Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 152006
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
306 PM CDT Tue May 15 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 306 PM CDT Tue May 15 2018

High pressure dominates the regional weather pattern tonight
through Wednesday, resulting in mainly sunny/clear skies. While
winds at the surface will be light tonight, model soundings show
10-20 kts above the steep nocturnal inversion. This, in
combination with a relatively dry near surface layer should
preclude widespread fog, but some development is still available,
especially in river valleys and the bog country of west-central
WI. Lows tonight will bottom out in the mid 40s to low 50s.

Wednesday will be a repeat of today, but with temperatures a few
degrees warmer. Most areas should top the 80 degree mark with mid
80s possible in favored warm spots. Light southerly winds in the
morning will shift to the west through the day.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 306 PM CDT Tue May 15 2018

Surface high pressure and very weak flow aloft will be in place over
the region Wednesday night into Thursday. This could lead to some
fog development early Thursday morning. A weak upper-level
disturbance is forecast to move from central Minnesota into northern
Wisconsin during the day Thursday. Overall forcing appears rather
weak, but up to 1000 J/kg MUCAPE will be present. A few scattered
showers and isolated thunderstorms may develop north of Interstate
94 Thursday afternoon, dissipating with the loss of diurnal heating
Thursday evening.

Attention then turns to a stronger shortwave ejecting from a western
CONUS longwave trough late Friday into Saturday. Precipitation
should hold off until Saturday morning when low-level convergence
begins to ramp up in response to the approaching shortwave. Showers
and thunderstorms will be likely as the feature moves across the
area Saturday afternoon into Sunday morning. At this time,
widespread severe convection appears unlikely, with only modest
instability and shear in place. Heavy rain could end up being the
biggest impact with this system, as PWAT values are progged to
exceed 1.5 in. However, the quick moving nature of this system may
preclude a flash flooding threat. Behind the departing system,
models favor surface high pressure building in under zonal flow
aloft.

Temperatures will remain above normal through Friday, returning to
near normal for the weekend into early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1228 PM CDT Tue May 15 2018

High pressure will drift across the region through the TAF period,
resulting in mostly sunny/clear skies and light winds. Light
northwest to northeast winds this afternoon will become variable
this evening into the overnight. Winds should then turn to the
southwest Wednesday morning at KRST. Given clear skies/light
winds, there is the potential for some fog overnight, but a drier
near surface layer should preclude widespread development. Will
keep fog out of the TAFs for now, but will monitor observational
trends and amend as necessary.

&&

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

$$

SHORT TERM...Rogers
LONG TERM...Hollan
AVIATION...Rogers



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