SPC AC 231249
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0749 AM CDT TUE JUN 23 2009
VALID 231300Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL HI PLNS/MID MO
VLY TO THE UPR MS VLY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE FL
PENINSULA...
...SYNOPSIS...
UPR RDG WILL CONTINUE TO BUILD SLOWLY W FROM THE CNTRL/SRN PLNS INTO
THE SRN RCKYS THIS PERIOD AS ELONGATED UPR LOW PERSISTS OFF THE E
CST. SPLIT FLOW PATTERN IN THE WEST WILL BECOME BETTER DEFINED AS
THE WLYS INCREASE ACROSS THE PACIFIC NW/S CNTRL CANADA...NORTH OF
LOW NOW IN THE PROCESS OF CLOSING OFF THE CA CST. LEAD DISTURBANCE
IN THE WLY JET...NOW OVER ERN MT...SHOULD CONTINUE ENE INTO WRN
ONTARIO BY THIS EVE AS WEAKER UPSTREAM IMPULSE IN BC REACHES SRN SK.
AT THE SFC...COLD FRONT ASSOCIATED WITH MT IMPULSE WILL MOVE
GENERALLY SE ACROSS THE NRN HALF OF THE PLNS AND THE UPR MS VLY/UPR
GRT LKS THROUGH THE PERIOD. THE BOUNDARY WILL PROVIDE A FOCUS FOR
STORMS...ESPECIALLY THIS AFTN/TONIGHT.
...CNTRL HI PLNS/MID MO VLY TO UPR MS VLY...
LONG-LIVED MCS NOW OVER NE NEB/CNTRL AND SE SD SHOULD CONTINUE
GENERALLY ENE THROUGH LATE THIS MORNING. IT IS UNCERTAIN ATTM
WHETHER OR NOT SYSTEM WILL INDEED WEAKEN BY THAT TIME AS IT IS ABOUT
TO ENTER A REGION OF ENHANCED SFC-BASED INSTABILITY CENTERED OVER NE
NEB AND NRN IA...WHERE SFC HEATING WILL BE UNINHIBITED. IN
ADDITION...A MODEST SLY LLJ WILL CONTINUE ACROSS REGION...LIKELY
ASSOCIATED WITH ENTRANCE REGION OF PASSING NRN STREAM UPR VORT /REF
MCD 1284/.
AT ANY RATE...GIVEN THE DEGREE OF EXPECTED DIURNAL DESTABILIZATION
/SBCAPE AOA 3000 J PER KG/...HI PWS...AND PRESENCE OF WEAK TO
MODERATE WSWLY SHEAR ON NRN FRINGE OF UPR RDG..POTENTIAL WILL
EXIST FOR DMGG WIND/MARGINALLY SVR HAIL AS SYSTEM TURNS AND/OR
REDEVELOPS A BIT S OF E AND MOVES INTO NW IA.
FARTHER W AND N...AIRMASS ALSO WILL DESTABILIZE ALONG/AHEAD OF COLD
FRONT EXTENDING FROM NRN MN SW INTO WRN NEB/NE CO. UPLIFT ALONG
FRONT...AND ANY BOUNDARIES LEFT FROM OVERNIGHT MCS...SHOULD SUPPORT
SCTD STORM DEVELOPMENT BY MID TO LATE AFTN. THIS ACTIVITY MAY FOCUS
PRIMARILY OVER NRN/CNTRL MN...WHERE LARGE SCALE UVV WILL EXIST CLOSE
TO UPR JET...AND IN WRN NEB/ERN WY/NE CO...WHERE LOW LVL UPSLOPE
FLOW WILL FOSTER DEVELOPMENT.
WHILE NOT PARTICULARLY STRONG...VEERING FLOW WITH HEIGHT SHOULD BE
SUFFICIENT FOR ORGANIZED/ROTATING STORMS IN THE CNTRL HI PLNS.
THESE MAY YIELD LARGE HAIL...DMGG WINDS AND POSSIBLY A BRIEF TORNADO
OR TWO. STRONGER...DEEP UNIDIRECTIONAL WSW FLOW WILL BE PRESENT TO
FOSTER POSSIBLE SMALL BOWING STRUCTURES WITH WIND/HAIL IN MN.
THE STORMS IN THE CNTRL HI PLNS MAY LINGER INTO THE EVE AND MERGE
INTO A SMALL CLUSTER OR TWO OF STRONG/POSSIBLY SVR STORMS TONIGHT AS
LLJ STRENGTHENS OVER REGION. A BRANCH OF THE LOW LVL FLOW SHOULD
ALSO VEER EWD ACROSS IA. THIS MAY SUPPORT LONGEVITY OF ANY CLUSTER
LEFT OVER THAT STATE FROM EARLIER IN THE DAY. WEAKER SHEAR AND
DIURNAL STABILIZATION SHOULD...HOWEVER...YIELD A GRADUALLY
DIMINISHING SEVERE THREAT.
...FL PENINSULA...
TSTMS EXPECTED TO INCREASE IN COVERAGE AND STRENGTH OVER WRN AND SRN
PARTS OF THE FL PENINSULA AS SFC HEATING FURTHER DESTABILIZES AXIS
OF CONFLUENCE ORIENTED ROUGHLY PARALLEL TO THE PENINSULA. SATELLITE
LOOPS SUGGEST THAT MUCH OF FL WILL REMAIN IN REGION OF UVV/UPR
DIVERGENCE THROUGH AT LEAST MIDDAY. COUPLED WITH MODERATE DEEP
UNIDIRECTIONAL NLY FLOW...HI PWS...AND VERY WARM SFC TEMPERATURES IN
AREAS NOT AFFECTED BY EARLIER STORMS...SETUP MAY SUPPORT UPSCALE
DEVELOPMENT INTO ORGANIZED CLUSTERS. FORWARD-PROPAGATING
SEGMENTS/STORM MERGERS COULD YIELD DMGG WINDS AND POSSIBLY A BRIEF
TORNADO THROUGH LATE AFTN.
...AL/GA...
SCTD DIURNALLY-ENHANCED TSTMS LIKELY WILL EXTEND UPSTREAM FROM FL
ACTIVITY INTO PARTS OF GA AND AL...ALONG NRN EXTENSION OF SAME
CONFLUENCE AXIS AFFECTING FL. WHILE CONVERGENCE AND UVV ARE
EXPECTED TO BE WEAKER IN THIS REGION RELATIVE TO POINTS S...
MOIST/UNSTABLE ENVIRONMENT AND MODEST DEEP NLY FLOW ON WRN FRINGE OF
OFFSHORE LOW WILL MAINTAIN A LOW PROBABILISTIC THREAT FOR LOCALLY
STRONG/SVR STORMS/STORM CLUSTERS THROUGH EARLY EVE.
..CORFIDI/GRAMS.. 06/23/2009
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