Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 280515
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1115 PM CST THU NOV 27 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 339 PM CST THU NOV 27 2014

AT 3 PM...A 1033 MB SURFACE HIGH...CENTERED OVER SOUTHEAST
MINNESOTA AND NORTHEAST IOWA...WAS PRODUCING PARTLY TO MOSTLY
SUNNY SKIES ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. DESPITE...
THE SUNSHINE...TEMPERATURES WERE VERY COLD RANGING FROM 3 IN
AUSTIN MINNESOTA TO 21 IN LONE ROCK WISCONSIN.

FOR TONIGHT AND FRIDAY...27.12Z MODELS ARE IN GOOD AGREEMENT THAT
A SHORT WAVE OVER WESTERN NORTH DAKOTA WILL MOVE QUICKLY SOUTHEAST
ACROSS NORTHERN MINNESOTA TONIGHT...AND NORTHERN WISCONSIN ON
FRIDAY. AS THIS SYSTEM APPROACHES...A BAND OF MODERATE TO STRONG
900 TO 600 MB FRONTOGENESIS WILL MOVE EAST ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. THIS BAND WILL MOVE EAST THROUGH
SOUTHEAST MINNESOTA AND NORTHEAST IOWA BETWEEN 28.06Z TO
28.10Z...AND THROUGH WESTERN WISCONSIN BETWEEN 28.09Z AND 28.18Z.
THERE IS PLENTY OF DRY AIR AHEAD OF THIS WAVE...SO THE INITIAL
LIFT WILL GO TO SATURATING THE AIR MASS BELOW 700 MB. ONCE
SATURATED THE SOUNDINGS INITIALLY SHOW THAT THE 850 MB TO 550 MB
LAYER WILL BE LOCATED IN THE DENDRITIC GROWTH ZONE NORTH OF
INTERSTATE 94...AND ONLY ABOUT 50 TO 100 MB SOUTH OF THIS
INTERSTATE. HOWEVER AS STRONG WARM AIR ADVECTION CONTINUES THROUGH
THE NIGHT...THE AMOUNT OF AREA IN THE DENDRITIC GROWTH ZONE BECOME
LESS AND LESS...WENT WITH THE HIGHEST SNOW TO LIQUID RATIOS THIS
INITIALLY...AND THEN DECREASE THEM ON FRIDAY. SNOW TOTALS WILL THE
GREATEST NORTH OF WISCONSIN 29 /FAR NORTHERN CLARK AND TAYLOR
COUNTIES IN NORTH CENTRAL WISCONSIN/ WHERE SNOW TOTALS ARE AROUND
3 INCHES. DUE TO THIS SNOW...ISSUED A WINTER WEATHER ADVISORY FROM
MIDNIGHT TONIGHT THROUGH 3 PM FRIDAY. FURTHER SOUTH...EXPECT SNOW
TOTALS OF 1 TO 3 INCHES BETWEEN INTERSTATE 94 AND WISCONSIN
29...AND FROM A TRACE TO AN INCH /NEAR INTERSTATE 90/ FOR THE
REMINDER OF THE AREA.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 339 PM CST THU NOV 27 2014

ON SATURDAY...VERY WARM AIR WILL BE BROUGHT ISENTROPICALLY OFF OF
THE CENTRAL PLAINS. UNFORTUNATELY THIS AIR WILL NOT MIX DOWN TO
THE SURFACE. AS A RESULT...ONLY HAVE HIGH TEMPERATURES RANGING
FROM THE MID 30S TO MID 40S. ONLY THING WE WILL HAVE TO WATCH IS
THAT THE MODELS MAY BE UNDOING SOME OF WARMING AS THEY TRY TO MELT
THE SNOW ON THE GROUND. LIKE YESTERDAY...THE NAM IS INITIALLY RUNNING
ABOUT 1 TO 2 INCHES TOO HIGH ON THEIR SNOW DEPTH. WE WILL HAVE TO
WATCH THIS PERIOD CLOSELY.

ARCTIC COLD FRONTS WILL MOVE QUICKLY SOUTHEAST ACROSS THE AREA ON
SUNDAY MORNING AND LATE SUNDAY NIGHT. THE 850 MB TEMPERATURES
BEHIND THE FIRST FRONT WILL FALL FROM A BALMY 8-14C AT 12Z SUNDAY
TO 0 TO -12C BY 00Z MONDAY...AND EVEN COLDER AIR MASS /-16 TO
-22C/ WILL MOVE INTO THE AREA BY 12Z MONDAY. HIGH TEMPERATURES
CURRENTLY RANGE FROM 8 TO 20F ON MONDAY. HOWEVER THE ECMWF SUGGEST
THAT THE TEMPERATURES WILL BE VERY SIMILAR TO WHAT THEY WERE THIS
AFTERNOON.

FROM WEDNESDAY NIGHT THROUGH THURSDAY...THE GFS AND ECMWF CONTINUE
TO DISAGREE ON WHETHER A LOW PRESSURE SYSTEM WILL AFFECT THE AREA
OR NOT. THE GFS KEEPS PERIODICALLY MOVING A LOW INTO THE AREA.
SOMETIMES IT IS LOCATED OF THE MID MISSISSIPPI RIVER VALLEY AND
OTHER TIMES TO THE NORTHWEST AND WEST OF THE AREA. MEANWHILE THE
ECMWF HAS KEPT HIGH PRESSURE ACROSS THE AREA. DUE TO THIS...MADE A
CHANGE TO THE MODEL CONSENSUS AND REMOVED THE 20 TO 30 PERCENT
PRECIPITATION CHANCES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1115 PM CST THU NOV 27 2014

THE BAND OF LIGHT SNOW CONTINUES TO ADVANCE QUICKLY EASTWARD AND
STILL LOOKS LIKE IT WILL OVERSPREAD BOTH TAF SITES OVERNIGHT. IT
SHOULD MOVE INTO KRST SHORTLY AFTER 06Z AND BASED ON UPSTREAM
OBSERVATIONS...IT COULD PRODUCE AN HOUR OR TWO OF IFR CONDITIONS.
STILL EXPECTING THE SNOW TO ARRIVE IN KLSE AROUND 09Z AND PRODUCE
MVFR CONDITIONS. STILL EXPECTING BOTH SITES TO HAVE ABOUT 3 TO 4
HOURS OF LIGHT SNOW BEFORE THE SHORT WAVE TROUGH AND FRONTOGENESIS
IN THE 850-700 MB LAYER MOVE PAST THE REGION. CONDITIONS SHOULD
THEN POP BACK UP TO VFR FOR A WHILE EARLY FRIDAY MORNING BEFORE
ANOTHER SHORT WAVE TROUGH AND SOME WEAK LOW LEVEL FRONTOGENESIS
ARRIVES. NOT EXPECTING THIS TO PRODUCE ANY PRECIPITATION BUT IT
SHOULD BE ENOUGH TO BRING THE CEILINGS BACK DOWN TO MVFR WHERE
THEY ARE EXPECTED TO REMAIN FOR THE REST OF THE PERIOD. AS WARMER
AIR STARTS TO SPREAD IN FRIDAY EVENING...SOME POTENTIAL EXISTS FOR
FOG TO DEVELOP WITH THE LOW LEVELS ALREADY SATURATED BELOW THE
INVERSION. THE 28.00Z NAM FORECAST SOUNDINGS CONTINUE TO SHOW A
LITTLE BIT OF TEMP/DEW POINT SPREAD AT THE SURFACE THROUGH 29.06Z
SO HAVE NOT INCLUDE ANY FOG AT THIS TIME.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY UNTIL 3 PM CST FRIDAY FOR WIZ017.

MN...NONE.
IA...NONE.
&&

$$

SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...04



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