Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221110
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
610 AM CDT Sat Apr 22 2017

.SHORT TERM...(Today and tonight)
Issued at 238 AM CDT Sat Apr 22 2017

Main forecast concerns are on afternoon relative humidity values and
high temperatures today and again on Sunday. Focus then turns to
increasing south winds on Monday and the potential for lower
relative humidity values across central Wisconsin before dew
points recover later in the day.

High pressure remains in control across the Upper Mississippi River
Valley today providing dry and quiet weather. Cirrus continues
across areas along and south of Interstate 90 this morning but we
should see these thin with time today. Forecast soundings show
deep mixing this afternoon with the potential to mix to 850 mb.
This will result in dew point values tanking this afternoon
leading to minimum relative humidity values in middle teens to
lower 20s. This will create some fire weather concerns, but the
good news is that winds will be very light and recent wet
conditions should limit the overall fire threat. The biggest
concerns will be fires starting easily in fine, grassy fuels.

Dry, cool, and quiet weather will continue across the forecast area
tonight. A cold front will edge southward out of southern Ontario
bringing precipitation chances to northern Minnesota through
Upper Michigan tonight into Sunday. Plan on lows tonight ranging
from the mid 30s over northern Wisconsin to the mid 40s over
northeast Iowa.

.LONG TERM...(Sunday through Friday)
Issued at 238 AM CDT Sat Apr 22 2017

The frontal boundary will remain over portions of northern
Minnesota/northern Wisconsin on Sunday with chances for any rain
staying north of the forecast area. Sunday will be another dry and
pleasant day across the region as southerly winds start to increase.
Once again forecast sounding show deep mixing across the region
which will result in afternoon relative humidity values falling
into the upper 20s at many locations. Further north across
northern Wisconsin, relative humidity values are expected to fall
into the upper 30s. Will have to keep a close eye on high
temperatures on Sunday with the deeper mixing. Have continued the
trend of warmer highs in valley locations but they may not be warm
enough. Plan on highs in the upper 60s to lower 70s, with the
potential for some mid 70s in valley locations.

The pressure gradient will continue to tighten across the region
Sunday night into Monday as low pressure deepens over South
Dakota/northern Nebraska. The big question will be, how quickly will
higher dew points and moisture make it back into the region ahead of
the low and approaching cold front from the west.  It will take some
time for moisture to return to the region, especially for portions
of western into central Wisconsin. Stronger winds are expected
across the region on Monday too, with sustained winds of 15 to 23
mph with gusts approaching 37 mph in open areas. After three days of
drying and these stronger winds, we could see some fire weather
concerns across western into central Wisconsin. Increasing mid to
high level clouds will help to limit how deeply we mix but those
clouds will arrive a little later in the afternoon across central
Wisconsin. The front will then meander into the area Monday night
into Tuesday as the surface low lifts northwest into southern
Ontario. Not expecting much rainfall out of this feature with the
main shortwave tracking just to our northwest.  The boundary then
stalls across the area on Tuesday.

A trough then pushes into the region late Tuesday into Wednesday
bringing chances for rain to the area. Forecast models are edging
into better agreement on bringing a surface low through the Upper
Mississippi River Valley during this timeframe but there remains
differences on timing. If trends continue precipitation chances will
need to be increased from Tuesday night into early Wednesday as
widespread rains are starting to look likely. An active pattern is
looking possible for the end of the week as a trough develops across
the central CONUS with more rainfall possible. A lot of
uncertainly beyond Wednesday so will maintain a model consensus
blend from midweek and beyond.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 610 AM CDT Sat Apr 22 2017

VFR conditions through the period with light/variable winds today
under high pressure becoming light southwesterly tonight. Only
some patches of high cirrus are expected at times.

&&

.HYDROLOGY...Through Tuesday
Issued at 238 AM CDT Sat Apr 22 2017

Recent heavy rains and wet soil conditions across the area have
led to minor flooding along portions of the Black, Trempealeau,
and Yellow Rivers in Wisconsin. Flood warnings continue for the
Black River at Galesville, the Trempealeau River at Dodge, and
the Yellow River at Necedah. Minor flooding is expected at these
locations. Monitor river forecasts and statements closely if you
live near or have interests along these rivers.

&&

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

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...JM
HYDROLOGY...Wetenkamp



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