Severe Thunderstorm Warning 127, NWS Twin Cities, MN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
238 PM CDT FRI JUL 16 2010

.DISCUSSION...

THE FORECAST CONCERN IS THE SEVERE WEATHER POTENTIAL FOR SATURDAY
AND SATURDAY NIGHT. THE LATEST MODELS CONTINUE TO TREND TOWARD A
MAJOR SEVERE WEATHER OUTBREAK DEVELOPING ACROSS THE UPPER MIDWEST
WITH THE MAIN FOCUS OVER CENTRAL AND SOUTHERN MINNESOTA.  IN
ADDITION...QUASI-LINEAR BOW STRUCTURE STORMS LATE SATURDAY EVENING
AND OVERNIGHT...WHICH COULD LEAD TO MORE WIDESPREAD WIND DAMAGE AND
HEAVY RAIN OVER EAST CENTRAL MN AND WESTERN WISCONSIN SATURDAY
NIGHT.

A SFC LOW PRESSURE WITH A WARM FRONT IS PROGGED TO LIFT NORTHEAST
OVER WESTERN MINNESOTA DURING THE DAY ON SATURDAY. MODELS SHOWED A
STRONG UPPER LEVEL JET (80 KNOTS OR GREATER) 250 MB MOVING OVER THE
AREA AS WELL. THIS PLACES MUCH OF OUR FORECAST AREA IN THE FAVORABLE
RIGHT REAR QUADRANT OF THE JET MAXIMUM. SEVERAL MINOR SHORTWAVE
TROUGHS WILL HELP INSTIGATE EARLIER DEEP CONVECTION AND THUNDERSTORM
DEVELOPMENT SATURDAY AFTERNOON OVER WESTERN MN...BEFORE A LARGE
MESOSCALE CONVECTIVE SYSTEM DEVELOPS DURING THE EVENING AND
OVERNIGHT.  TORNADO PARAMETERS INDICATED MODERATE TO HIGH
PROBABILITY OF EF1 OR GREATER TORNADOES OVER CENTRAL MINNESOTA LATE
AFTERNOON AND EVENING SATURDAY. ADAP PROGS INDICATED ABOUT 2500-3000
J/KG WITH LIFTED INDICES OF -6 TO -10 CELSIUS...WITH LEAST 30 TO 45
ZERO TO 1KM BULK SHEAR ACRS THE AREA.  SPC HAS OUTLOOK MUCH OF THE
FORECAST AREA UNDER A MODERATE RISK OF SEVERE STORMS. EXPECT
SUPERCELLS...CAPABLE OF PRODUCING  LARGE HAIL...DAMAGING WINDS AND
TORNADOES LIKELY.

IN THE NEAR TERM...WEAK SURFACE BOUNDARY OR TROUGH WILL HELP FOCUS
SOME LOW LEVEL MOISTURE OVER SOUTH CENTRAL MN INTO PARTS OF WESTERN
WISCONSIN EARLY THIS EVENING. SFC DEWPOINTS WERE IN THE MID/UPPER
60S. EXPECT SOME ISOLATED THUNDERSTORMS EARLY THIS
EVENING...OTHERWISE SKIES SHOULD BECOME MOSTLY CLEAR OVERNIGHT.
HIGH PRESSURE RIDGE CENTERED OVER THE NORTHERN PLAINS INTO SOUTHWEST
U.S. WILL KEEP MUCH OF THE AREA DRY THROUGH MIDDAY SATURDAY.

IN THE MEDIUM RANGE AND LONG RANGE FORECAST...ANOTHER WARM FRONT
WILL LAY ACROSS THE MIDWEST BY MONDAY EVENING...THEN SLOWLY LIFT
NORTH DURING THE PERIOD.   MOISTURE WILL BEGIN TO LIFT BACK NORTH
OVER SOUTH CENTRAL MN. SCATTERED THUNDERSTORMS ARE POSSIBLE OVER THE
SOUTHERN HALF OF MN MONDAY NIGHT.

THE WEATHER WILL REMAIN ACTIVE INTO NEXT WEEK AS UPPER RIDGE BUILDS
OVER THE NATION MIDSECTION...EXPECT RIDGE RIDERS(THUNDERSTORMS)
MOVING SOUTHEAST OVER THE FORECAST.

&&

.AVIATION.../18Z TAF ISSUANCE/

MAIN AVIATION CONCERNS DEAL WITH THE POSSIBILITY OF TSRA
DEVELOPING ACROSS SOUTHERN MN...MAINLY SOUTH OF HWY 14...OR SOUTH
OF THE MINNESOTA RIVER. HOWEVER...CURRENT THETA-E ADV IS ACROSS
THE HWY 212 CORRIDOR WITH MLCAPES ARND 1000 J/KG. INITIATION OF
TSRA WILL LIKELY BE SOUTH OF THE MSP...BUT KEPT CBS IN THE VCNTY
UNTIL LATER THIS AFTN. RWF WILL LIKELY BE THE MAIN AREA WHERE CBS
WILL BE MORE COMMON WITH VCTS. BUT NOT TOO CONFIDENT ON LOCATION
AND IF TSRA DEVELOP...AND THE ACTIVITY SHOULD REMAIN ISOLATED FOR
TAFS. WNDS WILL BE GENERALLY FROM THE W/NW...BRIEFLY N/NW BEHIND
SFC TROUGH THIS AFTN...BUT BECOMING LGT AND VARIABLE OVERNIGHT. BY
12Z...WNDS WILL BECOME MORE E/SE WITH TIME.

MSP...WILL CONTINUE CB IN THE VCNTY THRU 02Z...BUT MORE THAN
LIKELY THE CHC OF ANY TSRA OR VCTS WILL BE BEFORE 22Z. WNDS WILL
BECOME MORE W/NW THIS AFTN WITH A FEW GUSTS. WNDS WILL THEN BACK
TO THE S OVERNIGHT AND INCREASE DURING THE MORNING. MOST OF THE
CONVECTION ON SATURDAY SHOULD HOLD OFF UNTIL AFT 21Z. ..JLT..

&&

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

JM/JLT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
310 PM CDT FRI JUL 16 2010

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
171100-
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-
310 PM CDT FRI JUL 16 2010

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

.DAY ONE...TONIGHT

ISOLATED THUNDERSTORMS ARE POSSIBLE ACROSS PARTS OF SOUTH CENTRAL
AND SOUTHEAST MINNESOTA...MAINLY ALONG AND SOUTH OF THE INTERSTATE
90 CORRIDOR. A FEW STORMS COULD PRODUCE HAIL UP TO NICKEL SIZE AND
DAMAGING WINDS BEFORE 800 PM THIS EVENING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE
OUTLOOK AREA LATE SATURDAY AFTERNOON INTO SATURDAY NIGHT. A LOW
PRESSURE SYSTEM WILL LIFT NORTHEAST OVER MINNESOTA LATE IN THE DAY
ON SATURDAY. VERY WARM...MOIST AND UNSTABLE AIR WILL LIFT NORTHWARD
OVER MINNESOTA AND WESTERN WISCONSIN.  SEVER STORMS CAPABLE OF
PRODUCING VERY LARGE HAIL...DAMAGING WINDS AND EVEN A FEW TORNADOES.
HEAVY RAINS ARE ALSO POSSIBLE WITH THESE STORMS. THE BEST TIME FOR
INITIATION OF THUNDERSTORMS WILL BE LATE AFTERNOON AND EVENING ON
SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION IS POSSIBLE FOR A SHORT TIME ACROSS SOUTH
CENTRAL MINNESOTA EARLY THIS EVENING. ACTIVATION ACROSS MUCH OF THE
OUTLOOK AREA IS LIKELY LATE AFTERNOON OR EVENING ON SATURDAY.