Special Weather Statement, NWS Twin Cities, MN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1140 PM CDT TUE JUL 26 2011

.UPDATED FOR AVIATION DISCUSSION BELOW...

.DISCUSSION...

A VERY PRONOUNCED DRY LAYER /LOW TO MID LEVELS/ WAS ACROSS THE NE
FA THIS AFTN WITH SFC DEW PTS ARND 60 AND A PERSISTENT E/NE TO SE
WND. TSRA CONTINUED TO DEVELOP ACROSS ND AND PORTIONS OF NC/NE SD
WHERE THE MOISTURE GRADIENT/HIGHER INSTABILITY HAS SETUP THIS AFTN.

SHORT TERM CONCERNS DEAL WITH THE ONSET OR WHEN CAN THE TROPICAL
TYPE AIR MASS ADV ACROSS THE WESTERN FA THIS EVENING...AND HOW
THIS WILL TRANSLATE ACROSS THE REMAINDER OF THE FA BY LATE TONIGHT
AND INTO WED MORNING.

PREVIOUS MODEL RUNS HAVE PLACED TWO HIGHER QPF FIELDS ACROSS THE
UPPER MIDWEST. ONE AREA WAS ASSOCIATED WITH THE MAIN SHRTWV
MOVING ACROSS ND AND INTO N MN. THIS AREA WILL MAINLY AFFECT THE
FAR N FA. ANOTHER HIGHLIGHTED AREA WAS IN THE FAR SW FA WHICH IS
MORE IN LINE OF THE STRONGER THETA-E ADV POSSIBLY DEVELOPING AFT
MIDNIGHT. HOWEVER...REGIONAL RADAR HAS INDICATED MOST OF THE
CURRENT ACTIVITY REMAINS WITH THE MAIN WAVE ACROSS ND THIS AFTN.
HPC HAS PLACE THE HIGHER QPF AMTS IN THE SW FA...WITH A BROAD AREA
OF MODERATE /0.50 TO 0.75"/ QPF AMTS ACROSS THE N FA. EITHER WAY
IT WILL RAIN IN THE NEXT 24 HRS...ACROSS ALL OF THE FA WITH
EMBEDDED HEAVIER RAINFALL TOTALS WHERE TSRA BEGIN TO TRAIN.

DUE TO THE DRIER AIR MASS TO THE EAST...WILL HOLD OFF UNTIL AFT 09Z
FOR ANY LIKELY OR CATEGORICAL POPS IN THE SE 2/3 OF THE FA. SOME
ISOLD TSRA ACTIVITY IS POSSIBLE ACROSS ANY PART OF S MN...OR WC
WI DUE TO THE INITIAL ONSET OF THE ANTICIPATED MOISTURE ADV. BUT
THIS AREA WILL LIKELY SEE HIGH BASED TSRA AND LIGHTER RAINFALL
RATES.

SVR WX PARAMETERS ACROSS THE NW FA SEEMS FAIRLY STRAIGHT
FORWARD FOR A MCS/BOW ECHO TYPE TSRA COMPLEX LATER TONIGHT. THE
SVR WX WILL TRANSLATE INTO MORE OF A HEAVY RAINFALL EVENT AFT
MIDNIGHT...ESPECIALLY IN THE S FA AS TSRA POSSIBLY BEGIN TO TRAIN
AS THE UPPER LEVEL WNDS WILL BE NEARLY UNIDIRECTIONAL. THESE UPPER
LEVEL WNDS WILL ALSO KEEP THE FRONTAL BOUNDARY FROM MOVING TOO FAR
TO THE SOUTH OVER THE NEXT DAY OR SO. THEREFORE...WILL CONTINUE
CHC POPS IN THE FAR S AS SOME OF THE MODELS INDICATE ANOTHER WEAK
SHRTWV MOVING ACROSS SD...INTO S MN THU.

THE EXTENDED PERIOD REMAINS QUESTIONABLE AS THE UPPER RIDGE BUILDS
SOUTH OF MN...AND STRONG WESTERLY REMAIN NEAR THE CANADIAN/U.S.
BORDER. THE OVERALL MEAN OF THE 50H HEIGHTS INDICATE THAT THE
UPPER RIDGE IS EXPECTED TO BUILD ACROSS KS BY THIS WEEKEND...WITH
MORE OF A W/NW FLOW DEVELOPING ACROSS THE GREAT LAKES. THIS WOULD
MEAN THAT A FEW SHRTWV MAY AFFECT THE FA WITH PERIODIC FRONTAL
BOUNDARIES OR AIR MASS CHGS. THIS WOULD LEAD TO CHC OR SLIGHT CHC
POPS FROM SUNDAY THRU TUESDAY. HUMIDITY LEVELS WILL LIKELY RISE BY
LATE IN THE WEEKEND AS THE UPPER RIDGE BUILDS SLIGHTLY TO THE N
ACROSS THE NORTHERN PLAINS. ..JLT..

&&

.AVIATION... /06Z TAF ISSUANCE/
A LARGE MESOSCALE CONVECTIVE SYSTEM OVER WESTERN MINNESOTA WILL
CONTINUE TO SLOWLY ADVANCE EASTWARD OVERNIGHT/WEDNESDAY MORNING. A
LINE OF STRONG TO SEVERE THUNDERSTORMS CAPABLE OF PRODUCING WIND
GUST GREATER THAN 60 KNOTS WERE MOVING INTO CENTRAL MN. TWO MAIN
CLUSTERS OF STORMS WILL LIKELY CONGEAL OVER CENTRAL MN...WITH
ADDITIONAL DEVELOPMENT OVER EASTERN SODAK INTO EAST CENTRAL MN
OVERNIGHT AS THE MESOSCALE CONVECTIVE SYSTEM BACKBUILDS. SO THE MAIN
THREAT WILL BE HEAVY RAIN OVERNIGHT WITH CEILINGS AND VISIBILITIES
LOWERING TO LIFR CONDITIONS...MUCH OF THE ROUTES AND TAF SITES
SHOULD EXPERIENCE MARGINAL VFR CONDITIONS IN RAIN AND SCATTERED
THUNDERSTORMS. FRONTAL BOUNDARY FORECAST TO PUSH THROUGH EAST AND
BECOME NEARLY STATIONARY OVER WISCONSIN AND NORTHERN IOWA. WEATHER
CONDITIONS IMPROVING FROM WEST TO EAST DURING AFTERNOON OVER WESTERN
MN AND OVER EASTERN MN AND WESTERN WISCONSIN BY EARLY EVENING.

.KMSP...FREQUENT MARGINAL VFR WITH BRIEF PERIODS OF IFR CONDITIONS
OVERNIGHT IN HEAVY RAIN AND STRONG THUNDERSTORMS.  CONDITIONS
IMPROVING WEDNESDAY MORNING...AS THE FRONTAL BOUNDARY SLIDES OFF TO
THE EAST AND SOUTH. BECOMING SCATTERED CLOUDS AT OR ABOVE 4000 FEET
AGL...THEN CLEAR BY 10 PM WEDNESDAY NIGHT.  WINDS SOUTHEAST 10 TO 15
KNOTS WITH VARIABLE WINDS AND SPEED IN THUNDERSTORMS.  WINDS
BECOMING WESTERLY AROUND 10 KNOTS AND DIMINISHING TO UNDER 7 KNOTS
BEFORE SUNSET WEDNESDAY NIGHT.

&&

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

JLT/JM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
106 AM CDT WED JUL 27 2011

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
271100-
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-
106 AM CDT WED JUL 27 2011

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

.DAY ONE...OVERNIGHT

SEVERE THUNDERSTORMS ARE STILL POSSIBLE OVER PORTIONS OF SOUTHERN
AND CENTRAL MINNESOTA OVERNIGHT AS LOW PRESSURE MOVES TOWARD
WESTERN MINNESOTA. STRONG WINDS WOULD BE THE MAIN SEVERE WEATHER
THREAT. IN ADDITION...HEAVY RAIN IS LIKELY WITH THE STRONGER
STORMS...WHICH COULD CAUSE FLOODING. AREAS UNDER THE GREATEST
THREAT OF HEAVY RAIN WOULD BE PORTIONS OF CENTRAL MINNESOTA.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

THUNDERSTORMS WILL LINGER OVER PARTS OF SOUTH CENTRAL AND EAST
CENTRAL MINNESOTA AND WEST CENTRAL WISCONSIN WEDNESDAY
MORNING...WITH HEAVY RAIN STILL POSSIBLE.

THERE IS A SLIGHT RISK FOR SEVERE WEATHER FROM SOUTH CENTRAL
MINNESOTA INTO WEST CENTRAL WISCONSIN...MAINLY DURING THE
AFTERNOON AND EVENING. THE NEXT THREAT FOR THUNDERSTORMS ACROSS THE
OUTLOOK AREA WILL BE SUNDAY AND MONDAY.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION MAY BE NEEDED.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
222 AM CDT WED JUL 27 2011

MNZ044-045-052-053-061-WIZ014-270745-
ANOKA-CHISAGO-ISANTI-KANABEC-MILLE LACS-POLK-
222 AM CDT WED JUL 27 2011

...HEAVY RAIN DEVELOPING OVER ANOKA...CHISAGO...ISANTI...KANABEC...
MILLE LACS AND POLK COUNTIES THROUGH 245 AM CDT...

AT 217 AM CDT...WEATHER SERVICE RADAR WAS TRACKING STRONG
THUNDERSTORMS ALONG A LINE EXTENDING FROM 4 MILES NORTH OF ISLE TO
LEWIS LAKE TO 3 MILES NORTHEAST OF EAST BETHEL. THESE STORMS WERE
MOVING EAST AT 30 MPH.

WINDS UP TO 50 MPH ARE EXPECTED WITH THESE STORMS.

* LOCATIONS IN OR NEAR THE PATH OF THESE STORMS INCLUDE...
  BODUM.
  WARMAN.
  WYOMING.
  QUAMBA.
  HARRIS.

LAT...LON 4616 9342 4615 9304 4598 9304 4597 9313
      4574 9314 4573 9287 4565 9287 4565 9284
      4537 9275 4528 9329 4577 9349 4626 9359
      4626 9344
TIME...MOT...LOC 0721Z 262DEG 25KT 4621 9341 4578 9335
          4536 9311

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
241 AM CDT WED JUL 27 2011

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0239 AM     HAIL             ST FRANCIS              45.38N 93.36W
07/27/2011  M0.75 INCH       ANOKA              MN   TRAINED SPOTTER

&&

AZ

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
316 AM CDT WED JUL 27 2011

MNZ073>075-083-270915-
BLUE EARTH-BROWN-NICOLLET-REDWOOD-
316 AM CDT WED JUL 27 2011

...THUNDERSTORMS MOVING OVER BLUE EARTH...BROWN...NICOLLET AND
REDWOOD COUNTIES THROUGH 415 AM CDT...

AT 312 AM CDT...WEATHER SERVICE RADAR WAS TRACKING A CLUSTER OF
STRONG THUNDERSTORM NEAR SPRINGFIELD. THESE STORMS WERE MOVING EAST
AT 35 MPH.

ONE HALF INCH DIAMETER HAIL...WINDS UP TO 40 MPH...AND HEAVY
DOWNPOURS ARE EXPECTED WITH THESE STORMS.

* LOCATIONS IN OR NEAR THE PATH OF THES STORMS INCLUDE...
  SPRINGFIELD.
  MORGAN.
  COBDEN.
  EVAN.
  SLEEPY EYE.
  NEW ULM.

LAT...LON 4441 9514 4446 9432 4445 9427 4415 9432
      4414 9511
TIME...MOT...LOC 0814Z 256DEG 31KT 4427 9498