Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 170401
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1100 PM CDT Sun Apr 16 2017

.SHORT TERM...(This evening through Monday)
Issued at 230 PM CDT Sun Apr 16 2017

Main forecast concerns in the short term are on chances for a few
sprinkles tonight. Focus then turns to precipitation chances Tuesday
through Wednesday, with the potential for heavy rainfall
Wednesday into Thursday.

A weak shortwave trough moves through the region tonight as a 300 mb
jet streak moves overhead.  There is some very weak support for
perhaps a sprinkle or two from  04Z tonight through 14 Z Monday
morning as the right entrance region of the jet moves through.
Forecast soundings across the area show very dry sub cloud layer air
so not anticipating much more than an increase in clouds and perhaps
some virga.  High pressure then quickly builds in Monday providing
mostly sunny skies and light northwest winds. Plan on highs ranging
from the mid 50s over northern Wisconsin to the upper 60s across
northeast Iowa.

.LONG TERM...(Monday night through Sunday)
Issued at 230 PM CDT Sun Apr 16 2017

An upper level trough and surface low will slide across northern
Minnesota and Upper Michigan on Tuesday dragging a cold front
through the region. Showers and perhaps an isolated thunderstorm
or two are possible along the front. Any thunderstorm chances will
mainly be in the afternoon on Tuesday. Instability is lacking
with this feature with 0-4 KM MUCAPE values of only 250 to maybe
300 J/kg. So, not anticipating any severe thunderstorms with this
system.

High pressure and cooler temperatures return to the region early
Wednesday then a stronger low pressure tracks across Iowa/northern
Illinois.  At this time this system looks to bring widespread rain
and isolated thunderstorms to the area Wednesday afternoon into
Thursday morning. According to the GFS, most of the instability is
bottled up south of the warm front across, basically along and south
of Interstate 80.  The ECWMF is further north and would bring more
rain to the region and possibly produce some hydrology concerns,
such as river rises and potential flooding concerns.  Confidence is
too low to introduce any hydrology headlines to the forecast at
this point but will have to keep a close eye on this situation.(See
hydrology section below)

Cool high pressure then builds into the region late on Thursday
and looks to dominate the weather pattern all the way into the
weekend. High temperatures will be slightly below normal from
Wednesday into Saturday. There is the outside chance of some rain
showers across northeast Iowa and far southwest Wisconsin Saturday
into Saturday night but the Canadian is the only model showing
this. The operational GFS and ECWMF both indicate dry weather.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1100 PM CDT Sun Apr 16 2017

Cigs: a bkn mid level layer of clouds will sink southeast across the
area tonight, associated with an upper level shortwave. Models
favoring shifting this south by mid Monday morning, leaving skc-sct
vfr conditions for monday-monday night.

Vsby/wx: a few sprinkles associated with the mid clouds, otherwise
no impacts expected.

Winds: light winds flip to the northwest/north on Monday, but
generally stay on the lighter-side.

&&

.HYDROLOGY...Wednesday through Thursday
Issued at 230 PM CDT Sun Apr 16 2017

There is the potential for widespread 1 to 2+ inches of rainfall
across parts of the area from Wednesday through Thursday. If these
rainfall amounts would be realized, there would likely be river
flooding concerns. At this time it appears locations across
northeast Iowa and southwest into possibly central Wisconsin
would be on the nose of strong 850 mb moisture transport.
Depending on where the warm front sets up there could be a threat
for flash flooding. Precipitable water values are expected to
climb into the 1 to possibly 1.25 inch range which is 1 to nearly
2 standard deviations above climatology. Will have to keep a very
close eye on this storm system the next few days. If confidence
increases on the placement of heaviest rainfall, hydrology
headlines may be needed if the heavy rain threat shifts further
north than where it is currently expected. Continue to monitor
forecasts closely.


&&

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

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION....Rieck
HYDROLOGY...Wetenkamp



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