Special Weather Statement, NWS Twin Cities, MN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
422 AM CDT SAT JUL 10 2010

.DISCUSSION...

TWO MAIN CONCERNS THIS FORECAST PERIOD ARE THE SHOWER AND
THUNDERSTORM CHANCES THROUGH SUNDAY AND THEN THE POTENTIAL FOR A
MORE SIGNIFICANT SEVERE WEATHER EVENT WEDNESDAY.

CURRENT WATER VAPOR AND H5 ANALYSIS SHOWS BROAD SUB TROPICAL RIDGE
ACROSS THE SRN CONUS...WITH A PERTURBED WNW FLOW SET UP ACROSS THE
NRN HALF OF THE CONUS. MAIN TROUGHS OF INTEREST THIS MORNING ARE
CURRENTLY OVER THE ERN DAKS/WRN MN AND IDAHO/WYOMING/MONTANA. THE
FIRST WILL HELP SPREAD ISO/SCT SHRA/TSRA ACROSS MN THIS MORNING
AND THEN WISCONSIN THIS AFTERNOON...WHILE THE SECOND ONE WILL
VENTURE INTO SODAK THIS AFTERNOON AND SRN MN THIS EVENING. THE
SECOND ONE WOULD BE THE ONE PRIMARILY RESPONSIBLE FOR ANY SEVERE
WEATHER THIS EVENING/TONIGHT.

THIS MORNINGS WAVE...THOUGH SUBTLE...IS CAPTURED WELL BY THE 1.5
PV SFC ON THE 10.00 GFS. WEAK PVA...ALONG WITH SOME WEAK THETA-E
ADVECTION IS HELPING GENERATE ENOUGH LIFT TO REALIZE THE MUCAPES
CURRENTLY SHOWN ON THE SPC MESO ANALYSIS PAGE TO BE IN THE
1000-2000 J/KG. BY THE AFTERNOON INCREASED DAYTIME HEATING AND
INSTABILITY AHEAD OF THIS FEATURE...ALONG WITH AN INCREASING LLJ
AND MOISTURE TRANSPORT SHOULD AID IN THE EXPANSION OF SHRA/TSRA
ACTIVITY ACROSS W CENT WI THIS AFTERNOON...SO HAVE INCREASED POPS
THERE. BULK SHEAR IS EXPECTED TO BE BELOW 20 KTS...SO NONE OF THIS
IS EXPECTED TO BE SEVERE.

AS MENTIONED EARLIER...MAIN SEVERE TREAT WILL BE ASSOCIATED WITH
WAVE FURTHER WEST. AS THIS WAVE MOVES INTO THE DAKOTAS...A COLD
FRONT ASSOCIATED WITH A WAVE STAYING IN CANADA WILL DROP SE
THROUGH NODAK. NAM/GFS SIMILAR WITH DEVELOPING MLCAPES IN THE
2000-3000 RANGE BY THE AFTERNOON ACROSS ERN SODAK AHEAD OF THESE
FEATURES. SHOULD SEE STORMS INITIATE THERE...SPREADING INTO WRN MN
AROUND 00Z. WITH BULK SHEAR EXPECTED TO BE BETWEEN 25 AND 35
KTS...CERTAINLY IS POTENTIAL FOR SEVERE WEATHER TO BE
POSSIBLE...ESPECIALLY ACROSS ERN SODAK. FREEZING LEVELS WILL AGAIN
BE WELL OVER 10K FT...SO SEVERE HAIL WILL BE TOUGH TO COME
BY...BUT STEEP LOW LEVEL LAPSE RATES AND DEEP MIXED LAYER UP
THROUGH H85 SHOULD PROMOTE COLD POOL DEVELOPMENT AND AN ENHANCED
WIND THREAT. GIVEN TIMING OF WHEN THIS ACTIVITY IS EXPECTED TO
ENTER THE AREA...FEEL HIGHEST THREAT FOR SEVERE WEATHER WILL BE IN
WRN MN...WITH SOME FORM OF THUNDERSTORM ACTIVITY MAKING INTO ERN
MN BY SUNDAY MORNING...BUT WITH INCREASED STABILITY...AND A STABLE
NOCTURNAL BOUNDARY LAYER...SEVERE THREAT SHOULD BE DIMINISHED.

BIGGER QUESTION MARKS EXIST FOR SEVERE THREAT SUNDAY...BUT WITH
FRONT STARTING OUT IN THE MORNING FROM WRN LK SUPERIOR INTO W CENT
MN...IT WILL LIKELY BE A WET DAY FOR ALL BUT THE NORTHWEST CORNER
OF THE CWA. THE MAIN PROBLEMS FOR A SEVERE THREAT IS THAT THE
EXTENSIVE CLOUDS/RAIN SHOULD LIMIT INSTABILITY ACROSS THE AREA. ON
TOP OF THIS...THERE ARE INCREASING INDICATIONS THAT A SPLIT FLOW
SCENARIO WILL BE SETTING UP...WITH THE AREA CAUGHT BETWEEN THE
MAIN WAVE DRIVING THE FRONT ACROSS CANADA AND THE REMNANTS OF THE
CURRENT IDAHO WAVE THAT ARE FORECAST TO GO ACROSS IOWA. AS A
RESULT...BEST MOISTURE TRANSPORT/INSTABILITY WILL REMAIN SOUTH OF
THE AREA...AND BEING BETWEEN SYSTEMS...CWA WILL BE IN A BIT OF A
LULL FOR UPPER FLOW. THIS WEAKER UPPER FLOW WILL KEEP BULK SHEARS
20 KTS OR LESS AHEAD OF THE FRONT...FURTHER DIMINISHING THREAT
FOR THE SEVERE. WITH THAT SAID...DAY 2 OUTLOOK DOES HAVE THE SE
PART OF THE CWA IN SLIGHT RISK...AND ENOUGH INSTABILITY SHOULD BE
PRESENT TO AT LEAST BRING ABOUT THE TREAT FOR A FEW STORMS WITH
DAMAGING WINDS...BUT CONFIDENCE IN THE SEVERE THREAT IS LOW.

THIS FRONT WILL CLEAR THE AREA BY MONDAY MORNING...BRINGING ABOUT
TWO PLEASANT AND DRY DAYS MONDAY AND TUESDAY. AS THIS OCCURS...
DEEP UPPER LOW CURRENTLY SOUTH OF AK IS TO CONTINUE E INTO SW
CANADA. WILL BE GETTING FIRST BOUT OF WAA FROM THIS TUESDAY...AND
MAY HAVE TO DEAL WITH SOME OVERNIGHT CONVECTION TUESDAY NIGHT
ACROSS THE NW CWA...BUT MAIN ACTION WITH THIS SYSTEM STILL LOOKS
TO COME DURING THE DAY WEDNESDAY. ECMWF/GEM ARE THE PREFERRED
MODELS FOR THIS SYSTEM GIVEN THEIR CONTINUITY. THIS SYSTEM WILL
HAVE MUCH STRONGER DYNAMICS/DEEPER MOISTURE WORKING IN ITS
FAVOR...AND THE 10.00 ECMWF DOES CONTINUE TO GIVE THE INDICATION
OF A MORE SIGNIFICANT SEVERE WEATHER OUTBREAK BEING POSSIBLE THIS
DAY. WILL BE SOMETHING TO WATCH IN THE DAYS TO COME.

&&

.AVIATION... /06Z TAF ISSUANCE/

WEAK LOW LEVEL THETA-E ADVECTION WILL BE WORKING ACROSS THE MN CWA
OVERNIGHT AND ACROSS WEST CENTRAL WI SATURDAY MORNING. SOME MID
LEVEL CLOUDS SEEN IN SATELLITE IMAGERY ATTM IN EASTERN SD NEAR THE
LEADING EDGE OF THE THETA-E ADVECTION. HENCE...SMALL THREAT FOR SHOWERS
AND ISOLATED THUNDERSTORMS FOR THE MN TAFS OVERNIGHT. CONTINUED
TO USE VCNTY DUE TO THE NATURE OF THE ACTIVITY. OTHERWISE...VFR.
SURFACE WINDS WILL BECOME MORE SOUTH TO SOUTHWEST ON SATURDAY WITH
SPEEDS INCREASING TO 10 TO 14 KNOTS BY LATE MORNING. GUSTS IN THE
18-22 KNOT RANGE WILL ALSO OCCUR...MAINLY DURING THE AFTERNOON.

KMSP...VFR CONDITIONS EXPECTED THROUGH THE PERIOD. SMALL THREAT
FOR SHOWERS AND ISOLATED THUNDERSTORMS IN THE 11Z-15Z TIME FRAME.
LIGHT WINDS OVERNIGHT INCREASING TO 10 KNOTS SATURDAY MORNING FROM
THE SOUTH TO SOUTHWEST (200-230 DEG). GUSTS IN THE 18-20 KNOT
RANGE DURING THE AFTERNOON.

&&

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

MPG/RAH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
515 AM CDT SAT JUL 10 2010

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
111015-
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-
515 AM CDT SAT JUL 10 2010

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

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO
TONIGHT ACROSS MOST OF CENTRAL AND SOUTHERN MINNESOTA. THE PRIMARY
THREAT WITH THIS ACTIVITY WILL BE DAMAGING WINDS AND SOME LARGE
HAIL. A COLD FRONT DROPPING SOUTHEAST ACROSS NORTH DAKOTA DURING
THE DAY...ALONG WITH THE ARRIVAL OF AN UPPER WAVE FROM THE WEST
WILL HELP GENERATE THUNDERSTORMS THIS AFTERNOON ACROSS EASTERN
SOUTH DAKOTA. THIS ACTIVITY IS THEN EXPECTED TO MOVE INTO WEST
CENTRAL MINNESOTA AFTER 5 PM AND SPREAD EAST ACROSS MINNESOTA
THROUGH THE NIGHT...TAKING THE SEVERE THREAT WITH IT.

SCATTERED THUNDERSTORMS WILL CONTINUE TO SPREAD ACROSS CENTRAL
MINNESOTA THIS MORNING AND WILL EXPAND IN COVERAGE THIS AFTERNOON
ACROSS WEST CENTRAL WISCONSIN. THIS ACTIVITY IS NOT EXPECTED TO BE
SEVERE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

SEVERE THUNDERSTORMS ARE AGAIN POSSIBLE SUNDAY ACROSS SOUTH AND
EAST CENTRAL MINNESOTA INTO WEST CENTRAL WISCONSIN...AS DAMAGING
WINDS AND HAIL WILL CONTINUE TO BE A THREAT WITH THUNDERSTORMS
EXPECTED OUT AHEAD OF A COLD FRONT THAT WILL MOVE ACROSS THE
OUTLOOK AREA DURING THE DAY.

THERE ARE INCREASING INDICATIONS THAT A MORE SIGNIFICANT SEVERE
WEATHER EVENT WILL BE POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT AS A
STRONG COLD FRONT SWEEPS ACROSS THE REGION. THERE CURRENTLY
APPEARS TO BE THE POTENTIAL FOR HAIL...DAMAGING WINDS...AND
TORNADOES. STAY ABREAST OF FUTURE UPDATES TO THE FORECAST FOR THIS
EVENT AS MORE SPECIFIC DETAILS ON THE TIMING AND POSSIBLE THREATS
CAN BE ASCERTAINED.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION MAY BE NEEDED.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
610 AM CDT SAT JUL 10 2010

MNZ044-045-101215-
KANABEC-MILLE LACS-
610 AM CDT SAT JUL 10 2010

AT 606 AM CDT...WEATHER SERVICE RADAR IN CHANHASSEN WAS TRACKING A
STRONG THUNDERSTORM NEAR ONAMIA. THIS STORM WAS MOVING EAST AT 15
MPH.

HAIL UP TO DIME SIZE AND WINDS UP TO 40 MPH ARE EXPECTED WITH THIS
STORM.

* LOCATIONS IN OR NEAR THE PATH OF THIS STORM INCLUDE...
  BAYVIEW.
  WAHKON.
  ISLE.
  WARMAN.

LAT...LON 4624 9342 4616 9342 4616 9306 4616 9305
      4614 9304 4609 9305 4597 9368 4613 9377
      4625 9344
TIME...MOT...LOC 1110Z 249DEG 15KT 4608 9360