Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221824

Area Forecast Discussion
National Weather Service La Crosse WI
124 PM CDT Sat Jul 22 2017

.SHORT TERM...(Tonight through Sunday Night)
Issued at 124 PM CDT Sat Jul 22 2017

Water Vapor showing a mid-level circulation moving east along the
U.S./Canadian border. This will push a weak surface trough through
the area late this afternoon into this evening. Best forcing/p-v
advection with this mid-level feature swings across northern WI but
there will be enough surface convergence to trigger a scattered
storms further south into our area. RAP depicting 1000-2000J/kg
MUCAPE along with 20-25kt of 0-3km Bulk Shear. This looks to be
enough to support a few strong to possibly severe storms. Damaging
winds and a few larger hailstones would be the main threat.

Much needed drier/cooler air filters into the area Sunday as an area
of high pressure builds in from Canada. Plan on high temperatures in
the middle 70s to lower 80s with dew points in the upper 50s to
lower 60s.

.LONG TERM...(Monday through Saturday)
Issued at 124 PM CDT Sat Jul 22 2017

High pressure thankfully remains in control through monday,
providing another dry/pleasant day. Look for highs in the 70s with
dew points in the mainly in the 50s to lower 60s.

Shower and thunderstorms chances then return Tuesday, continuing
into Thursday as a mid-level trough and surface cold front slowly
make their way from the Northern Plains into the Upper Mississippi
River Valley. Too early to tell whether severe weather will be a
factor or not, but looks like later Tuesday afternoon into Tuesday
night could be a window of opportunity as the GFS and ECMWF both
show sufficient CAPE and shear. There is slight timing difference
between the two models, so details still need to be ironed out.
Otherwise, looks like seasonably warm conditions with a bit more
mugginess to the air as dew points start creeping up again.

Friday into Saturday look to be mainly dry as another Canadian highs
slides south into the region.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1242 PM CDT Sat Jul 22 2017

Broad MVFR/IFR cloud deck along and south of I-90 will continue to
sag southward through the afternoon, but would expect some lingering
MVFR ceilings at both TAF airfields until around 22.21Z before
completely clearing out. Attention then turns to a narrow line of
convection this evening mainly across northern/central WI, but could
drop as far south as KLSE. Will introduce VCTS in a narrow window
from 23.00Z to 23.02Z and monitor observations for additional
refinement. IF thunderstorms impact TAF airfield, could see brief
reductions in ceiling/visibility with gusty winds.

Skies expected to clear tonight with relatively light wind. Fog is
possible, especially in river valleys, but confidence not high
enough at this time to include in 18Z TAFs. If no fog develops
expect VFR conditions at both TAF airfields through the night and
into Sunday morning. Winds away from thunderstorms will be light
from the north-northwest, becoming variable at KLSE this evening and


Issued at 124 PM CDT Sat Jul 22 2017

Ongoing flooding across parts of northeast Iowa into
far southwest Wisconsin this afternoon. In particular, much of Clayton,
southern Fayette, and southern Grant Counties appear to be
hardest hit, with reports of 5-10 inches of rain falling. This
rainfall will take a while to work through the river systems, with the
biggest concerns focused along the Volga River and southern
reaches of the Turkey river, mainly south of Elkader.
Additionally, water continues to percolate down the Kickapoo
River, with the crest having just passed Gays Mills, and along the
Trempealeau River, with Dodge cresting earlier. High/flooding water
also remains along the La Crosse River. Flooding is expected to
continue for the next few days. Drier weather is on tap for Sunday
into Monday but then additional showers and storm chances are
expected to return Tuesday, lasting into Thursday.




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