Tornado in Wisconsin, June 19, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
330 PM CDT SUN JUN 19 2011

.VERY SHORT TERM...TONIGHT AND MONDAY. FORECAST CONFIDENCE MEDIUM.

DAYTIME HEATING THUNDERSTORMS IN THE DEEPER INSTABILITY AREAS WITH
THE WEAK CONVERGENCE OVER SOUTH CENTRAL WI DEVELOPING LATE THIS
AFTERNOON COULD PERSIST THROUGH THE EVENING SUNSET.

HRRR DEVELOPS SOME THUNDERSTORMS ALONG A SFC CONVERGENCE AREA AND
POSSIBLE AREA OF POSITIVE VORTICITY ADVECTION IN NE IOWA AND SPREADS
IT INTO SOUTHERN WI THIS EVENING. ADDED SLIGHT CHANCE POPS OVER THE
WESTERN FORECAST AREA FOR THE EARLY EVENING. RUC SNDGS AND LAPS SHOW
SOME STRETCHING POTENTIAL ALONG WITH CAPE INSTABILITY OVER WESTERN
CWA...SO ANY THUNDERSTORMS THAT GET A WEAK UPDRAFT HAVE THE
POTENTIAL TO SPIN UP A FUNNEL CLOUD. WILL WATCH CLOSELY.

SHORTWAVE OVER WESTERN IOWA THIS AFTERNOON HAS THE POTENTIAL TO
TRIGGER CONVECTION OVERNIGHT AND SPREAD INTO SOUTHWEST WI LATE
TONIGHT WITH THE WEAKENING LOW LEVEL JET. ANY STORMS WOULD RIDE
NORTHWARD ALONG A WARM FRONT MON MORNING INTO THE AFTERNOON. THE NAM
IS SLOWER WITH THIS FEATURE THAN THE GFS. CHANCE POPS TO ACCOUNT FOR
THIS SCENARIO.

DENSE FOG DEVELOPED OVER THE NEARSHORE WATERS FROM AT LEAST RACINE
TO PORT WASHINGTON. IT IS DEPICTABLE FROM ANIMATED VISIBLE SATELLITE
IMAGERY AND WEB CAMS. WEB CAMS OVER PARTS OF MILWAUKEE ALSO SHOW
VERY LOW CLOUDS...THESE CLOUDS COULD POTENTIALLY DROP TO THE SFC
WHEN DAYTIME HEATING ENDS AROUND SUNSET AND CREATE DENSE FOG OVER
THE CITY. IN ADDITION...ANY FOG FROM THE NEARSHORE COULD ADVECT
ONSHORE THIS EVENING AS WELL.

.SHORT TERM...MONDAY NIGHT THROUGH WEDNESDAY.

.MONDAY NIGHT...FORECAST CONFIDENCE MEDIUM.

UNCERTAINTY LIES IN WHERE SURFACE WARM FRONT AND 850 MB BAROCLINIC
ZONE SET UP AS LOW-LEVEL JET INCREASES. WILL KEEP LIKELY POPS
IN THE NORTH AND WEST CWA WITH FORCING DUE TO CONVERGENCE ON NOSE OF
INCREASING 850MB WINDS FOCUSING MORE TO THE WESTERN FORECAST
AREA...AND TO A LESSER EXTENT THE NORTH...THROUGH 12Z TUESDAY PER
850-700MB LAYER Q-VECTOR CONVERGENCE FORECASTS. LIFT AIDED BY UPPER
DIVERGENCE IN DIFFLUENT FLOW AHEAD OF JET MAX FOCUSED OVER SRN
MN/NERN IA AT 06Z TUESDAY THAT SHIFTS NORTHEAST ACROSS REGION
BETWEEN 06Z AND 12Z.

WARM AIR ADVECTION OVER STABILIZING BOUNDARY LAYER...WITH PERSISTENT
EASTERLY WINDS AHEAD OF SURFACE WARM FRONT...DEVELOPS A DEEP WARM
LAYER BETWEEN 900MB AND 600MB THAT CAPS EVEN ELEVATED CONVECTION IN
THE SOUTHEAST...SO CHANCE POPS THERE FOR NOW. HIGHER POPS MAY BE
NEEDED IF SFC FRONT/850MB BAROCLINIC ZONE LIFT FAR ENOUGH NORTH. MCS
COULD RUMBLE THROUGH LATE OVERNIGHT/EARLY IN THE MORNING.

INVERSION WILL SET UP THE POTENTIAL FOR ADVECTION FOG OFF THE
LAKE...ESPECIALLY EAST OF THE KETTLE MORAINE...SO WILL KEEP PREVIOUS
SHIFT/S ADDITION OF AREAS OF FOG FOR THE EASTERN COUNTIES. COOLER
LAKESHORE LOW TEMPERATURES...WITH WESTERN LOCATIONS SEEING LOWS
AROUND/SHORTLY AFTER MIDNIGHT...THEN STEADY OR SLOWLY RISING.

.TUESDAY AND TUESDAY NIGHT...FORECAST CONFIDENCE MEDIUM.

BEST CHANCE FOR SEVERE WEATHER COMES AS APPROACHING UPPER LOW COOLS
MID LAYERS STEEPENING LAPSE RATES...WITH INCREASING 0-6KM BULK SHEAR
TO 40-50 KTS WITH SPEED MAX MOVING UP ERN FLANK OF UPPER LOW. EXTRA
DYNAMIC FORCING FOR ASCENT COMES WITH DIFFERENTIAL CVA AS ALL MODELS
SHOW A VORTICITY LOBE ROTATING THROUGH SRN WI TUESDAY EVENING. IF
MCS DOES DEVELOP AND MOVES ACROSS SRN WI LATE MONDAY NIGHT INTO
TUESDAY MORNING...IT WILL STABILIZE ATMOSPHERE FOR THE LATE MORNING
INTO THE AFTERNOON. WILL GO WITH A LIKELY POP FOR THE DAY...THOUGH

.WEDNESDAY...FORECAST CONFIDENCE MEDIUM.

INSTABILITY WITH COLD POOL ALOFT AS UPPER LOW MOVES INTO
WISCONSIN...WITH SOUTH-SOUTHWEST FLOW BRINGING SURFACE THERMAL RIDGE
OVER MUCH OF SRN WI AS SURFACE LOW SLOWLY TRACKS FROM E CENTRAL MN
TO EITHER NW WI OR UPPER PENINSULA DEPENDING ON MODEL SOLUTION.
EITHER WAY LOOKS AS IF ENOUGH CAPE FOR PRECIPITATION MODE TO BE
THUNDERSTORMS. IN SPITE OF CLOUDS AND PRECIPITATION...
SOUTH-SOUTHWEST WINDS WILL BRING WARMTH UP TO THE LAKE SHORE WITH
HIGHS IN THE LOW TO MID 70S...BUT A BIT COOLER IN THE FAR WEST WHERE
COOLER AIR WRAPPING AROUND AND UNDER SURFACE LOW WILL REACH FIRST.

.LONG TERM...THURSDAY THROUGH SUNDAY. FORECAST CONFIDENCE LOW TO
MEDIUM.

IN SPITE OF FASTER PROGRESSION OF UPPER LOW VS GFS...ECMWF AND
CANADIAN DROP A SHORT WAVE TROUGH THROUGH WISCONSIN THURSDAY...SO
WILL KEEP POPS FOR THURSDAY/THURSDAY NIGHT. CYCLONIC FLOW STILL
CLIPPING EASTERN WISCONSIN ON FRIDAY...WITH A SHORT WAVE SLIDING
THRU SO HAVE TO LEAVE A SLIGHT CHANCE IN FOR FRIDAY...THOUGH
MAINLY FOR NORTHEAST CWA.  DRY WITH A SURFACE HIGH OVER WESTERN
GREAT LAKES SATURDAY. MODELS SHOWING A SHORT WAVE SUNDAY...MAINLY
EARLY BUT WITH EASTERLY SURFACE FEED OF DRY AIR AND DRY LOOK TO
FORECAST SOUNDINGS WILL NOT BRING IN ANY PRECIPITATION. 850 TEMPS
ON THE ECMWF FALL TO +5 TO +6C THURSDAY...BUT CANADIAN ONLY DIPS
TO +9C AT 12Z FRIDAY. A SLOW UPWARD TREND IN TEMPERATURES INTO THE
WEEKEND. WILL USE CONSENSUS BLEND FOR TEMPERATURES.

&&

.AVIATION...WITH SFC HIGH PRESSURE MOVING OVERHEAD...WINDS WILL BE
LIGHT OVERNIGHT WITH AN OVERALL EAST TO SOUTHEASTERLY COMPONENT. AT
LEAST IFR FOG WITH IFR CIGS EXPECTED TO DEVELOP LATE TONIGHT...BUT
CANNOT RULE OUT PATCHY DENSE FOG AND LOWER CIGS. DENSE FOG OVER LAKE
MI NEAR MILWAUKEE HAS THE POTENTIAL TO SPREAD INLAND AROUND SUNSET
THIS EVENING...SO MITCHELL FIELD COULD HAVE DENSE FOG FOR A PERIOD
OF TIME.

THUNDERSTORMS MAY DEVELOP LATE TONIGHT INTO MONDAY MORNING ALONG A
SHORTWAVE AS A WEAKENING LOW LEVEL JET AND CONVERGENCE SPREADS INTO
NRN IL/SRN WI AREA. NOT ENOUGH CONFIDENCE TO MENTION IT IN TAFS YET.

&&

.MARINE...DENSE FOG TO ABOUT 10 MILES OFFSHORE FROM SOUTHERN OZAUKEE
COUNTY TO RACINE COUNTY...DEDUCED BY VISIBLE SATELLITE ANIMATION AND
MILWAUKEE HARBOR WEBCAMS. DENSE FOG ADVY WILL BE EXPANDED UP TO
SHEBOYGAN...ALTHOUGH SHEBOYGAN WEBCAMS ARE CLEAR FOR NOW...AND ADVY
WILL BE EXTENDED THROUGH 9 PM. I DO NOT HAVE A GOOD FEEL FOR HOW
LONG THIS FOG WILL STICK AROUND. THE CONDITIONS ARE FAVORABLE FOR
DENSE FOG ANYWHERE ON THE LAKE WITH THE HIGH DEWPOINTS FLOWING INTO
THE AREA.

LATEST COAST WATCH AND MODIS IMAGERY HAS LAKE MI SFC TEMPS
MOSTLY IN THE MID 40S TO LOW 50S...CONFIRMED BY SRN LK MI BUOY.
STRONG WARM FRONT WELL TO THE SOUTH ALONG WITH HIGHER DEWPOINTS AND
LOW LEVEL HUMIDITY WILL GRADUALLY PUSH NORTHWARD OVER THE NEXT
SEVERAL DAYS INCREASING THE THREAT FOR DENSE FOG...ESPECIALLY
TONIGHT INTO TUE. CONVECTION CHANCES ALSO INCREASE AS THE WARM
FRONT APPROACHES.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...DENSE FOG ADVISORY UNTIL 10 PM CDT THIS EVENING FOR LMZ643>646.

&&

SHORT/LONG TERM...09/REM
VERY SHORT TERM/AVIATION/MARINE...13/MRC

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
148 PM CDT SUN JUN 19 2011

WIZ046-047-051-052-056>060-062>072-200930-
MARQUETTE-GREEN LAKE-FOND DU LAC-SHEBOYGAN-SAUK-COLUMBIA-DODGE-
WASHINGTON-OZAUKEE-IOWA-DANE-JEFFERSON-WAUKESHA-MILWAUKEE-
LAFAYETTE-GREEN-ROCK-WALWORTH-RACINE-KENOSHA-
148 PM CDT SUN JUN 19 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
WISCONSIN...SOUTH CENTRAL WISCONSIN AND SOUTHEAST WISCONSIN.

.DAY ONE...REST OF TODAY AND TONIGHT

INSTABILITY OVER SOUTHERN WISCONSIN MAY CAUSE WIDELY SCATTERED
THUNDERSTORMS THIS AFTERNOON.

A WARM FRONT LOCATED WELL TO THE SOUTH MAY ALSO TRIGGER
THUNDERSTORMS LATE TONIGHT OVER SOUTH CENTRAL WISCONSIN. THE
THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

STRENGTHENING LOW PRESSURE IN THE CENTRAL PLAINS ON MONDAY IS
EXPECTED TO MOVE SLOWLY NORTHWARD THROUGH WEDNESDAY. AN ASSOCIATED
WARM FRONT WILL APPROACH SOUTHERN WISCONSIN MONDAY AND MONDAY
NIGHT AND MOVE INTO THE AREA ON TUESDAY. THIS FRONT ALONG WITH
UNSTABLE CONDITIONS OVER SOUTHERN WISCONSIN WILL BRING SCATTERED
TO NUMEROUS THUNDERSTORMS TO THE AREA MONDAY INTO TUESDAY NIGHT.

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS ACROSS THE AREA
BOTH MONDAY AND TUESDAY. THE SEVERE WEATHER RISKS ON MONDAY WILL
BE LARGE HAIL AND DAMAGING WINDS. THE THREAT INCREASES FOR
TORNADOES ON TUESDAY AS THE LOW PRESSURE AREA MOVES THROUGH
MINNESOTA AND DRAGS A COOL FRONT THROUGH SOUTHERN WISCONSIN
INCREASING THE ATMOSPHERIC WIND SHEAR.

ISOLATED THUNDERSTORMS ARE POSSIBLE ON WEDNESDAY AS THE LOW
PRESSURE AREA WEAKENS...BUT LINGERS OVER WISCONSIN.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED MONDAY AND TUESDAY.

LMZ643>646-200930-
SHEBOYGAN TO PORT WASHINGTON WI-
PORT WASHINGTON TO NORTH POINT LIGHT WI-
NORTH POINT LIGHT TO WIND POINT WI-
WIND POINT WI TO WINTHROP HARBOR IL-
148 PM CDT SUN JUN 19 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE MICHIGAN.

.DAY ONE...REST OF TODAY AND TONIGHT

THERE IS A CHANCE FOR THUNDERSTORMS TODAY AS AN UPPER LEVEL
IMPULSE MOVES THROUGH WISCONSIN.

AREAS OF DENSE FOG DEVELOPED OVER THE NEARSHORE WATERS FROM PORT
WASHINGTON AND SOUTH AS MOIST AIR FLOWS OVER THE RELATIVELY COOL
WATER. A DENSE FOG ADVISORY IS IN EFFECT UNTIL 4 PM. PATCHY FOG MAY
PERSIST TONIGHT FOR ALL AREAS AS WARM...MOIST AIR CONTINUES TO PUSH
NORTHWARD INTO LAKE MICHIGAN.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

AN APPROACHING WARM FRONT AND LOW PRESSURE WILL BRING SCATTERED TO
NUMEROUS THUNDERSTORMS TO THE AREA MONDAY THROUGH TUESDAY NIGHT.
THERE IS A SLIGHT RISK FOR SEVERE WEATHER WITH THESE
THUNDERSTORMS.

INCREASINGLY WARM...MOIST AIR PUSHING ACROSS THE COOLER WATERS OF
LAKE MICHIGAN MAY CAUSE PATCHY DENSE FOG ON MONDAY AND TUESDAY.

ALSO...A TIGHTENING PRESSURE GRADIENT WILL CAUSE WINDS TO APPROACH
SMALL CRAFT ADVISORY LEVELS ON TUESDAY AND WEDNESDAY.

WWW.WEATHER.GOV/MKX

MRC