Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 262305

Area Forecast Discussion
National Weather Service La Crosse WI
605 PM CDT Mon Sep 26 2016

.SHORT TERM...(Tonight through Wednesday)
Issued at 230 PM CDT Mon Sep 26 2016

Models in good agreement with taking a closed 500 mb stacked low,
currently just north of Lake Superior, nearly due south on Tue.
Piece of upper level energy slated to swing around the low, driving
across the local area during the afternoon. Inverted trough hangs
west of the stacked low, with weak frontogenetic forcing along it,
dropping southward through the region during the afternoon/evening.
Add in cold air advection in the 925-700 mb layer and there will be
ample forcing mechanisms for areas of showers. The chance for
wetting looks a lot more likely now compared to previous days.
Amounts won`t be much, generally 1/10 of an inch or less. Higher
threat for showers in the east.

The low pressure system will take its time dropping southeast,
moving over southern MI by 18z Wed, toward the Ohio River valley Wed
night. Not as much upper level support, but good low level lapse
rates persist, and with the low just to the east/cyclonic flow,
shower chances will persist mostly for WI on Wed. Should be more
scattered in coverage compared to what is expected for Tue.

.LONG TERM...(Thursday through Monday)
Issued at 230 PM CDT Mon Sep 26 2016

As the trough slips southeast on Wed, the models cut the closed
upper level off from the mean flow, having it wobble over the oh/tn
river valleys. Toward the weekend, the GFS/Canadian start to lift
the upper level low northeast, swinging it over the New England
states. This solution would bring a much needed, prolonged period of
dry weather to the region with temperatures right around the late
September normals.

However - the EC continues to be an outlier, but consistent within
itself. The EC would retrograde the low back northwest, moving it
over the eastern Great Lakes for the weekend. More clouds and the
threat for showers would extended westward into at least Wisconsin
as a result. Eventually, the low would get a shove east for the
start of the new work week from a ridge/trough combo pushing
in from the west.

Going to keep the forecast dry for now...but consistency of the EC
is starting to give its solution some weight. The slowing down of
the GFS/Canadian solutions also suggest that they all might settle
into something in between what the 3 are leaning toward.
Something to watch.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 605 PM CDT Mon Sep 26 2016

VFR conditions expected through the night. The gradient will
remain rather tight over the region which is expected to keep the
west to northwest winds around 10 knots. As long as the winds stay
at these speeds there will not be any need to include low level
wind shear, but if the winds should drop, this could become an
issue with winds at 2000 feet staying between 35 and 40 knots
through the night. A short wave trough will rotate across the
Upper Midwest Tuesday afternoon. This wave will produce MVFR to
VFR ceilings along with some light showers. For now, will include
a VCSH for the late afternoon at both airports.




LONG TERM....Rieck
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