DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 AM CDT FRI JUN 19 2009
VALID 191300Z - 201200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM THE MID MS VLY THROUGH THE
OH VLY TO THE CNTRL APPALACHIANS...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
AREA...FROM THE CNTRL PLNS TO THE MID ATLANTIC CST...
...SYNOPSIS...
UPR RIDGE WILL REMAIN ANCHORED OVER THE GULF CST STATES AS A BROAD
TROUGH CONTINUES ACROSS THE WEST. SMALLER SCALE FEATURES WITHIN THE
WRN TROUGH WILL BE THE MAIN FACTORS GOVERNING CONVECTIVE DEVELOPMENT
THIS PERIOD.
LEAD IMPULSE NOW IN CO APPEARS TO BE AMPLIFYING ATTM IN WATER VAPOR
IMAGERY. THIS DISTURBANCE SHOULD CONTINUE ENE INTO WRN IA BY THIS
EVE...BEFORE TURNING MORE EWD AND FURTHER AMPLIFYING OVER THE UPR OH
VLY EARLY SATURDAY. FARTHER NW...ANOTHER TROUGH...NOW APPROACHING
THE PACIFIC NW...SHOULD MOVE SE INTO CNTRL CA BY 12Z SAT AS NW
MEXICO UPR LOW EDGES NE TOWARD THE AZ-NM BORDER.
AT LWR LEVELS...WEAK COLD FRONT NOW EXTENDING FROM MN TO THE CNTRL
PLNS SHOULD CONTINUE STEADILY E/SE ACROSS THE UPR GRT LKS AND MUCH
OF THE OH VLY BY THE END OF THE PERIOD...WHILE SRN PART STALLS
OVER SRN KS/NW OK. NW-SE WARM FRONT NOW IN THE LWR/MID OH VLY
SHOULD MOVE/REDEVELOP ADVANCE IRREGULARLY EWD...WITH ADVANCE STYMIED
AT TIMES BY OUTFLOW FROM ASSOCIATED CONVECTION.
...MID MS VLY/OH VLY TO CNTRL APPALACHIANS/MID ATLANTIC CST...
MODERATE WSWLY LLJ WILL MAINTAIN/ADVECT RICH LOW LVL MOISTURE ACROSS
THE MID MS AND LWR/MID OH VLYS TODAY ON NRN FRINGE OF GULF UPR
RIDGE. COUPLED WITH SFC HEATING AND EWD MOVEMENT OF RESIDUAL EML...
EXPECT STRONG SFC-BASED INSTABILITY TO DEVELOP...WITH SBCAPE LIKELY
TO BE AOA 3000 J/KG FROM NRN MO/SRN IA EWD INTO OH AND WRN PA/WV BY
AFTN.
TSTMS NOW OVER IND/OH ESSENTIALLY MARK SFC-850 MB WARM FRONT AND
SHOULD CONTINUE GENERALLY ESE THROUGH AT LEAST MIDDAY. SOME
INTENSIFICATION MAY OCCUR WITH THIS ACTIVITY...PARTICULARLY ON THE
WRN AND SRN FRINGES...WHERE CONVERGENCE/INSTABILITY SHOULD BE
GREATEST. THE COLD POOL WITH THESE STORMS MAY TEMPORARILY RETARD
EWD ADVANCE OF SFC WARM FRONT.
FARTHER W...LOOSELY-ORGANIZED STORM CLUSTER OVER IA ALSO MAY
INCREASE WITH SFC HEATING LATER THIS MORNING. WIND FIELD AND
THERMODYNAMIC SETUP APPEARS FAVORABLE FOR N-S ORIENTED BOWING
SEGMENTS WITH HIGH WIND. DOWNSTREAM DEVELOPMENT OF STORMS LIKELY
WILL BE COMPLICATED/AFFECTED BY OUTFLOW BOUNDARY IN NRN
IL/IND...LEFT BY OVERNIGHT MCS NOW IN OH. A NON-ZERO THREAT FOR
TORNADOES COULD EVOLVE LATE THIS MORNING/EARLY THE AFTN IF
SEMI-DISCRETE STORMS ARE ABLE TO FAVORABLY INTERACT WITH RECOVERING
BOUNDARY LAYER AIR IMMEDIATELY N/E OF STALLING GUST FRONT.
OTHER STORMS/STORM CLUSTERS LIKELY WILL FORM THIS AFTN AND EVE
FARTHER W ACROSS PARTS OF IA/MO...IN AREA OF INCREASING UVV AHEAD OF
APPROACHING CO/NEB SHORTWAVE TROUGH. REGION WILL BE IN BELT OF
ENHANCED /40-50 KT/ MID LVL WSW FLOW WITH THE TROUGH...YIELDING
AMPLE DEEP SHEAR FOR SUPERCELLS AND BOWS. THESE STORMS LIKELY WILL
EVOLVE INTO ONE OR TWO SVR FORWARD-PROPAGATING MCSS. THESE BOWING
SYSTEMS WILL POSE A THREAT FOR WIDESPREAD DAMAGING WIND AS THEY MOVE
RAPIDLY EWD. LARGE HAIL COULD ALSO ACCOMPANY THE STORMS....AS WELL
AS A FEW SUPERCELL TORNADOES. ISOLD TORNADOES MAY ALSO OCCUR INVOF
WARM FRONTAL SEGMENTS OVER THE MID/UPR OH VLY/CNTRL APPALACHIANS.
OVERALL...HOWEVER...TORNADO THREAT SHOULD BE SOMEWHAT LIMITED
RELATIVE TO STRAIGHT-LINE WINDS BY VEERED LOW LVL FLOW AND
RELATIVELY SMALL LOW LVL HODOGRAPHS.
STORMS/STORM CLUSTERS LIKELY WILL PERSIST INTO EARLY SAT FROM IND/OH
EWD ACROSS THE CNTRL APPALACHIANS TO THE MID ATLANTIC CST GIVEN
CONTINUED AMPLIFICATION OF UPR TROUGH AND ASSOCIATED EWD
DESTABILIZATION DESPITE TIME OF DAY.
...MN/CNTRL-NRN WI/NRN MI...
CLOUDS WILL LIMIT LOW LVL DESTABILIZATION HEATING FOR AT LEAST PART
OF THE DAY OVER THE UPR MS VLY/UPR GRT LKS...AND REGION WILL LIE N
OF STRONGEST MID/UPR LVL FLOW. BUT SUFFICIENT FORCING FOR ASCENT
LIKELY WILL DEVELOP TO SUPPORT A SEPARATE AREA OF STORMS LATER TODAY
IN FAR ERN MN OR...MORE LIKELY...CNTRL/NRN WI INTO NRN MI. THIS
ACTIVITY COULD YIELD SVR HAIL/LOCALLY DMGG WIND THROUGH TONIGHT.
...GRT BASIN...
A COLD FRONT ASSOCIATED WITH PACIFIC NW SHORTWAVE TROUGH WILL BE THE
FOCUS FOR SCTD HI-BASED DIURNALLY-ENHANCED STORMS. OTHER STORMS MAY
FORM AHEAD OF FRONT BY EVE IN ZONE OF INCREASING UVV. INVERTED-V
THERMODYNAMIC ENVIRONMENT WILL PROMOTE A THREAT OF ISOLD DMGG WIND
AND MARGINALLY SVR HAIL WITH STRONGER STORMS.
..CORFIDI/GRAMS.. 06/19/2009
