Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 242321
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
621 PM CDT SUN MAY 24 2015

.SHORT TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 300 PM CDT SUN MAY 24 2015

WAVES OF SHOWERS/STORMS CAN BE EXPECTED INTO TUESDAY AS VARIOUS
SHORTWAVE TROUGHS SPIN ACROSS THE REGION...ALONG WITH A WAVERING
FRONTAL BOUNDARY.

WARM AIR ADVECTION POWERED SHOWERS MAKING THEIR WAY NORTHWARD ACROSS
THE UPPER MISSISSIPPI RIVER VALLEY THIS AFTERNOON...MOVING NORTH OF
THE LOCAL AREA LATER THIS EVENING. MESO MODELS THEN IN GOOD
AGREEMENT THAT A NORTH-SOUTH BAND OF SHOWERS/ISOLATED THUNDERSTORMS
WILL DEVELOP IN RESPONSE TO FRONTOGENETIC FORCING SOUTH OF THE
DEPARTING RAIN SHIELD. TRENDS WOULD FAVOR SOUTHWEST WI...QUICKLY
EXITING TO THE EAST/NORTHEAST. THINK THE THUNDER THREAT IS
LOW...WITH MINIMAL/IF ANY INSTABILITY INDICATED...BUT ENOUGH FORCING
TO CONTINUE AT LEAST A SMALL CHANCE WITH THE EXPECTED CONVECTIVE
LINE.

OVERNIGHT A RIPPLE IN THE UPPER LEVEL FLOW WILL APPROACH FROM THE
SOUTH WITH AN ACCOMPANYING SWATH OF LOW LEVEL WARM AIR ADVECTION.
EXPECTING ANOTHER AREA OF RAIN WITH THIS SHORTWAVE...LIKELY INTO
NORTHEAST IA/SOUTHWEST WI BEFORE 12Z MONDAY. NOT MUCH/IF ANY
INSTABILITY INDICATED IN THIS STEAD EITHER...AND THE THUNDER THREAT
LOOKS LOW. MESO MODELS TREND EXITING THE RAIN NORTH OF THE FORECAST
AREA BY 18Z.

DRIER AIR WORKS IN POST THE MORNING SYSTEM...AND SHOULD DRY OUT MUCH
OF THE FORECAST AREA FOR THE LATE MORNING/AFTERNOON OF MEMORIAL DAY.
INSTABILITY IS SLATED TO CLIMB THOUGH...AROUND 1500 J/KG SBCAPES IN
THE NAM/GFS BY 00Z. 30-40 KTS OF 0-6 KM OF SHEAR BY THAT TIME TOO.
AN UPPER LEVEL TROUGH WILL BE APPROACHING FROM THE PLAIN STATES
MONDAY EVENING...WITH A FRONTAL BOUNDARY LIKELY ALREADY LAYING UP
NORTHEAST-SOUTHWEST ACROSS THE REGION. SHOULD SEE SOME CONVECTION
FIRE IN THE REGION OF THE BOUNDARY/AHEAD OF THE WAVE...LIKELY TAPING
INTO SOME OF THE INSTABILITY THAT LINGERS INTO THE EVENING. SOME
POTENTIAL FOR STRONGER - POSSIBLY SEVERE STORMS IF EVERYTHING COMES
TOGETHER.

THE TROUGH SWINGS THROUGH THE UPPER MISSISSIPPI RIVER VALLEY ON
TUE...AND SHOULD GENERATE YET ANOTHER ROUND OF SHOWERS. THE GFS/NAM
PRODUCE ABOUT 1000 J/JG OF MUCAPE...WITH ABOUT 20 KTS OF 0-3 KM
SHEAR. NOT SURE THERE WOULD BE ENOUGH/ANY CLEARING TO HELP GENERATE
THE INSTABILITY...BUT ENOUGH LIFT FOR AT LEAST ISOLATED THUNDER
CHANCES.


.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 300 PM CDT SUN MAY 24 2015

MODELS POINT TO A FAIRLY QUICK MOVING ZONAL UPPER LEVEL FLOW
PERSISTING INTO NEXT WEEKEND...SHUFFLING SHORTWAVE TROUGHS/RIDGES
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY.

GFS/ECMWF AGREE ON A DRY WEDNESDAY INTO THURSDAY AS A WEAK RIDGE A
LOFT SLIPS OVER THE REGION. A SHOWER/STORM THREAT WOULD RETURN THU
NIGHT-SAT AS AN UPPER LEVEL TROUGH TAKES AIM ON THE UPPER
MISSISSIPPI RIVER VALLEY...SLIDES A FRONT IN...AND THEN BITS OF
ENERGY IN THE SOUTHERN PORTION OF THE FLOW RIDE UP THE LINGERING
SURFACE BOUNDARY. MODELS ARE AT ODDS WITH HOW FAST THESE VARIOUS
FEATURES MOVE IN/OUT ALONG WITH PARTICULARS ON PLACEMENT. THE GFS IS
QUICKER IN AND OUT WITH THE PCPN MAKERS...WITH THE EC SLOWER AND
HANGING ONTO CHANCES INTO SAT. GEM IS SIMILAR TO THE GFS. WILL SIDE
WITH CONSENSUS SOLUTION FOR THE DETAILS THIS FAR OUT...WITH SOME
LEANINGS TOWARD THE GFS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 621 PM CDT SUN MAY 24 2015

ONE BAND OF -RA/RA HAS LIFTED NORTH OF THE TAF SITES WITH A WARM
FRONT REMAINING SOUTH OF THE AREA ACROSS CENTRAL IA TO NORTHERN IL.
BETWEEN THE RAIN BAND AND THE FRONT MVFR/IFR CIGS WERE COMMON...
WITH MVFR TO LCL IFR VSBYS IN BR ACROSS THE HIGHER TERRAIN LOCATIONS
ESPECIALLY WEST OF THE MS RIVER. THESE CONDITIONS WILL PREVAIL THRU
THE EVENING WITH THE LOWER LEVEL MOISTURE/SATURATION NORTH OF THE
WARM FRONT. BIGGEST QUESTION IS WHEN WILL THE WARM FRONT LIFT NORTH
OF THE TAF SITES. ONCE THE FRONT LIFTS THRU...SOUTHWEST WINDS
INCREASE...WITH DEEPER MIXING AND IMPROVING CIGS/VSBYS. ONE STRONGER
SHORTWAVE OVER OK EARLY THIS EVENING IS GOING TO LIFT NORTHEAST
TONIGHT...AND NORTH OF THE TAF SITES BY MID MORNING MON. THIS WAVE
IS LOOKING TO PASS WITH A ROUND OF -RA/-SHRA LATE TONIGHT/EARLY MON
MORNING...AND CARRY THE WARM FRONT NORTH OF THE TAF SITES BY MID
MORNING MON. SPREAD IMPROVING CIGS/VSBYS ACROSS THE TAF SITES BY
LATER MON MORNING AND FOR MON AFTERNOON...WITH SOME LOWER LEVEL
DRYING AND BRISK/GUSTY SOUTHWEST WINDS FOR MIXING BEHIND THE FRONT.

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION.....RRS


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