Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 231950

Area Forecast Discussion
National Weather Service La Crosse WI
250 PM CDT Wed Aug 23 2017

.SHORT TERM...(Tonight through Thursday)
Issued at 250 PM CDT Wed Aug 23 2017

Another quiet and beautiful day across the Upper Mississippi River
valley under northwest flow and surface ridge in area. Slightly more
moisture to work across Wisconsin in low to mid layers for daytime
cumulus once again.

Still watching short wave trough upstream that will swing through
area tonight and into Thursday morning. Feature looks strong enough
to sustain showers that are showing up now over far northern
Minnesota into Manitoba. Short term models in relatively good
agreement with bulk of rain threat after Midnight, and with higher
confidence now, have been trying to boost rain chances up, which
could linger into Thursday morning.

With wave passage by Thursday, still banking on any lingering light
rain or showers to dwindle as morning goes on, eventually stopping
altogether by afternoon, even though some guidance suggests it will
hold on longer. Last place for rain to end could be western areas.

Temperatures remain below normal and could be held down a bit with
any lingering cloud cover as well.

.LONG TERM...(Thursday night through Wednesday)
Issued at 250 PM CDT Wed Aug 23 2017

While not much in the way of impactful weather is expected at least
through the weekend, interesting forecast coming up with
uncertainities with rain.

Will be watching slow moving short wave materialize over central
corn belt by Thursday night with some cyclogensis expected in
response. Warm air advection and moisture transport will likely
trigger showers in lift zone, which could spread in from the west
southwest going into Friday. Better instability remains well west
though so will honor thunder-free forecast.

Pace at which this feature moves east looks slow so lots of
uncertainities on how widespread any of this advection zone
convection will be, but rain chances will continue into the weekend.

23.12z medium range guidance suggests wave could intenisfy a bit
over the weekend, and possibly become a closed low system. Rain
chances raised as feature passes through and then will have to watch
where this meanders into next week. May have to wait for stronger
impulse in northern flow to buckle and clense all this out during
next week, but long ways out yet.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1220 PM CDT Wed Aug 23 2017

VFR conditions are likely to persist through the TAF period. SCT-
BKN diurnal cumulus will dissipate late this afternoon, with
increasing mid-level cloud cover overnight tonight ahead of an
approaching weather system. This system could produce some relatively
high-based rain showers after midnight tonight. Due to
uncertainty in coverage, will not include in the TAFs yet, but
should they occur, conditions are expected to remain VFR.
Northwesterly winds will become light/variable tonight.




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