Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 172305
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
605 PM CDT SUN AUG 17 2014

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 230 PM CDT SUN AUG 17 2014

LATEST WATERVAPOR IMAGERY POINTED TO A SHORTWAVE TROUGH MOVING
SLOWLY EAST ACROSS WESTERN MN...RESPONSIBLE FOR AN AREA OF
SHOWERS/STORMS ACROSS MID/EASTERN SECTIONS OF THE GOPHER STATE.
ANOTHER UPPER LEVEL SHORTWAVE TROUGH WAS SWINGING INTO THE NORTHERN
PLAINS.

THIS FIRST SYSTEM WILL CONTINUE TO MAKE SLOW PROGRESS EAST
TONIGHT...GRADUALLY TRACKING INTO NORTHERN WI. MODELS SUGGEST THAT
THIS FEATURE WILL WEAKEN AND/OR GET PULLED INTO THE NEXT
SHORTWAVE...WHICH WILL TAKE A SPEEDIER PATH ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY ON MONDAY. 25 KT 850 MB JET WILL PROVIDE A
PUSH OF LOW LEVEL MOISTURE FOR THE SYSTEM TO WORK ON MONDAY.
ALTHOUGH WARM CLOUD DEPTHS AREN/T AS DEEP AS RECENT DAYS - ITS STILL
FORECAST TO BE AROUND 3.5 KFT WITH PWS AROUND 1.6. SO...HEAVY RAIN
STILL A GOOD BET WITH ANY OF THE STRONGER STORMS. MUCAPES BUILD IN
EXCESS OF 2000 J/KG BY 00 TUE...WITH THE BULK OF THE SHEAR IN THE 0-
3KM LAYER NEAR 25 KTS. FAIRLY SKINNY CAPE PROFILES ACROSS THE
FORECAST AREA FOR THE MOST PART - PER BUFKIT SOUNDINGS - ALTHOUGH A
BIT MORE FAVORABLE FOR STORM DEVELOPMENT ACROSS NORTHEAST IA.
OVERALL...DON/T SEE AN ORGANIZED SEVERE WEATHER THREAT AT THIS TIME.
BELIEVE HEAVY RAIN AND A CHANCE FOR SMALL HAIL THE MORE LIKELY
OUTCOMES.

ON THE WHOLE...WILL HAVE SOME SCATTERED SHOWERS/STORMS INTO THE
EVENING HOURS FOR SOUTHEAST MN...WITH CHANCES MOSTLY ALONG AND NORTH
OF I-90 THROUGH THE OVERNIGHT. THE GREATER THREAT FOR RAIN WILL COME
LATER IN THE DAY ON MONDAY...AND MOST LOCATIONS CAN EXPECT TO GET
WET.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 230 PM CDT SUN AUG 17 2014

DECENT AGREEMENT IN THE MODELS WITH THE OVERALL PATTERN FOR THE
LATER PART OF THE NEW WEEK. THE GFS/ECMWF POINT TO A FAIRLY
PROGRESSIVE PATTERN WITH SOME MINOR RIDGE BUILDING FRI. BOTH SLIDE
AN UPPER LEVEL SHORTWAVE TROUGH ACROSS THE NORTHERN PLAINS
WED...TRACKING NORTH OF THE REGION ON THU. AN ASSOCIATED SFC WARM
FRONT WILL LIFT ACROSS THE UPPER MISSISSIPPI RIVER VALLEY...WITH
FRONTOGENETIC LIFT AND WARM AIR ADVECTION ALONG IT LIKELY
RESULTING IN A BAND OF SHOWERS/STORMS.

ANOTHER SHORTWAVE TROUGH IS SLATTED TO MOVE OUT OF THE SOUTHERN
ROCKIES AND TAKE AIM ON THE UPPER MISSISSIPPI RIVER VALLEY FRI/SAT.
SOME DISAGREEMENTS BETWEEN THE MODELS ON
TIMING/POSITIONING/STRENGTH...WITH THE GFS THE QUICKER OF THE TWO.
OVERALL...BOTH SOLUTIONS POINT TO ANOTHER ROUND OF SHOWERS/STORMS.
WILL SIDE WITH CONSENSUS FOR RAIN CHANCES FOR NOW.

LOOKING AT A SLOW WARM UP THIS WEEK...WITH SOME MID-UPPER 80 DEGREE
READINGS LIKELY BEFORE THE WORK WEEK IS DONE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 605 PM CDT SUN AUG 17 2014

THE FIRST CONCERN IN THE FORECAST IS WHETHER FOG AND LOW STRATUS
WILL FORM AGAIN TONIGHT. A LIGHT SOUTHEAST FLOW IS IN PLACE ACROSS
THE AREA AND IS EXPECTED TO CONTINUE THROUGH MUCH OF THE NIGHT
WITH SPEEDS BETWEEN 5 AND 10 KNOTS. THIS SHOULD BE ENOUGH MIXING
TO KEEP THE FOG THAT FORMS FROM BECOMING DENSE BUT MVFR AND SOME
IFR CONDITIONS STILL POSSIBLE. MORE LIKELY WILL BE ANOTHER NIGHT
WITH LOW STRATUS AND IFR CEILINGS AND WILL CONTINUE TO SHOW THESE
CONDITIONS FOR BOTH SITES. CONDITIONS SHOULD BE SLOW TO IMPROVE
MONDAY MORNING WITH THE WEAK FLOW AND HIGH MOISTURE LEVELS AND
WILL KEEP THE LOW CEILINGS FOR MOST OF MONDAY MORNING. THE NEXT
CONCERN IS WITH THE POTENTIAL FOR SHOWERS OVERNIGHT. SHORT WAVE
TROUGH ACROSS THE DAKOTAS IS EXPECTED TO MOVE SLOWLY EAST TOWARD
THE REGION WITH SOME SCATTERED SHOWERS AHEAD OF IT. BASED ON THE
TIMING SHOWN BY MANY OF THE SHORT TERM MESO MODELS WILL PUSH THE
TIMING OF THESE BACK TO ABOUT 10Z WITH A VCSH FOR BOTH SITES. THIS
SHORT WAVE TROUGH WILL QUICKLY BE FOLLOWED BY ANOTHER FOR MONDAY
AFTERNOON. WITH SOME HEATING...EXPECT CAPE VALUES TO BUILD TO
BETWEEN 500 AND 1000 J/KG AND BASED ON THIS WILL SHOW VCTS FOR
BOTH SITES DURING THE AFTERNOON WITH VFR CONDITIONS.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION...04


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