Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 301127
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
627 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 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 627 AM CDT TUE JUN 30 2015

BR/FG WITH IFR/MVFR VSBYS AND SOME IFR CIGS WILL AGAIN PERSIST THRU
13-14Z THIS MORNING BEFORE DIURNAL WARMING/MIXING DISSIPATES IT.
NORTH TO NORTHEAST 925-850MB FLOW AROUND HIGH PRESSURE SETTLING OVER
NORTHERN MN/LK SUPERIOR WAS SPREADING SOME IFR/MVFR STRATO-CU
SOUTHWEST ACROSS WI AND TOWARD AT LEAST KLSE. THESE CLOUDS LOOK TO
ARRIVE ABOUT THE TIME THE FOG DISSIPATES...WITH SOME LOWER CIGS
LOOKING TO LINGER THRU THE MORNING. DRIER HIGH PRESSURE/SUBSIDENCE/
ANTI-CYCLONIC FLOW AND DIURNAL WARMING/MIXING SHOULD EVENTUALLY WIN
OUT WITH LOWER CLOUD DECKS LIFTING AND BECOMING SCT FOR THE
AFTERNOON. GOOD VFR EXPECTED TONIGHT AS THE SFC-850MB RIDGE AXIS
BUILDS OVER THE AREA. HOWEVER...BOUNDARY LAYER LIKELY TO DECOUPLE
TONIGHT WITH LATE NIGHT/EARLY MORNING BR/FG ONCE AGAIN A CONCERN...
ESPECIALLY AT KLSE. LEFT BR/FG AROUND 12Z WED OUT OF KLSE TAF FOR
NOW AS POTENTIAL THIS AFTERNOON/EVENING FOR SFC DEW POINTS TO DROP
AS THE LOWER LEVEL RIDGE AXIS BUILDS IN. LATER CYCLES WILL HAVE TO
KEEP AN EYE ON THIS AND CAN ADD BR/FG TO KLSE AFTER ABOUT 09Z
TONIGHT IF NEEDED.

&&

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

$$

SHORT TERM...DTJ
LONG TERM....DTJ
AVIATION.....RRS


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