Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 311117
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
617 AM CDT FRI JUL 31 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 232 AM CDT FRI JUL 31 2015

AREA REMAINS IN BROAD NORTHWEST UPPER FLOW...BETWEEN ACTIVE NORTHERN
JET ACROSS CANADA AND CONVECTION ACROSS CENTRAL PLAINS ALONG
INSTABILITY GRADIENT. THIS SHOULD BRING ANOTHER SUNNY DAY TO THE
AREA WITH SEASONAL TEMPERATURES AND MIXING OF DEW POINTS IN THE
AFTERNOON...ESPECIALLY ACROSS WISCONSIN. BASED ON TRENDS LAST FEW
DAYS...BUMPED UP HIGH TEMPERATURES TODAY A CATEGORY.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 232 AM CDT FRI JUL 31 2015

GENERAL NORTHWEST FLOW CONTINUES THROUGH MOST OF THE LONG TERM
FORECAST SO THE MAIN CHALLENGE WILL BE RAIN AND STORM THREATS...
ESPECIALLY AS INSTABILITY OVER THE PLAINS WORKS INTO THE CORNBELT
OVER THE WEEKEND.

WHILE MOST OF SATURDAY WILL REMAIN QUIET WITH A WARM FRONT SOUTHWEST
OF THE AREA...FOCUS IS ON SATURDAY NIGHT AS A MINOR WAVE HELPS TO
PUSH THIS FRONT NORTHEAST AS LOW LEVEL JET DEVELOPS. WHILE A
DISTINCT SHORT WAVE SEEMS LACKING IN RELATIVELY NOISY FLOW...SEEMS
TO BE A RELATIVELY LOCAL PUSH NORTHEAST DURING THE EVENING WHICH NOT
ONLY WOULD PUT AREA CLOSER TO CAPE GRADIENT...BUT ALSO BETTER LOW
LEVEL SHEAR ALONG BOUNDARY. THIS SETUP WILL HAVE TO BE WATCHED AS
LOW LEVEL HELICITY FROM MODELS CLIMBS RELATIVELY QUICKLY JUST AS
HIGHER MIXED LAYER CAPE VALUES WORK IN FROM THE SOUTHWEST. STEEP MID
LAYER LAPSE RATES...SUFFICIENT SUPERCELL SHEAR...AND DECENT LOW
LEVEL MOISTURE TRANSPORT ALL SUGGEST AT LEAST SOME POTENTIAL FOR
STRONGER TO SEVERE STORMS SATURDAY EVENING...PERHAPS DEVELOPING INTO
AN MCS OVERNIGHT. BUT LACK OF STRONGER WAVE COULD ALSO LIMIT
DEVELOPMENT OR NORTHEAST PUSH OF THIS WEATHER SO STILL DETAILS TO
WORK OUT. SPC DAY 2 OUTLOOK CERTAINLY SEEMS REASONABLE GIVEN
POTENTIAL.

ON SUNDAY...SHORT WAVE CLOSER TO UPPER TROUGH WILL MOVE INTO THE
WESTERN GREAT LAKES WITH ANOTHER THUNDERSTORM RISK. EVEN MORE
QUESTIONS ON HOW MUCH INSTABILITY WILL BE AROUND DEPENDING ON HOW
SATURDAY NIGHT SYSTEM PLAYS OUT...BUT WILL STILL HAVE PLENTY OF
SHEAR TO WORK WITH. COLD FRONT WILL BE PUSHING INTO WHAT AIRMASS
RECOVERS FROM EARLIER CONVECTION SO COULD SEE SOME REDEVELOPMENT
LATER IN DAY WITH STRONG TO SEVERE STORMS. THIS REMAINS VERY
CONDITIONAL WITH DETAILS TO BE WORKED OUT NEXT FEW PERIODS.

AS HEIGHT FALLS OVER EASTERN U.S....NORTHWEST FLOW WILL STRENGTHEN
EARLY NEXT WEEK...DRIVING FRONT BACK TO THE SOUTH AND SOUTHWEST.
THIS SHOULD MAKE FOR A FEW DRY DAYS WITH SLIGHT COOLING TREND. BUT
WAVES PASSING FLATTENING RIDGE TO THE WEST WILL BRING BACK
CONVECTION CHANCES BY MID WEEK ON.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 617 AM CDT FRI JUL 31 2015

BROAD UPPER LEVEL TROUGH ACROSS EASTERN CANADA AND THE GREAT
LAKES REGION WILL KEEP NORTHWESTERLY FLOW IN PLACE ACROSS THE AREA
TODAY AND TONIGHT. LOOK FOR GUSTY NORTHWEST SURFACE WINDS TODAY IN
THE 15-25KT RANGE...TAPERING OFF BY SUNSET. ANOTHER WEAK MID-LEVEL TROUGH
WILL ROTATE THROUGH THE REGION OVERNIGHT FOR SOME VFR CLOUD COVER
WITH BASES AOA 7KFT.

&&

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

$$

SHORT TERM...SHEA
LONG TERM...SHEA
AVIATION...DAS



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