Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 111148

Area Forecast Discussion
National Weather Service La Crosse WI
648 AM CDT Wed Oct 11 2017

.SHORT TERM...(Today and tonight)
Issued at 337 AM CDT Wed Oct 11 2017

10.08Z water vapor loop shows a strong cyclonic circulation moving
into northern IL with its surface low across central IN. Light rain
and/or drizzle continues across the southeast forecast area.
However, lingering precipitation is expected to weaken and dissipate
through 15Z as the low moves farther into the southern Great Lakes

For the rest of today, expect dry conditions as surface high
pressure noses south from Canada. Clear skies just to the north and
west across south central MN into northern WI will flirt with parts
of the forecast area this morning, but with light east-southeasterly
flow through the day and an expansive cloud deck stretching from MI
to northern AR, expect most areas to remain mostly cloudy. These
clouds will keep temperatures in check, topping out only in the mid
50s to lower 60s.

Moist southerly return flow develops tonight as high pressure drifts
into the Great Lakes region. This results in an ideal set-up for low
stratus/fog and potential drizzle with a nearly saturated layer from
the surface up to around 1.5 km. For now, expanded patchy fog and
drizzle to encompass most areas south of I-94. Temperatures aren`t
likely to move much from daytime highs, only dropping into the upper
40s to lower 50s.

.LONG TERM...(Thursday through Tuesday)
Issued at 337 AM CDT Wed Oct 11 2017

A southwest flow pattern will be in place on Thursday ahead of longwave
troughing to the west. Low-level moisture stuck beneath a strengthening
inversion with increasing warm advection will likely keep extensive
clouds around for much of Thursday, along with possibly some
drizzle. Some clearing could occur later Thursday/Thursday
evening, but with continued low-level southerly flow, it may be
tough to completely get rid of the trapped low-level moisture.
Temps will be seasonable in the 50s to low 60s.

For Friday and through the weekend, rain chances remain the
primary focus. Overall, confidence is increasing as models are
starting to come into better agreement. It`s looking like there
will be two primary rounds of rain. The first will be Friday afternoon
and evening as a shortwave trough ejects out of the western trough
dragging a front south across the area. Then there should be a
break in the precip later Friday night into Saturday as the front
slides just south of the region.

As the main upper trough kicks out of the Rockies Saturday into Sunday,
a surface wave will track northeastward along the preexisting baroclinic
zone. Although there are some timing differences yet, the surface low
is forecast to lift from Kansas on Saturday northeast into northern
lower Michigan by early Sunday. Rain should increase through the day
Saturday into Saturday night with strong low-level warm advection/moisture
transport ahead of the surface warm front. Precipitable water standard
anomalies reach +2-3 across southern parts of the area, greater than
1.25 inches, so there will be plenty of moisture to work with. The
forecast track would bring the heaviest rain generally across northeast
Iowa/southwest Wisconsin, with 1+ inch totals possible. Did also include
a thunder mention in these areas Saturday afternoon/evening with the
11.00Z GFS/ECMWF indicating some weak elevated instability working
northward along with a strengthening low-level jet. Would still expect
some minor timing/track adjustments over the next few days as
models continue to hone in on a solution. As the low lifts away on
Sunday, some lingering showers are possible. A strong push of
low-level cold advection with gusty northwest winds and
widespread clouds will help keep temps cool, mainly in the 50s.

A more zonal flow pattern looks to set up early next week with
surface high pressure providing a mainly dry stretch of weather
through the first half of the week. Temps are expected to trend
back upward through the first half of the week, with above average
highs in the 60s by Tuesday, and through mid-week.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 648 AM CDT Wed Oct 11 2017

Ceilings will be the primary challenge at TAF airfields over the
next 24 hours. Rain/drizzle from last evening and overnight has
finally dissipated with dry conditions expected through at least
12.06Z. However, MVFR ceilings have already settled in over the
area and are expected to continue for the vast majority of the
day. Could see some improvement back above 3000 ft agl at KLSE
this afternoon, but KRST likely to remain below.

Ceilings likely to lower even further later this evening and
especially overnight with patchy drizzle/fog possible. Will drop
KRST to IFR, but keep KLSE at low MVFR. Did not yet introduce
drizzle and/or visibility restrictions due to fog given timing/
coverage uncertainty, but later forecasts may need to add these
details as confidence increases.

Light north-northeast wind this morning will gradually turn go the
east-southeast through the period.




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