Winter Storm in Minnesota, February 23 to 25, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
307 PM CST FRI FEB 23 2007

.SHORT TERM...TODAY THROUGH MONDAY

FORECAST CONCERNS THIS PACKAGE REMAIN ON PRECIPITATION TYPE AND
AMOUNTS THROUGH THE PERIOD.

18Z SURFACE ANALYSIS SHOWED LOW PRESSURE DEEPENING IN EASTERN WY/CO
WITH BEST PRESSURE FALLS INTO THE CENTRAL PLAINS. SFC WARM FRONT
EXTENDED FROM CENTRAL NEB INTO NORTHERN MO. HIGH PRESSURE RIDGE
EXTENDED FROM NORTHERN ONT THRU MI TO KY/TN. TIGHT PRESSURE GRADIENT
BETWEEN THE TWO EXTENDED FROM MAN/ND/MN SOUTH TO KS/OK/MO. SOUTH
OF THE WARM FRONT...BRISK SOUTH SFC WINDS IN SOUTHERN PLAINS AND 25-
40KTS OF FLOW PER WIND PROFILERS WERE BRINGING PLENTIFUL GULF
MOISTURE NORTHWARD WITH SFC DEW POINTS ALREADY NEAR 40F IN SOUTH-
CENTRAL NEB. NORTH OF THE WARM FRONT BRISK SOUTHEAST WINDS OUT OF
THE HIGH WERE KEEPING TEMPS ACROSS MUCH OF MN/IA/WI IN THE MID 20S
TO MID 30S. AREA RADARS SHOW EFFECTS OF STRONG WARM ADVECTION/
ISENTROPIC LIFT AND MOISTURE TRANSPORT ALOFT WITH WIDESPREAD RETURNS
OVER EASTERN MN/IA AND WESTERN WI. ONLY FEW REPORTS OF PRECIP SO
FAR...MAINLY IN CENTRAL IA WHERE EVEN A FEW LIGHTENING STRIKES
NOTED.

NO MAJOR ERRORS NOTED WITH 23/12Z NAM/GFS INITIALIZATIONS...AND
OFFER QUITE SIMILAR SOLUTIONS FOR TONIGHT INTO MON BUT FOR SOME
MESO-SCALE FORCING/LIFT AND QPF PRODUCTION DETAILS. DPROG/DT OF
500MB HGTS AT 23/12Z SHOWED GFS/NAM RUNS OF 21/12Z AND 22/12Z
VERIFIED QUITE WELL ACROSS NOAM/EASTERN PAC. FOR 00-36HRS MODELS
CONTINUE TO CONVERGE ON A COMMON SOLUTION OF THEIR EARLIER RUNS...
WITH GFS OFFERING THE BETTER RUN-TO-RUN CONSISTENCY AS THE UPPER LOW
MOVES TO NEAR KS CITY. FROM 36-60HRS MODEL CONSISTENCY REMAINS GOOD
AS THE UPPER LOW MOVES INTO SOUTHEAST IA. SOME MODEL DIFFERENCES...
TOWARD SLOWING AS THE NEXT PIECE OF ENERGY REACHES THE WEST COAST
AND MORE SHORTWAVE RIDGING OVER CO/WY/MT. IN THE 60-84HR TIME-FRAME
MODEL RUN-TO-RUN CONSISTENCY BREAKS DOWN A BIT WITH THE EVOLUTION OF
THE UPPER LOW/TROUGH OVER THE AREA AS IT FILLS. TREND IS TOWARD A
STRONGER PIECE OF ENERGY APPROACHING THE WEST COAST AT 84HRS AND
LINGERING A MORE PRONOUNCED UPPER TROUGH OVER THE AREA AT 84HRS.
CHECK OF OBS VS. MODEL DATA AT 18Z SHOWED BOTH NAM/GFS WITH GOOD
DEPICTIONS OF THE SFC MASS FIELDS...THOUGH NAM WAS BETTER WITH THE
MOISTURE PLUME COMING NORTH ACROSS OK/KS. WV IMAGERY SHOWED BOTH
NAM/GFS WITH GOOD DEPICTIONS OF THE SHORTWAVE ENERGY IN THE WESTERN
CONUS TROUGH...AND THE TROUGH NEAR 150W. HOWEVER NAM LOOKED OVERDONE
WITH A SHORTWAVE OVER NORTHEAST NM. BLEND OF NAM/GFS APPEARED BEST
WITH THE 12Z-18Z PRECIP ACROSS THE CONUS. NO CLEAR SIGNAL WHICH
MODEL TO FAVOR THIS CYCLE...THOUGH GFS HAS SHOWN THE BETTER RUN-TO-
RUN CONSISTENCY THE PAST COUPLE DAYS. BIGGEST IMPACT OF FAVORING NAM
OR GFS IS WITH QPF TONIGHT...AS MODELS SETTLE DOWN AND OFFER QUITE
SIMILAR QPF/SNOW TOTALS FOR SAT THRU SUN. GENERALLY FAVORED A
GFS/NAM COMPROMISE THRU THE PERIOD. FORECAST CONFIDENCE AVERAGE FOR
THE MESO-SCALE DETAILS BUT REMAINS GOOD FOR THE LARGE SCALE.

IN THE SHORT TERM...BIG QUESTION REMAINS RELATED TO QPF...NOT IF BUT
HOW MUCH OVER THE COURSE OF THE NEXT 48HRS AS A TWO-PRONGED WINTER
PRECIP EVENT UNFOLDS ACROSS THE AREA. STRONG SHORTWAVE ROUNDING THE
BASE OF THE WESTERN CONUS TROUGH AND CLOSES OFF AN UPPER LOW NEAR
THE OK PAN-HANDLE BY 12Z SAT WITH THE SFC LOW DEEPENING INTO
SOUTHWEST KS. INITIAL SHOT OF STRONG 850-700M WARM ADVECTION/
ISENTROPIC LIFT AND MOISTURE TRANSPORT/CONVERGENCE WELL AHEAD OF THE
SFC/UPPER LOW LIFTS ACROSS THE AREA TONIGHT. THIS ALONG WITH DECENT
850-700MB FN CONVERGENCE AND SOME LAYERED -EPV ABOVE IT FOR GOOD
VERTICAL MOTION RESPONSE FROM THE FORCING. PRECIPITABLE WATER VALUES
OF 0.50 TO 0.75 INCH AVAILABLE FOR THE FORCING/LIFT. MODELS DIFFER
ON THEIR QPF AMOUNTS/PLACEMENT TONIGHT...NAM HEAVIEST NORTHEAST
HALF OF THE FORECAST AREA...GFS HEAVIEST WEST END INTO CENTRAL WI.
GFS LOOKS TO SUFFER SOME CONVECTIVE FEEDBACK WITH ITS PRECIP BULLS-
EYE...BUT IT HAS BEEN VERY CONSISTENT WITH THIS SIGNAL THE PAST FEW
RUNS. 23/18Z NAM HAS A QPF LOOK VERY SIMILAR TO 12Z GFS FOR TONIGHT
WITH A BAND OF 1/2 TO 3/4 INCH OF QPF NEAR A KCCY-KLSE-KISW LINE.
SHORT-TERM FORECASTER ALREADY ADDRESSED MANY OF THE ISSUES WITH
PRECIP/PRECIP TYPES TONIGHT IN INTERMEDIATE AFDARX AT 23/1746Z...AND
EXPANDED WINTER STORM WARNING INTO THE NORTHEAST THIRD OF THE
FORECAST AREA. GIVEN THE STRONG 850MB WARM ADVECTION TONIGHT...TEMPS
IN THE 900-800MB LAYER FLIRT WITH OR NOSE ABOVE 0C ACROSS ABOUT THE
SOUTHWEST HALF OF THE FORECAST AREA. MIX OF -SN/IP/-FZRA THESE AREAS
CONTINUES TO LOOK GOOD...WITH POTENTIAL FOR SIGNIFICANT ICING SOUTH
OF A KAUM-KDBQ LINE WHERE DOMINANT PRECIP TYPE MAY BE -FZRA. FURTHER
NORTH/EAST MODEL SOUNDINGS SUPPORT ALL SNOW OR A MIX OF IP/SN...WITH
A RATHER TIGHT GRADIENT IN PRECIP TYPES. THIS BAND LIFTS OUT OF THE
NORTH END OF THE FORECAST AREA BY MID MORNING SAT. APPEARS MUCH OF
THE FORECAST AREA TO GET A 6 TO 9 HR BREAK FROM THE WINTRY PRECIP...
BEFORE THE MAIN SHOT ARRIVES SAT AFTERNOON THRU SAT EVENING. DEEP
LAYERED FORCING/LIFT MOVES ACROSS AS THE SFC/UPPER LOW APPROACH.
IMPRESSIVE 500-300MB PV ADVECTION AND 300MB AGEOSTROPHIC FLOW/
DIVERGENCE IN STRONGLY DIFLUENT FLOW ALOFT AHEAD OF THE UPPER LOW
PROGGED ACROSS THE AREA LATE SAT AFTERNOON THRU MUCH OF SAT NIGHT.
THIS OVER A NICE TROWAL SIGNATURE...DEEP LAYERED QG CONVERGENCE AND
MORE FN CONVERGENCE AND CONTINUED 850-700MB WARM ADVECTION. STRONG
MOISTURE TRANSPORT CONTINUES WITH PW/S OF 0.50 TO 0.80 INCH. SUITE
OF SHORT RANGE MODELS ALL PRODUCE 0.50 TO 1.25 INCHES OF QPF ACROSS
THE FORECAST AREA FROM LATE SAT AFTERNOON THRU SAT NIGHT. MODEL
SOUNDINGS STILL SUPPORT A WINTRY MIX OF PRECIP TYPES ACROSS THE
SOUTHERN THIRD OF THE FORECAST AREA SAT...BUT BY LATE SAT AFTERNOON
ALL SOUNDINGS INDICATE PRECIP AS SNOW. DID ADD RAIN MENTION TO AREAS
ALONG/SOUTH OF A KCCY-KOVS LINE WHERE TEMPS SAT MAY SNEAK A DEGREE
OR TWO ABOVE 32F ON SAT. WILL CONTINUE WINTER STORM WARNING ON SAT
FOR SIMPLICITY AT THIS POINT...DESPITE MODELS INDICATING THE BREAK
IN PRECIP BEFORE PART 2 ARRIVES. FORCING/LIFT WEAKEN THRU THE DAY ON
SUN...BUT ENOUGH CONVERGENCE/LIFT REMAIN WITH THE SFC-500MB TROUGH
AXIS OVER THE AREA FOR POTENTIAL OF ANOTHER 1-2 INCHES OF -SN. SHORT
RANGE MODELS REMAIN QUITE CONSISTENT WITH PRODUCING 1 TO 2 INCHES OF
QPF ACROSS MOST OF THE FORECAST AREA FROM TONIGHT THRU SUN. NORTH OF
A KRST-KOVS LINE THE BULK OF THIS LOOKS TO FALL AS SNOW...AND USING
A SNOW-WATER RATIO OF 11 TO 1 THIS EQUATES TO A FOOT OR MORE OF
SNOW. POTENTIAL EXISTS ALONG A ZUMBRO FALLS-LA CROSSE-MAUSTON LINE
FOR UP TO 18 INCHES OF SNOW. ON TOP OF THIS...PRESSURE GRADIENT
CONTINUES TO TIGHTEN UP OVER THE AREA THRU SAT AFTERNOON/NIGHT WITH
SUSTAINED WINDS OF 20-30 MPH AND GUSTS 35 TO 40 MPH. MAY YET NEED TO
UPGRADE SOME OF THE MORE WIND PRONE AREAS TO BLIZZARD WARNING FOR
LATE SAT/SAT NIGHT AS THESE WINDS BLOW THE SNOW AROUND CREATING NEAR
WHITE-OUT CONDITIONS.

FAVORED WARMER OF TEMP GUIDANCE TONIGHT/SAT NIGHT WITH CLOUD COVER
AND PRECIP. FAVORED COOLER GFS GUIDANCE HIGHS SAT/SUN WITH WHAT
SHOULD BE FRESH SNOWCOVER OR FALLING SNOW/PRECIP AND THE BRISK EAST
WINDS. FAVORED BLEND GUIDANCE LOWS SUN NIGHT...THEN HPC GUIDANCE
HIGHS FOR MON...ALL OF WHICH BLEND QUITE WELL WITH NEIGHBORING
GRIDS.

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY

NOT A LARGE AMOUNT OF TIME SPENT IN DAY 4-7 PORTION OF FORECAST TO
BETTER FOCUS ON DETAILS OF IMPENDING WINTER STORM IN SHORT TERM.
23/00Z GFS/ECMWF RUNS OFFER REASONABLY SIMILAR SOLUTIONS TO EACH
OTHER AND THEIR PREVIOUS RUNS IN THE TUE-THU TIME-FRAME. GOOD
OVERALL MODEL CONSENSUS THAT ANOTHER STRONG STORM SYSTEM WILL LIFT
THRU THE UPPER MIDWEST CENTERED ON THU. HOWEVER...GFS ENSEMBLES AND
MODELS FROM RUN-TO-RUN STILL OFFER PLENTY OF VARIABILITY WITH THE
DETAILS OF STRENGTH/TRACK OF THE SFC LOW AND LOW LEVEL THERMAL
PROFILES OVER THE AREA...WHICH LEAD TO PRECIP TYPE ISSUES...WITH
THIS NEXT STORM SYSTEM. DID NOT MAKE MANY CHANGES TO PREVIOUS DAY
TUE-THU GRIDS WHICH ALREADY HAD CHANCE -SN OR -RA FOR WED/THU. MAY
YET NEED CHANCE -SN ON FRI IF SYSTEM SLOWS. GIVEN ALL THE
VARIABILITY IN THE DETAILS...FORECAST CONFIDENCE AVERAGE IN THE
LONG-TERM PORTION OF THE FORECAST. GFS MEX/ENSEMBLE MOS AND HPC
GUIDANCE DID TREND MINS/MAXES DOWN 2 TO 4 DEGREES THRU MUCH OF THE
PERIOD...WHICH SEEMS REASONABLE OVER WHAT SHOULD BE PLENTIFUL SNOW
COVER FROM THE SAT/SUN SYSTEM. FAVORED A GFS/HPC TEMP GUIDANCE
COMPROMISE...WHICH BLENDS WELL WITH NEIGHBORING GRIDS.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST SUNDAY
     FOR WIZ017-WIZ029-WIZ032-WIZ033-WIZ034-WIZ041-WIZ042-WIZ043-
     WIZ044-WIZ053-WIZ054-WIZ055-WIZ061.

MN...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST SUNDAY
     FOR MNZ079-MNZ086-MNZ087-MNZ088-MNZ094-MNZ095-MNZ096.

IA...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST SUNDAY
     FOR IAZ008-IAZ009-IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030.

RRS

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE LA CROSSE WI
1240 PM CST FRI FEB 23 2007

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-032>034-
041>044-053>055-061-241100-
ADAMS-ALLAMAKEE-BUFFALO-CHICKASAW-CLARK-CLAYTON-CRAWFORD-DODGE-
FAYETTE-FILLMORE-FLOYD-GRANT-HOUSTON-HOWARD-JACKSON-JUNEAU-LA CROSSE-
MITCHELL-MONROE-MOWER-OLMSTED-RICHLAND-TAYLOR-TREMPEALEAU-VERNON-
WABASHA-WINNESHIEK-WINONA-
1240 PM CST FRI FEB 23 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF NORTHEAST IOWA...
SOUTHEAST MINNESOTA...AND SOUTHWEST INTO CENTRAL WISCONSIN.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SNOW WILL BEGIN TO BREAK OUT LATE THIS AFTERNOON OVER THE AREA...AND
INCREASE IN INTENSITY AND COVERAGE THROUGH THE EVENING. SNOW WILL
CONTINUE THROUGH MUCH OF TONIGHT. A MIX OF SNOW...SLEET...AND
FREEZING RAIN IS POSSIBLE ALONG AND SOUTH OF A LINE FROM DODGE
CENTER THROUGH LANSING IOWA. SNOWFALL ACCUMULATIONS TONIGHT WILL
RANGE FROM 2 TO 5 INCHES OVER MUCH OF THE AREA...PARTICULARLY FROM
WINONA THROUGH LA CROSSE AND SPARTA. WHERE FREEZING RAIN OR SLEET
MIXES IN OVER NORTHEAST IOWA AND OTHER ADJACENT PORTIONS OF
SOUTHEAST MINNESOTA...ACCUMULATIONS WILL BE LESS...GENERALLY 1 TO 3
INCHES...WITH UP TO A TENTH OR TWO TENTHS OF AN INCH OF ICE.
SOUTHEAST WINDS OF 15 TO 30 MPH WILL CAUSE SOME BLOWING AND
DRIFTING OF THE SNOW. REFERENCE THE LATEST FORECAST...AND WINTER
WEATHER STATEMENTS FROM THE NATIONAL WEATHER SERVICE FOR DETAILS IN
YOUR PARTICULAR AREA.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

SNOW...OR A MIX OF SNOW...FREEZING RAIN AND SLEET WILL CONTINUE
ACROSS THE AREA ON SATURDAY...BECOMING HEAVY SATURDAY NIGHT WHEN
THE MOST SIGNIFICANT ACCUMULATIONS WILL OCCUR.  SIGNIFICANT ICE
ACCUMULATIONS WILL BE POSSIBLE ALONG AND SOUTH OF A AUSTIN TO
OELWEIN LINE SATURDAY AFTERNOON...BEFORE ALL PRECIPITATION CHANGES
OVER TO SNOW. STORM TOTAL SNOWFALL FOR THE ENTIRE EVENT...WILL
RANGE FROM 8 TO 12 AREAS IN MOST AREAS...THOUGH SIGNIFICANTLY LOWER
FOR ANY AREAS WHICH STAY FREEZING RAIN OR SLEET FOR A LONGER PERIOD
OF TIME.

AN ADDED COMPONENT OF THIS STORM WILL BE VERY STRONG EAST TO
SOUTHEAST WINDS...FROM 25 TO 35 MPH SATURDAY AFTERNOON AND NIGHT.
THIS WILL CAUSE NEAR WHITEOUT CONDITIONS...WITH THE POTENTIAL FOR
BLIZZARD CONDITIONS ACROSS THE AREA SATURDAY NIGHT BEFORE THE WINDS
RELAX INTO SUNDAY. THIS MAY ALSO CAUSE SIGNIFICANT PROBLEMS FOR ANY
AREAS RECEIVING ICE ACCUMULATIONS...WITH POWER LINES AND BRANCHES
COMING DOWN. THIS WOULD BE A GREATER THREAT FOR NORTHEAST IOWA INTO
ADJACENT PORTIONS OF SOUTHEAST MINNESOTA.

THIS SYSTEM HAS THE POTENTIAL TO BE A HIGH IMPACT...CRIPPLING STORM
VIA SNOW...ICE...AND HIGH WINDS. STAY TUNED TO LATER FORECASTS AND
STATEMENTS FOR SPECIFICS AND SNOWFALL AMOUNTS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED. HOWEVER...REPORTS OF
PRECIPITATION TYPE AND AMOUNTS WOULD BE GREATLY APPRECIATED THIS
WEEKEND.

.EMERGENCY MANAGEMENT COORDINATION...

A CONFERENCE CALL IS SCHEDULED FOR 1 PM THIS AFTERNOON.

BINAU