Winter Storm in Wisconsin, April 10 to 11, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
337 PM CDT THU APR 10 2008

.DISCUSSION...
THE CHALLENGE WITH THE FORECAST IS CLEARLY THE IMPACT OF THE LATE
WINTER/EARLY SPRING SYSTEM THE NEXT 24 TO 36 HOURS.

GOES WV LOOP SHOWING AN EXTREMELY IMPRESSIVE UPPER LOW CENTERED
OVER KANSAS WITH A DRY MID-LEVEL PUNCH SURGING NORTHWARD ON 100+
KT 500MB WINDS INTO SRN MN. IN THE LAYER BELOW THIS...WARM AIR HAS
NOSED INTO THE FORECAST AREA ON ESE 750-925MB WINDS EARLIER TODAY.
PRECIP TYPE IN MN HAS BEEN PREDOMINATELY RAIN OR LIGHT SLEET.
TAMDAR SOUNDINGS AROUND NOON IN AND NEAR MSP SHOWED A WARM LAYER
BETWEEN 2 AND 5C WITHIN THE 2500 TO 7000 FT LAYER. DOPPLER BRIGHT
BANDING ALSO INDICATING MELTING AND FREEZING LAYERS NEAR THESE
HEIGHTS. THIS WARM LAYER IS ALSO VERY DRY ON THOSE SOUNDINGS AND
ON MODEL ANALYSIS. THUS..EVAPORATIVE COOLING WILL LIKELY BEGIN TO
TRANSITION SOME PRECIP TO SNOW...ESPECIALLY WEST OF A MORA TO
NEW ULM LINE BY MID-EVENING. THE U.S. HIGHWAY 8 CORRIDOR OF WI
ALSO IS LIKELY FAR ENOUGH NORTH FOR A MORE SIMPLE CHANGEOVER TO
SNOW. WINDS HAVE GUSTED TO 50 MPH IN PLACES OF SOUTH CTRL MN AND
EXPECT THAT TO CONTINUE INTO THIS EVE WITH ONLY A VERY SLOW
DECREASE AS LOW BECOMES STACKED AND DEEPENING CEASES.

THE SURGE OF PRECIP FROM SRN MN IS ON A NOSE OF HIGH 850-700MB
THETA-E WHICH WILL NOSE NORTHWARD THIS EVE WITH NEARLY FULL
COVERAGE OF PRECIP. MOISTURE CONVERGENCE IN THIS LAYER IS
SUBSTANTIAL OVER WEST CTRL MN...AGAIN THE AREA WHERE THE THERMAL
PROFILE FAVORS PREDOMINATELY ALL SNOW. BANDING-LIKE SIGNATURES
ALREADY SHOWING UP ON RADAR AND CROSS SECTIONS FROM GUIDANCE
INDICATE SOME INDUCED INSTABILITY FROM FRONTOGENESIS IS LIKELY.
MIXING RATIOS FEEDING IN RANGE FROM 4 TO 6 G/KG ON
GUIDANCE...HOWEVER THERE MAY SOME OF THIS TAKEN UP BY SFC BASED
AND ELEVATED CONVECTION ACROSS NRN MO AND INTO IA. PV SFCS
INDICATE A GREAT DEAL OF LATENT HEAT RELEASE THIS EVE TO OUR
SOUTH FROM THIS CONVECTION...WHICH COMBINED WITH DRY SLOT AND
ASSOCIATED LOSS OF ICE NUCLEI...MAY SIGNIFICANTLY LOWER SNOWFALL
AMOUNTS PREDICTED THIS EVE ACROSS CTRL MN AND THE AFOREMENTIONED
AREA OF WEST CTRL WI. THIS HAS ALREADY PROMPTED CHANGING A PORTION
OF THE WARNING TO AN ADVISORY. UNCERTAINTY CONTINUES FOR THE
EASTERN PORTION OF THE WARNING AS WELL...WITH A SHARP GRADIENT IN
SNOWFALLS LIKELY. THE TREND IS DOWN RIGHT NOW IN SNOWFALL AMOUNTS
FOR THE TWIN CITIES AND OTHER AREAS OF ERN AND SRN MN. THINGS
STILL LOOK ON PAR FOR WEST CTRL MN...WITH THE WINDS ALSO
GENERATING SOME BLOWING OF SNOW.

SOME ELEVATED CONVECTION LIKELY TO MAKE IT INTO FAR SOUTHEAST
FORECAST AREA TONIGHT GIVEN SATELLITE TRENDS AND SURGE OF
K-INDICES. THIS SHOULD ONLY OVERSPREAD THE AREAS WHERE LIQUID
PRECIP IS EXPECTED IN SOUTH CENTRAL MN AND SOUTH OF I-94 IN WEST
CTRL WI.

COME FRIDAY THE SYSTEM WILL SHIFT EASTWARD WITH A TROUGH OF WARM
AIR ALOFT /TROWAL/ WRAPPING AROUND AND INTO THE FORECAST AREA.
MOIST ASCENT ON THIS WILL HELP TO CONTINUE SNOW DURING THE DAY
FRIDAY AND WITH THE COOLING PROFILE SPREAD IT EAST SOUTHEAST
ACROSS THE FORECAST AREA. TOUGH TO SAY STILL AT THIS POINT IF ANY
OF THE SNOW ON FRI WILL BE HEAVY. THERE ARE SOME SIGNATURES OF
FORCING WITHIN THIS AREA OF DEFORMATION BUT THERE HAS BEEN LITTLE
AGREEMENT ON PLACEMENT OF THIS. DURING THE DAY FRIDAY A 2 TO 4
INCH ADDITIONAL SNOW LOOKS REASONABLE FOR CTRL AND ERN MN AND WRN
WI. AGAIN...FOR SEVERAL AREAS INCLUDING THE SOUTHEAST HALF OF THE
TWIN CITIES...THIS WILL BE THE BEST CHANCE FOR SNOW ACCUMULATION.
WINDS WILL CONTINUE ON FRI LEADING TO SOME BLOWING OF PRIMARILY
THE FALLING SNOW IN RURAL OPEN AREAS...FURTHER REDUCING
VISIBILITIES.

SNOW SHOULD WIND DOWN QUICKLY TO A MORE OF A LIGHT SNOW/SNOW
SHOWERS FRI NIGHT WITH WINDS CONTINUING INTO SAT. COLD AIR
ADVECTION AHEAD OF A CANADIAN HIGH WILL KEEP TEMPS BELOW NORMAL
THIS WEEKEND. SOME NEAR 20 DEGREE LOWS ARE EXPECTED IN WEST CTRL
AREAS OVER THE FRESH SNOW. BEYOND...HAVE GONE EASY WITH THE WARM-
UP THROUGH MON AND INTO TUES...WITH THE LARGEST H8 TEMP
STANDARDIZED ANOMALIES ABOVE NORMAL COMING ON WEDS. 60 DEGREES OR
NEAR IT LOOKS LIKE IT SHOULD BE BACK DURING THE MIDDLE OF NEXT
WEEK.

&&

.AVIATION.../18Z TAF ISSUANCE/
NOTABLE CHANGES HAVE BEEN MADE TO THE 18Z TAFS. 12Z MODEL DATA
AND RECENT OBSERVATIONS CONTINUED TO INDICATE THE POTENTIAL FOR A
PROLONGED PERIOD OF A RAIN...SNOW...AND EVEN LIGHT ICE
PELLETS...ACROSS MUCH OF CENTRAL MN AND WEST CENTRAL WI THIS
AFTERNOON AND EVENING...MAINLY AT KMSP/KEAU/KRNH...WHERE THE
PRECIPITATION TYPE MAY NOT TRANSITION TO PURELY SNOW UNTIL CLOSER
TO DAYBREAK FRIDAY. HOWEVER...FOLLOWING A BRIEF RAIN/SNOW MIX THIS
AFTERNOON...ALL SNOW SHOULD DOMINATE KAXN/KRWF/KSTC THIS EVENING
AND TONIGHT...WHERE REDUCTIONS OF CEILINGS/VISIBILITIES INTO THE
IFR/LIFR CATEGORIES WILL BE POSSIBLE MAINLY BETWEEN 02Z AND 12Z.
AT KMSP/KRNH/KEAU...MAINLY MVFR CONDITIONS ARE EXPECTED UNTIL LATE
TONIGHT.

STRONG NORTHEASTERLY WINDS SUSTAINED AT SPEEDS OF 20 TO 30
MPH...WITH GUSTS INTO THE UPPER 30S...WILL ALSO PREVAIL THROUGH
TONIGHT.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WIND ADVISORY UNTIL 10 PM CDT THIS EVENING FOR BLUE EARTH-
     FARIBAULT-FREEBORN-GOODHUE-LE SUEUR-RICE-STEELE-WASECA.

     WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 AM CDT SATURDAY
     FOR ANOKA-BENTON-CARVER-CHISAGO-DOUGLAS-HENNEPIN-ISANTI-
     KANABEC-MILLE LACS-MORRISON-SIBLEY-TODD.

     WINTER STORM WARNING UNTIL 7 AM CDT SATURDAY FOR CHIPPEWA-
     KANDIYOHI-LAC QUI PARLE-MCLEOD-MEEKER-POPE-REDWOOD-RENVILLE-
     SHERBURNE-STEARNS-STEVENS-SWIFT-WRIGHT-YELLOW MEDICINE.

     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM CDT
     SATURDAY FOR DAKOTA-RAMSEY-SCOTT-WASHINGTON.

     WINTER WEATHER ADVISORY UNTIL 7 AM CDT SATURDAY FOR BROWN-MARTIN-
     NICOLLET-WATONWAN.

WI...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 AM CDT SATURDAY
     FOR BARRON-POLK-RUSK.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
348 PM CDT THU APR 10 2008

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
111100-
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-
348 PM CDT THU APR 10 2008

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

.DAY ONE...TONIGHT

WINTER PRECIPITATION...IN THE FORM OF SNOW AND OCCASIONALLY SOME
LIGHT SLEET...WILL SPREAD OVER PORTIONS OF CENTRAL MINNESOTA AND
WEST CENTRAL WISCONSIN THIS EVENING. THE MAIN ACCUMULATIONS
TONIGHT ARE EXPECTED IN WESTERN AND PORTIONS OF CENTRAL
MINNESOTA...GENERALLY WEST OF A MORA TO REDWOOD FALLS LINE. IN
WEST CENTRAL WISCONSIN...SNOWFALL ACCUMULATIONS ARE EXPECTED TO BE
ALONG AND NORTH OF THE U.S. HIGHWAY 8 CORRIDOR. THIS WILL LIKELY
MAKE TRAVELING HAZARDOUS AT TIMES.

PATCHY BLOWING SNOW IS ALSO EXPECTED IN WESTERN AND CENTRAL
MINNESOTA OVERNIGHT TONIGHT.

SOME ISOLATED THUNDERSTORMS ARE EXPECTED IN SOUTH CENTRAL
MINNESOTA INTO PORTIONS OF WEST CENTRAL WISCONSIN FROM MID-EVENING
INTO OVERNIGHT. THIS MAY PRODUCE LOCALLY HEAVY RAIN.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

PRECIPITATION WILL CHANGE TO PREDOMINATELY SNOW BY MID TO LATE
FRIDAY MORNING ACROSS THE AREA. ADDITIONAL SNOWFALL ACCUMULATIONS
OF TWO TO FIVE INCHES ARE EXPECTED IN CENTRAL MINNESOTA AND WEST
CENTRAL WISCONSIN THROUGH EARLY FRIDAY EVENING. SOME PATCHY
BLOWING SNOW IS ALSO POSSIBLE IN RURAL OPEN AREAS. THIS WILL
LIKELY MAKE TRAVELING HAZARDOUS AT TIMES.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS AND SNOWFALL OBSERVERS ARE URGED TO REPORT SNOWFALL
AMOUNTS TO THE NATIONAL WEATHER SERVICE THROUGH FRIDAY.