Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 290450
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1150 PM CDT SUN SEP 28 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 306 PM CDT SUN SEP 28 2014

MAIN FORECAST CONCERNS ARE WITH THE RAIN CHANCES MONDAY AND AGAIN
TUESDAY NIGHT.

SURFACE ANALYSIS THIS AFTERNOON SHOWS HIGH PRESSURE CENTERED OVER
LOWER MICHIGAN WITH THE RIDGE AXIS EXTENDING WEST OVER THE AREA. A
COLD FRONT EXTENDED FROM NORTHEAST MINNESOTA INTO EASTERN SOUTH
DAKOTA. SHOWERS WERE OCCURRING WELL BEHIND THE FRONT OVER
NORTHWEST MINNESOTA AND NORTHERN NORTH DAKOTA AHEAD OF A SHORT
WAVE TROUGH MOVING ACROSS SOUTHERN CANADA.

THE 28.12Z MODELS ALL HANDLE THE SHORT WAVE TROUGH ACROSS CANADA
VERY SIMILARLY. IT IS EXPECTED TO CONTINUE MOVING EAST INTO
ONTARIO BEFORE DROPPING SOUTHEAST ACROSS THE GREAT LAKES. THIS
TAKES THE BEST FORCING EAST OF THE AREA...BUT SOME WEAK PV
ADVECTION IN THE 500-300 MB LAYER DOES DROP ACROSS CENTRAL
WISCONSIN MONDAY. THIS OCCURS AS SOME WEAK QG CONVERGENCE OCCURS
IN THE 850-300 MB LAYER. THERE SHOULD ALSO BE SOME WEAK
FRONTOGENESIS IN THE 850-500 MB LAYER BEHIND THE FRONT ALONG WITH
ABOUT 1 UBAR/S OF UP GLIDE ON THE 300K ISENTROPIC SURFACE. ALL
THIS IS EXPECTED TO OCCUR BEHIND THE COLD FRONT WHICH SHOULD WORK
ITS WAY SOUTH ACROSS THE AREA IN THE MORNING AND EARLY AFTERNOON.
THE BEST CHANCES FOR RAIN SHOULD BE OVER EASTERN WISCONSIN CLOSER
TO THE SHORT WAVE TROUGH...BUT ENOUGH OTHER FORCING SIGNALS TO
MAINTAIN THE 20 TO 30 PERCENT RAIN CHANCES BEHIND THE FRONT. WITH
LITTLE OR NO CAPE EXPECTED TO BE IN PLACE BEHIND THE FRONT...WILL
CONTINUE TO NOT INCLUDE ANY THUNDER.

UPPER LEVEL RIDGING WILL BRIEFLY BUILD OVER THE UPPER MIDWEST FOR
MONDAY NIGHT AND TUESDAY BUT WILL THEN GET PUSHED EAST TUESDAY
NIGHT AS THE UPPER LEVEL LOW OVER THE DESERT SOUTHWEST STARTS TO
LIFT NORTHEAST. THE FORCING FROM THIS SYSTEM LOOKS TO REMAIN
SOUTHWEST OF THE AREA THROUGH TUESDAY AND THEN START TO SPREAD
OVER THE REGION TUESDAY NIGHT. THE MAIN DYNAMIC FORCING WILL
INITIALLY LIFT NORTH THROUGH THE DAKOTAS WITH SOME WEAK PV
ADVECTION IN THE 500-300 MB LAYER COMING ACROSS THE AREA. WEAK TO
MODERATE PV ADVECTION IN THE 1000-700 MB SHOULD COME THROUGH WITH
THE PASSAGE OF THE SHORT WAVE TROUGH. SOME WEAK ISENTROPIC UP
GLIDE WILL SPREAD OVER THE WESTERN SECTIONS OF THE AREA WITH THE
28.12Z GFS SHOWING AROUND 1 UBAR/S ON THE 295K SURFACE. THE MAIN
AXIS OF MOISTURE TRANSPORT SHOULD BE WEST OF THE AREA BUT THE
MODELS DO INDICATE THE EASTERN CONVERGENT SIDE OF THE AXIS DOES
SPREAD INTO THE AREA. EXPECT TO SEE A NORTH/SOUTH CORRIDOR OF
SHOWERS WITH SOME EMBEDDED STORMS...DEVELOP WEST OF THE AREA AND
THEN GRADUALLY SPREAD EAST TO ABOUT THE MISSISSIPPI RIVER TUESDAY
NIGHT. HAVE ADJUSTED THE RAIN CHANCES TO KEEP THE FIRST PART OF
TUESDAY EVENING DRY AND BRING IN UP TO 60 PERCENT RAIN CHANCES
OVERNIGHT OVER THE WESTERN SECTIONS OF THE AREA. NOT EXPECTING THE
RAIN TO BE ABLE TO PUSH INTO CENTRAL WISCONSIN SO HAVE KEPT THE
EASTERN SECTIONS OF THE AREA DRY.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 306 PM CDT SUN SEP 28 2014

THE FORCING IS EXPECTED TO INCREASE WEDNESDAY DESPITE THE MAIN
UPPER LEVEL LOW LIFTING INTO SOUTHERN CANADA OUT OF THE DAKOTAS. A
SECONDARY SHORT WAVE TROUGH IS EXPECTED TO COME THROUGH THE MEAN
LONG WAVE TROUGH UNDERNEATH THE UPPER LEVEL LOW. YET ANOTHER SHORT
WAVE TROUGH WILL THEN COME THROUGH WITH THE MEAN LONG WAVE TROUGH
FOR THURSDAY WITH A THIRD AND POTENTIALLY THE STRONGEST SHORT WAVE
TROUGH TO COME IN THURSDAY NIGHT. WILL ALL THIS FORCING...A
PROLONGED PERIOD OF RAIN CHANCES WILL OCCUR FROM WEDNESDAY THROUGH
FRIDAY WITH UP TO 60/70 PERCENT RAIN CHANCES WEDNESDAY INTO
THURSDAY NIGHT. IT WILL ALSO BE TURNING COOLER BEHIND THIS FRONT
WITH HIGHS FOR THE UP COMING WEEKEND LOOKING TO BE IN THE 50S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1150 PM CDT SUN SEP 28 2014

CHANGES ARE ON THEIR WAY AS A COLD FRONT CONTINUES TO DROP SOUTH
ACROSS MINNESOTA AND FAR NORTHWEST WISCONSIN. AHEAD OF IT...WINDS
HAVE GONE LIGHT WITH CLEAR SKIES IN A MOISTURE LADEN AIR MASS...SO
SOME FOG HAS STARTED TO DEVELOP DOWN IN THE VALLEYS/LOW SPOTS.
HAVE DOWNED THE VIS/CIGS FOR A PERIOD THIS MORNING AT LSE BEFORE
IMPROVING AS THE COLD FRONT GETS IN AROUND DAY BREAK. BEHIND THE
FRONT...CEILINGS WILL LIKELY START OUT AT VFR BUT SHOULD DROP TO
MVFR/IFR SHORTLY AFTER THE FRONT PASSES. A FEW RAIN SHOWERS WILL
BE POSSIBLE...BUT THE MAIN CONCENTRATION OF THE SHOWERS SHOULD BE
OFF TO THE NORTHEAST. AS THE WINDS COME AROUND TO THE
NORTHEAST...ANOTHER LOW DECK WILL MOVE IN AND STICK AROUND THROUGH
THE NIGHT.

&&

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

$$

SHORT TERM...04
LONG TERM...04
AVIATION...HALBACH


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