Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 071949
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
249 PM CDT TUE JUL 7 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 249 PM CDT TUE JUL 7 2015

PRETTY QUIET PERIOD COMING UP FOR THE AREA. HIGH PRESSURE AT THE
SURFACE CENTERED OVER WESTERN MINNESOTA AND EASTERN SOUTH DAKOTA
WILL MOVE TO THE EAST AND OVER THE GREAT LAKES THROUGH TONIGHT.
SOME POTENTIAL FOR VALLEY FOG TONIGHT WITH RELATIVELY CLEAR SKIES
AND LIGHT WINDS AT THE SURFACE. HOWEVER...THE 07.17Z RAP FORECAST
SOUNDINGS INCREASE THE WINDS JUST ABOVE THE SURFACE TO 10 KNOTS OR
GREATER CREATING A VERY SHALLOW LAYER OF LIGHT WINDS AND IT ALSO
DOES NOT PRODUCE SATURATION AT THE SURFACE KEEPING A 3C TEMP/DEW
POINT SPREAD. THESE SIGNALS ARE NOT FAVORABLE FOR VALLEY FOG TO
FORM AND THE AVIATION FORECASTER ALSO IS NOT ENTHUSED ABOUT
FOG...SO WILL LEAVE IT OUT OF THE FORECAST.

THE HIGH WILL MOVE AWAY FROM THE REGION WEDNESDAY AS A SYSTEM
APPROACHES FROM THE SOUTHWEST. THE 07.12Z MODELS ARE NOW IN
CONSENSUS AGREEMENT THAT THIS SYSTEM WILL PASS TO THE SOUTH OF THE
AREA WITH THE RAIN ALSO STAYING TO THE SOUTH. THE PREVIOUS
FORECAST HAD MOVED TO A DRY SOLUTION AND WILL MAINTAIN THIS. HIGH
PRESSURE WILL FOLLOW BEHIND THIS SYSTEM AND REMAIN OVER THE UPPER
MIDWEST THROUGH THURSDAY NIGHT.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 249 PM CDT TUE JUL 7 2015

SOUTHWEST FLOW ALOFT WILL ESTABLISH ITSELF OVER THE UPPER MIDWEST
FRIDAY WITH AN EMBEDDED SHORT WAVE TROUGH EXPECTED TO MOVE ACROSS
THE REGION. THE 07.12Z MODELS ARE SHOWING SOME SPREAD ON THE
TIMING WITH THIS SHORT WAVE TROUGH. THE 07.12Z ECMWF IS THE
STRONGEST WITH THE WAVE BRINGING IT ACROSS FRIDAY NIGHT AND
SATURDAY MORNING WHILE THE 07.12Z GFS AND GEM LOOK TO BE MUCH
WEAKER WITH IT. A WEAK SURFACE BOUNDARY SHOULD COME THROUGH WITH
THIS SHORT WAVE TROUGH...BUT AGAIN...DIFFERENCES ON THE TIMING
WITH THE GFS BLOWING IT THROUGH FRIDAY AND FRIDAY NIGHT WHILE THE
ECMWF JUST STARTS TO GET IT TO THE AREA BY LATE FRIDAY NIGHT AND
THEN HOLDS IT TO THE SOUTH SATURDAY. WITH THESE
INCONSISTENCIES...HELD THE RAIN CHANCES TO 50 PERCENT OR LOWER
WITH THIS SYSTEM. FOR NOW...THERE CONTINUES TO BE A CONSENSUS
SIGNAL THAT THE REMAINS OF THE CURRENT WEST COAST UPPER LEVEL LOW
WILL TOP THE RIDGE AXIS OVER THE ROCKIES AND THEN SLIDE SOUTHEAST
ACROSS THE REGION FOR SUNDAY AND MONDAY. THIS WILL BRING ANOTHER
CHANCE OF RAIN TO THE AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1235 PM CDT TUE JUL 7 2015

BROKEN CUMULUS OVER THE AIRFIELDS TODAY...BUT SHOULD DISSIPATE AS
WE NEAR SUNDOWN. WITH HIGH PRESSURE BUILDING IN...SUBSIDENCE AND
LIGHT WINDS ANTICIPATED. COOL AIRMASS AS WELL...SO THIS SUGGESTS
AT LEAST THE POSSIBILITY FOR VALLEY FOG. WE DID HAVE RECENT
RAINFALL TO HELP MOISTEN THE BOUNDARY LAYER...BUT GOOD DRYING
TODAY WORKING TO OFFSET THAT TO A DEGREE. PER PREVIOUS FORECASTER
THINKING...FEEL IT IS AT LEAST PLAUSIBLE THAT VALLEY FOG WILL FORM
AND WILL THUS MAINTAIN THE BCFG THAT WAS INTRODUCED FOR KLSE.


&&

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

$$

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



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