Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 240737
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
237 AM CDT THU JUL 24 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 237 AM CDT THU JUL 24 2014

MAIN CONCERN FOR THIS FORECAST REMAINS THUNDERSTORM COMPLEX EXPECTED
TONIGHT AND EARLY FRIDAY...WHICH COULD BE BIGGEST IMPACT OF ANY
WEATHER THROUGH NEXT WEEK.

A QUIET MORNING ON TAP WITH LARGE AREA OF HIGH PRESSURE OVER WESTERN
GREAT LAKES. STILL MONITORING FOG DEVELOPMENT BUT WILL LIKELY BE
LIMITED TO FAVORED VALLEYS IN WISCONSIN GIVEN DEW POINT DEPRESSION
EARLY THIS MORNING AND RECENT STRETCH OF DRY WEATHER.

ENDED UP RAISING TEMPERATURES FOR TODAY BASED ON TRENDS FROM
YESTERDAY...AS HIGH PRESSURE BEGINS TO SHIFT EAST. SHOULD BE JUST AS
WARM IF NOT A FEW DEGREES WARMER MOST LOCATIONS.

AS UPPER LOW OVER WASHINGTON STATE MOVES INTO AND PAST CANADIAN
ROCKIES TODAY...LOW LEVEL RESPONSE WILL BE STRONGEST OVER NORTHERN
PLAINS INITIALLY. THIS AREA OF WARM AIR ADVECTION AND RELATIVELY
STRONG LOW LEVEL MOISTURE TRANSPORT WILL THEN MIGRATE EAST OVERNIGHT
AND COULD INCREASE AS LOW LEVEL JET STRENGTHENS LEADING TO STORM
COMPLEX WHICH SHOULD BE CENTERED ON AREA COME DAYBREAK FRIDAY
MORNING.

DETERMINISTIC OUTCOME OF 24/00Z GUIDANCE FAIRLY CONSISTENT WITH
TIMING NOW ALTHOUGH AXIS OF POSSIBLE MCS STILL A BIT UNCERTAIN.
PREFER BLEND OF NAM/ECMWF THAT DRIVES BRUNT OF COMPLEX ACROSS
SOUTHERN MINNESOTA...FAR NORTHEAST IOWA...AND INTO SOUTHWEST
WISCONSIN MAINLY BETWEEN 25/08Z AND 25/15Z. 0-3KM MUCAPE VALUES GET
AS HIGH AS 1200 TO 2000 J/KG TONIGHT BUT VALUES DROP AND SHIFT SOUTH
TOWARDS FRIDAY MORNING LIKELY LEADING TO WEAKENING STORMS AS THEY
PASS THROUGH. BEST SHEAR REMAINS IN 0-3KM LAYER SO BESIDES SOME
HEAVY RAIN...COULD SEE SOME GUSTY WINDS WITH ANY STRONGER
ELEVATED STORMS WITH DRIER LOW LEVELS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 237 AM CDT THU JUL 24 2014

WITH ONGOING MCS...SOME QUESTION ON HOW LONG COMPLEX WILL LINGER
FRIDAY MORNING. BEST LOW LEVEL FORCING GRADUALLY SHIFTS EAST DURING
THE DAY BUT STORMS COULD CERTAINLY LINGER UNTIL AFTERNOON IN PARTS
OF THE AREA.

MEDIUM RANGE GUIDANCE HAS DISCREPENCIES AFTER THIS INITIAL MCS BASED
ON WHETHER SHORT WAVE ENERGY EJECTS OUT OF DEVELOPING WESTERLY FLOW
AS UPPER LOW BEGINS TO DROP INTO NORTHERN U.S. SOME HINTS OF
REDEVELOPMENT ALONG BOUNDARY FRIDAY NIGHT BUT CONFIDENCE IS LOW WITH
SOME MODELS KEEPING THINGS DRY.

SHOULD BE BETWEEN ANY FEATURES ON SATURDAY WITH DRYING WEST WIND BUT
AS UPPER LOW MOVES ACROSS WESTERN GREAT LAKES SUNDAY...ADDITIONAL
SHOWERS CERTAINLY POSSIBLE.

AS LARGE UPPER LOW ESTABLISHES OVER HUDSON BAY...COLDER...BELOW
NORMAL REGIME SETS UP FOR MUCH OF NEXT WEEK. NORTHWEST FLOW WITH
LITTLE IN THE WAY OF WAVES TO RESOLVE SO COULD SEE DRY WEATHER AND
HIGHS MAINLY IN THE 70S. SPORADIC MODEL GUIDANCE TO INCLUDE RAIN
CHANCES HAS BEEN THROWN OUT FOR DRIER SOLUTIONS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1058 PM CDT WED JUL 23 2014

THE FIRST AVIATION CONCERN REMAINS VALLEY FOG/STRATUS POTENTIAL
AT LSE THIS MORNING. SOME PASSING CLOUDS DURING THE EVENING CAUSED
THE TEMPERATURE/DEWPOINT SPREAD TO HOLD UP...STILL AT 12 DEGREES
AS OF 03Z. THIS IS QUITE HIGH AND MAY BE TOO HIGH TO ALLOW FOR FOG
FORMATION AT LSE GIVEN THE SHORTER NIGHT. THEREFORE...HAVE
IMPROVED THE VISIBILITY IN THE 11-13Z TEMPO GROUP TO MVFR. ON THE
OTHER HAND...WITH THE CLOUDS NOW CLEARED OUT AND CLEAR SKIES
LIKELY TO CONTINUE...THINK THERE STILL IS A DECENT CHANCE OF AN
LIFR STRATUS DECK TO FORM IN THE VALLEY. THUS THAT CONTINUES IN
THE TEMPO GROUP.

NEXT AVIATION CONCERN IS FOR THE EVENING WITH SHOWER AND
THUNDERSTORM POTENTIAL. WARM AND MORE HUMID AIR ARRIVING WELL
ABOVE THE SURFACE...NEAR 10000 FT...LOOKS TO ERUPT ISOLATED-
SCATTERED HIGH BASED SHOWERS AND THUNDERSTORMS. FOR NOW HAVE
INCLUDED ONLY VCSH AT BOTH SITES...BUT COULD SEE A VCTS NEED IN
LATER TAFS...ESPECIALLY AT RST CLOSER TO 06Z. LOOKING AHEAD TO
AFTER 06Z...SHOWER AND THUNDERSTORM CHANCES WILL INCREASE FURTHER
AS A WAVE OF LOW PRESSURE MOVES INTO IOWA.

&&

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

$$

SHORT TERM...SHEA
LONG TERM...SHEA
AVIATION...AJ



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