Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 302331
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
631 PM CDT Fri Sep 30 2016

.SHORT TERM...(This evening through Saturday)
Issued at 251 PM CDT Fri Sep 30 2016

Latest water vapor imagery indicating upper level cut-off/closed
low over the Ohio River Valley and shortwave ridge over the
Northern and High Plains. Pieces of energy rotating around the
upper level cut-off low is producing isolated/scattered showers
over parts of eastern Wisconsin and Illinois per latest mosaic
radar.

The 30.12z GFS/NAM/ECMWF are in good agreement in lifting upper
level closed/cut-off low into the Great Lakes Region tonight into
Saturday. A series of impulses wrapping around the upper level
cut-off low will continue to advect moisture into the area. Weak
lift in association with the impulses and dry air over much of
the forecast area...will inhibit the potential for showers across
the forecast area. With the better chances mainly east of the
Mississippi River and occurring late tonight into Saturday
morning.

.LONG TERM...(Saturday night through Friday)
Issued at 251 PM CDT Fri Sep 30 2016

Upper level cut-off/closed low tracks into the eastern Great
Lakes Region Saturday night and allows any isolated/scattered
showers to be east of the forecast area. Then...upper level ridge
amplifies/builds over the central United States/Great Lakes region
and provides dry weather across the forecast area Sunday into
Monday. Temperatures should warm into the 60s to around 70 degrees
Monday. If skies clear over the forecast area Sunday
night...there is the potential for fog formation in river
valleys...as the 30.12z GFS/NAM bufkit soundings show inversion
developing and deep layer light winds. At this time...have left
mention of fog out of the forecast.

Main forecast concerns are precipitation chances Tuesday night into
Thursday. Considerable differences occur between the deterministic
30.12z GFS/ECMWF/GEM through the period...as the models differ on
strength of the upper level ridge amplifying over the central
United States Monday night/Tuesday and placement/timing of the
upper level closed low/trough slowly moving into the Upper Midwest
Tuesday night into Thursday. This will have impacts on timing of
the shower/thunderstorm chances and how widespread the
showers/thunderstorms will be across the forecast area Tuesday
night into Thursday. The 30.12z GFS/ECMWF/GEM continue to show
strong warm air advection out ahead of the upper level closed
low/trough Tuesday and will provide above normal temperatures
across the forecast area Tuesday. Slightly below normal
temperatures are expected later in the week...as cooler air
filters into the forecast area behind surface front/upper level
trough.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 631 PM CDT Fri Sep 30 2016

VFR stratus moved into both TAF sites today, resulting from
easterly flow around low pressure in Indiana bringing moisture
westward. Further lowering in ceilings is expected tonight as the
easterly flow persists, with many locations across southern into
eastern WI reporting MVFR and IFR conditions. Nighttime cooling
should also help in lowering ceilings. Additionally we could see
some MVFR BR impact the sites late in the night into Saturday
morning. Cannot rule out a few light showers/drizzle as well
during the BR time period. Daytime heating on Saturday should
help to mix out the BR and bring ceilings up to MVFR.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...AJ


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