Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 281959
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
300 PM CDT SUN JUN 28 2015

.SHORT TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 300 PM CDT SUN JUN 28 2015

ANOTHER CLUSTER OF SHOWERS/STORMS TRACKING SOUTHWARD ACROSS THE
REGION AT MID AFTERNOON...BEING DRIVING BY AN UPPER LEVEL
DISTURBANCE. SOME INSTABILITY HAS DEVELOPED - ESPECIALLY WEST WHERE
SUN BROKE THROUGH THE CLOUDS. ABOUT 1000 SBCAPE VIA THE RAP.
HOWEVER...HRRR/RAP BUFKIT SOUNDINGS SHOW A VERY SKINNY CAPE
PROFILE...PROHIBITIVE OF STRONG UPDRAFTS. WEAK SHEAR ALSO WOULDN/T
SUPPORT UPDRAFTS. A FEW STRONGER STORMS CAN/T BE RULED OUT...BUT
DON/T SEE A SEVERE RISK AT THIS TIME. LOOKS MORE LIKE HEAVY
DOWNPOURS AND LIGHTNING. PERHAPS HAIL UP TO 1/2 INCH. MOST OF THE
ACTIVITY SHOULD DIE OFF BY LATE EVENING WITH THE LOSS OF THE DAYTIME
HEATING.

ANOTHER SHORTWAVE TROUGH IS SLATED TO DROP ACROSS THE WESTERN
RIDGE...DIVING SOUTHEAST ACROSS THE UPPER MISSISSIPPI RIVER VALLEY
MONDAY AFTERNOON/EVENING. APPROX 100 KT 300 MB JET STREAK HELPING
THIS SHORTWAVE ALONG...AND WILL ALSO ENHANCE ITS LIFT IN ITS LEFT
EXIT REGION. DECENT FRONTOGENETIC FORCING LEADS THE SHORTWAVE INTO
THE REGION. WITH SOME MORNING SUN - MORESO TO THE WEST - INSTABILITY
WILL BUILD AHEAD OF THE APPROACHING SHORTWAVE...AS MUCH AS 2000 J/KG
OF SBCAPE. WIND SHEAR IS A BIT HEALTHIER COMPARED TO
TODAY...ALTHOUGH DEEPER AND STRONGER OVER WESTERN MN. LOCALLY 30-40
KTS OF 0-6 KM SHEAR PROGGED BY THE NAM/GFS...WITH 20-30 KTS IN THE 0-
3 KM LAYER. STRONGEST OVER NORTHEAST IA/SOUTHEAST MN. CAPE PROFILE
VIA GFS BUFKIT SOUNDINGS RATHER ANEMIC BUT THE NAM SHOWS SOMETHING A
BIT MORE SUPPORTIVE OF STRONGER UPDRAFTS. CAN/T RULE OUT A FEW
STRONG TO SEVERE STORMS AS A RESULT. SPC UPGRADED DAY2 OUTLOOK TO
INCLUDE A SLIGHT RISK FOR MUCH OF THE LOCAL AREA...AND CAN/T QUIBBLE
WITH THAT. THE MAIN QUESTION WILL BE IF THE SHORTWAVE CAN GET HERE
IN TIME TO TAP INTO THE INSTABILITY.

FOR TUE...THE SHORTWAVE LINGERS ACROSS EASTERN WI WITH A NORTH-SOUTH
RUNNING SFC FRONT RESTING ALONG THE LAKE MICHIGAN SHORELINE. ENOUGH
LIFT AND SATURATION FOR SOME SHOWER/ISOLD STORM DEVELOPMENT FOR THE
EASTERN 1/2 OF WISCONSIN. DEPENDING ON HOW FAR EAST THE SHORTWAVE
MAKES IT...COULD HAVE SOME RAIN CHANCES FOR PARTS OF WESTERN WI.
WILL KEEP THE SMALL CHANCES FOR THE WI PORTION OF THE FORECAST AREA
WITH THIS IN MIND.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 300 PM CDT SUN JUN 28 2015

MODELS REMAIN IN GOOD AGREEMENT WITH KEEPING THE REGION UNDER
NORTHWEST FLOW INTO NEXT WEEKEND...ALTHOUGH THEY SHOW SOME
FLATTENING LATER IN THE WEEK AS THE WEST COAST RIDGE BECOMES LESS
AMPLIFIED. VARIOUS SHORTWAVES WILL MOVE ALONG THE FLOW AND COULD
INTERACT WITH AFTERNOON INSTABILITY TO PRODUCE SHOWERS/STORMS ACROSS
THE REGION. BUT THERE ARE DIFFERENCES IN THE MODELS ON TIMING AND
PLACEMENT OF THE FEATURES...GENERALLY FAVORING KEEPING THE
PERTURBATIONS SOUTHWEST OR NORTH OF THE LOCAL AREA. OUT OF ALL THE
DAYS...WED HOLDS PERHAPS THE BEST CHANCE FOR ANOTHER ROUND OF
SHOWERS/STORMS...WITH THE GFS/ECMWF DROPPING ONE OF THOSE SHORTWAVES
THROUGH THE FORECAST AREA. THE GEM KEEPS IT WEST WITH THE NAM
LEANING THAT WAY. NOT A LOT OF CONSISTENCY BETWEEN OR WITHIN THE
MODELS IN THIS TIME FRAME. OVERALL...WILL CONTINUE THE SMALL RAIN
CHANCES THROUGH MUCH OF THE 7 DAY FORECAST PERIOD DUE TO THE MODEL
DIFFERENCES AND TYPE OF FLOW WE ARE IN.

&&


.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1225 PM CDT SUN JUN 28 2015

PLAN ON SCATTERED SHRA/TS THIS AFTERNOON AS A MID-LEVEL TROUGH DROPS
THROUGH THE REGION. DUE TO THE SCATTERED NATURE OF THIS
CONVECTION...WENT WITH VCTS AT BOTH KRST/KLSE TAF SITES AFTER 19Z
WITH MAINLY VFR CONDITIONS EXPECTED. EXPECT SOME AMENDMENTS AS THE
AFTERNOON WEARS ON IF SHRA/TS ENCROACH THE AERODROMES. THIS
CONVECTION IS THEN EXPECTED TO DIE OFF TOWARD 02Z WITH LOSS OF
SURFACE HEATING. LIGHT WINDS OVERNIGHT AND A MOIST LOWER BOUNDARY
LAYER FROM TODAY/S RAINFALL WILL LEAD TO IDEAL STRATUS/FOG
CONDITIONS OVERNIGHT. HIGHER CONFIDENCE IS AT KLSE WHERE WINDS ARE
EXPECTED TO DECOUPLE MORE IN THE RIVER VALLEY.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION.....DAS


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