Damaging Winds and Heavy Rain in Wisconsin, August 6, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
330 PM CDT SAT AUG 6 2011

.SHORT TERM...TONIGHT AND SUNDAY.

LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A BROAD SURFACE
LOW PRESSURE MOVING OVER THE SOUTHERN HALF OF MINNESOTA THIS
AFTERNOON.  NORTH OF THE LOW...LEAD SHORTWAVE IMPULSE IS GENERATING
A CLUSTER OF SHOWERS AND STORMS THAT HAVE BEGUN TO PUSH INTO
NORTH-CENTRAL WISCONSIN.  THE STORMS REMAIN BELOW SEVERE
LIMITS...BUT HAVE BEEN BUILDING INTO AN AREA OF 1K J/KG OF ML CAPE
AND NO CIN OVER WEST CENTRAL WISCONSIN.  NOT OUT OF THE QUESTION
THAT AN ISOLATED DAMAGING WIND GUST COULD OCCUR THROUGH EARLY THIS
EVENING OVER N-C WISCONSIN WITH ANY STORMS.  ADDITIONAL STORMS HAVE
BEGUN TO FIRE OVER THE U.P. ALONG A COOL FRONT WHICH CONNECTS TO THE
SURFACE LOW.  AS A SHORTWAVE TROUGH OVER THE PLAINS PUSHES A SURFACE
LOW INTO THE STATE TONIGHT...THUNDERSTORM POTENTIAL IS THE MAIN
FORECAST CONCERN.

TONIGHT...OPERATIONAL MODELS NOT IN THE BEST OF AGREEMENTS WITH THE
TRACK OF A SURFACE LOW ACROSS THE NORTHERN MISSISSIPPI VALLEY
TONIGHT...SO STUCK WITH A MIDDLE OF THE ROAD APPROACH AND HPC'S
PREFERRED GUIDANCE INCLUDING THE SREF AND GFS.  SE MOVING SHORTWAVE
TROUGH WILL DRIVE A SURFACE LOW FROM NORTHERN MISSISSIPPI VALLEY TO
WEST-CENTRAL WISCONSIN.  A LEAD SHORTWAVE IMPULSE WILL TRACK OVER FAR N-C
WISCONSIN WITH SHOWERS AND STORMS THROUGH EARLY THIS EVENING AND
HAVE EXPANDED AND INCREASED POPS OVER CENTRAL WISCONSIN TO ACCOUNT
FOR A SOUTHWARD TREND TOWARDS THE INSTABILITY.  AN ISOLATED DAMAGING
WIND GUST CANNOT BE RULED OUT WITH THESE STORMS AS DAYTIME
INSTABILITY LINGERS INTO THIS EVENING OVER NORTH-CENTRAL WISCONSIN.
ANOTHER ROUND OF CONVECTION IS EXPECTED TO DEVELOP AHEAD OF THE LOW
OVER CENTRAL MINNESOTA OR WESTERN WISCONSIN LATER THIS AFTERNOON OR
EARLY THIS EVENING WHICH WILL TRACK ESE TOWARDS CENTRAL WISCONSIN
THIS EVENING AND EASTERN WISCONSIN OVERNIGHT.  DAYTIME INSTABILITY
WILL SUBSIDE THIS EVENING AND GET PUSHED SOUTH...AND ELEVATED
INSTABILITY WILL ALSO GRADUALLY WEAKEN WITH TIME.  WILL STILL HAVE
PLENTY FOR SHOWERS AND STORMS...WHICH COULD DROP SOME DECENT
RAINFALL TOTALS...SMALL HAIL...AND MODERATELY GUSTY WINDS.

SUNDAY...LOW PRESSURE MOVES OVER CENTRAL WISCONSIN INTO LOWER
MICHIGAN.  SHOWERS WILL BE LIKELY ALONG AND TO THE NORTH OF THE
SURFACE LOW TRACK...FROM ABOUT WAUSAU TO GRB.  CANNOT RULE OUT
THUNDER AHEAD OF THE LOW EITHER...BUT SEVERE CHANCES LOOK TO BE EAST
OF THE REGION. SHOWERS AND A FEW STORMS WILL BE SLOWLY EXITING IN
THE AFTERNOON FROM WEST TO EAST WITH THE MOVEMENT OF THE SHORTWAVE
TROUGH AXIS.  LOWERED TEMPS ACROSS THE NORTH FIGURING CLOUDS AND
SHOWER ACTIVITY WILL KEEP TEMPS COOL.  HIGHS RANGING THROUGH THE 70S.

.LONG TERM...MONDAY THRU NEXT SATURDAY.
TRANSISTION INTO WNW UPPER FLOW CONTINUES DURING FIRST PART OF
PERIOD AS SERIES OF SHORTWAVE TROFS MOVE ACROSS N GREAT LAKES
REGION. TEMPS WILL AVERAGE A BIT BELOW NORMS WITH A COUPLE OF
CHANCES OF PRECIP AHEAD OF TROFS. 06/12Z MODELS IN GENERAL
AGREEMENT ON THIS TRANSITION AND OVERALL TIMING OF SHORTWAVES.

SIGNIFICANT MODEL DIVERGENCE STARTS TO SHOW UP AT END OF PERIOD
(AND BEYOND THIS FORECAST) WITH RESPECT TO LARGE UPPER LOW OVER
HUDSON BAY. 06/12Z GFS BRINGS SLUG OF VERY COOL AIR INTO GREAT
LAKES LATE IN THE WEEKEND AS LOBE OF ENERGY ROTATES ACROSS
REGION. PREV GFS AND ECMWF SLIDE LOW E AND BUILD UPPER RIDGE BACK
TOWARD CENTRAL PART OF CONUS.

PREVIOUS FORECAST OVERALL WAS IN GOOD SHAPE THRU END OF THE WEEK SO
LITTLE ADJUSTMENT WAS NEEDED. 06/12Z GFS MOS TEMP GUID SEEMED A
COUPLE DEGS ON THE HIGH SIDE AFTER MONDAY FOR SEVERAL SITES. STAYED
CLOSE TO PREVIOUS FORECAST TEMPS. DID ADJUST MAX TEMPS FOR MONDAY
UP A DEG OR SO WITH WEAK WAA AND SOME SUN AHEAD OF LATE MON/TUE
SYSTEM.
&&

.AVIATION...THUNDERSTORM COMPLEX MOVING OVER NW WISCONSIN WILL
APPROACH RHI AROUND MID-AFTERNOON AND EXIT BY EARLY THIS EVENING.
ANTICIPATE A LULL IN THE ACTION THIS EVENING BEFORE LOW PRESSURE
APPROACHES FROM THE WEST.  MODELS HAVE VARIED TIMING IN REGARDS WHEN
THE 2ND ROUND OF PRECIP ARRIVES.  USED THE SREF/GFS TO APPROX. THIS
TIMING...WHICH BRINGS SHOWERS AND THUNDERSTORMS INTO THE CENTRAL
WISCONSIN TAF SITES DURING THE OVERNIGHT HOURS...AND INTO THE
EASTERN TAF SITES LATE TONIGHT.  SOME FOG POSSIBLE AT GRB/ATW BEFORE
THE PRECIP ARRIVES.  SHOWERS AND LOW CIGS/VSBYS TO LINGER INTO
TOMORROW MORNING...THEN IMPROVING CONDITIONS TOMORROW AFTERNOON.
&&

.MARINE...TRACK OF SURFACE LOW WILL BE CRITICAL TO POTENTIAL SMALL
CRAFT ADVISORY CONDITIONS...WHICH ISNT NAILED DOWN YET BY THE LATEST
GUIDANCE.  CURRENT THINKING WILL BRING THE LOW ACROSS NW TO EC
WISCONSIN...WHICH WILL KEEP A BAGGIER PRESSURE GRADIENT THROUGH
TOMORROW...AND A LIGHTER WIND REGIME.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

MPC/JKL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREEN BAY WI
228 PM CDT SAT AUG 6 2011

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-071930-
VILAS-ONEIDA-FOREST-FLORENCE-NORTHERN MARINETTE-LINCOLN-LANGLADE-
MENOMINEE-NORTHERN OCONTO-DOOR-MARATHON-SHAWANO-WOOD-PORTAGE-
WAUPACA-OUTAGAMIE-BROWN-KEWAUNEE-WAUSHARA-WINNEBAGO-CALUMET-
MANITOWOC-SOUTHERN MARINETTE-SOUTHERN OCONTO-
228 PM CDT SAT AUG 6 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST
WISCONSIN.

.DAY ONE...TONIGHT

THUNDERSTORMS ARE LIKELY TONIGHT. ALTHOUGH AN ISOLATED DAMAGING WIND
GUST WILL BE POSSIBLE OVER CENTRAL AND NORTH-CENTRAL WISCONSIN
THROUGH THIS EVENING...MAINLY GUSTY WINDS TO 40 MPH...SMALL HAIL AND
HEAVY RAINFALL WILL BE POSSIBLE WITH THESE STORMS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH SATURDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED OVER CENTRAL AND NORTH-CENTRAL
WISCONSIN THIS EVENING.

LMZ521-522-541>543-071930-
THE BAY OF GREEN BAY SOUTH OF A LINE FROM CEDAR RIVER MI TO ROCK
ISLAND PASSAGE-LAKE MICHIGAN FROM WASHINGTON ISLAND TO SHEBOYGAN-
228 PM CDT SAT AUG 6 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST LAKE
MICHIGAN AND THE WATERS OF GREEN BAY.

.DAY ONE...TONIGHT

THERE IS A CHANCE FOR THUNDERSTORMS LATE TONIGHT. SOME OF THESE
STORMS MAY PRODUCE GUSTY WINDS THAT POSE A HAZARD TO BOATERS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH SATURDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

MPC/JKL

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREEN BAY WI
418 PM CDT SAT AUG 6 2011

WIZ018-019-062215-
LANGLADE-LINCOLN-
418 PM CDT SAT AUG 6 2011

...SIGNIFICANT WEATHER ADVISORY...

AT 410 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR SPIRIT...MOVING EAST AT 30 MPH.

PENNY SIZE HAIL...WINDS UP TO 50 MPH...FREQUENT CLOUD TO GROUND
LIGHTNING...BRIEF HEAVY DOWNPOURS...ARE POSSIBLE WITH THIS STORM.

* THE THUNDERSTORM WILL BE NEAR...
  IRMA AROUND 435
  PARRISH BY 510 PM CDT...

GUSTY WINDS MAY CAUSE SMALL BRANCHES TO BE BLOWN DOWN...AND LOOSE
OBJECTS TO BLOW AROUND. STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS
TREES. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS
PASSED.

TE