Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 122339
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI 200
639 PM CDT Tue Sep 12 2017

.SHORT TERM...(Tonight through Thursday)
Issued at 230 PM CDT Tue Sep 12 2017

Summer-ish feel to the air for the rest of the work week as high
pressure slides to the east and warm, southerly winds usher in
warmer air. Highs in the 80s are expected through Friday, likely
into Sat. Aside from a small shower threat in the west Thu night,
should continue dry for next few days.

For tonight, good setup for fog in the river valley and other low
lying areas. Some short term models hint that the fog could be more
expansive in western and central WI. Dense fog advisories were
needed for parts of the region this morning with a similar airmass.
Will monitor and issue if conditions warrant.

.LONG TERM...(Friday through Tuesday)
Issued at 230 PM CDT Tue Sep 12 2017

The prolonged period of dry weather looks to come to an end this
weekend - at least for some. The models remain in good agreement
with crashing an upper level shortwave into the PAC NW, digging it
into the west coast before lifting it northeast across the plains on
Sat, then lifting it into southern Canada Sunday. Both the GFS and
EC keep the bulk of the shortwave energy west/north of the local
area. That said, some hints that a weak ripple or two could proceed
the main trough Thu night, coupled with low level warm air
advection. The interaction could result in a few showers - mostly
across MN. The main threat looks to be Sat night into Sun when the
associated sfc cold front slides across the Upper Mississippi River
valley. Good slug of 850mb moisture transport ahead of the front,
along with some instability - even during the overnight hours. The
stronger, deeper shear continues to look displaced from the
instability, post the front. Decent set up for showers and storms.

Models differ on what to do for the start of the new work week. Both
bring high pressure in for Monday, but the GFS wants to bring a
shortwave up from the central plains to across the local area for
Tue night. EC doesn`t have a whiff of this feature. Leaning toward
the EC for now.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 639 PM CDT Tue Sep 12 2017

Surface ridge will remain over region through forecast period with
VFR conditions prevailing for most areas. Only break from that will
be threat for early morning valley fog, with a few hours of IFR
possible at KLSE and other valley locations. Will also see low level
flow start to become a bit more southerly on Wednesday.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...Shea



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