Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 241138
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
638 AM CDT Mon Apr 24 2017

.SHORT TERM...(Today and tonight)
Issued at 232 AM CDT Mon Apr 24 2017

Main forecast concerns today are on near critical fire weather
conditions through early this evening.  Focus then turns to rain
chances and temperatures through the week.

The latest surface analysis placed low pressure over south central
South Dakota with a warm front extending east through central
Minnesota into central Wisconsin. Very dry air remains in place
across the region and as winds increase today, near critical fire
weather conditions are expected. Dew point values are only in the
lower 30s across much of the region all the way into northern
Missouri and southern Illinois. Forecast soundings show deep
mixing today, even with high clouds overspreading the region, we
should still see mixing to around 850 mb. This will result in
strong and gusty winds by early this afternoon and a drop in dew
points. Afternoon relative humidity values are expected to drop
into the 20s to lower 30s. The worst conditions will likely be
across portions of northeast Iowa and southwest into central
Wisconsin, where relative humidity values could fall into the
lower 20s. Plan on south winds increasing to 15 to 23 mph with
gusts to around 35 mph. We may even see a few gusts to around 40
mph across the open areas of southeast Minnesota, northeast Iowa,
and the bluff tops along the Mississippi River. A shortwave trough
and cold front will approach the region from the west today but
with the very dry air in place we aren`t expected much in the way
of measurable rainfall. Mesoscale models indicate some showers
developing across the area late this afternoon into this evening.
However, after looking at the corresponding forecast soundings, it
is very dry below 700 mb. Cannot rule out a few sprinkles or
perhaps a very light rain shower but that will be about it for
precipitation.

.LONG TERM...(Tuesday through Sunday)
Issued at 232 AM CDT Mon Apr 24 2017

The front then stalls across the region on Tuesday and will interact
with a shortwave lifting through the Upper Mississippi River Valley
from the southwest. Showers will overspread much of the region,
especially Tuesday afternoon into Tuesday night as surface low
pressure deepens and lifts northward across the region. A cold front
will then swing through Tuesday night and we may see a few
thunderstorms near and ahead of the front.  Have added a slight
chance for thunderstorms across much of the area. Another trough
then looks to move across the region Wednesday into Thursday
bringing more rain to the region and much colder temperatures. There
is considerable uncertainty regarding how low pressure will evolve
across the western Great Lakes and Upper Mississippi River Valley
during this timeframe so have leaned heavily on a model consensus
blend. Given the uncertainty, precipitation type is a concern. If
the low is deeper and colder air wraps in, we may see some snow.
If it lifts north faster we may not be seeing any precipitation
when colder air arrives. So, will have to keep a close eye on the
forecast models the next few days to refine forecast details in
the Wednesday to Thursday timeframe. We should then see a break in
precipitation chances Thursday night. Another trough looks to
lift into the region for the weekend with more rain expected.
Again, forecast details are highly uncertain with the forecast
models showing varying solutions. One this is for sure, it will
remain on the cool side. Below normal temperatures are expected
from Wednesday all the way through the weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 638 AM CDT Mon Apr 24 2017

Southerly winds will increase and become gusty by mid/late
morning ahead of a low pressure trough to the west. Gusts around
30 kts are expected at KRST and around 25 kts at KLSE. Winds will
decrease and become less gusty by early evening. Some high clouds
are expected today with lowering VFR ceilings tonight. A few
showers/sprinkles are possible late this afternoon and this
evening, but confidence in these occurring is low given the very
dry air mass. In addition, as surface winds decrease with an
increasing inversion this evening, increasing winds just above the
surface may require inclusion of LLWS in the TAFS, depending on
the strength of the low-level jet.

&&

.FIRE WEATHER...Late this morning through early this evening
Issued at 232 AM CDT Mon Apr 24 2017

Outdoor burning is not advised today. Near critical fire weather
conditions expected today due to strong gusty winds combined with
low relative humidity. Plan on south winds increasing to 15 to 23
mph today with gusts to around 35 mph at times. The strongest
winds will be across the open areas of southeast Minnesota,
northeast Iowa, and the bluff tops near the Mississippi River.
Relative humidity values are expected to drop into the 20s to
lower 30s. The lowest values are expected across portions of
northeast Iowa into southwest and central Wisconsin.

&&

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

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...JM
FIRE WEATHER...Wetenkamp



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