Extreme Cold in Iowa, February 10, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1051 PM CST SAT FEB 9 2008

.UPDATE...

COUNTY SHERIFF DEPARTMENTS IN THE WIND PRONE COUNTIES OF SOUTHEAST
MINNESOTA REPORT THAT THE VISIBILITY IS NO LONGER BEING REDUCED
THAT MUCH FROM BLOWING SNOW. AIRPORT BASED SURFACE OBSERVATIONS
FROM THESE AREAS STILL SHOW SOME REDUCE VISIBILITIES
OCCURRING...BUT BASED ON THE INFORMATION FROM THE SHERIFFS PLAN TO
LET THE WINTER WEATHER ADVISORY EXPIRE AT MIDNIGHT AS SCHEDULED.
WILL KEEP A MENTION OF PATCHY BLOWING SNOW IN THE ZONES FOR
SOUTHEAST MINNESOTA FOR THE REMAINDER OF THE NIGHT.

04

&&

.PREV DISCUSSION... /ISSUED 336 PM CST SAT FEB 9 2008/

SHORT TERM...TONIGHT THROUGH MONDAY NIGHT

VERY DANGEROUS WIND CHILLS AND STRONG WINDS ARE THE MAIN CONCERNS
TONIGHT AND SUNDAY MORNING...AND HOW MUCH SNOW WILL FALL FROM
SUNDAY NIGHT INTO MONDAY NIGHT ARE THE MAIN CONCERNS WITH THIS
PART OF THE FORECAST.

AT 230 PM...THE ARCTIC COLD FRONT EXTENDED FROM MEDFORD SOUTHWEST
THROUGH LA CROSSE AND OELWEIN IOWA. WITH AROUND 5 MICROBARS OF OMEGA
AND STRONG FRONTOGENETIC FORCING ALONG AND AHEAD OF THIS FRONT...
MODERATE TO BRIEFLY HEAVY SNOW DEVELOPED ALONG IT. MOST OF THE SNOW
TOTALS HAVE BEEN RUNNING AROUND AN INCH OF LESS. AT THE PRESENT
SPEED...THIS FRONT SHOULD BE CLOSE TO EXITING THE EASTERN FORECAST
AREA BY THIS EVENING...SO JUST RAN THE ZONES BEGINNING WITH
TONIGHT. WE WILL HANDLE THE REMAINING SNOWFALL WITH SHORT TERM
FORECASTS.

THE BIGGEST STORY FOR TONIGHT WILL BE THE FALLING TEMPERATURES...
STRONG NORTHWEST WINDS...AND VERY DANGEROUS WIND CHILLS. THE
MODELS CONTINUE TO SHOW THAT THERE WILL BE RAPID DECLINE IN THE
TEMPERATURES LATE THIS AFTERNOON AND EVENING. DESPITE STRONG
NORTHWEST WINDS...THE TEMPERATURES WILL CONTINUE TO FALL...BUT AT
A SLIGHTLY SLOWER DECLINE OVERNIGHT. BY SUNDAY MORNING...THE LOW
TEMPERATURES WILL RANGE FROM 10 TO 20 BELOW. THERE MAY BE EVEN A
FEW PLACES COLDER ACROSS NORTH CENTRAL AND CENTRAL WISCONSIN.

IN ADDITION TO THESE BITTERLY COLD TEMPERATURES...THE SURFACE
PRESSURE GRADIENT BEHIND THE COLD FRONT IS SUPPORTIVE OF STRONG
NORTHWEST WINDS IN THE 25 TO 35 MPH RANGE. WITH UNIDIRECTIONAL FLOW
ALOFT...STRONG SUBSIDENCE...AND A TROPOSPHERIC FOLD ASCENDING DOWN
TO 600 MB MOVING THROUGH TONIGHT...THERE WILL LIKELY BE A GOOD
TRANSPORT OF THE STRONG WINDS FROM ALOFT TO THE SURFACE. WIND
GUSTS WILL LIKELY BE UP AROUND 45 MPH. THIS WILL LIKELY CAUSE SOME
BLOWING AND DRIFTING OF THE NEWLY FALLEN SNOW THIS EVENING AND
DURING THE EARLY PART OF THE OVERNIGHT. THIS MAY CAUSE SOME BRIEF
WHITE OUT CONDITIONS ACROSS SOUTHEAST MINNESOTA...NORTHEAST IOWA...AND
IN GRANT COUNTY IN SOUTHWEST WISCONSIN. AS A RESULT OF THIS AND
WIND CHILLS BETWEEN 20 AND 35 BELOW...WE WILL KEEP THE WINTER
WEATHER ADVISORY GOING FOR THE ENTIRE AREA.

THE COMBINATION OF THE STRONG WINDS AND BITTERLY COLD TEMPERATURES
WILL RESULT IN VERY DANGEROUS WIND CHILLS OVERNIGHT. WIND CHILLS
THROUGH MUCH OF THE OVERNIGHT AND SUNDAY MORNING WILL BE IN THE 40
TO 45 BELOW RANGE RANGE. WIND CHILLS THIS COLD WILL FREEZE EXPOSED
SKIN IN LESS THAN 10 MINUTES. THIS IS ALSO A VERY DANGEROUS
SITUATION FOR OUTDOOR PETS. IF POSSIBLE...TRY AND GET THEM INTO
AN AREA AWAY FROM THE WIND AND COLD. ALSO GIVE THEM SOME EXTRA
FOOD AND MAKE SURE THEY HAVE PLENTY OF WATER. IT APPEARS THAT THE WIND
SPEEDS MAY LINGER LONGER THAN WE INITIALLY ANTICIPATED ON SUNDAY
AFTERNOON. IF THIS TREND CONTINUES...WE MAY HAVE ISSUE A WIND
CHILL ADVISORY FOR SUNDAY AFTERNOON.

FINALLY FOR TONIGHT...THE CLOUDS FORECAST IS RATHER TRICKY FOR
THIS EVENING. THE MODELS CONTINUE TO SHOW THAT THERE WILL BE QUITE
A BIT OF LOW LEVEL MOISTURE TRAPPED BELOW THE 900 MB SUBSIDENCE
INVERSION. HOWEVER LOOKING UPSTREAM ACROSS CENTRAL MINNESOTA MANY
OF THESE LOW CLOUDS HAVE ALREADY CLEARED OUT. HOWEVER THERE IS ONE
ADDITIONAL PATCH OF LOW CLOUDS ACROSS EASTERN NORTH DAKOTA AND
NORTHWEST MINNESOTA. AS A RESULT...I WENT IN MANY PLACES WITH A
PARTLY CLOUDY EVENING...AND A MOSTLY CLEAR TONIGHT.

ON SUNDAY NIGHT...SOME WEAK WARM AIR ADVECTION STARTS TO DEVELOP
ACROSS MINNESOTA AND IOWA AS A SHORT WAVE TROUGH APPROACHES THE
AREA FROM THE DAKOTAS. THE GFS CONTINUE TO BE THE ONLY MODEL WHICH
GENERATES ANY PRECIPITATION ACROSS SOUTHEAST MINNESOTA AND
NORTHEAST IOWA. SINCE THIS HAS BEEN A RATHER CONSISTENT SIGNAL...I
INTRODUCED A SMALL SNOW CHANCE FOR THE OVERNIGHT.

ON MONDAY AND MONDAY NIGHT...THE MODELS CONTINUE TO BE IN VERY
GOOD AGREEMENT THAT A STRONG SHORT WAVE TROUGH WILL MOVE THROUGH
THE UPPER MISSISSIPPI RIVER VALLEY. THIS SYSTEM WILL ENHANCE THE
WARM AIR AND MOISTURE ADVECTION BACK INTO THE REGION. IT ALSO
DRAWS MOISTURE INTO THE AREA FROM A SYSTEM PASSING TO OUR SOUTH.
BOTH MODELS SHOW THAT WE WILL SEE PRECIPITATION RANGING FROM 0.15
TO AROUND A 0.25 INCH DURING THIS TIME PERIOD. IN ADDITION...THERE
IS SOME MODERATE TO STRONG OMEGA NEAR THE -15C ISOTHERM. THIS
SYSTEM REMINDS ME A LOT OF THE LOW PRESSURE SYSTEM THAT BROUGHT
THE 8.5 INCHES OF VERY FLUFFY SNOW TO LA CROSSE FROM JANUARY
21-22. THE SNOW TO WATER EQUIVALENT WITH THAT SYSTEM WAS AROUND
30 TO 1 WITH THAT SYSTEM. THE LATEST COBB OUTPUT IS SHOWING SNOW
TO LIQUID WATER RATIOS OF AROUND 18 TO 1. THIS WOULD AMOUNT TO
3 TO 5 INCHES OF SNOW. CLEARLY IN THE RANGE OF A SNOW ADVISORY. FOR
THE TIME BEING...I HAVE RAISED THE SNOW CHANCES INTO THE LIKELY
RANGE AND ADDED THE MENTION OF SNOW ACCUMULATIONS. IF THIS TREND
CONTINUES...WE WILL LIKELY HAVE TO RAISE THE SNOW CHANCES EVEN
FURTHER AND MAY HAVE TO EVENTUALLY GO OUT WITH A SNOW ADVISORY.

LONG TERM...TUESDAY THROUGH SATURDAY

ANOTHER STRONG SHORT WAVE TROUGH WILL MOVE THROUGH INTO THE
NORTHERN PLAINS ON WEDNESDAY. THIS SYSTEM WILL CAUSE THE ARCTIC
COLD FRONT TO RETURN SOUTHWARD INTO THE AREA. THIS FRONT WILL ACT
AS THE FOCUS FOR AN INTENSIFICATION OF THE FRONTOGENESIS AT BOTH
THE SURFACE AND ALOFT. IN ADDITION...THE GULF OF MEXICO MOISTURE
WILL BE SURGING NORTHWARD TOWARD THE REGION. THE GFS AND ECMWF
HAVE HAD DIFFERING SOLUTIONS ON THIS SYSTEM FOR THE LAST COUPLE OF
DAYS. AS A RESULT...I HAVE ONLY WENT WITH LOW CHANCES OF SNOW.
HOWEVER BOTH THE 12Z SOLUTIONS OF BOTH MODELS HAVE COME A
CONSENSUS THAT OUR AREA MAY BE UNDER THE GUN FOR ADDITIONAL
ACCUMULATING SNOW. THE LATEST GUIDANCE SUGGEST THAT TOTALS MAY BE
IN THE EXCESS OF 6 INCHES. THIS SYSTEM LOOKS LIKE YET ANOTHER
STORM SYSTEM THAT WE WILL HAVE TO WATCH THIS WEEK.

BEHIND THIS STORM SYSTEM IT LOOKS LIKE WE WILL ONCE AGAIN SEE A
PLUNGE OF ARCTIC AIR INTO THE REGION FOR FRIDAY INTO SATURDAY. THE MAIN
QUESTION WITH THIS IS HOW COLD THIS AIR MASS MAY BE. HPC GUIDANCE
WAS WAY TO WEIGHTED TOWARD THE 00Z ECMWF...SO IT WAS CONSENSUS BY
US AND THE SURROUNDING OFFICES TO GO AT LEAST 3 TO 4F COLDER THAN
THEM DURING THIS PERIOD.

AVIATION...LATE THIS AFTERNOON THROUGH SUNDAY MORNING

AS AN ARCTIC COLD FRONT EXITS...IFR/MVFR CONDITIONS IN SNOW AND
BLOWING SNOW EXPECTED TO IMPROVE BETWEEN 21Z-03Z THIS EVENING.
HOWEVER...STRONG NORTHWEST WINDS WITH GUSTS AROUND 35KTS WILL
CONTINUE THROUGH THE NIGHT...BEFORE SUBSIDING SUNDAY MORNING.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WIND CHILL WARNING UNTIL 12 PM CST SUNDAY FOR WIZ017-WIZ029-
     WIZ032-WIZ033-WIZ034-WIZ041-WIZ042-WIZ043-WIZ044-WIZ053-
     WIZ054-WIZ055-WIZ061.

MN...WIND CHILL WARNING UNTIL 12 PM CST SUNDAY FOR MNZ079-MNZ086-
     MNZ087-MNZ088-MNZ094-MNZ095-MNZ096.

IA...WIND CHILL WARNING UNTIL 12 PM CST SUNDAY FOR IAZ008-IAZ009-
     IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030.

&&

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE LA CROSSE WI
340 PM CST SAT FEB 9 2008

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-032>034-
041>044-053>055-061-101100-
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-
340 PM CST SAT FEB 9 2008

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

.DAY ONE...TONIGHT

DANGEROUS WIND CHILLS OF 35 TO 45 BELOW WILL DEVELOP TONIGHT...
AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS THE NORTHERN GREAT
LAKES. FROST BITE CAN DEVELOP IN AS LITTLE AS 10 MINUTES WITH WIND
CHILLS THIS COLD.

STRONG NORTHWEST WINDS OF 25 TO 35 MPH...WITH HIGHER GUSTS...WILL
CAUSE SOME BLOWING AND DRIFTING SNOW. THIS SHOULD BE ESPECIALLY THE
CASE IN OPEN AND UNSHELTERED AREAS OF SOUTHEAST MINNESOTA AND
NORTHEAST IOWA...AND ALONG THE RIDGETOPS OF SOUTHWEST WISCONSIN.

WINTER WEATHER HEADLINES ARE IN EFFECT TONIGHT INTO SUNDAY MORNING
TO ACCOUNT FOR THESE DANGEROUS WINTER CONDITIONS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

DANGEROUS WIND CHILLS WILL LINGER SUNDAY MORNING...IN THE 35 TO 45
BELOW RANGE. CONDITIONS WILL IMPROVE BY THE AFTERNOON THOUGH...AS THE
WINDS DECREASE AND TEMPERATURES MODERATE.

NEXT...AN UPPER AIR DISTURBANCE WILL BRING SNOW CHANCES BACK TO THE
REGION FOR MONDAY INTO TUESDAY. SOME ACCUMULATIONS APPEAR POSSIBLE
AT THIS TIME. ANOTHER DISTURBANCE WILL BRING MORE SNOW CHANCES FOR
WEDNESDAY NIGHT INTO THURSDAY.

.SPOTTER INFORMATION STATEMENT...

ANY SNOWFALL OR WIND GUST REPORTS WOULD BE APPRECIATED.
OTHERWISE...SPOTTER ACTIVATION WILL NOT BE NEEDED.

.EMERGENCY MANAGEMENT COORDINATION...

NO CALL IS SCHEDULED.

THOMPSON