Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 172318
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
618 PM CDT THU APR 17 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 308 PM CDT THU APR 17 2014

MAIN FORECAST CONCERNS ARE ON RAIN CHANCES THIS WEEKEND WITH THE
POTENTIAL FOR ISOLATED THUNDERSTORMS. FOCUS THEN TURNS TO AN ACTIVE
WEATHER PATTERN NEXT WEEK.

LATEST SURFACE OBSERVATIONS SHOWED LOW PRESSURE NEAR GREEN BAY
WISCONSIN...MOVING EAST OF THE REGION. MEANWHILE...HIGH PRESSURE WAS
MOVE ACROSS THE DAKOTAS AND HEADING EAST TOWARD THE UPPER
MISSISSIPPI RIVER VALLEY. THE HIGH WILL MOVE INTO THE REGION TONIGHT
PROVIDING COOL AND QUIET WEATHER. WILL HAVE TO KEEP AN EYE OUT FOR
SOME PATCHY FOG OVER THE NEWLY FALLEN SNOW OVER NORTH CENTRAL
WISCONSIN. THE AIRMASS MOVING INTO THE REGION TONIGHT IS VERY DRY SO
CONCERNED THE FOG MAY NOT FORM. ALSO...GUIDANCE IS KEEPING DEWPOINTS
IN THE 20S ACROSS MUCH OF THE AREA OVERNIGHT SO WILL HAVE TO KEEP A
CLOSE EYE ON THE POTENTIAL FOR FOG DEVELOPMENT OVER MUCH OF THE
FORECAST AREA. ALSO...GUIDANCE ISN/T PICKING UP ON THE CLEARING THAT
WILL LIKELY OCCUR TONIGHT SO ITS STRUGGLING TO DROP TEMPERATURES LOW
ENOUGH TO ALLOW FOR FOG DEVELOPMENT. WILL HAVE TO KEEP A VERY CLOSE
EYE ON CLOUD TRENDS AND DEWPOINTS THIS EVENING. WITH THE CLOUDS OVER
THE REGION TODAY LIMITING MIXING...THE HIGH BUILDING IN TONIGHT
ALLOWING FOR MOSTLY CLEAR SKIES ALONG WITH CALM TO LIGHT WINDS...FOG
COULD BECOME A CONCERN. DECIDED TO ADD AREAS OF FOG TO NORTHERN
CLARK AND ALL OF TAYLOR COUNTY FOR TONIGHT. OTHERWISE...PLAN ON
MOSTLY CLEAR SKIES EARLY IN THE NIGHT WITH LOW TEMPERATURES RANGING
FROM THE LOWER 20S TO TEENS OVER NORTH CENTRAL WISCONSIN TO THE
UPPER 20S TO LOWER 30S ACROSS NORTHEAST IOWA.

THE HIGH WILL PUSH EAST OF THE REGION ON FRIDAY AS RIDGING STARTS TO
BUILD ACROSS THE PLAINS. A SHORTWAVE TROUGH IS EXPECTED TO MOVE
ACROSS CENTRAL MINNESOTA INTO CENTRAL WISCONSIN WHICH WILL CREATE
INCREASE MID TO HIGH LEVEL CLOUDS AS IT MOVES THROUGH. CANNOT RULE
OUT A FEW SPRINKLES MAKING IT TO THE SURFACE BUT CLOUD BASES LOOK
RATHER HIGH AT 8KFT WITH A VERY DRY SUB CLOUD LAYER. THE MAIN IMPACT
FROM THIS WEAK SHORTWAVE WILL BE AN INCREASE IN CLOUD COVER. 925 MB
TEMPERATURES WARM FROM -2 C TONIGHT TO 2 C OVER NORTH CENTRAL
WISCONSIN TO 8 C OVER NORTHEAST IOWA.  THE CLOUD WILL LIMIT SOME OF
THE HEATING TOMORROW BUT WE SHOULD STILL SEE HIGH TEMPERATURE
RANGING FROM THE LOWER 40S OVER NORTH CENTRAL WISCONSIN TO THE MID
TO UPPER 50S ACROSS NORTHEAST IOWA.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 308 PM CDT THU APR 17 2014

SOUTHERLY FLOW WILL BE IN PLACE ACROSS THE REGION FRIDAY NIGHT INTO
SATURDAY AHEAD OF AN APPROACHING WEAK COLD FRONT. LOW PRESSURE IS
EXPECTED TO TRACK ACROSS SOUTHERN MANITOBA ON SATURDAY PUSHING A
WEAK COLD FRONT INTO THE REGION LATE SATURDAY AFTERNOON INTO
SATURDAY NIGHT. THE FRONT WILL BECOME A NEARLY STATIONARY BOUNDARY
LATE SATURDAY AFTERNOON INTO SUNDAY NIGHT AS FLOW ALOFT TURNS
ZONAL AND A TROUGH EDGES EAST OUT OF THE SOUTHWEST CONUS. THIS
BOUNDARY WILL BE THE FOCAL POINT FOR SHOWERS AND POSSIBLY A FEW
ISOLATED THUNDERSTORMS AS NUMEROUS SHORTWAVES TRACK ACROSS THE
REGION AND INTERACT WITH THE BOUNDARY. TIMING THESE WAVES AND THE
ASSOCIATED PRECIPITATION WILL BE A BIT CHALLENGING IN THE ZONAL
FLOW REGIME. LEANING TOWARD THE 12Z ECMWF AND 12Z GFS THINKING THE
FIRST ROUND OF SHOWERS AND STORMS WOULD EDGE INTO HE FORECAST AREA
LATE SUNDAY AFTERNOON INTO SUNDAY EVENING. A SHORT WAVE THEN LIFTS
INTO THE AREA FROM THE CENTRAL PLAINS LATE SATURDAY NIGHT INTO
SUNDAY MORNING AND SHOULD KEEP SHOWERS AND STORMS GOING IN
VICINITY OF THE BOUNDARY. ANOTHER WAVE MOVES THROUGH SUNDAY
AFTERNOON INTO SUNDAY NIGHT THEN A STRONGER WAVE FINALLY PUSHES
THROUGH ON MONDAY AND SHOVES THE BOUNDARY EAST OF THE REGION.
OVERALL INSTABILITY IS LIMITED OVER THE AREA THIS WEEKEND INTO
EARLY NEXT WEEK WITH CAPE VALUES HOVERING IN THE 400-500 J/KG
RANGE...MAINLY ELEVATED. THESE CAPE VALUES WILL BE ENOUGH TO
SUPPORT ISOLATED TO SCATTERED THUNDERSTORM ACTIVITY BUT THESE
STORMS ARE NOT EXPECTED TO BE SEVERE WITH ONLY WEAK SHEAR IN
PLACE. EVEN THOUGH WE WILL BE SEEING PERIODS OF SHOWERS AND A FEW
THUNDERSTORMS THIS WEEKEND TEMPERATURES WILL BE WARMER. PLAN ON
HIGHS IN THE UPPER 50S TO UPPER 60S SATURDAY INTO SUNDAY. WE MAY
EVEN SEE A FEW 70 DEGREE READINGS OVER PORTIONS OF NORTHEAST IOWA
INTO FAR SOUTHWEST WISCONSIN.

A BRIEF BREAK IN PRECIPITATION CHANCES MONDAY NIGHT INTO LATE
TUESDAY NIGHT AS HIGH PRESSURE SLIDES OVERHEAD. A VIGOROUS WAVE
LOOKS TO LIFT INTO THE REGION WEDNESDAY NIGHT AND THURSDAY AND
COULD POTENTIALLY BRING SOME SEVERE THUNDERSTORMS TO THE AREA. A
LITTLE TOO FAR OUT TO NAIL DOWN THE EXACT DETAILS. GOING OFF OF
THE 12Z ECMWF AND GFS IT APPEARS A NEGATIVELY TILTED TROUGH COULD
LIFT INTO THE UPPER MISSISSIPPI RIVER VALLEY LATE WEDNESDAY NIGHT
INTO THURSDAY. WITH THE GULF OF MEXICO WIDE OPEN WE SHOULD BE ABLE
TO GET DEWPOINTS INTO THE MID 50S TO LOWER 60S. 0-6 KM SHEAR IS
ALSO LOOKING IMPRESSIVE...RANGING FROM 45 TO 50 KTS....AND 0-1KM
MUCAPE CLIMBS TO 1500 TO 2500 J/KG FOR AREAS ALONG AND SOUTH OF
INTERSTATE 90 THURSDAY AFTERNOON. DEFINITELY A PERIOD TO KEEP A
CLOSE EYE ON.


&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 618 PM CDT THU APR 17 2014

A TOUGH AVIATION FORECAST WITH MVFR CLOUDS STILL STUCK OVER THE
TAF SITES. SOME OF THE CLOUDS HAVE TURNED CELLULAR AROUND
RST...SUGGESTING THEY COULD CLEAR SHORTLY WITH SUNSET.
HOWEVER...OVER THE LAST 20 MINUTES...THE CELLULAR NATURE WAS
FILLING BACK IN. LOW LEVEL FLOW WITHIN THE CLOUDS IS PROGGED TO
TURN FROM THE CURRENT NORTHWEST TO NORTHEAST BY 03Z...FAVORING A
MORE PESSIMISTIC FORECAST GIVEN EXTENSIVE CLOUD OVER CENTRAL
WISCONSIN. PRESENTLY HAVE CLEARING OF 04Z AT RST AND 06Z AT
LSE...BUT THIS COULD NEED FURTHER DELAYING WITH THE RAP MODEL
SUGGESTING CLEARING WAITS UNTIL ALMOST 09Z. ONCE CLEARING
OCCURS...VFR CONDITIONS ARE LIKELY THROUGH THE REST OF THE TAF
PERIOD WITH ONLY SOME ALTOSTRATUS MOVING ACROSS ON FRIDAY.

NO MAJOR ISSUES EXPECTED IN THE WIND DEPARTMENT. PLAN ON WINDS TO
DIMINISH THIS EVENING BELOW 10 KT. WINDS WILL THEN INCREASE OUT OF
THE EAST ON FRIDAY AS HIGH PRESSURE TRACKS FROM MINNESOTA INTO
LAKE MICHIGAN.

&&

.HYDROLOGY...
ISSUED AT 308 PM CDT THU APR 17 2014

RECENT RAINFALL AND SNOWMELT IS KEEPING RIVER LEVELS ELEVATED
ALONG THE MISSISSIPPI. MINOR FLOODING IS OCCURRING AT WABASHA AND
A FLOOD WARNING IS IN EFFECT UNTIL LATE SUNDAY NIGHT. MINOR
FLOODING IS EXPECTED AT MCGREGOR BY EARLY FRIDAY MORNING AND A
FLOOD WARNING REMAINS IN EFFECT.  RAINFALL THIS WEEKEND INTO NEXT
WEEK AND ADDITIONAL SNOWMELT OVER CENTRAL INTO NORTHERN MINNESOTA
WILL LIKELY KEEP RIVER LEVELS ELEVATED ALONG THE MISSISSIPPI
THROUGH THE END OF APRIL.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

$$

SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...AJ
HYDROLOGY...WETENKAMP



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