Hail and Heavy Rain in Minnesota, August 18 to 19, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1058 PM CDT TUE AUG 18 2009

.UPDATE...

ADDED AVIATION DISCUSSION FOR 06Z TAFS BELOW...

&&

.DISCUSSION...

THE FORECAST CHALLENGE FOR THIS CYCLE FOCUSES ON THUNDERSTORM
CHANCES LATE TONIGHT THROUGH WEDNESDAY.

A PLEASANT AFTERNOON WITH SURFACE RIDGING OVER THE FORECAST AREA
TODAY. THE GOES WV LOOP SHOWS A SHORT WAVE DISTURBANCE SHIFTING
EAST INTO MO WITH STREAM OF MID AND UPPER LEVEL MOISTURE FROM THIS
REMAINING SOUTHEAST OF THE AREA. MORE POTENT JET AND ASSOCIATED
TROUGH DIVING INTO THE UPPER CONUS ROCKIES WITH LEAD SHORT WAVE
MOVING INTO THE NEBRASKA PANHANDLE AND TOWARDS AREA LATE TONIGHT.
PROFILERS INDICATE RETURN FLOW HAS BEGUN IN THE LOWER TROP OVER
THE LOWER HIGH PLAINS. THIS AREA SHOULD BEGIN TO SEE AN INCREASE
IN MID-LEVEL CLOUDS BY EVENING WHICH WILL SPREAD INTO THE WRN
FORECAST AREA AND EVENTUALLY ACROSS MUCH OF THE REGION LATER
TONIGHT. WHILE MIXING HAS AIDED IN DRYING THE LOWER PORTION OF THE
ATMOSPHERIC COLUMN OVER THE REGION...ISENTROPIC ASCENT AND
MOISTURE ADVECTION AND CONVERGENCE IS STRONG ENOUGH TONIGHT THAT
SCATTERED SHOWERS/STORMS ARE EXPECTED TO DEVELOP NEAR OR INTO
MN...PRIMARILY OVERNIGHT. HAVE INCREASED POPS IN WRN AND CTRL MN
FOR THIS EXPECTED ACTIVITY. PARAMETERS INDICATE THUNDER HOWEVER
A LOW SEVERE POTENTIAL. SRLY WINDS SHOULD REMAIN FAIRLY CONSTANT
OVERNIGHT...ALLOWING TEMPERATURES TO LEVEL OUT. HAVE ADJUSTED THE
HOURLY TEMPS TO FIT THAT SCENARIO.

UPPER-LEVEL HEIGHT FALLS ASSOCIATED WITH THE DIGGING TROUGH
OVERSPREAD THE REGION WEDNESDAY. DEEPENING SFC LOW IS EXPECTED TO
EVOLVE EAST INTO WRN MN LATE IN THE DAY WITH A COLD FRONT
EXTENDING TO ITS SOUTH. AMPLE CLOUD COVER IS EXPECTED TO LIMIT
INSTABILITY IN ERN MN AND WRN WI. HOWEVER...THE CONTINUED WARM AIR
ADVECTION ALOFT REGIME MAY LEAD TO SCT SHOWERS AT TIMES THROUGH
THE DAY. WRN AND SWRN MN WILL HAVE A GREATER POSSIBILITY OF SEEING
INSTABILITY RETURN DURING THE AFTN. HAVE INCREASED THUNDER CHANCES
IN THAT AREA DURING THE LATER AFTN. FRONT SHOULD MOVE EAST THROUGH
WEDNESDAY NIGHT ALLOWING FOR CONTINUED LIKELY POPS. THE LOW LEVEL
JET NOSE WILL BE SHIFTING EAST AS WELL...FAVORING COVERAGE OVER
ERN MN AND WRN WI DURING THE EVE. LIMITED SFC DEW POINT RETURN
ALONG WITH THE AFOREMENTIONED CONCERNS ON CLOUD COVER IS EXPECTED
TO LIMIT SFC BASED INSTABILITY...HOWEVER DYNAMICS WILL
COUNTERBALANCE THAT SOMEWHAT AND KEEP THE POSSIBILITY FOR SCT
SEVERE STORMS DURING THE AFTN AND EVE.

THE SYSTEM UPPER LEVEL LOW CENTER WILL BE DIRECTLY OVER THE
FORECAST AREA THURSDAY AFTN. COOL MID-LEVEL TEMPS AND ASSOCIATED
LIFTED INDICES INDICATE SCT SHOWERS AND STORMS ARE LIKELY DURING
THE AFTN. TEMPS WILL BE MUCH COOLER WITH AFTN CLOUDS AND COOL AIR
ADVECTION. HIGHS MAY STRUGGLE TO REACH 70F IN SOME PLACES.

A VERY PLEASANT WEEKEND IS EXPECTED WITH A STRONG CANADIAN HIGH
OVER THE CTRL UNITED STATES. AS FOR THE LONG RANGE HAVE FAVORED A
00Z ECMWF AND 12Z GFS BLEND...WHICH OFFER THE NEXT SYSTEM TO
ARRIVE SOMETIME IN THE EARLY PART OF THE NEXT WORKWEEK.
OVERALL...THE TEMPERATURES LOOK TO BE NEAR OR SLIGHTLY BELOW
NORMAL FOR DAYS 7-10.

&&

.AVIATION.../06Z TAF ISSUANCE/
THE MAIN FORECAST CHALLENGE INITIALLY IS THE ONSET OF THE
PRECIPITATION.  WEATHER CONDS WILL DETERIORATE DURING THE PERIO AS
SFC LOW PRESSURE SYSTEM MOVES OVER MN LATE IN THE DAY WEDNESDAY.
AN UPPER LEVEL DISTURBANCE WILL CONTINUE TO DRIVE THE PRECIP
EASTWARD OVERNIGHT INTO WESTERN AND CENTRAL MN...THEN OVER EASTERN
MN AND WESTERN WISCONSIN ON WEDNESDAY. MARGINAL VFR FLYING CONDS
ANTICIPATE IN SHRA/AND ISOLD TSRA OVERNIGHT. CEILING WILL LOWER
BETWEEN 3000-5000 FEET AGL AND VISBILITY NEAR 4-5 MILES IN RAIN.
ANOTHER SHORTWAVE TROUGH WILL ROTATE OVER AREA LATE IN THE DAY WED.
WX CONDS LOWERING TO 1500-3000 FEET BY EARLY THURSDAY MORNING.

&&

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

MTF/JM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
720 PM CDT TUE AUG 18 2009

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
191200-
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-
720 PM CDT TUE AUG 18 2009

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

.DAY ONE...TONIGHT

THUNDERSTORMS ARE EXPECTED TO ENTER WEST CENTRAL MINNESOTA AFTER
MIDNIGHT...AND EXPAND EASTWARD TOWARD CENTRAL MINNESOTA OVERNIGHT.
THESE THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THUNDERSTORMS WILL BE POSSIBLE WEDNESDAY MORNING INTO THURSDAY AS
ANOTHER FRONTAL SYSTEM MOVES ACROSS THE REGION. AT THIS TIME...IT
APPEARS A FEW SEVERE THUNDERSTORMS WILL BE POSSIBLE WEDNESDAY
AFTERNOON IN SOUTH CENTRAL MINNESOTA AS A COLD FRONT SWEEPS INTO
MINNESOTA.

ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE ON MONDAY AS A LOW
PRESSURE SYSTEM APPROACHES THE AREA.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION WILL NOT BE NEEDED.