Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261932

Area Forecast Discussion
National Weather Service La Crosse WI
230 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 inbetween what the 3 are leaning toward. Something to


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1227 PM CDT Mon Sep 26 2016

Brisk/gusty W to NW sfc/low level winds will be the main issue at
the TAF sites this period. Good VFR conditions expected thru
tonight/Tue morning as the drier W/NW low/mid level flow continues
over MN/IA/WI. Perhaps a few diurnal cu/strato-cu in the 5K-6K ft
range during the afternoons. Tighter pressure gradient over the area
this afternoon along with warming/mixing to around 850mb to result
in W/NW winds 15-25kt G25-35kt thru about 23z, with the stronger
winds across the higher terrain, open country areas like KRST. Winds
to diminish to 10-15kts this evening with diurnal cooling/
stabilization. May yet need a mention for LLWS later tonight/early
Tue if sfc winds drop below 10kts, as winds around 2K ft progged to
be in the 30-35kt range around 12z Tue. Winds increase again later
Tue morning with diurnal warming/deeper mixing. Some relax of the
gradient and winds aloft for Tue, with winds after 15z mostly 10-
20kt G20-25kt.




LONG TERM....Rieck
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