Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 010501
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1100 PM CST SAT JAN 31 2015

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 350 PM CST SAT JAN 31 2015

AT 3 PM...A CANADIAN COLD FRONT HAD MOVED SOUTH INTO NORTHEAST
IOWA AND SOUTHWEST WISCONSIN. NORTH WINDS IN THE WAKE OF THIS
FRONT HAVE BEEN BRINGING DRY AIR INTO THE REGION. SURFACE DEW
POINTS WERE IN THE TEENS ALONG AND NORTH OF INTERSTATE 94...AND IN
THE 20S ACROSS THE REMAINDER OF THE AREA. MEANWHILE FURTHER TO THE
WEST AND SOUTHWEST...A WARM FRONT WAS ADVANCING SLOWLY NORTH
ACROSS NORTH CENTRAL AND NORTHWEST IOWA. DEW POINTS ACROSS CENTRAL
IOWA HAVE CLIMBED INTO THE MID 30S.

FOR THIS EVENING...THE 900 TO 800 MB FRONTOGENESIS WILL
DRAMATICALLY INCREASE ACROSS NORTHERN IOWA...FAR SOUTHERN
WISCONSIN...AND NORTHERN ILLINOIS AS A SHORT WAVE TROUGH MOVES
SLOWLY EAST ACROSS THE CENTRAL PLAINS. AS THIS OCCURS...EXPECT A
SNOW BAND TO DEVELOP ACROSS THE AFOREMENTIONED AREAS LATE THIS
AFTERNOON/EARLY EVENING AND THEN MOVE SLOWLY NORTH INTO THE
INTERSTATE 90 CORRIDOR BY MID TO LATE EVENING. AT THE SAME
TIME...DRY AIR WILL STILL BE ADVECTING SOUTH INTO THE AREAS NORTH
OF THE INTERSTATE 90 CORRIDOR. THIS WILL GREATLY LIMIT THE
NORTHWARD EXPANSION OF THE SNOW. THE HOP WRF...ARW...RAP...AND NMM
SEEM TO HAVE A VERY GOOD HANDLE ON ITS NORTHWARD PROGRESSION SO
FOLLOWED THEM CLOSELY. SOUNDINGS CONTINUE TO SHOW THAT THE
TEMPERATURE PROFILES WILL BE ONLY IN THE DENDRITIC GROWTH ZONE FOR
50 TO 100 MB. AS A RESULT...EXPECT SNOW TO LIQUID RATIOS TO BE IN
THE 10-13 TO 1 RANGE. THROUGH MIDNIGHT...SNOW AMOUNTS WILL RANGE
UP TO A HALF NEAR INTERSTATE 90...TO 1 TO 3 INCHES ACROSS
NORTHEAST IOWA AND SOUTHWEST WISCONSIN.

FOR OVERNIGHT...THE MODELS ARE IN GENERAL AGREEMENT AS THE WEAK
SURFACE LOW MOVES EAST TO KANSAS CITY THAT SOME WEAK 925 AND 850
MB MOISTURE TRANSPORT WILL MOVE NORTHWARD INTO AREAS GENERALLY
SOUTH OF INTERSTATE 94. AS THE 925 AND 850 MB WINDS BECOME EAST
AND SOUTHEAST...THE NORTHERN EXTENT OF SNOW SHOULD SHIFT NORTHWARD
TO NEAR THE INTERSTATE 94 CORRIDOR. WHILE THE MODELS ARE SHOWING
THIS...WE WILL HAVE TO MONITOR THE 90 AND 94 CORRIDORS CLOSELY TO
SEE WHETHER THIS DOES IN DEED OCCURS. IN ADDITION...THE MUCH OF
THE FRONTOGENESIS WILL REMAIN ACROSS NORTHEAST IOWA AND SOUTHWEST
WISCONSIN. THE COMBINATION OF THE DRY AIR AND THE BEST FORCING
SOUTH MAY HAVE IMPACT OF THE QPF ALONG AND NORTH OF INTERSTATE
90. AS A RESULT...THERE WAS A SLIGHT DECREASE NOTED IN THE 31.15Z
SREF QPF AMOUNTS AT BOTH LA CROSSE AND ROCHESTER. AS THE ARCTIC
COLD FRONT...CURRENTLY OVER NORTHERN MINNESOTA...MOVES SOUTH OVER
OVERNIGHT THE AIR MASS WILL COOL. THIS WILL ALLOW A SLIGHT
INCREASE IN HOW MUCH OF THE TEMPERATURE PROFILE IS LOCATED IN THE
DENDRITIC GROWTH ZONE. AS A RESULT...INCREASED SNOW TO LIQUID
RATIOS INTO THE 12-16 TO 1 RANGE. FROM MIDNIGHT THROUGH 6 AM...
SNOW TOTALS WILL LIKELY RANGE UP TO 2 INCHES BETWEEN INTERSTATE 90
AND 94...AND 2 TO 4 INCHES ACROSS SOUTHWEST WISCONSIN AND
NORTHEAST IOWA.

ON SUNDAY MORNING...MUCH OF THE 925 MB AND 850 MB MOISTURE
TRANSPORT WILL MOVE EAST INTO FAR SOUTHERN LOWER MICHIGAN AND
NORTHERN PORTIONS OF ILLINOIS...INDIANA...AND OHIO. IN
ADDITION...THE UPPER LEVEL DIVERGENCE WILL BE DECREASING AS A
140 KNOT 250 MB JET MOVES EAST INTO EASTERN ONTARIO. THIS WILL
RESULT IN LESS QPF DURING THIS TIME PERIOD. HOWEVER AT THE SAME
TIME...THE ARCTIC COLD FRONT WILL BE MOVING SOUTH INTO CENTRAL
IOWA AND NORTHERN ILLINOIS. THIS WILL COOL THE TEMPERATURE PROFILE
EVEN FURTHER. WHILE THERE WILL BE 200 TO 300 MB IN THE FAVORABLE
DENDRITIC GROWTH ZONE...ONLY THE ABOUT HALF OF THIS WILL BE
CO-LOCATED WITH OMEGA. AS RESULT...THE SNOW TO LIQUID RATIOS WILL
NOT BE QUITE AS HIGH AS THEY POTENTIALLY WOULD BE. AS A RESULT...
ONLY INCREASED THE SNOW TO LIQUID RATIOS INTO THE 15-17 TO 1
RATIO. FROM 6 AM TO NOON...SNOW TOTALS WILL BE UP TO AN INCH ALONG
AND NORTH OF INTERSTATE 90...AND 1 TO 2 INCHES ACROSS NORTHEAST
IOWA AND SOUTHWEST WISCONSIN.

ON SUNDAY AFTERNOON...AN INVERTED TROUGH TRAILING THE DEEPENING
LOW OVER THE OHIO RIVER VALLEY WILL CONTINUE TO PRODUCE LIGHT SNOW
FOR AREAS ALONG AND SOUTH OF INTERSTATE 90. WHILE THE QPF WILL BE
LESS THAN A TENTH OF AN INCH. HIGHER SNOW TO LIQUID RATIOS /15-20
TO 1/ WILL PRODUCE A FEW TENTHS OF AN INCH NEAR INTERSTATE 90 AND
UP TO AN INCH FOR NORTHEAST IOWA AND SOUTHWEST WISCONSIN.

SNOW TOTALS FOR THIS EVENT LOOK TO BE AROUND AN IN NEAR INTERSTATE
94...1 TO 4 INCHES NEAR INTERSTATE 90 /HIGHEST UNCERTAINTY DUE TO
UNCERTAINTY ON THE INFLUENCE OF THE DRY AIR - THIS IS ALSO WHY WE
DID NOT EXPAND THE WINTER WEATHER ADVISORY INTO THIS AREA/...3 TO
7 INCHES NEAR THE MINNESOTA IOWA BORDER EAST...AND 7 TO 10 INCHES
ACROSS NORTHEAST IOWA AND SOUTHWEST WISCONSIN.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 350 PM CST SAT JAN 31 2015

ON MONDAY NIGHT...AND FROM TUESDAY AFTERNOON INTO TUESDAY
NIGHT...THE MODELS CONTINUE TO STRUGGLE ON THE LOCATION OF THE
BAROCLINIC ZONE. AS A RESULT...THE MODELS HAVE BEEN HAVING ISSUES
ON WHERE THESE SNOW BANDS WILL OCCUR. WHILE THERE HAS BEEN ISSUES
ON PLACEMENT...THE AMOUNT OF MOISTURE ASSOCIATED WITH THE SYSTEM
LOOKS LOW...SO ONLY EXPECTING UP TO AN INCH WITH EACH SYSTEM.

ON FRIDAY NIGHT AND SATURDAY...THE 31.12Z MODELS ARE NOW SHOWING
THAT STRONG WARM AIR ADVECTION WILL DEVELOP AHEAD OF AN
APPROACHING SHORT WAVE AND A RETREATING ARCTIC COLD FRONT. WHILE
THERE IS GOOD AGREEMENT BETWEEN THE OPERATIONAL GFS AND
ECMWF...THE 31.00Z ECMWF 50 MEMBER ENSEMBLE IS NOT IN THAT GOOD
AGREEMENT. AS A RESULT...JUST KEPT THE PRECIPITATION LOWER THAN
NORMALLY WOULD OCCUR WHEN THERE IS GOOD AGREEMENT BETWEEN THE
OPERATIONAL GFS AND ECMWF.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1100 PM CST SAT JAN 31 2015

SNOW HAS MOVED IN WITH DROPPING CIGS AND VSBYS. EXPECT KRST/KLSE TO
HOVER IN THE 1-2SM RANGE MOST OF THE TIME...WITH SOME DIP TO 1/2-
3/4SM AT KRST FROM TIME TO TIME. CIGS SHOULD HOLD NEAR 1 KFT...KRST
MOSTLY BELOW AND KLSE MOSTLY ABOVE.

THE BULK OF THE HEAVIER SNOWS WILL FALL THROUGH MID MORNING
SUNDAY...WITH GRADUAL IMPROVEMENT THROUGH THE REST OF THE DAY.
AMOUNTS NEAR 4 INCHES APPEAR LIKELY AT THIS TIME.

INCREASING PRESSURE GRADIENT WILL RESULT IN INCREASING WINDS/GUST
OVERNIGHT...PERSISTING INTO SUNDAY AFTERNOON. COULD BE SOME BLSN AT
KRST AS A RESULT...LIKELY CONTINUING SOME VSBY RESTRICTIONS EVEN
WHEN ACCUM SNOWS HAVE STOPPED.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WARNING UNTIL 9 PM CST SUNDAY FOR WIZ061.

     WINTER WEATHER ADVISORY UNTIL 9 PM CST SUNDAY FOR WIZ053>055.

MN...WINTER WEATHER ADVISORY UNTIL 9 PM CST SUNDAY FOR MNZ094>096.

IA...WINTER STORM WARNING UNTIL 9 PM CST SUNDAY FOR IAZ018-019-029-
     030.

     WINTER WEATHER ADVISORY UNTIL 9 PM CST SUNDAY FOR IAZ008>011.

&&

$$


SHORT TERM...BOYNE
LONG TERM....BOYNE
AVIATION.....RIECK



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