Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 131911

Area Forecast Discussion
National Weather Service La Crosse WI
211 PM CDT Wed Sep 13 2017

.SHORT TERM...(Tonight through Thursday)
Issued at 211 PM CDT Wed Sep 13 2017

A surface ridge over the eastern part of the forecast area will
continue to shift off to the east through tonight, with low pressure
forming in the Dakotas and beginning to move eastward. Models are in
good agreement with the pressure gradient tightening ahead of this
low, bringing increasing southerly winds to the area for Thursday.
Winds look to remain strong enough aloft over most of the area
tonight to suppress widespread valley fog formation, but could see a
bit of fog in central and southwest Wisconsin where winds remain a
bit lighter. That said, the RAP has been trending less windy aloft,
so could see a bit of stratus in the valleys by Thursday morning.

Otherwise, the main forecast concern for this period will be high
temperatures on Thursday. The previously mentioned increasing
southerly flow will bring 925 mb temperatures ranging from 22 to 28
C to the forecast area. This will lead to high temperatures in the
mid 80s for most locations, with a few areas in far western portions
of the forecast area approaching 90. Any precipitation chances
during this period look to stay well to the northwest along a
surface boundary.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 211 PM CDT Wed Sep 13 2017

13.12Z Models showing a weak mid-level trough ejecting northeast out
of the Plains Thursday night along with some weak 850-700mb moisture
transport. This should be enough to fuel a lower-end chance of
elevated/altocumulus showers across portions of MN and IA into
western WI.

Friday is looking unseasonably warm and capped off as we get solidly
into the warm sector of deepening low pressure moving out of the
Central Plains into MN. Other than a few mid/high level clouds,
expecting full mixing in southerly flow with 925mb temperatures
climbing into the 24-27C range. This is expected to push highs in
the middle 80s to near 90 across the area.

Shower/thunderstorm chances will be seen Saturday into Sunday
morning as a cold front slowly makes its way across the region.
Severe threat appears minimal at this time as the front comes
through Saturday night with diminishing CAPE and fairly weak shear.
Will continue to monitor frontal timing. Pre-cold frontal high
temperatures still look a bit warm with readings in the 80s. Post-
frontal temperatures Sunday look a bit more seasonable with highs
topping off in the upper 60s to the middle 70s.

For Monday through Wednesday...southwest flow aloft will push a
couple systems across the area for occasional shower/thunderstorm
chances. Otherwise, temperatures are expected to be at or a few
degrees above seasonal normals.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1226 PM CDT Wed Sep 13 2017

VFR conditions expected through the period. Latest RAP model
guidance has trended a bit less windy aloft, indicating the
potential for some stratus in the Mississippi River valley which
would impact KLSE. However, confidence is not very high in this
scenario playing out, so have not included any mention.




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