SPC AC 190529
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 AM CDT SAT MAY 19 2007
VALID 191200Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM MT THROUGH NERN WY AND
EXTREME WRN SD...
...SYNOPSIS...
SHORTWAVE RIDGING WILL PREVAIL OVER THE MIDDLE OF THE COUNTRY WHILE
CUTOFF UPPER LOW CONTINUES SLOWLY EAST OFF THE ATLANTIC SEABOARD AND
AN UPPER TROUGH MOVES INTO THE PACIFIC NW AND NRN ROCKY MOUNTAIN
REGION. SHORTWAVE TROUGH NOW MOVING THROUGH SRN MANITOBA WILL CREST
UPPER RIDGE AND CONTINUE SEWD THROUGH THE GREAT LAKES REGION DURING
THE DAY. COLD FRONT WILL CONTINUE TO SETTLE SWD INTO THE GREAT LAKES
WWD THROUGH SD AND INTO MT.
...MT THROUGH NERN WY...
ELY BOUNDARY LAYER FLOW IN POST FRONTAL ZONE WILL CONTRIBUTE TO
UPPER 40S TO AROUND 50 DEWPOINTS ADVECTING WWD INTO THE HIGH PLAINS
OF MT BENEATH 8 C/KM 700-500 MB LAPSE RATES. STRONG SURFACE HEATING
WILL FURTHER DESTABILIZE THE ATMOSPHERE WITH MLCAPE FROM 1000 TO
1500 J/KG. WV IMAGERY CURRENTLY SHOWS A SHORTWAVE TROUGH MOVING
THROUGH BASE OF LARGER SCALE UPPER TROUGH AND APPROACHING THE NRN CA
COAST. THIS FEATURE WILL LIKELY CONTINUE NEWD INTO THE NRN ROCKY
MOUNTAIN REGION SATURDAY. HEIGHT FALLS AND INCREASING ASCENT ALONG
WITH HEATING AND DESTABILIZATION OVER THE HIGHER TERRAIN WILL
CONTRIBUTE TO THE DEVELOPMENT OF STORMS ACROSS PARTS OF WRN MT
THROUGH NRN WY DURING THE AFTERNOON. ACTIVITY WILL SUBSEQUENTLY
SPREAD EWD DURING THE EVENING. DEEP SHEAR WILL LIKELY INCREASE AS
UPPER TROUGH APPROACHES WITH ESELY LOW LEVEL FLOW VEERING TO SWLY
AND INCREASING ABOVE 700 MB. SUPERCELLS WILL LIKELY BE THE INITIAL
STORM MODE. LARGE HAIL WILL BE THE PRIMARY THREAT WITH THIS
ACTIVITY. AN ISOLATED TORNADO OR TWO MAY ALSO BE POSSIBLE.
HOWEVER...ACTIVITY WILL LIKELY BE SOMEWHAT HIGH BASED GIVEN THE
MODEST LOW LEVEL MOISTURE. STORMS MAY EVENTUALLY EVOLVE INTO AN MCS
OR TWO AS THEY SPREAD EWD THROUGH THE HIGH PLAINS OF MT WITH AN
INCREASING THREAT FOR DAMAGING WIND INTO THE EVENING.
...UPPER MS VALLEY INTO THE WRN GREAT LAKES...
AXIS OF BOUNDARY LAYER DEWPOINTS IN THE LOWER 50S MAY PERSIST IN
PRE-FRONTAL WARM SECTOR OVER PARTS OF THE UPPER MS VALLEY. THIS
ALONG WITH SURFACE HEATING AND STEEP LAPSE RATES WILL CONTRIBUTE TO
AN AXIS OF MLCAPE NEAR 1500 J/KG FROM SD INTO SRN MN AND WI.
SHORTWAVE TROUGH EXPECTED TO MOVE SEWD INTO THE GREAT LAKES WILL
RESULT IN SLIGHT SUPPRESSION OF UPPER RIDGE IN THIS REGION. STORMS
MAY DEVELOP ALONG FRONT AS THE CAP WEAKENS AND THE BOUNDARY LAYER
DESTABILIZES DURING THE AFTERNOON...ESPECIALLY FROM PARTS OF ERN SD
INTO SRN MN AND WI. STORMS WILL SUBSEQUENTLY SPREAD SEWD. MODEST
MID-UPPER LEVEL FLOW WITH DEEP SHEAR AOB 30 KT WILL SUPPORT MAINLY
MULTICELLS. ISOLATED HAIL AND DAMAGING WIND WILL BE POSSIBLE WITH
THE STRONGER STORMS THROUGH MID EVENING.
..DIAL/TAYLOR.. 05/19/2007
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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