Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 110859
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
359 AM CDT FRI APR 11 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 358 AM CDT FRI APR 11 2014

THE MAIN FORECAST CONCERNS ARE ON THE FIRE WEATHER CONCERNS THIS
AFTERNOON AND THE RAIN CHANCES THROUGH THE PERIOD.

WATER VAPOR SATELLITE THIS MORNING SHOWS A SHORT WAVE TROUGH
MOVING ACROSS THE EASTERN DAKOTAS WITH A FEW SHOWERS OUT AHEAD OF
IT OVER MINNESOTA. SURFACE OBSERVATIONS INDICATE THERE IS NOT
MUCH TO THESE SHOWERS WITH NO VISIBILITY RESTRICTIONS BEING
REPORTED. THE 11.00Z HI-RES ARW SEEMS TO HAVE THE BEST HANDLE ON
THESE SHOWERS AND SUGGESTS SOME SCATTERED ACTIVITY WILL BE
POSSIBLE THIS MORNING AS THE SHORT WAVE TROUGH MOVES ACROSS
MINNESOTA AND WISCONSIN. THE SOUTHERN EXTENT OF THE SHOWERS SHOULD
BE ABOUT THE IOWA/MINNESOTA BORDER AND WILL HAVE 20 TO 30 PERCENT
RAIN CHANCES TO COVER THIS ACTIVITY.

THE NEXT NORTHERN STREAM SHORT WAVE TROUGH WILL CROSS THE NORTHERN
ROCKIES TONIGHT AND MOVE ACROSS THE UPPER MIDWEST AND NORTHERN
GREAT LAKES SATURDAY. BOTH THE NAM AND GFS INDICATE THE BEST PV
ADVECTION WILL STAY NORTH OF THE AREA...BUT THERE SHOULD STILL BE
SOME WEAK PV ADVECTION IN THE 500-300 MB LAYER ACROSS THE FORECAST
AREA. ONCE THIS WAVE MOVES PAST...THE UPPER LEVEL FLOW TURNS TO
THE SOUTHWEST WITH SEVERAL SHORT WAVE TROUGHS EXPECTED TO BE
EMBEDDED IN THIS FLOW. THESE WAVES WILL START TO AFFECT THE AREA
SATURDAY NIGHT WITH THE STRONGEST ONE EXPECTED MOVE ACROSS SUNDAY.
SEVERAL ROUNDS OF WEAK TO MODERATE PV ADVECTION WILL OCCUR WITH
THESE WAVES. THE GFS INDICATES THAT ALL OF THESE WAVES WILL
PRODUCE MODERATE TO STRONG QG CONVERGENCE AS THEY PASS THROUGH.

AT THE SURFACE...AN AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP
TONIGHT AHEAD OF THE SHORT WAVE TROUGH COMING ACROSS THE NORTHERN
ROCKIES. STRONG WARM AIR ADVECTION AHEAD OF THIS LOW WILL RESULT
IN 10 TO 15 UBAR/S OF UP GLIDE ON THE 295K ISENTROPIC SURFACE.
THE LOW WILL THEN MOVE EAST OF THE AREA SATURDAY NIGHT PUSHING A
COLD FRONT THROUGH THE AREA. AS THE NEXT ROUND OF SHORT WAVE
TROUGHS COME OUT OF THE SOUTHWEST AND INTERACT WITH THE
FRONT...THE WARM AIR ADVECTION OVER THE BOUNDARY SHOULD RESULT IN
7-12 UBAR/S OF UP GLIDE AGAIN ON THE 295K SURFACE. THE BEST
FRONTOGENESIS WILL OCCUR LATE SATURDAY NIGHT INTO SUNDAY WITH THIS
EXPECTED TO BE MODERATE TO STRONG IN STRENGTH IN THE 850-500 MB
LAYER. WILL ALL THIS FORCING...EXPECT TO SEE SEVERAL ROUNDS OF
RAIN THROUGH THE WEEKEND. THE FIRST ROUND OF RAIN WILL MOVE IN
LATE TONIGHT AND RAISED THE RAIN CHANCES UP TO 60 ACROSS THE FAR
WEST. MOST OF THE AREA SHOULD SEE SOME RAIN SATURDAY MORNING WITH
THE PASSAGE OF THE SHORT WAVE TROUGH AND SURFACE LOW AND INCREASED
THE CHANCES TO 50 PERCENT ACROSS THE FAR SOUTH UP TO 90 PERCENT
IN THE NORTH. AS THE FRONT SLIDES ACROSS THE AREA SATURDAY
AFTERNOON AND NIGHT...THE BEST RAIN CHANCES START TO GET CONFINED
TO THE EAST AND SOUTHERN SECTIONS. WILL GO WITH 50 TO 80 PERCENT
CHANCES SATURDAY AFTERNOON FROM WEST TO EAST AND THEN 20 TO 70
SATURDAY NIGHT FROM NORTH TO SOUTH. WITH THE STRONG SHORT WAVE
TROUGH AND FRONTOGENESIS SUNDAY...SPREAD THE CHANCES BACK NORTH
SOME WITH 40 TO 80 PERCENT CHANCES FROM NORTH TO SOUTH.

GENERALLY LIMITED THE THUNDER CHANCES THROUGH THE PERIOD. WHILE
THE FORCING WILL DEFINITELY BE STRONG ENOUGH TO PRODUCE
THUNDER...SOME CONCERNS ON JUST HOW MUCH CAPE WILL BE AVAILABLE.
THE MODELS LOOK TO SURGE TOO MUCH LOW LEVEL MOISTURE NORTHWARD
SATURDAY SUGGESTING A 15 TO 20 DEGREE RISE IN SURFACE DEW POINTS
SATURDAY MORNING TAKING THE DEW POINTS FROM THE MID 30S INTO THE
50 TO 55 DEGREE RANGE. HOWEVER...IT LOOKS LIKE THE MODELS HAVE
INITIALIZED TOO MUCH MOISTURE OVER THE OKLAHOMA INTO ARKANSAS AND
FARTHER SOUTHWARD WHICH IS THE SOURCE REGION FOR THE MOISTURE THEY
BRING INTO THE UPPER MIDWEST.

TOTAL RAINFALL AMOUNTS FROM LATE TONIGHT THROUGH SUNDAY COULD
EXCEED AN INCH OVER THE SOUTHEAST HALF OF THE AREA...WITH UP TO
TWO INCHES POSSIBLE ACROSS THE FAR SOUTH. UNSURE WHAT THE
HYDROLOGIC RESPONSE IN THE RIVERS WILL BE FROM THIS RAIN AS THE
LATEST SOIL TEMPERATURES HERE THE OFFICE INDICATE NO FROST IS LEFT
IN THE GROUND. IF THIS IS THE CASE FOR MUCH OF THE AREA...A LOT OF
THIS RAIN COULD BE ABSORBED AND NOT TURNED INTO RUN OFF.
ALSO...THE RAIN WILL BE FALLING OVER AN EXTENDED PERIOD OF
TIME...BETWEEN 48 AND 60 HOURS. WILL LET THE DAY SHIFT COORDINATE
THE QPF WITH THE RFC AND ISSUE ANY HYDROLOGIC PRODUCTS IF
NECESSARY.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 358 AM CDT FRI APR 11 2014

THIS SYSTEM WILL STILL HAVE SOME GOOD FORCING OVER THE AREA SUNDAY
NIGHT BEFORE MOVING OFF TO THE EAST MONDAY. UNFORTUNATELY...COLDER
AIR WILL START TO GET DRAWN INTO THE AREA SUNDAY NIGHT TO ALLOW
FOR A CHANGE OVER OF THE RAIN TO SNOW. THE BEST CHANCE FOR
ACCUMULATIONS WILL BE OVER THE SOUTHEAST PART OF THE AREA...BUT
EVEN THERE...AMOUNTS SHOULD BE UNDER AN INCH. THE NEXT CHANCE FOR
SOME PRECIPITATION LOOKS TO BE WEDNESDAY NIGHT INTO
THURSDAY...ALTHOUGH CONFIDENCE IS NOT HIGH AS THE GFS AND 11.00Z
ECMWF SHOW CONSIDERABLY DIFFERENT UPPER AIR PATTERNS. BOTH HAVE A
GENERAL LONG WAVE TROUGH OVER EASTERN CANADA INTO THE GREAT LAKES.
THE GFS THEN SHOWS RIDGING OVER THE AREA AHEAD OF A CUT OFF LOW
OVER THE CENTRAL ROCKIES WHILE THE ECMWF SHOWS NO SIGN OF THIS LOW
AND EXTENDS THE LONG WAVE TROUGH ACROSS THE MIDWEST. WILL STAY
WITH THE MODEL CONSENSUS GRIDS WITH 20 TO 30 PERCENT PRECIPITATION
CHANCES. TEMPERATURES LOOK TO BE BELOW NORMAL FOR MUCH OF THE WEEK
RESULTING IN THE POSSIBILITY OF RAIN DURING THE DAY AND SNOW AT
NIGHT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1134 PM CDT THU APR 10 2014

LIGHT WINDS TO START OFF TODAY WILL INCREASING OUT OF THE
SOUTHWEST AND EVENTUALLY NORTHWEST DURING THE AFTERNOON
HOURS...RESULTING FROM THE PASSAGE OF A LOW PRESSURE TROUGH.
SPEEDS OF 10-15 KT ARE LIKELY WITH GUSTS OF 15-20 KT POSSIBLE.
EXPECT THE WINDS TO DIMINISH LATE IN THE AFTERNOON AND THROUGH THE
EVENING AS THE PRESSURE GRADIENT WEAKENS. LOOKING AHEAD...LOW
LEVEL WIND SHEAR APPEARS LIKELY AT BOTH TAF SITES BETWEEN 06-12Z
SATURDAY.

A DRY AIRMASS IN PLACE BOTH AHEAD OF AND BEHIND THE LOW PRESSURE
TROUGH WILL HELP TO CONTINUE VFR CONDITIONS THROUGH THE TAF
PERIOD.


&&

.FIRE WEATHER...
ISSUED AT 358 AM CDT FRI APR 11 2014

ANOTHER CRITICAL FIRE WEATHER DAY IS EXPECTED THIS AFTERNOON. ONCE
THE SHOWERS MOVES PAST THE REGION...STRONG SUBSIDENCE WILL DEVELOP
ALONG WITH A WELL MIXED BOUNDARY LAYER. BOTH THE NAM AND GFS
INDICATE THE DEEPEST MIXING WILL GENERALLY BE SOUTH OF A LAKE CITY
TO BLACK RIVER FALLS LINE WHERE THERE IS THE POTENTIAL TO MIX UP
TO 800 OR 750 MB. THE DRIER AIR IN THIS MIXED LAYER SHOULD ALLOW
DEW POINTS TO DROP INTO THE MIDDLE TO UPPER 20S RESULTING IN
MINIMUM RH/S BETWEEN 20 AND 25 PERCENT. THE WINDS SHOULD BE OUT OF
THE WEST WITH SUSTAINED SPEEDS OF 15 TO 20 MPH WITH GUSTS TO
AROUND 25 MPH.

&&

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

$$

SHORT TERM...04
LONG TERM...04
AVIATION...AJ
FIRE WEATHER...04



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