Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 302041
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
341 PM CDT THU APR 30 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 341 PM CDT THU APR 30 2015

THIS PERIOD CONTAINS TRANQUIL WEATHER WITH A SMALL CHANCE FOR VERY
LIGHT SHOWERS FRIDAY AFTERNOON AND EVE.

CURRENT WATER VAPOR SHOWING A MODERATELY VIGOROUS UPPER
TROPOSPHERIC SHORTWAVE TROUGH OVER SOUTHERN MT WHICH MATCHES
MORNING GFS ANALYSIS OF 500-300MB QG CONVERGENCE WELL. WATER VAPOR
SHOWING A NUMBER OF SMALLER SCALE WAVES ALONG THE TROUGH AXIS THAT
EXTENDS FROM ERN MT INTO SASKA CANADA. REGIONAL RADARS SHOWING
ECHO AHEAD OF THE AXIS IN THE DAKOTAS TO WY...LINING UP WELL WITH
FORCING. A FEW SURFACE OBSERVATIONS OF VERY LIGHT RAIN THERE TOO.
OTHERWISE...RIDGE AXIS CONTINUES TO BUILD INTO THE GREAT LAKES
WITH VERY CLEAN WEATHER.

MODEL CONSENSUS IS TO LIFT THE QG FORCING AREA E-NE OUT OF MT
INTO NRN WI...AND INTO LOWER-MID LEVEL DRY AIR REGION. WITH THE
BETTER DYNAMICS LIFTING NORTH OF THE AREA...SHOWERS THAT DEVELOP
OVERNIGHT SHOULD BE ON A SLOWLY DIMINISHING TREND AS THEY SHIFT
INTO THE FORECAST AREA FRIDAY. THE HI RES WINDOW RUNS DO BRING
ECHO ACROSS THE AREA. THIS MAY CAUSE SOME SPRINKLES HERE AND
THERE...AS THE LOWEST 10KFT ARE QUITE DRY. LOW LEVEL FORCING IS
NOT PRESENT TO ASSIST. THUS...VERY MINOR RAIN CHANCES FRIDAY.
CLOUDS WILL HAVE SOME IMPACT ON WARMING...AS THEY MAY BE HIGHER
/8-10KFT/...BUT THICK.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 340 PM CDT THU APR 30 2015

LATER SUNDAY AFTERNOON AND NIGHT CONTINUES TO LOOK WET WITH A
CONVECTIVE LINE OF RAIN MOVING NW-SE THROUGH THE AREA OVERNIGHT.
THIS IS VERY WELL AGREED UPON FROM THE ENSEMBLE OF 30.12Z
DETERMINISTIC FORECAST MODELS. SEVERE WEATHER ANALYSIS SHOWS AN
UNCAPPED AND UNSTABLE ENVIRONMENT AHEAD OF AN APPROACHING FRONT
WITH ABOUT 1500 J/KG OF MLCAPE. THIS COULD PROVIDE SOME NICE POP
IN THE LATER AFTERNOON ACROSS SERN MN...BUT WIND SHEAR STRENGTH IS
MINIMALLY SUPPORTIVE...WITH MOST SHEAR IN THE 0-3KM LAYER /NEAR
20-25KTS/ AND VERY LITTLE /NIL/ DEEP SHEAR. SO...PULSE HAIL WITH
PRETTY GOOD 500-700MB LAPSE RATES LOOKS POSSIBLE...EVOLVING INTO A
MAINLY NON-SEVERE LINE AND PROPAGATING SOUTHEAST. A LOW SEVERE
WEATHER THREAT IS MENTIONED IN THE HAZ WEATHER OUTLOOK WHICH LOOKS
APPROPRIATE FOR NOW AS THERE ARE MANY DAYS UNTIL SUNDAY AFTERNOON
TO REFINE. SPC DAY 4-8 DID NOT INCLUDE A RISK. MOST AREAS WILL
PROBABLY SEE AROUND AN INCH OF WATER FROM THIS WEATHER.

UNTIL THAT TIME/FRONT...TEMPERATURES CONTINUE TO INCREASE...AND
SOME MINIMAL FORCING IN THE LOWER-LEVELS IS AROUND SATURDAY NIGHT
WITH SOME ISENTROPICALLY-LIFTING WEAK MOISTURE TRANSPORT
CONVERGENCE. HAVE INCLUDED SOME SMALL TSRA CHANCES FOR THAT PERIOD
WITH CONCENTRATION SOUTH TOWARD THE MOISTURE SOURCE. STILL HAVE
SOME DOUBTS THAT MOISTURE RETURN WILL BE ENOUGH TO CAUSE SHRA
UNTIL SUNDAY.

MONDAY-WEDNESDAY...THE FRONT WILL PUSH THROUGH MONDAY MORNING IT
APPEARS AND THEN STALL AROUND I-80. HAVE TRIED TO PUSH RAIN
CHANCES FURTHER SOUTH MONDAY NIGHT AND TUESDAY...BUT FEEL THESE
WILL PROBABLY TREND FURTHER SOUTH. AN ACTIVE I-80 BOUNDARY
WITHOUT A LOW EJECTING OUT OF THE SOUTHWEST FLOW TYPICALLY WILL
NOT RETURN THE FRONT NORTH...AS THE MODELS WOULD LIKE TO DO. THIS
SHOULD HAPPEN AS SOUTHWEST LOW EJECTS INTO WEDNESDAY.

FAIRLY RAINY END OF NEXT WEEK AS THE SOUTHWEST LOW EJECTS INTO
THE GREAT LAKES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1236 PM CDT THU APR 30 2015

A RIDGE OF HIGH PRESSURE WILL GRADUALLY SLIDE EAST AWAY FROM THE
AREA. AS THIS OCCURS...THE WINDS  SHIFT FROM NORTHEAST TO
SOUTHEAST BY THE EVENING...AND SOUTH AND SOUTHWEST ON FRIDAY
MORNING. WIND SPEEDS WILL REMAIN LESS THAN 10 KNOTS THROUGH THE
PERIOD. AS FAR AS CLOUDS...THERE WILL BE MAINLY A SCATTERED DECK
OF CLOUDS ABOVE 15K FEET.


&&

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

$$

SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...BOYNE



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