Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 281119
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
619 AM CDT THU AUG 28 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 348 AM CDT THU AUG 28 2014

AT 3 AM...A MESOSCALE CONVECTIVE COMPLEX WAS LOCATED IN EASTERN
NEBRASKA AND SOUTHWEST IOWA. LIKE THE 27.18Z MODELS...THE 28.00Z
MODELS ARE MUCH SLOWER AT BRINGING THE 925 MB AND 850 MB MOISTURE
TRANSPORT INTO OUR AREA TODAY. THIS TRANSPORT DOES NOT MOVE INTO
SOUTHEAST MINNESOTA AND NORTHEAST IOWA UNTIL MID MORNING AND INTO
WESTERN WISCONSIN UNTIL THIS AFTERNOON. THIS IS MAINLY DUE TO THE
SHORT WAVE TROUGH BEING A BIT SLOWER AT EJECTING OUR OF THE
CENTRAL PLAINS. DUE TO THIS...SIGNIFICANTLY SLOWED THE INCREASE IN
PRECIPITATION CHANCES FOR AREAS WEST OF THE MISSISSIPPI
RIVER...AND KEPT WESTERN WISCONSIN DRY THIS MORNING. WITH MOISTURE
TRANSPORT LOOKING THE STRONGEST FOR THIS AFTERNOON AND EVENING...
WENT WITH THE HIGHEST PRECIPITATION CHANCES FOR THIS TIME
PERIOD....AND THEN SLOWLY LOWERED THEM AFTER MIDNIGHT AS THE
MOISTURE TRANSPORT SHIFTS NORTH AND EAST OF THE FORECAST AREA.

LIKE THE PAST COUPLE OF DAYS...IT LOOKS LIKE OUR PRECIPITABLE
WATER VALUES WILL BE AROUND 2 INCHES AND THE WARM CLOUD LAYER
DEPTHS WILL BE UP TO 4.5 KM. AS RESULT...WE WILL HAVE GOOD WARM
CLOUD LAYER COALESCENCE PROCESS GOING ON FROM LATE THIS MORNING
INTO TONIGHT. WITH LIMITED MOST UNSTABLE CAPES ACROSS THE AREA
TODAY...NOT SEEING MUCH SUPPORT OF THUNDERSTORMS...SO LOWERED
THEIR CHANCES TO 40 PERCENT OR LESS. THIS IS A GOOD
THING...BECAUSE WE SEE FAVORABLE 0-6 KM SHEAR FOR SUPERCELL
DEVELOPMENT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 348 AM CDT THU AUG 28 2014

ON FRIDAY...THE AREA WILL BE SOUTH OF THE WARM FRONT. AS A
RESULT...ML CAPES WILL BE ABLE TO CLIMB UP INTO THE 2 TO 3K RANGE
DURING THE LATE MORNING AND AFTERNOON. WITH WEAK 850 MB MOISTURE
TRANSPORT INTO THE AREA...EXPECT SCATTERED SHOWERS AND
THUNDERSTORMS TO DEVELOP DURING THE DAY. THE HIGH CHANCES LOOK TO
BE DURING THE EARLY MORNING AND LATTER PARTS OF THE AFTERNOON.
WHILE THE AREA HAS MUCH BETTER INSTABILITY THAN TODAY...BOTH THE
0-3 KM AND 0-6 KM SHEAR IS FAIRLY WEAK. AS A RESULT...NOT
EXPECTING ANY ORGANIZED SEVERE WEATHER. HOWEVER CANNOT COMPLETELY
RULE OUT THE POSSIBILITY THAT THERE COULD BE A FEW PULSE SEVERE
STORMS DURING THE AFTERNOON. IN ADDITION TO LOWER SHEAR
VALUES...THERE IS ALSO LESS PRECIPITABLE WATER /AROUND 1.5 INCHES/
AND THE WARM CLOUD LAYER DEPTHS ARE ABOUT 1 KM LOWER /AROUND
3.5 KM/ THAN TODAY...THUS...THE HEAVY RAIN CHANCES ARE BIT LOWER
IN AREAS WHICH DO NOT SEE THUNDERSTORMS.

ON FRIDAY NIGHT AND SATURDAY MORNING...THE SHORT WAVE TROUGH MOVES
THROUGH THE FORECAST AREA. THIS TOUGH ALSO PICKS UP A TUTT
/TROPICAL UPPER TROPOSPHERIC TROUGH/ LOW FROM THE NORTHWEST GULF
OF MEXICO AND BRINGS IT NORTHWARD TOWARD THE REGION. WITH
MODERATE 850 MB MOISTURE TRANSPORT AND THE AREA IN THE RIGHT
REGION OF THE 200 MB JET...THIS LOOKS LIKE OUR NEXT BEST CHANCES
FOR SHOWERS AND THUNDERSTORMS. LIKE FRIDAY...PRECIPITABLE WATER
VALUES WILL BE AROUND 1.5 INCHES AND WARM CLOUD LAYER DEPTHS WILL
BE AROUND 3.5 KM. BOTH OF THESE ARE LOWER THAN THEY WERE
YESTERDAY. AS A RESULT...LOWERED THE OVERALL RAINFALL TOTAL FROM
TODAY THROUGH SATURDAY INTO THE 2 TO 3 INCH RANGE. THERE WILL
LIKELY STILL BE SOME PLACES WHICH SEE LOCALLY HIGHER AMOUNTS.

ON SUNDAY NIGHT...THE MODELS ARE IN GOOD AGREEMENT THAT THE COLD
FRONT WILL BE MOVING THROUGH THE AREA. DUE TO THIS TIMING...THE
ML CAPES ARE GENERALLY LESS THAN 1200 J/KG. LIKE YESTERDAY...IT
LOOKS LIKE THE FAVORABLE 0-3 KM AND 0-6 KM SHEAR WILL BE POST
FRONTAL. DUE TO THIS...NOT OVERLY EXCITED ABOUT SEVERE WEATHER
WITH THIS FRONT AT THIS TIME...BUT WILL HAVE TO WATCH IT CLOSELY
DURING THE HOLIDAY WEEKEND TO MAKE SURE THIS DOES NOT CHANGE. ALSO
WITH THIS TIMING...WAS ABLE TO LOWER THE AFTERNOON PRECIPITATION
CHANCES ON LABOR DAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 610 AM CDT THU AUG 28 2014

ALL EYES FOCUSED ON APPROACHING MCV/SHORT WAVE AND ATTENDANT BAND
OF SHRA/TSRA. LOOKING FOR ARRIVAL AT TAF LOCATIONS 15-17Z
TIMEFRAME. AIRMASS AHEAD OF THE APPROACHING SYSTEM ONLY MARGINALLY
UNSTABLE SO THUNDER CHANCE IS VERY LIMITED. AS DAYTIME HEATING
WORKS ON THE BOUNDARY LAYER COULD SEE SOME INSTABILITY THAT MIGHT
LEAD TO A FEW THUNDERSTORMS. KEPT THIS POSSIBILITY IN THE TAFS.
LOOKS LIKE A SMALL LULL IN THE RAIN ACTIVITY LATER TONIGHT INTO
FRIDAY. BUT MODELS INSIST IN LOW STRATUS WITH A SATURATED LOWER
ATMOSPHERE. HAVE INCLUDED THIS AS WELL AS VISIBILITY RESTRICTIONS
IN THE LATTER PERIODS OF THE TAF.

&&

.HYDROLOGY...TODAY THROUGH SATURDAY MORNING
ISSUED AT 348 AM CDT THU AUG 28 2014

IT CONTINUES TO LOOK LIKE WE WILL SEE PERIODS OF HEAVY RAIN
DURING THIS TIME PERIOD. THE HIGH PRECIPITABLE WATER VALUES
/AROUND 2 INCHES/ WILL BE FOUND ACROSS THE AREA THROUGH TONIGHT
AND THEN LOWER TO AROUND 1.5 INCHES FROM FRIDAY INTO SATURDAY
MORNING. IN ADDITION...THE WARM CLOUD LAYERS DEPTHS LOOK TO BE
LOWER FROM FRIDAY INTO SATURDAY MORNING...THUS LOWERING THE
CHANCES FOR HEAVY RAIN A BIT. IN ADDITION...IT LOOKS LIKE THE
PRECIPITATION WILL BE PROGRESSIVE. DUE TO THIS...THINKING THAT
MOST AREAS WILL SEE 2 TO 3 INCHES OF RAIN AND IT WILL
PERIODIC...SO PLANNING ON KEEPING THE ESF GOING.

&&

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

$$

SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...MW
HYDROLOGY...BOYNE



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