Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 200846
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
346 AM CDT SUN APR 20 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 346 AM CDT SUN APR 20 2014

THE MAIN FOCUS THROUGH TONIGHT IS ON THE PRECIPITATION CHANCES AS
A FRONT DRIFTS SOUTH ACROSS THE REGION.

RAIN SHOWER ACTIVITY HAS BEEN PICKING UP SOUTH OF THE FRONT WHICH
CURRENTLY EXTENDS FROM NORTHWEST IOWA TOWARD THE TWIN CITIES ON UP
INTO NORTH CENTRAL WISCONSIN. 20.07Z RAP ANALYSIS SUGGEST THAT
THERE IS LITTLE TO NO 0-3KM MUCAPE REGIONALLY...WHICH IS WHY THERE
HAS NOT BEEN MUCH IF ANY THUNDER ACTIVITY WITH THESE SHOWERS
OVERNIGHT. CONFIDENCE IS NOT ALL THAT GREAT WITH TIMING IN WHEN
THESE ROUNDS OF SHOWERS WILL BECOME MORE WIDESPREAD AS THE 20.07Z
RAP/20.00Z NAM & GFS APPEAR TO PUSH SURFACE DEW POINTS TOO HIGH
TOO FAST WHICH DEVELOPS TOO MUCH INSTABILITY. WITH BROAD/WEAK
FORCING IN PLACE FOR TODAY...HAVE CONTINUED TO LEAVE PRECIPITATION
CHANCES PRETTY MUCH AS IS...WITH AN UPTICK GOING INTO TONIGHT AS
THE MID LEVEL TROUGH TO THE SOUTHWEST APPROACHES AND HELPS TO PUSH
SOME BETTER LOW LEVEL MOISTURE TRANSPORT INTO THE REGION. SEVERE
WEATHER STILL LOOKS UNLIKELY DUE TO THE LACK OF INSTABILITY/DEEP
SHEAR.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 346 AM CDT SUN APR 20 2014

AS THIS SYSTEM FINALLY PUSHES OFF TO THE EAST ON MONDAY...COLDER
AIR WILL MOVE IN FROM THE WEST LATER IN THE DAY AS A SECONDARY
COLD FRONT DROPS THROUGH THE REGION AS A SURFACE LOW MOVES INTO
SOUTHERN ONTARIO.

AFTER A RIDGE OF HIGH PRESSURE MOVES THROUGH ON TUESDAY...THE
FOCUS GOES TO A DEEPER MID LEVEL TROUGH THAT WILL BRING A FEW
ROUNDS OF PRECIPITATION IN WITH IT. DESPITE SOME MINOR DIFFERENCES
BETWEEN THE 20.00Z GFS/ECMWF/GEM...THEY ALL SUGGEST THAT THE FIRST
ROUND OF RAIN WILL COME IN ON WEDNESDAY WITH THE LEAD WARM AIR
ADVECTION. NOT MUCH INSTABILITY TO WORK WITH HERE...BUT 0-3KM
MUCAPE DOES INCREASE GOING INTO THURSDAY AS THE MAIN MOISTURE FEED
COMES UP INTO THE REGION AHEAD OF THE COLD FRONT. STILL NOT MUCH
INSTABILITY THERE...BUT RAIN LOOKS FAIRLY CERTAIN WITH ALL OF THE
20.00Z GUIDANCE SHOWING THIS BAND OF RAIN MOVING THROUGH FROM THE
MORNING INTO THE AFTERNOON ON THURSDAY. SOME OF THE HEAVIEST RAIN
WILL LIKELY OCCUR DURING THIS TIME FRAME BEFORE THE COLD FRONT
COMES THROUGH. THE LAST ROUND OF RAIN WILL OCCUR ON FRIDAY IN THE
COLD AIR ADVECTION SIDE OF THE SYSTEM WHERE SOME SCATTERED SHOWERS
LOOK LIKE THEY WILL DEVELOP AS IT MOVES OFF TO THE EAST.

SOME DIFFERENCES SHOW UP GOING INTO THE WEEKEND WITH THE 20.00Z
GFS SHOWING THE RIDGE BEING FURTHER SOUTH THAN WHAT THE ECMWF IS
SHOWING. THE ECMWF WOULD PRODUCE SOME PRECIPITATION ACROSS
SOUTHEAST MINNESOTA TO NORTHEAST IOWA AND SOUTHWEST WISCONSIN ON
SATURDAY WITH THERE POSSIBLY BEING SOME P-TYPE ISSUES THERE SHOULD
IT OCCUR.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1024 PM CDT SAT APR 19 2014

WEAK COLD FRONT EXTENDING FROM SOUTHWEST MINNESOTA INTO NORTHWEST
WISCONSIN HAS BASICALLY STALLED...AND UP TO THIS POINT ALL SHOWER
ACTIVITY HAS STAYED TO THE NORTHWEST OF THE TAF SITES. THIS COULD
CHANGE EARLY THIS MORNING AS STRONGER WINDS ABOVE THE SURFACE
TRANSPORT MORE MOISTURE INTO THE REGION. HAVE VCSH AT BOTH TAF
SITES FROM 09-12Z TO COVER THIS POTENTIAL. ADDITIONALLY...THESE
WINDS RESULT IN THE NEED FOR LOW LEVEL WIND SHEAR AT LSE. AFTER
12Z AND THROUGH THE REST OF THE TAF PERIOD...PERIODS OF SHOWERS
ARE LIKELY...ESPECIALLY PRIOR TO 15Z AND AFTER 19Z AS THE FRONT
DROPS DOWN INTO THE TAF SITES. THESE TIME PERIODS COINCIDE WITH
THOSE STRONGER WINDS INITIALLY AND INSTABILITY IN THE AFTERNOON.
THERE COULD EVEN BE SOME THUNDERSTORMS IN THE AFTERNOON...THOUGH
GIVEN ISOLATED COVERAGE EXPECTED HAVE KEPT THEM OUT OF THE TAF FOR
NOW. DESPITE ALL THE RAIN POTENTIAL...ANTICIPATING MAINLY VFR
CONDITIONS THROUGH THE TAF PERIOD. A SOUTH FLOW OF DRY AIR SHOULD
HELP KEEP CEILINGS VFR. SHOULD SOME HEAVIER RAIN FALL WITH SAY A
THUNDERSTORM...THE VISIBILITY COULD DROP TO MVFR FOR A BRIEF TIME.


&&

.HYDROLOGY...
ISSUED AT 346 AM CDT SUN APR 20 2014

AN ELONGATED PERIOD OF LIGHT RAIN IS EXPECTED THROUGH MONDAY AS A
FRONTAL BOUNDARY REMAINS STALLED ACROSS THE REGION. RAINFALL
AMOUNTS OF A HALF INTO TO AN INCH ARE POSSIBLE WITH SOME OF THE
HIGHER RAINFALL AMOUNTS LIKELY BEING MORE LOCALIZED RATHER THAN
WIDESPREAD. AFTER A BREAK LATE MONDAY INTO TUESDAY...ANOTHER
PERIOD OF RAINY CONDITIONS ARE EXPECTED FOR WEDNESDAY THROUGH
FRIDAY. SOME MODERATE TO HEAVY RAIN LOOKS POSSIBLE ON
THURSDAY AHEAD OF A COLD FRONT. RIVERS REMAIN ELEVATED AND MAY
STAY THIS WAY IF THIS RAINFALL ALL OCCURS.

&&

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

$$

SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...AJ
HYDROLOGY...HALBACH



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