Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 231710
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1210 PM CDT Sun Jul 23 2017

.UPDATE...
Issued at 1210 PM CDT Sun Jul 23 2017

Carried a small chance of shower/thunderstorms across portions of
central into southwest WI (soueast of a Mauston to Boscobel
line) through mid-afternoon as soundings indicating fairly steep
lapse ratse and a slightly convergent wind flow across that area.
High pressure/drier air is making inroads into the area and this
should push shower/thunder chances southeast of the area by
mid/late afternoon. Otherwise, a nice late afternoon/early
evening setting up with the drier air moving in.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 337 AM CDT Sun Jul 23 2017

High Impact Weather Potential: Thankfully nothing much into the
early work week period. Ongoing flooding concerns remain, but we
won`t be adding any water to the area through Tuesday.

Finally a much-needed and honestly well-deserved period of quiet
weather across the region as we wrap up the weekend and push into
the early work week. A rather robust shortwave currently drifting
across western Lake Superior continues to push a weak cold front
across the area, earlier responsible for a smattering of evening
showers and storms, but with notably drier air behind that boundary
courtesy of high pressure centered over the western High Plains and
associated northerly flow from Canada. Combo of clearing skies
and light winds/moist soils has led to some mainly river valley
fog developing, which should stick around until 8-9 am before
burning off.

High pressure is expected to work from the northern High Plains
today through the eastern Great Lakes by Tuesday, ensuring a nicer
stretch of cooler and noticeably less humid conditions. Will need
to closely watch cloud trends for a few periods as there have
been hints at times that some stratus and/or stratocumulus will
develop beneath cooler air aloft, and may at times try to get
trapped beneath a sharper nocturnal inversion. Additionally, as
the upper trough drops into the Great Lakes this afternoon, will
likely see a few showers develop into eastern Wisconsin within
better forcing, but can`t rule out a few sprinkles farther west in
some better cumulus buildup. Regardless of how the specifics end
up, the next few days don`t look bad at all by late July
standards.

.LONG TERM...(Tuesday Night through Saturday)
Issued at 337 AM CDT Sun Jul 23 2017

Looking like a brief window for some possible more active weather
toward midweek, but with increasing signals thereafter for elongated
high pressure to dominate much of the north-central CONUS into late
week and next weekend. Strengthening return flow late Tuesday but
especially Tuesday night and Wednesday should draw moisture back
into the region, in advance of the next upper trough and cold front
working in our direction from the northern Plains. Uptick in
associated instability should deliver at least some risk for more
showers and storms.

At the moment at least, the severe risk appears marginal given a
lack of deep layer shear ahead of the front, though PWAT values
cruising back up toward 2 inches don`t exactly make this
forecaster happy, as some risk for heavy rains could result
pending convective evolution. Thankfully, the window for storms
appears narrow, being cut off quickly by Wednesday night onward,
as the aforementioned ridge of high pressure heads south into the
area, providing another stretch of much less humid and cooler
conditions right on through next weekend as we wrap up the month
of July.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1210 PM CDT Sun Jul 23 2017

Water Vapor satellite imagery showing a mid-level trough rotating
southeast across the area late this morning. Steep lapse rates exits
under this trough, and this is expected to spark a few shra/ts east
of the Mississippi River (but remaining southeast of the KLSE TAF
site). So, just VFR cumulus expected at both KRST/KLSE. Will then
have to watch for fog at both TAF sites late tonight/early Monday
morning as a ridge of high pressure build in overhead. Light
winds/clear skies and moist lower boundary layer from recent heavy
rain will set the stage for patchy fog. Not totally confident on
coverage or how dense it will be though as models do indicate some
MVFR/VFR stratocumulus drifting over the area along with northeast
winds at 10 to 15kt just off the surface at 500-1000feet. This
will likely inhibit widespread development. Will keep a close eye
on it.

&&

.HYDROLOGY...
Issued at 337 AM CDT Sun Jul 23 2017

Very high water continues to funnel down the Volga and Turkey
Rivers this morning, with the crest along the Volga River looking
like it has just passed the town of Volga as of 3 AM. Other high
water continues to work down the Kickapoo, La Crosse, and
Trempealeau Rivers, though thankfully the crest on all 3 of those
rivers has passed all locations.

Looking ahead, a stretch of much-needed dryness will begin today
through much of Tuesday, before our next chance for showers and
storms briefly returns Tuesday evening into Wednesday night. There
is a risk that some locally heavy rains could fall during that
midweek stretch, so something to watch closely the next few days.
Otherwise, another longer stretch of dry weather appears
increasingly likely from Thursday onward into next weekend.

&&

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

$$

UPDATE...DAS
SHORT TERM...Lawrence
LONG TERM...Lawrence
AVIATION...DAS
HYDROLOGY...Lawrence


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