Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 182303
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
600 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 00Z TAFS through 00Z Friday evening)
Issued at 600 PM CDT Thu May 18 2017

Cigs: a lot of diurnal elements to the cloud deck current across the
TAF sites, and expect it to mostly dissipate with sundown. High/mid
level clouds return by 12z or so Fri morning, increasing and
lowering by the afternoon as an upper level shortwave trough/low
level warming works across the area. Could get into some mvfr cigs
Friday night - with ifr/mvfr looking likely Sat.

Vsby/WX: expecting some scattered showers with the shortwave Fri
afternoon, but how far north they work it not clear. The NAM would
keep them south while the GFS/EC would bring to I-90. Going to add
some vcsh for now. Don`t anticipate much for vsby reductions with
any showers. Rain becomes more likely overnight Friday through Sat.
Would expect at least periods of MVFR vsby with these activity.
Thunder threat looks small.

Winds: directions become northeast-east tonight, and should hold
there through Friday with sfc low expected to slide just south of
KRST/KLSE.

&&

.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...Rieck
HYDROLOGY...Boyne


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