Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 182040
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
337 PM CDT Thu May 18 2017

.SHORT TERM...(This evening through Friday)
Issued at 337 PM CDT Thu May 18 2017

As subsidence increases and drier air advects into the region
tonight, skies will gradually clear this evening. Under mostly
clear skies and light winds overnight, temperatures will fall into
the lower and mid 30s in central and north-central Wisconsin. Due
to this a Frost Advisory has been issued for Adams, Clark,
Jackson, Juneau, Monroe, and Taylor counties late tonight and
Friday morning.

On Friday, weak moisture transport will gradually develop south of
Interstate 94. As this overcomes some dry air initially,
precipitation will begin to fall across the area. The highest rain
chances will be found south of Interstate 90.

.LONG TERM...(Friday night through Thursday)
Issued at 337 PM CDT Thu May 18 2017

Friday night into Saturday, a surface low will lift northeast from
the Central Plains into the Upper Mississippi River Valley. As
this occurs, moderate to strong 925 mb and 850 mb moisture
transport will develop across the region. Precipitable water
values will climb into the 1 to 1.5 inch range south of Interstate
90. This could result in the potential for some heavy rain. With
some areas already in flood, we will have to watch this closely.
If the surface low is able to get far enough north, there could be
enough instability and shear for the potential of some supercell
development. The GFS has its surface based CAPEs climbing into the
1,000 to 2,000 J/kg range and 0-6 km shear over 50 knots.
Meanwhile the NAM has similar shear, but it keeps its instability
well to our southeast.

From Monday afternoon into Tuesday evening, another short wave
trough will move through the region. With limited instability, only
expecting some showers and isolated thunderstorms from this system.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1238 PM CDT Thu May 18 2017

Main taf concerns are MVFR ceiling conditions across the area this
afternoon. Surface low over the eastern Great Lakes Region continues
to wrap clouds and drizzle/light rain showers into the area this
afternoon. Latest metars indicate ceilings in the MVFR range and a
few of the drizzle/light rain showers have produced reduced
visibilities into IFR very briefly. With the daytime heating
ceilings should slowly rise into VFR around 00-01z Friday at both
RST/LSE taf sites and the light rain showers/drizzle will move
east of the region. Surface ridge builds into northern Wisconsin
and northern Minnesota and provide VFR conditions at RST/LSE taf
sites tonight. Another surface low pressure system is expected to
track into the Central Plains states and spread periods of showers
into the area. Any precipitation to impact the taf sites look to
be after 15z Friday and will leave mention out of the tafs for
now.

&&

.HYDROLOGY...
Issued at 337 PM CDT Thu May 18 2017

Emergency management and local officials in northwest Jackson
County continue to report that 11 county and township roads remain
closed due to high water. Due to this, a Flood Warning remains in
effect for this area through midnight tonight.

River flooding continues along the Black River. Dodge is forecast
to crest at 12 feet on Saturday which is major flood stage and
just 0.8 feet below the record flood of 12.75 feet on September
25, 2010 and its second highest stage of 12.29 feet on June 29,
1998. The river crested at 9.5 feet (moderate flooding) in Arcadia
earlier this morning. This river is expected to slowly fall
during the upcoming weekend. Finally at Black River Falls, the river
is currently cresting around 51.4 feet which is causing moderate
flooding for this location.

In addition to the river flooding along the Black River, there is
also going to be minor to moderate flooding along the Wisconsin
River at Castle Rock Dam this weekend.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory from midnight tonight to 9 AM CDT Friday for
     WIZ017-029-034-042>044.

MN...None.
IA...None.
&&

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...DTJ
HYDROLOGY...Boyne



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