Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 101738
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1238 PM CDT THU JUL 10 2014

.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 333 AM CDT THU JUL 10 2014

WATER VAPOR IMAGERY SHOWING A DEEP MID-LEVEL TROUGH OF LOW PRESSURE
MOVING EAST INTO THE GREAT LAKES REGION WITH INTERIM RIDGING WORKING
IN FROM THE NORTHERN PLAINS. ALSO NOTED WAS A FAIRLY VIGOROUS TROUGH
RACING EAST ACROSS MT. THIS WILL BE OUR WEATHER-MAKER FOR TONIGHT
INTO FRIDAY. OTHERWISE...IR IMAGERY AND SURFACE OBSERVATIONS SHOWING
SCATTERED ALTOCUMULUS ACROSS THE ARX FORECAST AREA WITH TEMPERATURES
RANGING FROM THE UPPER 40S ACROSS NORTH CENTRAL WI...TO THE 50S AND
A FEW LOWER 60S ELSEWHERE.

FOR TODAY...WILL BE WATCHING THAT MID-LEVEL TROUGH OVER MT REACHING
THE MINNESOTA/DAKOTAS BORDER BY LATE THIS AFTERNOON. WARM AIR
ADVECTION/ISENTROPIC ASCENT AND MOISTURE TRANSPORT IN THE 850-700MB
LAYER KICKS IN IN LATER THIS AFTERNOON AHEAD OF THE WAVE. THIS WILL
GO INTO GENERATING AN INCREASE IN ALTOCUMULUS/ACCAS INTO THE AREA.
THINKING ANY SHOWERS WILL HOLD OFF WEST OF THE AREA...CLOSER TO THE
BETTER AXIS OF MOISTURE TRANSPORT. OTHERWISE... TEMPERATURES WILL
RESPOND TO THE WARM AIR ADVECTION WITH HIGHS TOPPING OFF IN THE
UPPER 70S TO A FEW LOWER 80S. IN ADDITION...SLOW INCREASE IN DEW
POINTS WILL MAKE IT FEEL A BIT MORE HUMID THROUGH THE AFTERNOON...
ESPECIALLY ALONG AND WEST OF THE MISSISSIPPI RIVER.

FOR TONIGHT...LOOK FOR AN UPTICK IN SHOWERS AND THUNDERSTORM
ACTIVITY THROUGH THE NIGHT AS THAT MID-LEVEL WAVE PUSHES INTO THE
REGION WITH INCREASING MOISTURE TRANSPORT. NAM SHOWING BEST CAPE
ELEVATED IN THE 2-7KM LAYER IN THE 500-800J/KG RANGE WITH SHEAR IN
THE 10-20KT RANGE WITHIN THAT LAYER. SO SCENARIO LOOKS LIKE CLUSTERS
OF SHOWER/THUNDERSTORMS THAT WILL BE PULSING UP AN DOWN IN INTENSITY
WITH NO SEVERE WEATHER EXPECTED. OVERNIGHT LOWS WILL BE IN THE 60S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 333 AM CDT THU JUL 10 2014

LOOK FOR THAT WAVE TO MOVE EAST THROUGH THE AREA MAINLY DURING THE
FRIDAY MORNING HOURS WITH LIKELIHOOD OF SHOWERS AND THUNDERSTORMS
SLOWLY ON THE DECLINE INTO CHANCY POPS THROUGH THE AFTERNOON HOURS
AS THE WAVE DEPARTS. AS A RESULT OF THE CLOUD COVER AND
PRECIPITATION...PLAN ON TEMPERATURES BEING HELD DOWN MOSTLY IN THE
MIDDLE 70S.

FOR FRIDAY NIGHT THROUGH SATURDAY...A WEAK TROUGH WILL BE PUSHING
THROUGH THE REGION...CONTINUING SHOWER/THUNDERSTORM CHANCES. ON
SATURDAY...MODELS SHOW ANOTHER MID-LEVEL TROUGH DROPPING THROUGH THE
AREA WITH GFS/NAM SHOWING 0-1KM MLCAPE IN THE 1300-2000J/KG ACROSS
THE SOUTH WITH 0-6KM BULK SHEAR INCREASING INTO THE 30-40KT RANGE.
HOWEVER...MODELS NOT REALLY KEYING IN ON ANY SURFACE CONVERGENCE TO
TRIGGER SUSTAINED CONVECTIVE UPDRAFTS. THINKING SEVERE THREAT WILL
BE MINIMAL UNLESS BETTER SURFACE CONVERGENCE CAN BE REALIZED.

FOR SATURDAY NIGHT...ECMWF SEEMS TO BE THE OUTLIER AS THE GFS/NAM
SHOW A WEAK FRONTAL BOUNDARY TO OUR SOUTH...KEEPING BULK OF
SHOWER/THUNDERSTORMS TIED WITH IT. THE ECMWF WANTS TO BLOW UP AN MCS
NORTH OF THIS BOUNDARY LAYER AND STEERS IN INTO OUR SOUTHERN
FORECAST AREA. WENT WITH MODEL CONSENSUS POPS FOR NOW KEEPING
HIGHEST CHANCES SOUTH OF I-90.

A SECONDARY COLD FRONT SWINGS THROUGH THE AREA ON SUNDAY AS AN
ANOMALOUSLY DEEP UPPER CLOSED LOW STARTS PUSHING SOUTH OUT OF
MANTITOBA/ONTARIO. AGAIN...NOT MUCH FOR SURFACE CONVERGENCE ALONG
THE FRONT...HOWEVER...GFS PRODUCES AMPLE 0-1ML CAPE IN THE 1500-
2000J/KG RANGE WITH 0-6KM BULK SHEAR OF 45-50KT. WILL HAVE TO KEEP A
CAUTIOUS EYE ON THIS FOR SEVERE THUNDERSTORM POTENTIAL.

FOR MONDAY INTO TUESDAY...LOOK FOR FOR A SHARP DOWNWARD TEMPERATURE
TREND WITH POSSIBLE RECORD LOW HIGHS BY TUESDAY. THIS IS DUE TO AN
ANOMALOUSLY DEEP CLOSED LOW MOVING OVERHEAD WITH GEFS MODEL SHOWING
850MB TEMPERATURES AROUND 2 STANDARD DEVIATIONS BELOW NORMAL...OR
NEAR RECORD COLD TERRITORY. THIS TRANSLATES TO HIGH TEMPERATURES
ACROSS THE AREA IN THE LOWER TO MIDDLE 60S. IN ADDITION...CLOUD
COVER AND SCATTERED SHOWERS WILL MAKE IT FEEL EVEN MORE RAW. SEE
CLIMATE SECTION BELOW FOR FURTHER DETAILS CONCERNING NEAR RECORD LOW
HIGHS.

MODELS SHOWING THIS DEEP LOW LIFTING NORTHEAST INTO QUEBEC ON
WEDNESDAY WITH TEMPERATURES RECOVERING..BUT STILL SOME 10 BELOW
NORMAL WITH HIGHS TOPPING OFF IN THE 70S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1238 PM CDT THU JUL 10 2014

THE MAIN FOCUS AT THE TAF SITES IS WITH THE RAIN AND THUNDER
CHANCES TONIGHT INTO TOMORROW MORNING. SOME MINOR DROPS IN
VISIBILITY ARE CURRENTLY OCCURRING DUE TO SMOKE THAT IS IN THE AIR
FROM SOME CANADIAN WILDFIRES...BUT SHOULD STAY VFR THROUGH THIS
AFTERNOON. RAIN SHOWERS ARE FORECAST TO MOVE IN FROM THE WEST
LATER TONIGHT...PARTICULARLY AFTER MIDNIGHT. THERE DOES NOT APPEAR
TO BE MUCH INSTABILITY FOR THE SHOWERS TO WORK WITH...SO HAVE
REMOVED THE VCTS FROM THE FORECAST. THESE RAIN SHOWERS MAY
CONTINUE INTO THE MORNING HOURS TOMORROW...BUT CONFIDENCE WAS ONLY
HIGH ENOUGH TO PUT A VCSH INTO THE FORECAST.

&&

.HYDROLOGY...
ISSUED AT 333 AM CDT THU JUL 10 2014

WATER LEVELS ON THE MISSISSIPPI RIVER CONTINUE ON A DOWNWARD TREND.
MCGREGOR AND GUTTENBERG IOWA ARE THE ONLY ARX FORECAST POINTS THAT
REMAIN IN FLOOD. THESE POINTS ARE EXPECTED TO FALL BELOW FLOOD STAGE
TODAY. FOR THE CURRENT AND FORECAST RIVER LEVELS...SEE OUR INTERNET
PAGE AT WWW.WEATHER.GOV/LACROSSE.

&&

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

$$

SHORT TERM...DAS
LONG TERM...DAS
AVIATION...HALBACH
HYDROLOGY...DAS



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