Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 300755
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
255 AM CDT TUE JUN 30 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 255 AM CDT TUE JUN 30 2015

LATEST WATER VAPOR SATELLITE IMAGERY SHOWING SHORTWAVE TROUGH
PUSHING INTO THE OHIO RIVER VALLEY AND SUBSIDENCE BEHIND
SHORTWAVE TROUGH OVER EASTERN MINNESOTA AND NORTHERN WISCONSIN.
LATEST 07Z SURFACE ANALYSIS INDICATED WEAK COLD FRONT EXTENDING
FROM SOUTHERN ONTARIO INTO NORTHEAST NEBRASKA. WITH RELAXED
PRESSURE GRADIENT...MOIST BOUNDARY LAYER AND CLEAR SKIES OVER THE
FORECAST AREA. PATCHY FOG HAS DEVELOPED MAINLY ALONG AND EAST OF
THE MISSISSIPPI RIVER.

THE 30.00Z GFS/NAM ARE IN GOOD AGREEMENT TRACKING SURFACE FRONT INTO
THE OHIO RIVER VALLEY TODAY INTO TONIGHT AND BUILD SURFACE RIDGE
INTO NORTHERN MINNESOTA AND NORTHERN WISCONSIN. SUBSIDENCE
UNDERNEATH SURFACE RIDGE WILL ALLOW FOR ANY PRECIPITATION TO BE
SUPPRESSED WEST OF THE FORECAST AREA TODAY.

THE MAIN CONCERN TONIGHT IS THE POSSIBILITY OF FOG FORMATION ACROSS
PARTS OF THE FORECAST AREA. SURFACE RIDGE AXIS CENTERED OVER
CENTRAL/NORTHERN WISCONSIN WILL PROVIDE MOSTLY CLEAR SKIES AND LIGHT
NORTHEASTERLY WINDS NEAR/AT THE SURFACE. HOWEVER...WITH SLIGHTLY
DRIER AIR ADVECTING INTO THE AREA DURING THE DAYTIME HOURS TODAY
AND NORTHEASTERLY WINDS ALOFT AND NEAR THE SURFACE...THIS WILL
PREVENT ANY FOG FORMATION ACROSS MUCH OF THE FORECAST AREA.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 255 AM CDT TUE JUN 30 2015

THE 30.00Z GFS/NAM/ECMWF ARE IN DECENT AGREEMENT AMPLIFYING UPPER
LEVEL RIDGE OVER THE WESTERN UNITED STATES AND UPPER LEVEL TROUGH
OVER THE EASTERN UNITED STATES WEDNESDAY INTO THURSDAY. WITH
SHORTWAVE ENERGY AND ASSOCIATED MOISTURE CONVERGENCE/LIFT WEST OF
THE FORECAST AREA...PLUS SURFACE RIDGE ENTRENCHED OVER THE GREAT
LAKES REGION. FORECAST AREA WILL REMAIN DRY WEDNESDAY INTO
THURSDAY.

THE 30.00Z GFS/NAM/ECMWF ARE TRENDING DRIER FOR THURSDAY NIGHT...AS
SURFACE RIDGE REMAINS IN CONTROL AND BETTER/DEEPER FORCING/MOISTURE
CONVERGENCE IS WEST OF THE FORECAST AREA WITH WEAK/VERY LITTLE FORCING/LIFT
OVER THE WESTERN FORECAST AREA. HAVE REDUCED PRECIPITATION CHANCES
ACROSS FORECAST AREA AND CONFINED SMALL CHANCES OF PRECIPITATION
TO THE EXTREME WESTERN PART OF THE FORECAST AREA.

MAIN FORECAST CONCERNS FRIDAY THROUGH MONDAY ARE PRECIPITATION
CHANCES SUNDAY INTO MONDAY. THE 30.00Z GFS/ECMWF/GEM ARE IN DECENT
AGREEMENT IN WEAKENING UPPER LEVEL TROUGH OVER THE EASTERN UNITED
STATES AND DEVELOP WEST TO EAST ZONAL FLOW ACROSS THE NORTHERN
TIER STATES THIS WEEKEND. THE BIGGEST DIFFERENCES BETWEEN THE
MODELS IS TIMING THE SHORTWAVE TROUGH INTO THE GREAT LAKES REGION
THIS WEEKEND AND THE STRENGTH OF THE UPPER LEVEL TROUGH DIGGING
OVER THE NORTHERN PLAINS SUNDAY INTO MONDAY. THE 30.00Z
GFS/ECMWF/GEM SHOW DECENT MOISTURE CONVERGENCE AND LIFT IN
ASSOCIATION WITH SHORTWAVE TROUGH EMBEDDED IN THE WEST TO EAST
ZONAL FLOW. WILL CONTINUE WITH PRECIPITATION CHANCES SUNDAY INTO
MONDAY ACROSS THE FORECAST AREA. TEMPERATURES THROUGH FORECAST
PERIOD WILL REMAIN NEAR OR SLIGHTLY BELOW NORMAL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1150 PM CDT MON JUN 29 2015

SKIES HAVE CLEARED OUT BEHIND THE EVENING CONVECTION AND WITH THE
ABUNDANT LOW LEVEL MOISTURE...ALREADY STARTING TO SEE SOME FOG
FORM. NO REPORTS OF LOW CLOUDS YET BUT THEY ARE FLOATING BY THE
OFFICE SKYCAM. GOOD SET UP FOR FOG TO FORM AT BOTH TAF SITES AND
THE 30.03Z RAP FORECAST SOUNDINGS SHOWS LOW LEVEL SATURATION
OCCURRING AT BOTH TAF SITES. WILL START WITH MVFR FOR BOTH SITES
AND TAKE THEM DOWN TO IFR FOR LATE TONIGHT INTO TUESDAY MORNING.
EXPECTING THE FOG TO DISSIPATE BY MID MORNING...BUT THE LOW LEVEL
STRATUS DECK MAY HOLD ON A LITTLE LONGER WITHOUT GOOD MIXING TO
HELP BREAK IT UP. ONCE THE STRATUS IS GONE...SHOULD BE VFR
CONDITIONS FOR THE REMAINDER OF THE PERIOD AS HIGH PRESSURE EDGES
IN FROM THE NORTHEAST.


&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...04



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