Hail and Damaging Winds in Minnesota, August 3, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
630 PM CDT MON AUG 3 2009

.UPDATED FOR AVIATION DISCUSSION BELOW...

.DISCUSSION...
NOT TOO MANY CHANGES IN THE FORECAST PACKAGE AS CONCERNS WITH LOW
CHANCE RAINFALL REMAINS THE PRIMARILY PROBLEM. ALTHOUGH A COLD
FRONT WILL MOVE THROUGH THE REGION TONIGHT...WEAK SURFACE
CONVERGENCE AND THE LACK OF INSTABILITY WILL LEAD TO LOW
PERCENTAGE AS CURRENT FORECAST STATES. THE SHORT WAVE THAT WILL
ENHANCE SOME LIFT LATE TODAY...AND INTO TONIGHT WAS MOVING INTO
THE FAR WESTERN DAKOTAS...WHICH IS PROGGED TO MOVE INTO THE FAR
WESTERN CWA BY MID/LATE EVENING. HOWEVER...INSTABILITY WILL BE
LIMITED AND MAINLY DURING THE EVENING TIME FRAME...SO LATER
SHIFTS MAY NEED TO ADJUST TIMING AND OVERALL COVERAGE.

AS WITH PREVIOUS FORECAST DISCUSSIONS...THE OVERALL WEATHER
PATTERN WILL CHANGE BY THE END OF THE WEEK AS THE PERSISTENT RIDGE
ACROSS THE DESERT SW...SLOWLY BUILDS ACROSS THE CENTRAL PLAINS.
THIS WILL LEAD TO MORE WESTERLY FLOW BY MID/LATE WEEK...THEN
SOUTHWEST FLOW BY THE WEEKEND. THE MAIN FORECAST PROBLEMS/CONCERNS
WILL BE THE ONSET OF THIS RIDGE AND HOW WILL THE SURFACE FEATURES
BE REFLECTIVE IN RELATION TO TIMING OF THE WARM FRONTAL BOUNDARY
AND DIURNALLY DRIVEN CONVECTION. BEST CHANCES FOR WIDESPREAD
CONVECTION WILL BE FRIDAY/SATURDAY AS THE LEADING EDGE OF THE
CAPPING INVERSION SPREADS NORTHEAST ACROSS THE FORECAST AREA.
AFTER THE FLOW BECOMES MORE SOUTHWESTERLY (AS CURRENTLY PROGGED BY
MID/LONG RANGE MODELS) SURFACE FEATURES WILL LIKELY BEGIN TO STALL
SOMEWHERE ACROSS THE UPPER MIDWEST AS THE UPPER FLOW BECOMES
PARALLEL TO THE SURFACE FRONTAL BOUNDARY. LOTS OF UNCERTAINTIES
BECOME APPARENT AS THIS DEVELOPS AND HOW SETTLE SHORT WAVES
INTERACT WITH THE LARGE SCALE FLOW. ONE ITEM THAT SEEMS APPARENT
IS THAT THE INCREASING CAPPING INVERSION WILL LIKELY PLACE THE
HIGHEST CHANCES OF RAINFALL DURING THE EVENING/OVERNIGHT
PERIOD...AND LESS DURING THE HEAT OF THE DAY. TEMPERATURES WILL
ALSO PLAY HAVOC IN THE EXTENDED PERIOD AS IF MCSS DEVELOP ALONG THE
WEAKNESS OF THE CAP...AND SPREAD EAST/SOUTHEASTWARD WITH THE MEAN
85/25H FLOW. CURRENTLY I AM LEANING TOWARD SLIGHTLY WARMER THAN
NORMAL TEMPERATURES OR AT LEAST HIGHER THAN GUIDANCE VALUES AS
THICKNESS VALUES INCREASE SUBSTANTIALLY. IF ANY SUNSHINE DEVELOPS
IN THE WEEKEND/EARLY NEXT WEEK...TEMPERATURES WILL LIKELY SOAR
INTO THE 90S.

IN ANOTHER NOTE...BOTH THE ECMWF/GFS T-5 DAY MEAN HEIGHTS AT ALL
LEVELS INDICATED THAT NEXT WEEK LOOKS EVEN WARMER THAN THE
THIS WEEKEND AS THE RIDGE REMAINS IN TACK ACROSS THE MID SECTION
OF THE NATION. ..JLT..

&&

.AVIATION.../00Z TAF ISSUANCE/
LINE OF WEAK CONVECTION FIRED ALONG SFC FNTL BNDRY LATE THIS
AFTERNOON ACROSS NW MN.  MODELS TREND THIS SOUTH INTO CENTRAL FA
04Z-07Z PERIOD.  NAROW INSTABILITY AXIS ASSOCIATED WITH FEATURE.
EXPECT CONVECTION TO WANE TOWARD SUNSET...PERHAPS AFFECTING
KAXN/KSTC/KRWF TAF SITES.  WILL MENTION CB AT KSTC/KRWF WITH TEMPO
-TSRA AT KAXN EARLY EVENING.  BANDED AC TO DROP SOUTH BEHIND SYSTEM
AS WELL AS ANOTHER WAVE DROPS SOUTH OVER THE AREA.  THIS COULD
CONTINUE -SHRA THREAT...BUT DONT BELIEVE IT WILL BE WIDESPREAD
ENOUGH TO MENTION IN EASTERN TAF SITES.  OTHERWISE...SFC WINDS WILL
BECOME N-NW WITH FROPA AND THEN BECOME NW AGAIN DURING TUE MORNING
AS SFC HIGH DROPS SOUTHEAST ACROSS THE DAKOTAS AND WESTERN MN.  SOME
INDICATION OF MORE MID/HIGH LEVEL CLOUDS DROPPING INTO THE WESTERN
DURING THE AFTERNOON...ASSOCIATED WITH ANOTHER WEAK SHORT WAVE.

&&

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

JLT/DWE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1127 AM CDT MON AUG 3 2009

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
041630-
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-
1127 AM CDT MON AUG 3 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORM CHANCES WILL INCREASE FROM NORTH TO SOUTH FROM LATE
THIS AFTERNOON AND INTO TONIGHT ACROSS PORTIONS OF CENTRAL AND
SOUTHERN MINNESOTA...AND WEST CENTRAL WISCONSIN AS A COOL FRONT
AND UPPER LEVEL TROUGH MOVE ACROSS THE AREA. ANY STORMS THAT
DEVELOP ARE EXPECTED TO REMAIN BELOW SEVERE LEVELS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SCATTERED THUNDERSTORMS WILL BE POSSIBLE ACROSS WESTERN MINNESOTA
LATE WEDNESDAY...AND INTO THURSDAY...WITH ADDITIONAL THUNDERSTORMS
POSSIBLE ACROSS THE REGION OVER THE WEEKEND AND EARLY NEXT WEEK.
MOST OF THE CONVECTION WILL BE IN THE EVENING AND OVERNIGHT
PERIOD...WITH ONLY ISOLATED THUNDERSTORMS DURING THE DAYLIGHT
HOURS.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION WILL NOT BE NEEDED.

JLT