Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 020441
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1141 PM CDT FRI MAY 1 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 333 PM CDT FRI MAY 1 2015

THIS EVENING WE WILL CONTINUE TO HANDLE THE HIT AND MISS RAIN
SHOWERS...WHICH ARE PRODUCING UP TO ABOUT 0.10 INCHES...AS THEY
SHIFT EAST. THE BEST RADAR ECHO /N OF LA CROSSE/ SEEMS TO BE
ASSOCIATED WITH A SMALLER SCALE TROUGH/CURL SEEN IN WATER VAPOR
NEAR RED WING AT 20Z. THIS AREA WITH ENHANCED LIFT WILL BE THE
LONGEST LIVED OF THE SHOWERS... WHICH WERE OTHERWISE ON A
WEAKENING TREND. HAVE ADJUSTED RAIN CHANCES FROM RED WING EAST TO
WAUSAU TO ACCOUNT FOR MEASURABLE SHOWERS UP TO A TENTH OF AN INCH.
THIS WILL CONTINUE TO CLEAR EAST SLOWLY OVERNIGHT.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 333 PM CDT FRI MAY 1 2015

MAIN FORECAST EMPHASIS WAS PUT ON SUNDAY AND SUNDAY EVENING
WEATHER. CONSENSUS MODEL FORECASTS HAVE REMAINED CONSISTENT WITH
THE BROADER PICTURE IDEA OF CONVECTIVE DEVELOPMENT ALONG A COLD
FRONT LATER SUNDAY AFTERNOON IN MN...SHIFTING SOUTHEAST THROUGH
THE AREA OVERNIGHT. IT DOES SEEM THERE IS A SLIGHT CREEP TO A
FASTER SOLUTION IN THE MODEL TRENDS.

MODERATE SOUTH-SOUTHWEST FLOW SUNDAY DURING THE DAY WILL BRING
925MB TEMPERATURES UP ANOTHER 3C FROM SATURDAY. IN THIS PRE-
FRONTAL POSITION SUNDAY...WITH DEEPER MIXING INDICATED /800-850
MB/...FORCING OFF TO THE NORTHWEST...AND WINDS OF 15-30 MPH AT
LEAST...WARM PROD OF AIR SHOULD BE REALIZED...ESPECIALLY IN THE
SOUTHERN FORECAST AREA. THUS...HAVE INCREASED HIGHS THAT DAY INTO
THE 80S...WELL ABOVE THE UNDER-PERFORMING MODEL GUIDANCE AS OF
LATE ON HIGHS...BUT AM ALSO BANKING ON GOOD AMOUNT OF SUNSHINE.
WIND SPEEDS HAVE BEEN ADJUSTED UP BASED ON DEEPER MIXING. THE
01.12Z NAM IS MOST AGGRESSIVE WITH THE LOW-LEVEL WIND FIELD WITH
THE NAM MOS SUSTAINED AT 24KTS AT KRST...BUT FOR NOW HAVE TAKEN
THAT AS AN OUTLIER. HAVE BROUGHT UP WIND GUSTS TO 25-33 MPH SUNDAY.

SEVERE WEATHER CHANCES FOR SUNDAY AFTERNOON AND EVENING STILL LOOK
POSSIBLE WITH LARGE HAIL AND DAMAGING WIND THE MAIN THREATS. THE
ENVIRONMENT REMAINS VERY CONSISTENT WITH ABOUT 1500 J/KG OF
MLCAPE AND MODERATE/CURVING HODOGRAPHS IN THE LOWEST 0-3KM. THIS
USES AN AVERAGE DEWPOINT AROUND 56-57F...UNDERCUTTING MODEL
SURFACE DEWPOINTS. WITH FRONTAL LINE FORCING AND COLD POOL
DOMINATED SYSTEM...WOULD EXPECT A LINE TO FORM AND MOVE THROUGH
THE FORECAST AREA. DEEPER MIXING COULD LEAD TO ENHANCED DOWNDRAFTS
AS SOUNDINGS DO APPEAR TO HAVE AN INVERTED-V STRUCTURE. SEVERE
CHANCES WOULD BE HIGHEST OVER THE NORTHWEST FORECAST AREA...AND
WOULD EXPECT ISOLATED SEVERE REPORTS /PROBABLY NW OF A LINE FROM
WAUSAU-LSE-WATERLOO/. THIS IS A BIT FURTHER SOUTHEAST THAN SPC
MARGINAL AREA CURRENTLY. THIS ISOLATED SEVERE STORM WORDING IS IN
THE HAZARDOUS WEATHER OUTLOOK. A GOOD VISUALIZATION OF THE
REFLECTIVITY FORECAST CAN TO BE SEEN IN THE 4KM NAM CONUS NEST RUN
FROM 01.12Z.

MONDAY-MONDAY NIGHT...FRONTAL BOUNDARY TREND IN THE MODEL GUIDANCE
CONTINUES TO SHIFT SOUTH WITH STRONGER RIDGING MOVING INTO THE
GREAT LAKES. HAVE AGAIN PUSHED TO DRY THE FORECAST FURTHER SOUTH
WITH THE FRONTAL BOUNDARY NEARLY ON I-70 AND THE 850MB FRONT AND
AXIS OF DILITATION AROUND I-80.

TUESDAY AND WEDNESDAY WILL SEE THE LARGE SCALE PATTERN SHIFT AS
THE LONG WAVE TROUGH EJECTS OUT OF THE SOUTHWESTERN U.S. THIS WILL
BRING THE FRONTAL ZONE ALONG I-80 BACK NORTHEAST AND PROVIDE A
FOCUS FOR RAIN CHANCES. UPPER LOW AND MOISTURE PLUME WILL THEN
SHIFT IN LATE IN THE WEEK FOR THU-FRI WITH HIGHER RAIN CHANCES.
WOULD THINK SOME DETAIL COULD BE GIVEN TO THIS FORECAST ONCE IT

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1141 PM CDT FRI MAY 1 2015

VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. PLAN ON SCT-
BKN CEILINGS AT THE TAF SITES TONIGHT INTO TOMORROW WITH CLOUD
BASES IN THE 5 TO 7 KFT RANGE. WINDS WILL BE ON THE INCREASE
TOMORROW  AS THE PRESSURE GRADIENT TIGHTENS AHEAD OF A TROUGH
OVER THE NORTHERN PLAINS. LOOK FOR SOUTHWEST WINDS TO INCREASE TO
10 TO 13 KTS FROM LATE SATURDAY MORNING INTO SATURDAY AFTERNOON.
SOME OF THE WIND GUSTS COULD APPROACH 19 KTS AT KRST AND 16 KTS AT
KLSE. WILL HAVE TO KEEP A CLOSE EYE ON THE POTENTIAL FOR AN
ISOLATED SHOWER OR THUNDERSTORM LATE SATURDAY AFTERNOON INTO
SATURDAY EVENING. CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE A
MENTION OF A SHOWER OR THUNDERSTORM IN THE TAF AT THIS TIME.

&&

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

$$

SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...WETENKAMP


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