SPC AC 200601
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0101 AM CDT SUN JUL 20 2008
VALID 201200Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NORTH CENTRAL
PLAINS/UPPER MIDWEST TO THE NORTHEAST STATES/NEW ENGLAND...

...NORTH CENTRAL PLAINS TO THE OHIO VALLEY/WESTERN GREAT LAKES...
OVERNIGHT STRONG/SEVERE MCS ACROSS THE MIDWEST WILL LIKELY SERVE TO
REDEFINE/SHIFT THE EFFECTIVE WEST-EAST SURFACE FRONT SOUTHWARD
ACROSS THE MIDWEST FOR THE UPCOMING DAY 1 PERIOD. REMNANTS OF THIS
MCS /INCLUDING A POTENTIAL MCV/ MAY SPARK RENEWED/PERIPHERAL
INTENSIFICATION ACROSS PORTIONS OF THE OHIO VALLEY/WESTERN GREAT
LAKES BY AFTERNOON...INCLUDING DOWNSTATE PORTIONS OF IL/INDIANA INTO
OH/PA...WHERE AMPLE HEATING AND A RESIDUAL MOIST AIRMASS /UPPER 60S
TO LOWER 70S F DEWPOINTS/ WILL LEAD TO CORRIDORS OF MODERATE TO
STRONG INSTABILITY. A BELT OF 30-40 KT MID LEVEL WESTERLY FLOW WILL
CONTRIBUTE TO WELL-ORGANIZED STORMS...WITH POTENTIAL FOR MULTIPLE
SEVERE TSTM CLUSTERS/BOWING SEGMENTS WITH A RISK OF DAMAGING WINDS
AND SOME HAIL.
FARTHER WEST...WESTERN SEGMENT OF THE FRONT WILL LIKELY REMAIN
QUASI-STATIONARY FROM CENTRAL NEB TO NEAR THE IA/MO BORDER...WHERE
IT WILL BE EFFECTIVELY DEFINED BY THE OVERNIGHT MCS/REMNANT OUTFLOW
WITH EAST EXTENT. A STOUT ELEVATED MIXED LAYER/CAPPING SHOULD LIMIT
TSTM DEVELOPMENT FOR MUCH OF THE AFTERNOON ACROSS NEB/SOUTHERN SD
INTO IA. HOWEVER...PHASING MID LEVEL TROUGH OVER THE UPPER MIDWEST
AND BOUNDARY LAYER CONVERGENCE/STRONG HEATING SHOULD FOSTER ISOLATED
TO SCATTERED TSTM DEVELOPMENT BY LATE AFTERNOON/EARLY EVENING. AS A
SOUTHERLY LOW LEVEL JET INCREASES/VEERS DURING THE EVENING...AND
IMPINGES ON THE LOW TO MID LEVEL FRONTAL ZONE...TSTMS MAY FURTHER
INCREASE/GROW UPSCALE INTO A SEVERE QUASI-LINEAR MCS WITH A
CONTINUED RISK FOR DAMAGING WINDS/SEVERE HAIL WELL THROUGH THE
EVENING.

...NORTHEAST STATES INTO SOUTHERN NEW ENGLAND...
GRADUAL HEIGHT FALLS AND ONE OR MORE SUBTLE IMPULSES ALONG THE
CANADIAN BORDER...ALONG WITH A RESIDUAL MOIST/UNSTABLE BOUNDARY
LAYER SOUTH OF A WEST-EAST SURFACE FRONT...SHOULD LEAD TO AN UPSWING
IN TSTM COVERAGE/INTENSITY DURING THE AFTERNOON ACROSS MUCH OF THE
NORTHEAST STATES. BENEATH MODERATELY STRONG WESTERLY FLOW /40+ KT AT
500 MB/...POTENTIAL WILL EXIST FOR SEVERE MULTICELLS/SOME SUPERCELLS
WITH PRIMARY RISKS OF DAMAGING WINDS AND SEVERE HAIL. SUBSEQUENT
OUTLOOKS MAY BE ABLE TO DELINEATE POTENTIAL FOR SOMEWHAT HIGHER
SEVERE PROBABILITIES.

...MN/WI...
NORTH OF THE PRIMARY SURFACE FRONT ACROSS THE CORN BELT...MID LEVEL
LOW WILL OPEN/MIGRATE EAST-SOUTHEASTWARD ALONG THE INTERNATIONAL
BORDER TODAY. IN SPITE OF LIMITED BOUNDARY LAYER CONVERGENCE...COOL
TEMPERATURES ALOFT /-12 TO -14 C AT 500 MB/ AND WEAK TO MODERATE
INSTABILITY WILL SUPPORT A RISK OF SEVERE HAIL/WIND AMIDST A
STRONGLY SHEARED ENVIRONMENT.

...COASTAL NC...
PER LATEST NHC GUIDANCE...TROPICAL STORM CRISTOBAL IS EXPECTED TO
REMAIN OFF THE NC COAST. STRONGEST WIND FIELDS SHOULD REMAIN
OFFSHORE ACCORDINGLY...KEEPING ANY MINI-SUPERCELL/TORNADO RISK OFF
THE COAST.
..GUYER/JEWELL.. 07/20/2008