Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 161720
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1220 PM CDT Sun Apr 16 2017

.SHORT TERM...(Today and tonight)
Issued at 332 AM CDT Sun Apr 16 2017

08Z surface analysis shows a cold front from near Medford to La
Crosse to Oelwein. The vast majority of showers and storms from
last evening have moved into eastern WI and northern IL, although
some areas of fog have developed across western WI within the
weak flow regime ahead of the front. While visibility may briefly
drop to 1/2 mile or less at times through 12Z, increasing
northwest winds behind the front will quickly scour out low-level
moisture.

For the rest of today, expect dry conditions and mostly sunny
skies as high pressure builds across IA. Model soundings show the
afternoon boundary layer deepening to around 1 km with roughly 20
to 30 kts to mix to the surface. This will result in breezy
westerly winds today, gusting at times between 20 and 30 mph. Deep
mixing will also enhance near surface drying with dew points
falling into the low-mid 30s by mid afternoon. With high
temperatures in the low-mid 60s, this will allow humidities to
drop to 25 percent in some places. See Fire Weather section below
for additional information.

A weak, fast moving clipper system moves across northern MN/WI
tonight, resulting in increasing mid-level clouds. Model soundings
show saturation occurring around 10 kft, but there remains a
rather dry sub-cloud layer. There could be some sprinkles from
this system, but confidence too low at this point to add mention
to the current forecast. Temperatures tonight will drop into the
low to mid 40s.

.LONG TERM...(Monday through Saturday)
Issued at 332 AM CDT Sun Apr 16 2017

Monday will be another dry day as high pressure from the southern
Canadian Prairies noses southward into the Upper MS River Valley.
Skies look to be partly to mostly sunny with light winds.
Temperatures will range from the mid 50s across north central WI
to the upper 60s across far southwest WI.

Attention then turns to the next eastern Pacific short-wave and
cold frontal passage on Tuesday. Despite PWAT values back to near
one inch ahead of the front, latest model runs have trended drier
with total rainfall, now topping out around one-quarter inch or
less. This may be a result of a farther north low track, the
progressive nature of the system, and overall lack of instability
(100 J/kg or less MUCAPE) limiting thunderstorm potential. Deep
layer shear is quite strong with frontal passage, but given weak
instability, severe weather is not expected. Instead, will
highlight a slight chance for thunderstorms Tuesday afternoon.

Expect a short dry period Tuesday night into Wednesday morning,
but rain chances quickly return Wednesday afternoon into Wednesday
night as another short-wave lifts northeastward in southwest flow
aloft. There exist some slight differences is surface low track
between models, but a GFS/ECMWF consensus would keep the low
south of the forecast area through 12Z Thursday. Strong mid-level
frontogenesis north of the surface low, however, will result in
widespread rain across the area. Thunderstorms should be limited
with MUCAPE generally a few hundred J/kg or less, but with a
prolonged period of stronger convergence acting on PWAT values
near an inch, rainfall amounts could top one inch in places. Given
recent rainfall and saturated soil conditions, this could cause
additional hydrology concerns. See hydro section below.

Lingering showers should continue into Thursday with a return to
dry conditions by Thursday night. Friday looks dry and seasonably
cool with high pressure across the region. Then another more
potent low moves into the Ohio River Valley region for Saturday
with perhaps some showers on the northwest periphery of the
system clipping the southeast half of the forecast area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1220 PM CDT Sun Apr 16 2017

VFR conditions expected through the period. West to northwest
winds will gust to 20-30 kts through late afternoon before quickly
subsiding this evening and becoming light overnight. Increasing
midlevel clouds around 10-15 kft are expected for a time tonight
into early Monday as a weak weather system drops by to the north.
The accompanying surface boundary will shift winds back to the
northwest or north Monday morning.

&&

.FIRE WEATHER...
Issued at 332 AM CDT Sun Apr 16 2017

Deep mixing this afternoon will allow dew point temperatures to
fall into the lower to mid 30s. When combined with high
temperatures in the lower to mid 60s, minimum RH could drop as low
as 25 percent in places. Westerly winds will also be breezy,
gusting at times between 20 and 30 mph. That said, fuel moisture
will still be rather high given recent rainfall, limiting today`s
overall fire potential.

&&

.HYDROLOGY...
Issued at 332 AM CDT Sun Apr 16 2017

Elevated river levels will be a concern this week. Recent rainfall
(heavy in places) have caused area rivers to respond with the
Trempealeau River at Dodge and the Black River at Black River
Falls nearing minor flood stage today. Additional showers and
isolated thunderstorms Tuesday and Wednesday night into Thursday
may result in additional rises on area rivers and streams. With
saturated soils, any additional rainfall may also result in
localized flash flooding.

&&

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

$$

SHORT TERM.....Rogers
LONG TERM......Rogers
AVIATION...JM
FIRE WEATHER...Rogers
HYDROLOGY......Rogers



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