Area Forecast Discussion
Issued by NWS La Crosse, WI

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982
FXUS63 KARX 261739
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1239 PM CDT TUE JUL 26 2016

.SHORT TERM...(Today and tonight)
Issued at 345 AM CDT Tue Jul 26 2016

At 3 AM, a 1019 mb surface high pressure area was centered over
western Iowa. With the light surface winds, areas of fog have
developed across western Wisconsin. Dense fog is currently being
reported at both Medford and Boscobel. We have also noticed from
our office that a layer of stratus has developed across on the
western side of the Mississippi Channel. We will be watching this
area closely this morning.

Elsewhere 2 small thunderstorm complexes have developed early
this morning on the nose of moderate to strong 925 mb to 850 mb
moisture transport across the Minnesota arrowhead and southeast
North Dakota. The latest RAP shows that the convective system over
the Minnesota arrowhead will move across Lake Superior and slowly
weaken. Meanwhile the convective system over southeast North
Dakota will move into central Minnesota this morning and
dissipate.

Additional showers and storms will develop across North
Dakota during the day ahead of a short wave trough which is
currently located over western North Dakota. This short wave
trough will move through northwest Wisconsin this evening and
northeast Wisconsin during the overnight. There will be weak to
moderate 850 mb moisture transport ahead of this wave. In
addition, there will be 1500 to 2000 J/kg 0-3 km most unstable
CAPES. The NSSL, CR HRRR, and NMM develop scattered showers and
storms across Taylor and Clark counties in north-central
Wisconsin. Due to this, kept a 20 to 30 percent chance of
precipitation in the forecast. With weak 0-3 km and 0-6 km shear,
not anticipating any organized severe storms in either of these
counties.

.LONG TERM...(Wednesday through Monday)
Issued at 345 AM CDT Tue Jul 26 2016

From Wednesday into Thursday night, a short wave trough and
surface cold front will move slowly south and southeast through
the Upper Mississippi River Valley. The 0-1 km mixed layer CAPES
will be in the 1000 to 1500 J/kg on Wednesday afternoon and 500 to
1000 J/kg on Thursday afternoon. While the 0-3 and 0-6 km shear
are weak across the Upper Mississippi River Valley, there is
favorable deep shear west of Interstate 35 in Iowa on Wednesday
afternoon. Like yesterday, it continues to look like both the 925
and 850 mb moisture transport will be very weak, precipitable
water values be generally less than 1.5 inches, and the warm
cloud layer depths only extend up to 3700 feet. As a result, not
anticipating any issues with heavy rain.

Another short wave trough will move through the region from Friday
night into Saturday. This system looks pretty similar to its
predecessor. Due to this, not anticipating a severe or flooding
threat from this system.

Sunday and Monday continue to look dry as an upper level ridge
builds across the region. As this occurs, temperatures will warm
back into the lower to mid 80s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1239 PM CDT Tue Jul 26 2016

High pressure sitting over northern Illinois will stay nearly
stationary through the next 24 hours, helping to keep conditions
mostly VFR at both TAF sites. However, valley fog remains a
concern at LSE as a similar setup exists compared to this morning.
The combination of a deep layer of light winds, relatively high
dewpoints and nighttime cooling will result in fog development in
valleys. Does it get into LSE? One big concern is hints of
altostratus and cirrus moving into LSE late in the night,
something that would very much disrupt the fog development. Given
this concern, have only VCFG in the TAF. If valley fog forms, it`s
likely to occur in the 11-13Z time period.

Looking ahead - the threat for showers and storms to the TAF
sites increases late Wednesday into Wednesday night as a low
pressure system over the Dakotas moves into the region.

&&

.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...AJ



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