Flash Flood and Hail in Minnesota, August 10 to 11, 2007

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1115 PM CDT FRI AUG 10 2007

.UPDATE...06Z AVIATION DISCUSSION BELOW

&&

.DISCUSSION...
A QUICK SPIN THROUGH THE LATEST MODEL GUIDANCE SHOWS A FAIRLY
SUBSTANTIAL CAP OVER THE SOUTHWESTERN HALF OF THE FORECAST
AREA...WHICH SHOULD PREVENT ANY SURFACE BASED CONVECTION /OR ANY
CONVECTION FOR THAT MATTER/ FROM DEVELOPING UNTIL STRONGER FORCING
ARRIVES LATER TONIGHT. CONVECTION ONGOING ACROSS THE DAKOTAS AND
NORTHWEST MINNESOTA IS MOVING AWAY FROM THE AREA AT PRESENT...SO
SHOULD NOT HAVE AN IMMEDIATE EFFECT ON THE FORECAST AREA. LATEST
RUC GUIDANCE SHOWS A 35 TO 40 KT LOW LEVEL JET DEVELOPING LATE
THIS EVENING AND OVERNIGHT...WHICH SHUD TRANSITION INTO WESTERN
MINNESOTA AROUND MIDNIGHT. WE TRIMMED POPS...ESPECIALLY IN THE
SOUTHERN PART OF THE AREA...PRIOR TO 06Z...BUT LEFT THE AFTER 06Z
POPS ALONE.

VERY MINOR TWEAKS WERE MADE TO OTHER FORECAST GRIDS...MAINLY TO
ACCOUNT FOR RECENT OBSERVATIONAL TRENDS.

&&

.AVIATION.../06Z TAF CYCLE/
PRESENT MODELS TREND DAKOTAS ACTIVITY NORTHEAST ACROSS MAINLY THE
AXN/STC TAF AREAS THROUGH 12Z SAT.  WILL MENTION VCNTY THUNDER AT
MSP FOR NOW...AS MOST OF COMPLEX LIFTS TO THE NORTH.  HARD TO
DECIPHER TREND OF MODELS AFTER THAT...WITH CONVECTIVE FEEDBACK
ISSUES...ALTHOUGH SURFACE FRONT APPEARS TO MOVE THROUGH ESATERN MN
AFTER 22Z OR SO.  WILL HOLD ONTO PROBS FOR SAT AFTERNOON IN MSP/RNH
AND THUNDER AT EAU LATE AFTERNOON /EARLY EVENING AS FORNT MOVES
THROUGH.

&&

.PREV DISCUSSION... /ISSUED 339 PM CDT FRI AUG 10 2007/

DISCUSSION...
MODEL TRENDS HAVE SLOWED A BIT..WHICH WILL DELAY CONVECTION
CHANCES THIS EVENING...BUT MORE IMPORTANTLY POSSIBLY INCREASING
SVR CHANCES OVER MAINLY EASTERN HALF OF CWA ON SATURDAY. FOR THIS
EVENING...BEST LOW LEVEL CONV WILL BE WEST OF MOST OF CWA...OVER
SOUTHERN AND EASTERN NORTH DAKOTA AND NORTHERN SOUTH DAKOTA. 850
MB THETA E ADVECTION INCREASE OVER EASTERN NORTH DAKOTA AND WEST
CENTRAL MN AFTER MID NIGHT AS LOW LEVEL JET CRANKS UP. SOME OF
THESE STORMS COULD PRODUCE SOME HAIL AND HEAVY RAIN. OVERNIGHT IN
CENTRAL MN. 850 MB MOISTURE TRANSPORT MAXIMIZES AFTER MIDNIGHT ON
BOTH NAM AND GFS. WILL PLACE THE HIGHEST POPS OVER CENTRAL
MN...WHICH WILL ALSO BE JUST NORTHEAST OF +12 C AT 700 MB. COULD BE
SOME ONGOING STORMS SATURDAY MORNING WHICH WILL ALSO MOVE INTO
PARTS OF WI. PROVIDED ENOUGH HEATING CAN RECOVER...SHOULD BECOME
QUITE UNSTABLE OVER CENTRAL AND EAST CENTRAL MN LATE SATURDAY
AFTERNOON AHEAD OF THE FRONT. STRONG THICKNESS DIFLUENCE SIGNATURE
ON GFS FROM EAST CENTRAL MN INTO WI. ALSO HINT OF WEAK CIRC ALONG
FRONT. PROBABLY MOST SIG THREAT OF SVR WE HAVE HAD FOR A WHILE.

SUNDAY LOOKS QUIET BUT WARM FRONT WILL BE PUSHING BACK INTO AREA
ON MONDAY. A LITTLE PROBLEMATIC ON THUNDERSTORM CHANCES AS WARM
MID LEVEL TEMPS WILL BE MOVING IN AGAIN. HAVE SMALL CHANCES SUNDAY
NIGHT OVER THE SOUTH AND THEN EAST CENTRAL MN AND WESTERN WI
MONDAY NIGHT. LONGER RANGE SHOWING INCREASING NORTHWEST FLOW BY
END OF WEEK...WITH TREND OF UPPER RIDGE SHIFTING WEST A BIT. UPPER
JET FAVORABLE WITH BOUNDARY JUST SOUTH OF AREA ON WEDNESDAY WITH
ONE MORE CHANCE OF STORMS FAR SOUTHERN MN BEFORE DRYING AND COOLING
MOVE IN.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

KAT/DWE/JPR

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
407 PM CDT FRI AUG 10 2007

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
111100-
DOUGLAS-TODD-MORRISON-MILLE LACS-KANABEC-STEVENS-POPE-STEARNS-
BENTON-SHERBURNE-ISANTI-CHISAGO-LAC QUI PARLE-SWIFT-CHIPPEWA-
KANDIYOHI-MEEKER-WRIGHT-HENNEPIN-ANOKA-RAMSEY-WASHINGTON-
YELLOW MEDICINE-RENVILLE-MCLEOD-SIBLEY-CARVER-SCOTT-DAKOTA-
REDWOOD-BROWN-NICOLLET-LE SUEUR-RICE-GOODHUE-WATONWAN-BLUE EARTH-
WASECA-STEELE-MARTIN-FARIBAULT-FREEBORN-POLK-BARRON-RUSK-
ST. CROIX-PIERCE-DUNN-PEPIN-EAU CLAIRE-
407 PM CDT FRI AUG 10 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND
SOUTH CENTRAL MINNESOTA...AND WEST CENTRAL WISCONSIN.

.DAY ONE...TONIGHT

THUNDERSTORM CHANCES WILL INCREASE LATER TONIGHT OVER MUCH OF
CENTRAL AND SOUTH CENTRAL MINNESOTA. THE SEVERE WEATHER THREAT IS
SOMEWHAT DIMINISHED AS THE MOST SIGNIFICANT STORMS WILL REMAIN
IN THE DAKOTAS. HOWEVER...THUNDERSTORMS WITH LARGE HAIL AND STRONG
WINDS WILL BE POSSIBLE OVER PARTS OF CENTRAL MINNESOTA AFTER
MIDNIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A RATHER ACTIVE PERIOD IS ANTICIPATED WITH SEVERE THUNDERSTORMS
POSSIBLE SATURDAY AFTERNOON AND EVENING TO THE EAST OF A LINE FROM
MORA THROUGH MANKATO. SEVERE THUNDERSTORM RISK ON SATURDAY WOULD
INCLUDE THE TWIN CITIES...OWATONNA AND RED WING ALONG WITH RICE LAKE...
CHIPPEWA FALLS...BALDWIN AND EAU CLAIRE WISCONSIN.

AN ACTIVE PERIOD OF THUNDERSTORMS CAN BE ANTICIPATED FOR MUCH OF
SOUTH CENTRAL AND CENTRAL MINNESOTA ALONG WITH PART OF WESTERN
WISCONSIN OVER THE PERIOD FROM MONDAY THROUGH THURSDAY. WITH THE
PASSAGE OF CLUSTERS OF THUNDERSTORMS OR MESOSCALE CONVECTIVE
SYSTEMS AS THEY ARE TERMED...TYPICAL SEVERE THUNDERSTORM RISK MOST
OFTEN IS FROM 60 TO 75 MPH STRAIGHT-LINE WIND DAMAGE ON THE
LEADING EDGE OF SQUALL LINES. THE LATE AFTERNOON AND EARLY EVENING
HOURS FREQUENTLY YIELD THE GREATEST FREQUENCY OF SURFACE WIND
DAMAGE REPORTS.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION WILL BE NEEDED FREQUENTLY OVER THE NEXT
5 TO 7 DAYS.

JPR