Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 211135
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
635 AM CDT THU AUG 21 2014

.UPDATE...
ISSUED AT 535 AM CDT THU AUG 21 2014

A LINE OF STRONG TO SEVERE STORMS WAS APPROACHING THE INTERSTATE
35 CORRIDOR AT 530 AM THIS MORNING. THESE STORMS HAVE HAD A
HISTORY OF PRODUCING QUARTER SIZE HAIL AND WIND GUSTS OF 55 TO 60
MPH. THE LINE IS EXPECTED TO HOLD TOGETHER AS IT PUSHES INTO
SOUTHEAST MINNESOTA/NORTHEAST IOWA THIS MORNING. IN FACT...THE
REAR INFLOW JET IS BECOMING MORE APPARENT WITH THE LINE STARTING
TO SHOW A BOWING STRUCTURE. THE MAIN HAZARDS FROM THIS LINE OF
STORMS WILL BE DAMAGING WINDS AS IS PUSHES INTO THE FORECAST AREA.
THE LINE SHOULD HOLD TOGETHER AS IT APPROACHES THE MISSISSIPPI
RIVER AROUND 730 AM THIS MORNING AND COULD HOLD TOGETHER INTO
SOUTHWEST WISCONSIN. ALSO...THE STORMS ARE PRODUCING HEAVY
RAINFALL WHICH COULD LEAD TO LOCALIZED FLOODING ESPECIALLY IN
URBAN AREAS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 344 AM CDT THU AUG 21 2014

MAIN FORECAST CONCERNS THIS MORNING ARE ON STRONG TO POSSIBLY SEVERE
STORMS MOVING ACROSS THE AREA. FOCUS THEN TURNS TO ANOTHER ROUND OF
STRONG TO SEVERE STORMS LATE THIS AFTERNOON INTO THIS EVENING.

LATEST RADAR SHOWED AN EXPANSIVE AREA OF THUNDERSTORMS OVER MUCH OF
WESTERN MINNESOTA MOVING WEST. THIS ACTIVITY IS EXPECTED TO PUSH
INTO SOUTHEAST MINNESOTA AND POSSIBLY SOUTHEAST MINNESOTA IN THE 5
AM TO 6 AM TIMEFRAME. THE ACTIVITY COULD GROW UPSCALE INTO A
SQUALL LINE WITH THE POTENTIAL FOR DAMAGING WINDS. HOWEVER IT IS
STRUGGLING TO ORGANIZE THIS MORNING WITH MORE OF A THREAT FOR
HEAVY RAINFALL WHICH COULD POTENTIALLY LEAD TO FLASH FLOODING
CONCERNS. WHILE MOST AREAS COULD TAKE SOME RAIN WITH 1 HOUR FLASH
FLOOD GUIDANCE RUNNING IN THE 2 TO 2.5 INCH RANGE...URBAN AREAS
AND AREAS THAT HAVE RECENTLY RECEIVED HEAVY RAINFALL WOULD HAVE
AN ENHANCED RISK OF EXPERIENCING  FLASH FLOODING CONCERNS. WITH
PRECIPITABLE WATER VALUES RUNNING RIGHT AROUND 2 INCHES AND WARM
CLOUD DEPTHS OF 4.0 KM...THE STORMS WILL BE VERY EFFICIENT RAIN
PRODUCERS. THERE IS MORE THAN ENOUGH MUCAPE TO WORK WITH AHEAD OF
THE DEVELOPING MESOSCALE CONVECTIVE COMPLEX WITH MUCAPE VALUES
RUNNING RIGHT AROUND 2000 J/KG OVER SOUTHEAST
MINNESOTA...NORTHEAST IOWA...AND FAR SOUTHWEST  WISCONSIN. IN
ADDITION...1 TO 7 KM BULK SHEAR VALUES ARE HOVERING RIGHT AROUND
30S KTS THIS MORNING AND THE 0-3 KM SHEAR VECTOR IS ORIENTED
NEARLY PERPENDICULAR TO THE LINE OF STORMS MOVING IN THIS MORNING.
CONSIDERING ALL OF THIS...SOME OF THE STORMS WILL BE CAPABLE OF
DAMAGING WIND GUSTS AND HEAVY RAINFALL.

AFTER THE FIRST ROUND OF STORMS THIS MORNING...ANOTHER ROUND OF
STORMS ARE EXPECTED THIS AFTERNOON INTO EARLY THIS EVENING AS A
SHORTWAVE TROUGH MOVES THROUGH. 0-1KM MUCAPE VALUES ARE EXPECTED
TO CLIMB INTO THE 1700 TO 2500 J/KG RANGE WITH 0-6 KM BULK SHEAR
VALUES INCREASING INTO THE 30 TO 35 KT RANGE. ALSO...A FRONTAL
BOUNDARY WILL BE STALLED OVER THE AREA...ESSENTIALLY A WARM FRONT
THAT HAS BEEN REINFORCED BY THE MORNING CONVECTION. LATEST
THINKING IS THAT STORMS WILL FIRE OVER CENTRAL INTO EAST CENTRAL
MINNESOTA DURING THE AFTERNOON HOURS THEN RACE SOUTHEAST INTO
LOCATIONS ALONG AND EAST OF THE MISSISSIPPI RIVER. THE MAIN
HAZARDS FROM THESE STORMS APPEAR TO BE DAMAGING WIND GUSTS AND
HEAVY RAINFALL. CANNOT RULE OUT ISOLATED LARGE HAIL AS WELL. WILL
HAVE TO KEEP A CLOSE EYE ON THE POTENTIAL FOR AN ISOLATED TORNADO
NEAR THE BOUNDARY LATE THIS AFTERNOON INTO THIS EVENING.
HOWEVER...THE TORNADO THREAT APPEARS LOW AT THIS TIME GIVEN WEAK
0-1 KM SHEAR. THE STORMS WILL TAPER OFF LATE THIS EVENING INTO THE
OVERNIGHT HOURS AS THE BOUNDARY SLIPS SOUTH OF THE FORECAST AREA.
WARM AND MUGGY CONDITIONS ARE EXPECTED TODAY WITH HIGHS CLIMBING
INTO THE MID TO UPPER 80S ALONG AND WEST OF THE MISSISSIPPI RIVER.
THESE TEMPERATURE COMBINED WITH DEW POINTS IN THE LOWER 70S WILL
PRODUCE HEAT INDEX VALUES OF 95 TO 98 DURING THE AFTERNOON HOURS.

A LATE ADDITION...ADDED AREAS OF FOG TO THE NORTHWEST HALF OF THE
AREA. RECENT RAIN...HIGH DEWPOINTS...SKIES CLEARING OUT AND
DIMINISHING WINDS THROUGH THE NIGHT WILL LIKELY CAUSE FOG TO FORM.
THERE COULD EVEN BE SOME DENSE FOG.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 344 AM CDT THU AUG 21 2014

THE WARM FRONT STARTS TO EDGE BACK TO THE NORTH LATE FRIDAY
AFTERNOON INTO FRIDAY NIGHT. SHOWERS AND THUNDERSTORMS ARE POSSIBLE
ALONG THE FRONT FRIDAY NIGHT MAINLY SOUTHWEST OF THE INTERSTATE
94 CORRIDOR. THE HIGHER CHANCES FOR THIS ACTIVITY WILL BE SOUTH OF
INTERSTATE 90. THE WARM FRONT THEN LIFTS NORTH ACROSS THE REGION
ON SATURDAY BRINING THE STEAMY AIRMASS BACK INTO THE AREA. A FEW
SHOWERS AND STORMS ARE POSSIBLE ALONG THE FRONT AS IT MOVES THOUGH
BUT GIVEN THE STRENGTH OF THE RIDGE BUILDING IN WE MAY NOT SEE
MUCH PRECIPITATION. AN UPPER TROUGH OVER THE NORTHWEST  CONUS
THEN MAKES ITS WAY EAST LATE SATURDAY INTO SUNDAY AS THE RIDGE
OVER THE MISSISSIPPI RIVER VALLEY EXTENDING  INTO THE WESTERN
GREAT LAKES STARTS TO EDGE EAST. A FEW SHORTWAVES TRACK OVER
MINNESOTA AND WESTERN IOWA SATURDAY NIGHT THROUGH SUNDAY  GENERATING
SHOWERS AND THUNDERSTORMS BUT THESE LOOK TO STAY WEST OF THE
FORECAST AREA. THE ECMWF IS DRY DURING THIS TIMEFRAME WHILE THE
GFS BRINGS THESE WAVE A LITTLE FURTHER EAST PRODUCING
PRECIPITATION OVER THE FORECAST AREA. HAVE INCORPORATED A BLEND OF
THE TWO BUT WOULD BE SUPPRESSED TO STAY DRY THROUGH MUCH OF THE
DAY ON SUNDAY AS WELL. HAVE WARMED TEMPERATURES ON SUNDAY ACROSS
THE ENTIRE FORECAST AREA. HIGHS LOOK TO RANGE FROM THE MID 80S
OVER NORTH CENTRAL WISCONSIN TO THE LOWER TO MID 80S OVER
SOUTHWEST WISCONSIN INTO PORTIONS OF NORTHEAST IOWA. THESE
TEMPERATURES COMBINED WITH DEW POINTS IN THE LOWER 70S WILL
PRODUCE HEAT INDEX VALUES OF 95 TO 102 AND A HEAT ADVISORY MAY BE
NEEDED...ESPECIALLY OVER SOUTHWEST INTO CENTRAL WISCONSIN. UPPER
RIDGE FINALLY PUSHES EAST AND STARTS TO BREAK DOWN EARLY NEXT WEEK
AS SOUTHWEST FLOW ALOFT SETS UP OVER THE UPPER MISSISSIPPI RIVER
VALLEY. THIS WILL SET THE STAGE FOR AN ACTIVE PATTERN GOING INTO
THE EARLY PART OF NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 635 AM CDT THU AUG 21 2014

A COMPLEX OF SHOWERS AND THUNDERSTORMS MOVING INTO RST AS OF 11Z
IS ON TRACK TO MOVE INTO LSE BETWEEN 12-13Z. CEILINGS AND
VISIBILITIES ARE LIKELY TO LOWER TO IFR...WITH THE CEILING
LOWERING AIDED BY IFR STRATUS LIFTING NORTH OUT OF NORTHEAST IOWA
AND FAR SOUTHWEST WI. ANTICIPATING THE HEAVIER PRECIPITATION CORES
TO BE OUT OF RST BY 14Z AND LSE BY 15Z...WITH THE RAIN ENDING BY
16Z AT RST AND 17Z AT LSE. CEILINGS SHOULD CLIMB TOO THROUGH THE
MORNING...AIDED BY DAYTIME HEATING. MUCH OF THE AFTERNOON LOOKS
VFR. HOWEVER...MORE SHOWERS AND THUNDERSTORMS MAY FIRE UP ALONG
I-90...ALONG A WARM FRONT SITUATED IN PLACE AT THAT TIME. THESE
COULD KNOCK AT LEAST VISIBILITIES DOWN TO IFR AGAIN. APPEARS THERE
WILL BE A 2 HOUR WINDOW OF STORMS BUT THOUGH TO PIN DOWN WHEN
THAT WILL OCCUR BESIDES SOMETIME BETWEEN 21-02Z.

CONFIDENCE IS FAIRLY HIGH THAT SKIES WILL CLEAR OUT THIS EVENING.
A LIGHT WIND FIELD IN PLACE OVERNIGHT PLUS RECENT RAIN AND HIGH
HUMIDITY IN THE AIR SHOULD YIELD FOG AT BOTH TAF SITES. RST LIKELY
TO FALL FIRST GIVEN EARLIER CLEARING AND WINDS DROPPING OFF
SOONER. BOTH TAF SITES COULD SEE EITHER LIFR OR VLIFR CEILINGS
AND VISIBILITIES LATE IN THE NIGHT.

&&

.HYDROLOGY...TODAY INTO TONIGHT
ISSUED AT 344 AM CDT THU AUG 21 2014

THUNDERSTORMS WILL MOVE ACROSS THE FORECAST AREA THIS MORNING AND
ARE EXPECTED TO PRODUCE HEAVY DOWNPOURS AT TIMES. RAINFALL AMOUNTS
OF 1 TO 2 INCHES ARE EXPECTED WITH LOCALLY HIGHER AMOUNTS
POSSIBLE WHICH COULD LEAD TO LOCALIZED FLOODING. 1 HOUR FLASH
FLOOD GUIDANCE RANGES FROM 1.5 TO 2.5 INCHES ACROSS THE AREA SO
THE SOILS CAN TAKE SOME RAINFALL. THE MAIN CONCERN INITIALLY WILL
BE OVER URBAN AREAS AND IF ANY OF THE STORMS WOULD HAPPEN TO TRAIN
THERE COULD BE A FLASH FLOOD THREAT THIS MORNING. ANOTHER ROUND OF
STORMS IS EXPECTED THIS AFTERNOON INTO THIS EVENING. THESE STORMS
WILL ALSO BE CAPABLE OF PRODUCING HEAVY DOWNPOURS. DEPENDING ON
HOW MUCH RAIN FALLS OUT OF THE MORNING ACTIVITY...THE AFTERNOON
AND EVENING STORMS COULD BRING A THREAT FOR FLASH FLOODING.

&&

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

$$

UPDATE...WETENKAMP
SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...AJ
HYDROLOGY...WETENKAMP



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