Metro all clear: PDS Tornado Watch SE MN & WI

Update 3:30pm:

Particularly Dangerous Situation tornado watch issued until 11pm for much of Wisconsin & southeast Minnesota.

Cities included in the watch are Rochester, Eau Claire, Menomonie, & La Crosse.

-Latest La Crosse radar loop

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This is a dangerous situation! A major tornado outbreak is possible/likely in Wisconsin through tonight.

-SPC

-La Corsse NWS

-Twin Cities NWS

URGENT – IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 120

NWS STORM PREDICTION CENTER NORMAN OK

320 PM CDT SUN APR 10 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

PARTS OF NORTHEAST IOWA

PARTS OF WESTERN NORTHERN MICHIGAN

SMALL PART OF SOUTHEAST MINNESOTA

MUCH OF WISCONSIN

LAKE SUPERIOR

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 320 PM UNTIL

1100 PM CDT.

…THIS IS A PARTICULARLY DANGEROUS SITUATION…

DESTRUCTIVE TORNADOES…LARGE HAIL TO 4 INCHES IN DIAMETER…

THUNDERSTORM WIND GUSTS TO 70 MPH…AND DANGEROUS LIGHTNING ARE

POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 105 STATUTE

MILES EAST AND WEST OF A LINE FROM 5 MILES NORTH NORTHWEST OF

IRONWOOD MICHIGAN TO 45 MILES SOUTH OF CAMP DOUGLAS WISCONSIN.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU0).

REMEMBER…A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS.

DISCUSSION…RAPID DEVELOPMENT OF SEVERE SUPERCELL THUNDERSTORMS

IMMINENT ALONG THE COLD FRONT FROM WI/MN BORDER INTO NERN IA. AIR

MASS HAS DESTABILIZED AHEAD OF FRONT WITH MLCAPES TO 2000

J/KG…COUPLED WITH A VERY INTENSE WIND FIELD WILL LEAD TO POTENTIAL

OF BOTH VERY LARGE HAIL AND TORNADOS WITH ANY SUPERCELL. THERE IS

THE THREAT OF LONG LIVED SUPERCELLS ALONG WITH STRONG/DAMAGING

TORNADOES.

PH

Update 3pm:

The threat for severe weather has shifted east today. The storms just took too long to develop, and now a cold front has pushed through the metro and runs from near Rochester to Hudson, WI.

Temps dropped 15 degrees at the Weather Lab in Deephaven from 74 to 59 between 1:30pm & 3pm Sunday.

The atmosphere has stabilized over the metro, but storms may still develop in southeast Minnesota and Wisconsin…with the most favored area along and east of a line from Rochester to Eau Claire.

SPC has shifted the risk area east accordingly.

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A band of showers and a few rumbles of thunder behind the front may still move through tonight into early Monday. Expect windy & colder conditions Monday, with a return to nice weather and highs in the 60s for Tuesday.

PH

Update 2:30pm:

Prime area for development appears to be from near Albert Lea to Stillwater in the next hour. See latest Twin Cities NWS forecast discussion text below…

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GOES 1km visible satellite & temps overlay shows best development potential in SE MN & Western WI.

PH

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN

218 PM CDT SUN APR 10 2011

.DISCUSSION…

.MESOSCALE…

CONDITIONS ARE COMING TOGETHER FOR CONVECTIVE INITIATION BY 330

PM…WITH RAPID DEVELOPMENT LIKELY AFTER…SOME OF WHICH IS

PROBABLE TO BE TORNADIC IN THE REGION. THE MOST FAVORED AREA IN

OUR CWA IS WESTERN WISCONSIN.

THE LATEST HAND SURFACE ANALYSIS DEPICTS THE PRIMARY SURFACE LOW

DEEPENING NEAR LAKE MILLE LACS WITH A STRONG WARM FRONT REACHING

EAST OF THERE AND A COLD FRONT EXTENDING DUE SOUTH…DRAPED ABOUT

30 MILES WEST OF I-35 /AND SEEN ON THE KMPX RADAR/. A SECONDARY

SURFACE CIRCULATION HAS BEEN ANALYZED ALL DAY ON THE COLD FRONT

AND IS APPROACHING MASON CITY. THIS IS OF PARTICULAR INTEREST AS

IT IS WHERE THE INHIBITION HAS RAPIDLY DECREASED…IN FACT THERE

IS NOW NONE ANALYZED OVER CENTRAL INTO NORTHERN IA ON THE LATEST

SPC MESOANALYSIS. JUST AHEAD OF THIS AREA IS POOLED 64-66 SURFACE

DEW POINTS AND ENHANCED MOISTURE CONVERGENCE. THIS AREA OF

SOUTHEAST MN IS ALSO AT THE NOSE OF A VERY STRONG MID-LEVEL JET

/90-100 KT AT 500MB PER PROFILERS AND SEEN ON WATER VAPOR/

ALLOWING FOR DEEPER ASCENT AND SHEAR…ALONG WITH FURTHER MID-

LEVEL COOLING. THE ELEVATED LAPSE RATES ARE ALREADY DRY ADIABATIC

PER THE 18Z MPX SOUNDING. SO THIS INDICATES THAT DEVELOPMENT

SHOULD BE RAPID ONCE THE SURFACE WARMTH AND MOISTURE CAN CONNECT

IN THE VERTICAL WITH SUCH LAPSE RATES. THE CURRENT HRRR AND VSREF

MODELS INDICATE THAT AROUND 330 PM IS THE FAVORED DEVELOPMENT

TIME…WITH THE AREA OF ALBERT LEA TO THE ST. CROIX RIVER VALLEY

MOST LIKELY. STORMS SHOULD EVOLVE TO THE NORTHEAST RAPIDLY. THE

DEEP LAYER SHEAR MAGNITUDE OF 60 TO 70 KTS AND THE FRONTAL

ORIENTATION FAVOR DISCRETE SUPERCELLS…WITH POSSIBLE SPLITS. THE

0-1KM SHEAR VALUES ARE AROUND 20 KTS RIGHT NOW ACROSS THE CWA WARM

SECTOR…AND ARE FORECAST TO INCREASE BY THE RUC TO 25-30 KTS OVER

THE EASTERN TWO TIERS OF COUNTIES. WITH OTHER PARAMETERS IN PLACE

OVER THAT AREA BETWEEN 3:30PM-6PM AND THE SECONDARY SURFACE LOW

MOVING THAT WAY…THAT LOCATION IS THE MOST FAVORED FOR TORNADOES

IN THE FORECAST AREA. EXPLICIT CONVECTIVE RUNS OF THE NMM AND HRRR

HAVE ALSO BEEN INDICATING WHAT APPEAR TO BE SUPERCELL STRUCTURES

NEAR LADYSMITH TO EAU CLAIRE IN THAT TIME. AS FOR OTHER

THREATS…THEY PRETTY MUCH ALL ARE IN PLAY AS DCAPE VALUES ARE

QUITE LARGE…AND THERE IS PLENTY OF INSTABILITY ABOVE -20C FOR

LARGE HAIL. WE HAVE ADAPTED A HIGH TEMPORAL RESOLUTION INTO THE

FORECAST GRIDS THROUGH EARLY EVENING…AND MENTIONED THE CHANCE

FOR TORNADOES IN THE EASTERN TWO TIERS OF COUNTIES…GIVEN IT IS

THE FIRST EVENT OF THE YEAR…ANOMALOUSLY EARLY…AND THAT THERE

ARE SOME PARAMETERS IN LINE FOR STRONG TORNADOES IN THAT AREA. THE

THREAT SHOULD BE EAST OF THE AREA BY 8 PM…POSSIBLY AS EARLY AS 6

PM.

Update 1:35pm:

Tornado watch likely by 2pm according to SPC mesoscale discussion!

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MESOSCALE DISCUSSION 0396

NWS STORM PREDICTION CENTER NORMAN OK

0130 PM CDT SUN APR 10 2011

AREAS AFFECTED…EXTREME SERN MN…NERN IA…NWRN IL AND MUCH OF WI

CONCERNING…SEVERE POTENTIAL…TORNADO WATCH LIKELY

VALID 101830Z – 102030Z

OUTBREAK OF SEVERE STORMS IS EXPECTED THIS AFTERNOON…INITIALLY

FROM ERN MN THROUGH NERN IA…THEN SPREADING RAPIDLY EWD THROUGH WI

AND EXTREME NWRN IL. SUPERCELLS WITH STRONG TORNADOES…VERY LARGE

HAIL AND DAMAGING WIND WILL BE THE MAIN THREATS. A TORNADO WATCH

WILL LIKELY BE ISSUED BY 20Z.

THIS AFTERNOON A COLD FRONT EXTENDS FROM A DEEP LOW PRESSURE AREA IN E-CNTRL MN SSWWD THROUGH SRN MN…NWRN IA INTO SERN NEB WITH A WARM

FRONT FROM THE SURFACE LOW IN E-CNTRL MN THROUGH NRN WI. THE LOW

WILL DEVELOP EWD TO NEAR THE WI BORDER BY 21Z. NEWD ADVECTION OF

HIGHER THETA-E AIR ALONG A STRONG SSWLY LLJ BENEATH EML PLUME /8.5

C/KM LAPSE RATES/ AND DIABATIC WARMING IS RESULTING IN NEWD

DESTABILIZATION WITH TIME. HOWEVER…THE BOUNDARY LAYER REMAINS

CAPPED BY THE WARM EML AS EVIDENCED BY 18Z MINNEAPOLIS SOUNDING.

UPPER JET IS SHIFTING NEWD INTO THE UPPER MS VALLEY. RAPID ACCAS

DEVELOPMENT RECENTLY OBSERVED FROM NERN IA THROUGH SWRN WI IS LIKELY INDICATIVE OF NEWD EXPANDING ZONE OF AGEOSTROPHIC FORCING WITHIN THE UPPER JET EXIT REGION. THIS FORCING IN CONJUNCTION WITH FRONTAL CONVERGENCE WILL LIKELY MAINTAIN A DEEPER ZONE OF ASCENT THAT SHOULD EVENTUALLY ERODE THE CAP ENOUGH FOR STORMS TO DEVELOP ALONG THE COLD FRONT FROM ERN MN INTO NERN IA. STORMS WILL LIKELY MAINTAIN DISCRETE MODES FOR SEVERAL HOURS AND WILL BE EMBEDDED WITHIN STRONG DEEP LAYER WIND AND VERTICAL SHEAR SUPPORTIVE OF SUPERCELLS. LARGEST HODOGRAPHS ARE EXPECTED ACROSS CNTRL THROUGH NRN WI WHERE NEAR SURFACE WINDS SHOULD REMAIN BACKED TO SLY EAST OF THE SURFACE LOW WITH 0-1 KM STORM RELATIVE HELICITY EXCEEDING 250 M2/S2. STORMS DEVELOPING WITHIN THIS ENVIRONMENT WILL LIKELY BECOME CAPABLE OF PRODUCING STRONG TORNADOES…VERY LARGE HAIL AND DAMAGING WIND.

..DIAL.. 04/10/2011

It looks like storms may develop rapidly this afternoon near the east metro and in southeast Minnesota into western Wisconsin. There is a moderate risk for severe weather and possibly some tornadoes.

Storm development could be rapid. No watches yet…but they could happen soon.

There is a moderate risk for severe storms from the east metro east into Wisconsin through tonight according to SPC.

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SPC: Moderate risk from metro east.

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Greatest tornado threat includes east metro & much of Wisconsin.

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Large hail likely with storms.

Stay tuned today as the severe weather threat unfolds.

-Twin Cities NWS

PH

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