SPC AC 080532
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 AM CDT WED JUL 08 2009
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN/CNTRL PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE SERN
STATES...
...NRN/CNTRL PLAINS...
SLOW MOVING UPR LOW OVER THE PAC NW WILL BEGIN TO EJECT NEWD
WEDNESDAY AS A HEALTHY MID-LVL JET STREAK TRANSLATES FROM NRN CA TO
THE NRN PLAINS BY WEDNESDAY NIGHT. A LEE LOW OVER NERN WY WILL
DEEPEN AS IT MOVES NEWD ACROSS NCNTRL SD AND INTO ERN ND DURING THE
LATE AFTN/NIGHT. A WRMFNT WILL LIFT NWD FROM THE CORN BELT TO A SRN
MN AND SRN ND LINE BY WEDNESDAY EVENING.
SELY LLVL FLOW WILL STRENGTHEN ON WEDNESDAY ACROSS THE REGION AS
PRESSURES FALL OVER THE NRN ROCKIES IN ADVANCE OF THE UPR SYSTEM.
THIS WILL ADVECT SFC DEW POINTS IN THE 50S WWD INTO ERN MT/NERN WY
AND LWR/MID 60S ACROSS NEB/SD AND MOST OF ND. THIS WILL CONTRIBUTE
TO SUBSTANTIAL DESTABILIZATION DURING PEAK HEATING WITH MLCAPES
RANGING FROM 1000 J/KG IN ERN PARTS OF MT/WY TO WELL OVER 2500 J/KG
ON THE PLAINS. MOST OF THE DAY WILL REMAIN CAPPED... ESPECIALLY
OVER THE PLAINS AS H7 TEMPERATURES INCREASE TO 11-12 DEG C OVER ERN
WY...SD AND NEB.
AS THE LARGE SCALE FORCING FOR ASCENT SPREADS NEWD...UPSLOPE FLOW IN
MT...WY AND THE BLACK HILLS REGION WILL DEEPEN AND HIGH-BASED
MOUNTAIN CONVECTION WILL DEVELOP BY MID-AFTN. AS THE ACTIVITY
PROGRESSES ONTO THE PLAINS...THEY WILL BECOME STRONGER AS THEY TAP
THE MOIST AND UNSTABLE BOUNDARY LAYER. VERTICAL SHEAR WILL BE MORE
THAN SUFFICIENT FOR INITIAL STORMS TO BE SUPERCELLS WITH VERY LARGE
HAIL AND ISOLD TORNADOES...ESPECIALLY OVER SWRN ND AND CNTRL/WRN SD.
ISOLD TSTMS...WILL ALSO BE POSSIBLE ALONG NRN EDGE OF THE STRONGER
CAP/INVOF WRMFNT SEWD FROM CNTRL SD INTO CNTRL IA. HERE...NWLY BULK
SHEAR IN EXCESS OF 45 KTS AND MAGNITUDE OF INSTABILITY WILL ALSO BE
FAVORABLE FOR ROTATING STORMS WITH LARGE HAIL...DMGG WIND GUSTS AND
ISOLD TORNADOES.
WEDNESDAY NIGHT...AS STRONGER FORCING ARRIVES...EVENING STORMS WILL
EVOLVE INTO A QLCS /EMBEDDED LEWPS...BOWS AND ROTATING STORMS/ OVER
THE WRN DKTS...WITH LOW PROBABILITIES OF PRE-FRONTAL SUPERCELLS
/PENDING CAPPING CONCERNS/. APPROACH OF 60-70 KT WSW MID-LVL
FLOW...RETURN OF MOIST BOUNDARY LAYER AND INCREASING/ SUSTAINED LLVL
CONVERGENCE WILL LIKELY KEEP THREATS FOR SFC-BASED STORMS ACROSS AT
LEAST SRN ND AND NRN/CNTRL SD WELL INTO THE NIGHT. ACTIVITY WILL
TURN ESE AND MOVE INTO NWRN IA/WRN MN BY 12Z THU. DMGG WINDS WILL
BECOME MORE OF A THREAT OVERNIGHT. PARTS OF THE REGION MAY NEED A
MDT RISK IN LATER OUTLOOKS...ONCE EFFECTS OF MORNING CONVECTION ON
MOISTURE RETURN/DESTABILIZATION ARE BETTER KNOWN.
...SERN STATES...
AMPLIFICATION OF THE ERN STATES UPR TROUGH WILL OCCUR WEDNESDAY AS A
MODEST IMPULSE DIGS SEWD FROM THE MID-SOUTH INTO THE SERN STATES.
THIS WILL INDUCE A SFC LOW OVER ERN AL/WRN GA WEDNESDAY
MORNING...MOVING NEWD ALONG A RESIDUAL BAROCLINIC ZONE TO THE SC CST
BY EVENING. THE FRONT WILL SETTLE SWD TOWARD THE NRN GULF CST IN
WAKE OF THE LOW. AIR MASS ALONG/S OF THE FRONT WILL REMAIN VERY
MOIST WITH PWATS IN EXCESS OF 2 INCHES. LLVL LAPSE RATES SHOULD
STEEPEN IN ADVANCE OF THE FRONT AND CONTRIBUTE TO MLCAPES OF
1500-2000 J/KG. MID-LVL FLOW ALONG BASE OF THE IMPULSE WILL LIKELY
BE STRONGER THAN RECENT DAYS ALONG WITH SLIGHTLY COOLER MID-LEVEL
TEMPERATURES. MOREOVER...DRIER MID-LVL AIR MASS WILL LIKELY SPREAD
ACROSS THE REGION. UPSHOT WILL BE FOR A FEW STRONG/SVR
TSTMS...LIKELY EVOLVING INTO SMALL SCALE BOWS...GIVING DMGG WIND
GUSTS AND PERHAPS HAIL. ACTIVITY SHOULD DIMINISH DURING THE
EVENING.
FARTHER S...ANOTHER BAND OF STORMS IS EXPECTED TO FORM INVOF OUTFLOW
BOUNDARIES FROM THE ERN GULF OF MEXICO EWD ACROSS NRN FL. FLOW THIS
FAR S WILL BE SOMEWHAT LESS THAN FARTHER N...SO ONLY ISOLD DMGG WIND
GUSTS ARE EXPECTED.
..RACY/HURLBUT.. 07/08/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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