Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 061107
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
607 AM CDT WED MAY 6 2015

.UPDATE...
ISSUED AT 442 AM CDT WED MAY 6 2015

SURFACE OBSERVATIONS INDICATE THE DENSE FOG HAS EXPANDED INTO
SOUTHWEST WISCONSIN AND A CHECK WITH OFFICIALS IN GRANT COUNTY
CONFIRM THAT IT IS REDUCING THE VISIBILITY. BASED ON THIS...HAVE
EXPANDED THE DENSE FOG ADVISORY ACROSS THE REST OF NORTHEAST IOWA
INTO SOUTHWEST WISCONSIN.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 300 AM CDT WED MAY 6 2015

COMPLEX WEATHER PATTERN WILL LEAD TO PLENTY OF CLOUDS AND SOME
CHANCE FOR SHOWERS AND EMBEDDED THUNDERSTORMS TODAY INTO TONIGHT
FOR SOME AREAS. CLOSED CIRCULATION EJECTING OUT OF THE MEAN TROUGH
ALONG THE WEST COAST OF THE CONUS...SPINNING OVER COLORADO
OVERNIGHT. FRONTOGENETIC FORCING ON THE LEADING EDGE OF THE
WARM/MOIST ADVECTION LEADING TO SHOWERS FROM CENTRAL MN ACROSS
PRIMARILY THE NORTHERN HALF OF WI. MEANWHILE...STRONGER DYNAMIC
FORCING NEARER THE MAIN LOW CENTER LEADING TO CONVECTIVE
DEVELOPMENT FROM KS/MO UP INTO IA. MAIN CIRCULATION AND FORCING
WILL MOVE NORTH INTO THE DAKOTAS TONIGHT. CONTINUED MOISTURE
TRANSPORT INTO OUR AREA SUGGESTS THAT SOME SHOWERS AND ISOLATED
THUNDERSTORMS COULD DEVELOP AND AFFECT PORTIONS OF SOUTHEAST MN
AND NORTHEAST IA LATER TODAY AND TONIGHT. HOWEVER IT DOES APPEAR
THE BETTER SUPPORT WILL REMAIN FURTHER WEST. HAVE BEEN MAINTAINING
RAIN CHANCE GRADIENT DIMINISHING FURTHER EAST FOR A FEW DAYS NOW
AND WILL KEEP THE GENERAL TREND THROUGH THURSDAY MORNING.

DESPITE PLENTY OF CLOUDS AND SOME RAIN...WARM ADVECTION AND ANY
RANDOM PEEK AT THE SUN WILL HELP TEMPERATURES MAKE IT UP INTO THE
70S. AND A FEW LOCALIZED 80 DEGREE READINGS ARE NOT OUT OF THE
QUESTION.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 300 AM CDT WED MAY 6 2015

VERY UNSETTLED PATTERN WILL MAKE THE TIMING DETAILS OF THE
FORECAST CHALLENGING FOR THE NEXT WEEK TO 10 DAYS. DAKOTAS WAVE
CONTINUES NORTH INTO CANADA...WITH SECONDARY SHORT WAVE TROUGH
HELPING TO KICK THE TRAILING SURFACE COLD FRONT THROUGH THE AREA
THURSDAY NIGHT INTO FRIDAY. GULF WILL BE WIDE OPEN AT THIS POINT
SO MOISTURE RETURN AND INSTABILITY SHOULD DRIVE SOME CONVECTION
THROUGH THE REGION WITH RAIN LIKELY DURING THIS TIMEFRAME...
SUPPORTED BY ALL MODELS. STILL SOME UNCERTAINTY ON JUST HOW FAR
AND HOW FAST THE FRONT MOVES SOUTH OF THE AREA ON FRIDAY. GFS MOST
ROBUST WITH THE SURGE OF COOLER/DRIER AIR. ECMWF TRENDING THAT WAY
TOO LEADING TO A BIT HIGHER CONFIDENCE THAN YESTERDAY AT THIS
TIME. OPTED TO FAVOR THE GFS FOR THIS PERIOD DUE TO THE TREND.

MAIN LONG WAVE TROUGH FINALLY LOOKING TO FULLY EJECT OUT OF THE
DESERT SOUTHWEST OVER THE WEEKEND...TAKING ITS TIME TRACKING INTO
THE UPPER MIDWEST BY LATE MON/TUE. MODELS IN SURPRISINGLY GOOD
AGREEMENT WITH PLACEMENT AND TIMING OF FEATURES AS THIS TAKES
PLACE. MAIN SURFACE LOW DEEPENS ALONG THE LEE OF THE ROCKIES BY
SUNDAY MORNING. IF THIS TIMING HOLDS...SUNDAY AFTERNOON/EVENING
COULD BE INTERESTING WITH SEVERAL PARAMETERS FALLING INTO PLACE
FOR A SEVERE WEATHER OUTBREAK FROM THE PLAINS UP TOWARD IA. LATE
SUNDAY INTO MONDAY LOOKS PRETTY WET UNDER THIS SCENARIO AS THE
SYSTEM SLOWLY TRAVERSES THE TRI-STATE REGION.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 607 AM CDT WED MAY 6 2015

DENSE FOG CONTINUES TO PRODUCE IFR CONDITIONS AT KRST AND BOTH THE
06.09Z RAP AND 06.06Z NAM SUGGEST THIS WILL HOLD ON UNTIL ABOUT
14Z OR SO AND THEN RAPIDLY DISSIPATE AS THE MIXING INCREASES. PLAN
TO SHOW SOME IMPROVEMENT OUT OF LIFR TO IFR AROUND 14Z AND THEN
IMPROVE THE VISIBILITY TO VFR AND CEILINGS TO MVFR AROUND 16Z.
VFR CONDITIONS SHOULD PREVAIL BY EARLY AFTERNOON AS THE WINDS
START TO GUST OUT OF THE SOUTHEAST. THE VISIBILITY HAS NOT DROPPED
AS LOW AT KLSE AND EXPECT THAT THIS WILL IMPROVE TO VFR BY MID
MORNING. THE CEILINGS SHOULD COME UP TO MVFR BY MID MORNING AND
THEN VFR BY EARLY AFTERNOON. AS THE WARM FRONT FROM THE SOUTH
STARTS TO APPROACH LATE THIS AFTERNOON...THE NAM SUGGESTS A SHORT
WAVE TROUGH WILL MOVE ACROSS THE AREA. THESE TWO FEATURES SHOULD
PRODUCE ANOTHER ROUND OF SHOWERS AND POSSIBLY SOME STORMS FROM
LATE AFTERNOON INTO THE OVERNIGHT HOURS. HAVE INTRODUCED VCSH FOR
BOTH TAF SITES TO COVER THIS BUT DID NOT PUT ANY THUNDER IN YET AS
THE NAM SOUNDINGS SHOW THE CAPE STAYS UNDER 500 J/KG FOR RIGHT
NOW. IF THESE TRENDS CONTINUE...EXPECT THAT THE SHOWERS WILL HAVE
TO BECOME PREVAILING WITH AT LEAST THE INCLUSION OF A VCTS.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR WIZ054-061.

MN...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR MNZ086-087-
     094-095.

IA...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR IAZ008>011-
     018-019-029-030.

&&

$$

UPDATE...04
SHORT TERM...MW
LONG TERM...MW
AVIATION...04



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