SPC AC 250511
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1211 AM CDT TUE JUL 25 2006
VALID 251200Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS IN NRN NEW ENGLAND...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE UPPER MIDWEST/WRN
GREAT LAKES...
...SYNOPSIS...
A COUPLE OF SHORTWAVE TROUGHS WILL DIG SEWD FROM THE NRN ROCKIES
INTO THE GREAT LAKES AREA...WHERE A WEAK LONGWAVE TROUGH IS
CURRENTLY SITUATED. THE FIRST SHORTWAVE TROUGH WILL WEAKEN AND MOVE
INTO NRN MN LATE TUESDAY AFTERNOON...WHILE A STRONGER TROUGH DIVES
SEWD TO NEAR LAKE SUPERIOR BY WED MORNING. IN ASSOCIATION WITH THESE
TROUGHS...A WEAK COLD FRONT WILL PUSH EWD INTO THE ERN DAKOTAS
DURING THE AFTERNOON...WHILE THE REMNANTS OF THE FRONT THAT MOVED
ACROSS MN/WI MONDAY...ARE FORECAST TO STRETCH ACROSS CENTRAL MN/WI
DURING THE AFTERNOON HOURS. OTHERWISE...AN UPPER TROUGH IN QUEBEC
WILL BRUSH NEW ENGLAND AND A MID/UPPER LEVEL TROUGH OVER THE NWRN
GULF OF MEXICO IS FORECAST TO LIFT SLOWLY NWD TOWARD THE TX COAST.
...NRN NEW ENGLAND...
STRONG FORCING ASSOCIATED WITH QUEBEC TROUGH SHOULD RESULT IN A BAND
OF THUNDERSTORMS TO MOVE EWD ACROSS THE REGION TODAY. DUE TO STRONG
WINDS ALOFT...DEEP LAYER SHEAR WILL BE SUFFICIENT FOR SEVERE STORMS.
THE NEGATIVE FOR SEVERE WEATHER WILL BE POOR LAPSE RATES...WEAK
INSTABILITY...MLCAPES LESS THAN 1000 J/KG AND THE POSSIBILITY OF
HEATING BEING RESTRICTED DUE TO CLOUDS. HOWEVER... IF SOME HEATING
OCCURS AND THE STORMS DEVELOP INTO BANDS/LINES... THEN THE
ENVIRONMENTAL WINDS WOULD BE SUPPORTIVE OF ISOLATED SEVERE WIND
GUSTS. THE STORMS SHOULD END BY EARLY EVENING AS THE MAIN LARGE
SCALE LIFTING MOVES NEWD OUT OF THE AREA.
...UPPER MIDWEST/WRN GREAT LAKES REGION...
THOUGH CONVECTIVE INITIATION IS SOMEWHAT UNCLEAR ACROSS THE
AREA...THINK STORMS WILL BE INITIATED TUESDAY AFTERNOON ALONG COLD
FRONT MOVING THROUGH THE ERN DAKOTAS. ALSO...A SEPARATE AREA OF
THUNDERSTORMS SHOULD FORM ACROSS SRN/CENTRAL MN/WI BY LATE AFTERNOON
AS LOW LEVEL JET STRENGTHENS AND IMPINGES UPON SURFACE BOUNDARY. AIR
MASS ACROSS THE TWO AREAS WILL BE MODERATELY UNSTABLE AND DEEP LAYER
SHEAR FROM 25-35 KT SHOULD SUPPORT CLUSTERS OF SEVERE MULTICELLS.
THE ERN DAKOTA STORMS SHOULD WEAKEN SHORTLY AFTER SUNSET AS THEY
MOVE EWD INTO A MORE STABLE BOUNDARY LAYER. THE STORMS OVER
SRN/CENTRAL MN/WI MAY REMAIN STRONG UNTIL MID EVENING AS LOW LEVEL
JET PROVIDES ADDITIONAL LIFT. HOWEVER... EXPECT THESE STORMS TO
WEAKEN THEREAFTER AS THE AIR MASS STABILIZES FROM OUTFLOWS AND A
DEEPENING STABLE BOUNDARY LAYER. THE STORMS MAY DEVELOP/SOUTHWARD
INTO NRN IA/IL AS THE LOW LEVEL JET VEERS...BUT EXPECT THIS ELEVATED
CONVECTION TO REMAIN MOSTLY NON-SEVERE.
...SOUTHWESTERN U.S....
MID/HIGH LEVEL MOISTURE CIRCULATING AROUND UPPER HIGH AND INCREASE
IN BOUNDARY LAYER MOISTURE FROM THE SOUTH SUGGESTS SCATTERED
THUNDERSTORMS SHOULD ONCE AGAIN DEVELOP ACROSS THE HIGHER TERRAIN OF
NRN/ERN AZ DURING THE AFTERNOON. ENELY MID LEVEL WINDS AT 10 TO 15
KT SHOULD CARRY THE STORMS INTO THE DESERT FLOORS WHERE
TEMPERATURES WILL BE ABOVE 100F...RESULTING IN VERY STEEP LOW LEVEL
LAPSE RATES. THIS SUGGESTS THE POSSIBILITY OF ISOLATED STRONG/SEVERE
WIND GUSTS...THOUGH THE SLOW MOTION OF STORMS PRECLUDES A SLIGHT
RISK ATTM.
...UPPER TX COAST...
AS MID/UPPER LEVEL LOW OVER THE NWRN GULF MOVES SLOWLY NWD AND
POSSIBLY INTENSIFIES...LOW AND DEEP LAYER SHEAR PROFILES ARE
FORECAST TO STRENGTHEN ACROSS THE REGION BY LATE TUESDAY NIGHT.
THOUGH THE AIR MASS WILL BE QUITE WARM AND MOIST...INSTABILITY WILL
BE LIMITED. HOWEVER...IF CELLULAR STORMS CAN DEVELOP...SHEAR WOULD
SUPPORT SUPERCELLS AND THE VERY SMALL POSSIBILITY OF A TORNADO
TOWARD THE END OF THE PERIOD.
..IMY.. 07/25/2006
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