Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 012333
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
633 PM CDT WED JUL 1 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 340 PM CDT WED JUL 1 2015

BEEN MONITORING THE SHORTWAVE TROUGH SHIFTING THROUGH MN/IA TODAY
AND THE ONGOING BATTLE BETWEEN FORCING AND DRIER LOW-LEVELS. OVER
THE PAST HOURS THERE HAS BEEN A BIT BETTER RESPONSE TO THE
FORCING AND 50DBZ ECHO IN NERN IA...AND LIGHT RAIN. SO FAR NO
LIGHTNING. FORECAST WILL CONTINUE TO TREND THAT SYSTEM OUT THROUGH
THE LATER AFTERNOON AND EARLY EVENING WITH CLEARING UPSTREAM
SLOWLY MOVING SOUTH. CURRENT FORECAST IS TO HAVE ALL CLEAR
SKIES...EXCEPT FOR SMOKE...NORTH OF MN/IA BORDER TO RICHLAND
COUNTY BY ABOUT 7-8 PM.

CLEARING SKIES OVERNIGHT AND DEEP LIGHT WINDS TO 10KFT WILL
PROVIDE IDEAL RADIATIONAL COOLING WITH A STRONG INVERSION IN THE
RIVER VALLEYS LIKELY. THIS MAKES RIVER VALLEY FOG IN THE MISS
POSSIBLE...AND LIKELY IN THE WI RIVER. DEWPOINTS THIS AFTERNOON
IN THE MISS RIVER WERE NEAR 50F AND DEWPOINT DEPRESSIONS OF
20F...DEFINITELY CAN BE OVERCOME /RESEARCH SHOWS 35F DEPRESSION
IS HARD TO OVERCOME/. WHILE IT IS PRETTY EARLY IN THE YEAR FOR FOG
/MAINLY BECAUSE OF SHORT DARKNESS HOURS/...HAVE INTRODUCED PATCHY
FOG IN THE VALLEYS/TRIBS...A BIT MORE IN THE WI RIVER VALLEY.
WATER TEMPERATURES NEAR 70 WILL FAVOR A MOISTURE FLUX AS WELL.
THIS FOG COVERAGE MAY NEED TO BE INCREASED. IN CENTRAL WI...HAVE
DRASTICALLY LOWERED THE LOWS TONIGHT...CLOSER TO THIS MORNINGS
LOWS...IN THE 30S.

WATER VAPOR SHOWING ANOTHER STRONG SHORTWAVE TROUGH APPROACHING
NORTHEAST MT AT 20Z. THIS TROUGH WILL TRAVEL A BIT FURTHER
SOUTHWEST THAN TODAYS WAVE PER 01.12Z MODEL CONSENSUS. THE WAVE
WILL PASS THROUGH IOWA DURING THE DAY AND AT LEAST GENERATE CLOUDS
WEST OF THE MISS RIVER. THIS IS A STRONG WAVE AND DO HAVE A BIT OF
CONCERN THAT MID-LEVEL FRONTOGENESIS COULD PRODUCE SOME SHOWERS A
BIT FURTHER NORTHEAST. HAVE INCREASED CLOUD AND LOWERED HIGHS IN
NERN IA THURSDAY...BUT AM HOLDING OFF WITH RAIN CHANCES FOR NOW.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 340 PM CDT WED JUL 1 2015

WARM UP BEGINS FRIDAY AFTER WHAT COULD BE ANOTHER QUITE COOL NIGHT
IN WI UNDER HIGH PRESSURE. HAVE LOWERED THE CENTRAL WI AREA LOWS
BUT THEY MAY NEED TO COME DOWN MORE.

MODEL CONSENSUS IS TO BRING A LOW PRESSURE SYSTEM THROUGH THE
GREAT LAKES AND BY LATER AFTERNOON...MOISTURE RETURNS AHEAD OF THE
FRONT ON A TRAJECTORY FROM THE DAKOTAS. LOW-LEVEL WARMING AND PRE-
FRONTAL WESTERLY FLOW WILL ALLOW MLCAPES TO BUILD TO NEAR
1000-1500 J/KG BY LATE FRIDAY AFTERNOON...WITH THE FRONT IN NWRN
WI TO THE TWIN CITIES. WHILE THE 01.12Z NAM IS MOST AGGRESSIVE WITH
THIS SYSTEM /PROBABLY BECAUSE OF ITS HYPER DEWPOINTS/...THERE IS
CONSISTENT CONVERGENCE IN THE LOWEST 0-2KM SUGGESTED BY THE 01.12Z
MORNING MODEL SUITE. THE NAM 4KM NEST HAS AN ISOLATED-SCT TSRA
LINE APPROACHING THE NW FORECAST AREA BY 7 PM FRIDAY. THE 01.12Z
ECMWF HAS SIMILAR TIMING BUT IS WEAKER WITH THE CONVERGENCE...
WHILE THE GFS IS SLOWER. BOTTOM LINE IS THERE SEEMS TO BE SOME
CHANCE OF A FEW STORMS FRIDAY AFTERNOON AND EVENING BEFORE
SUNSET...BUT THE ENVIRONMENT ISNT TERRIBLY EXCITING. HAVE ADDED
SOME SLIGHT CHANCES OF RAIN TO THE EXTREME NORTH-NORTHWEST
FORECAST AREA.

THIS WEAK FRONT LINGERS ACROSS THE AREA SATURDAY. THERE IS SOME
DISAGREEMENT ON JUST WHERE IT ENDS UP...SRN/CENTRAL/NRN WI...BUT
IT COULD PROVIDE SOME CONVERGENCE AGAIN FOR ISOLATED TSRA DURING
THE DAY. AGAIN...THIS ISNT TERRIBLY EXCITING BUT GRB/MKX/ARX HAVE
ALL COLLABORATED A SMALL CHANCE OF RAIN FOR SATURDAY. THE LARGER
EVOLUTION IS FOR THE LOW-LEVEL RIDGE TO SLIDE EAST AND SOUTHERLY
FLOW SHOULD OVERWHELM THE FRONT BY EVENING...DIMINISHING TSRA
CHANCES DUE TO LACK OF CONVERGENCE.

SUNDAY-WEDNESDAY...THE BIGGEST CHANGE WAS A TREND TOWARD A SLOWER
FRONTAL PASSAGE FOR THE SUNDAY-MONDAY SYSTEM. RAIN CHANCES HAVE
BEEN PULLED FOR SUNDAY WITH GOOD CONSENSUS THAT TIMING WILL BE
LATER....MAINLY MONDAY. THIS MAY NEED TO BE SLOWED FURTHER IN
FUTURE FORECAST. THERE IS SOME SIGNIFICANT TROUGH ENERGY MOVING
THROUGH SRN CANADA AND ALONG THE BORDER...BUT IT APPEARS THE AREA
WILL HAVE WEAKER WIND SHEAR PROFILES FOR SEVERE WEATHER. MAINLY A
LINE OF STORMS AND RAIN...ESPECIALLY WITH A MORNING ARRIVAL. THAT
SYSTEM LOOKS TO BE THE BEST RAIN CHANCE OF THE WEEK. IT IS LOOKING
NEAR NORMAL ON TEMPERATURES.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 633 PM CDT WED JUL 1 2015

A 10 TO 15K DECK OF CLOUDS ALONG AND SOUTH OF INTERSTATE 90 WILL
CONTINUE TO MOVE SOUTH AND OUT OF THE AREA THIS EVENING. THIS WILL
RESULT IN A MAINLY CLEAR OVERNIGHT. MODEL SOUNDINGS CONTINUE TO
SHOW A VERY DEEP LAYER OF LIGHT WINDS UP TO 10K FEET AND A LIGHT
SOUTHEAST SURFACE WIND DEVELOPING OVERNIGHT. BOTH OF THESE ARE
FAVORABLE FOR THE DEVELOPMENT OF FOG /ESPECIALLY IN THE VALLEYS/.
BOTH THE NAM AND RAP SOUNDINGS SHOW A VERY SHALLOW SATURATED LAYER
NEAR THE GROUND. MEANWHILE THE GFS SOUNDINGS DOES NOT SHOW THIS
DEVELOPING. ANOTHER FAVORABLE THING FOR FOG IS THAT LOW
TEMPERATURES WILL BE 15 TO 20 DEGREES COLDER THAN THE RIVER
TEMPERATURES. HOWEVER AT THE SAME TIME...WE HAVE HAVE NOT SEEN
PRECIPITATION IN A COUPLE OF DAYS AND THE NIGHTS ARE RELATIVELY
SHORT. BOTH OF THESE ARE NEGATIVES TO FOG FORMATION. AT THIS
TIME...THINK THAT THE BEST CHANCES FOR FOG FORMATION WILL BE
ACROSS CENTRAL WISCONSIN AND IN THE KICKAPOO AND WISCONSIN RIVER
VALLEYS. HOWEVER CANNOT COMPLETELY RULE IT POSSIBLY DEVELOPING IN
THE MISSISSIPPI TRIBUTARIES AND THEN MIGRATING INTO THE MAIN
CHANNEL BY MORNING. DUE TO THIS...WILL JUST LEAVE THE 4SM
REDUCTION CAUSED BY BR AND LA CROSSE BETWEEN 02.10Z AND 02.14Z.

&&

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

$$

SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...BOYNE


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