALE DISCUSSION 1501.
...NORTHEAST CO/EASTERN WY...
WEAK MID LEVEL IMPULSE APPEARS TO BE CROSSING NORTHEAST CO AT
EARLY/MID AFTERNOON. IN THE WAKE OF THIS FEATURE...LIMITED FORCING
ON THE LARGE SCALE AND CAPPING ACROSS THE CENTRAL HIGH PLAINS SHOULD
TEND TO CURB THE COVERAGE OF ANY SEVERE TSTMS LATER THIS
AFTERNOON/EARLY EVENING. WHILE A FEW STORMS CAPABLE OF HAIL/WIND
WILL BE POSSIBLE...MAINLY ACROSS THE CO/WY FRONT RANGE...A
CATEGORICAL SLIGHT RISK DOES NOT APPEAR WARRANTED.
..GUYER.. 07/09/2009
.PREV DISCUSSION... /ISSUED 1152 AM CDT THU JUL 09 2009/
...CENTRAL/ERN NEB INTO NERN KS/NWRN MO...
SEWD MOVING MCS OVER WRN IA HAS SHOWN SIGNS OF WEAKENING DURING THE
LAST HOUR. IT IS LOCATED ON THE ERN EDGE OF CAPPING INVERSION
ASSOCIATED WITH THE PLUME OF STEEPER MID LEVEL LAPSE RATES EXTENDING
ACROSS THE CENTRAL PLAINS. AN OUTFLOW BOUNDARY HAS BEEN GENERATED
THAT EXTENDS FROM NEAR OMA TO ONL...BUT THE CAP HAS INHIBITED DEEP
CONVECTION FROM DEVELOPING UP TO NOW. CONTINUED HEATING AND
DESTABILIZATION AHEAD OF THE OUTFLOW BOUNDARY AND ACTIVE MCS IS
EXPECTED TO OCCUR INTO THE AFTERNOON...AND STRENGTHENING/DEVELOPMENT
OF NEW UPDRAFTS REMAIN POSSIBLE ALONG THE BOUNDARY AND LEADING EDGE
OF THE MCS.
THERE IS ALSO POTENTIAL FOR ADDITIONAL STORMS TO DEVELOP BY MID/LATE
AFTERNOON ALONG THE FRONT OVER CENTRAL NEB. CURRENT CLOUD COVER IS
INHIBITING DIABATIC HEATING AT THIS TIME...BUT IS EXPECTED TO
GRADUALLY DIMINISH THIS AFTERNOON. SURFACE DEW POINTS IN THE 65-70F
RANGE COUPLED WITH STEEP LAPSE RATES AND AFTERNOON HEATING WILL
RESULT IN MLCAPE OF 1500-2500 J/KG LATER TODAY. STRONG WESTERLY MID
LEVEL WINDS OF 35-40 KT AND VEERING WIND PROFILES WITH HEIGHT ARE
PROVIDING 35-45 KT DEEP LAYER SHEAR WHICH WILL ENHANCE STORM
ORGANIZATION AND INTENSITY. SEVERE STORMS INCLUDING A FEW
SUPERCELLS ARE EXPECTED TO DEVELOP AND SPREAD EWD/SEWD THROUGH THE
EVENING HOURS...WITH THREAT FOR LARGE HAIL...DAMAGING WINDS...AND A
FEW TORNADOES.
...UPPER MS VALLEY...
UPPER TROUGH IS MOVING ENEWD ACROSS SERN MANITOBA TOWARD NWRN
ONTARIO. THE SURFACE FRONT WILL MOVE EWD INTO NWRN MN AND FAR SERN
SD THIS AFTERNOON. LOW LEVEL MOISTURE WILL SLOWLY INCREASE INTO MN
AHEAD OF THE FRONT...BUT EXTENSIVE CLOUDS OVER MOST OF THE AREA WILL
INHIBIT HEATING. STRONGEST DESTABILIZATION IS EXPECTED OVER ERN SD
INTO SRN MN WHERE VISIBLE IMAGERY INDICATES CLEARING SKIES.
SCATTERED STORMS ARE EXPECTED TO DEVELOP ALONG/EAST OF THE FRONT
...AND STRONG DEEP LAYER SHEAR ASSOCIATED WITH JET STREAK MOVING
ACROSS THE AREA WILL AID DEVELOPMENT OF A FEW SEVERE STORMS.
...NERN CO/ERN WY...
UPSLOPE WINDS WILL DEVELOP THIS AFTERNOON WITH A SUBSEQUENT INCREASE
IN LOW LEVEL MOISTURE AND INSTABILITY. MODELS DEVELOP A STRONG CAP
ACROSS MUCH OF THE AREA SUGGESTING THAT CONVECTIVE DEVELOPMENT IS
LIKELY TO REMAIN ISOLATED IN COVERAGE. STRONG DIRECTIONAL SHEAR AND
MLCAPE OF 1000-1500 J/KG INDICATE A CONDITIONAL THREAT FOR A FEW
SEVERE STORMS WITH ANY SUSTAINED UPDRAFTS THAT CAN DEVELOP.
...GULF COAST INTO NRN CENTRAL FL...
STRONG STORMS ARE EXPECTED TO DEVELOP ACROSS THE AREA THIS AFTERNOON
WITHIN MODEST WESTERLY FLOW ALOFT. A FEW WET MICROBURSTS ARE
EXPECTED TO OCCUR.
...ERN OK/ERN TX...
ELEVATED CONVECTION HAS WEAKENED THIS MORNING...BUT POTENTIAL EXISTS
FOR REDEVELOPMENT OF STORMS THIS AFTERNOON. STEEP LAPSE RATES AND
ATTENDANT VERY UNSTABLE AIR MASS /MLCAPE OF 2000-3000 J PER KG/
COUPLED WITH 25-30 KT NLY FLOW ALOFT INDICATE POTENTIAL FOR ISOLATED
SEVERE STORMS TO DEVELOP.
...SERN AZ...
SUBTLE SHORT WAVE TROUGH IS INDICATED OVER NRN MEXICO AND IS
EXPECTED TO TURN NWWD TOWARD AZ. 12Z TUS SOUNDING EXHIBITS MODERATE
MID LEVEL LAPSE RATES AND AMPLE MOISTURE /PW OF 1.39 IN/ FOR
THUNDERSTORMS TO DEVELOP THIS AFTERNOON. AS HEATING OCCURS A DRY
ADIABATIC PBL WILL DEVELOP WITH INCREASED POTENTIAL FOR ISOLATED WET
MICROBURSTS TO OCCUR.
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