Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 262332

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

.SHORT TERM...(This evening through Wednesday)
Issued at 327 PM CDT Tue Jul 26 2016

Main forecast concerns for tonight:

1)Cloud trends along with low chances for showers and storms
across northern areas.

2)Patchy to areas of valley fog if skies stay clear through the
late night hours.

Current water vapor imagery showed a couple of shortwave troughs
moving east across the Dakota`s triggering showers and
thunderstorms. Meanwhile a cold front stretched from western Upper
Michigan through southeast North Dakota, drifting south.  Weak
frontogenesis was noted in the 900-700 mb layer with the front. The
frontogenesis drifts south into northern Wisconsin and north-central
Minnesota tonight but weakens considerably. Any lingering showers
or thunderstorms associated with it should be on a weakening trend
this evening. Mid and high level cloud from the showers and storms
over the Dakota`s will spread eastward into the upper Mississippi
River Valley tonight and this will likely have an impact on valley
fog potential. Skies will become mostly clear for the evening
hours then we should see an increase in clouds during the late
evening into the overnight. Current thinking is that
temperature/dewpoint spreads and clear skies for a good portion of
the night should allow for at least patchy to areas of fog in the
Mississippi tributaries and across central Wisconsin Cranberry

A shortwave trough and possibly weak MCV (Mesoscale Convective
Vortex) will slide into the area on Wednesday as a the weak cold
front meanders in from the north. With daytime heating, and these
two features moving through, we should see scattered showers and
thunderstorms develop, mainly during the afternoon hours. Shear is
rather weak so not anticipating any severe storms, but cannot rule
out a strong storm or two with hail and gusty winds. Showers and
storms look to continue into Wednesday evening.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 327 PM CDT Tue Jul 26 2016

Ongoing showers and storms are expected to gradually taper off late
Wednesday night into midday Thursday as high pressure builds in
from the north. Some of this activity could linger into the
afternoon but then will end Thursday night. Thursday into Friday
will be cooler as the Canadian high settles in. Plan on highs
mainly in the 70s. The high will be the dominate weather feature
going into the weekend but cannot rule out some small chances for
showers and thunderstorms late Sunday into Monday as a warm and
unstable airmass tries to push back into the region. Temperatures will
be on a warming trend early next week. We may even see some 90
degree readings by next Tuesday.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 632 PM CDT Tue Jul 26 2016

Potential still exists for valley fog at KLSE overnight as surface
high pressure remains nearly stationary across the region.
However, several caveats to consider: 1) convective debris clouds
from the north/west and other mid-level cloud cover may limit
noctural cooling, 2) 23Z dew point depression is still rather
large at 23F, and 3) more recent high resolution forecast guidance
now suggests winds aloft may be a bit too strong for fog to
develop. Even if fog develops along the tributaries and into the
main Mississippi channel, there`s still the question of whether it
will reach the KLSE airfield. For now, will continue idea of VCFG
from 27.10Z to 27.13Z and re-evaluate later this evening. VFR
conditions will be the rule at KRST through the night with light
southwest wind. In fact, expect VFR at both TAF sites through the

Looking ahead, will need to consider adding rain/thunder for at
least KRST sometime around 28.00Z as a low pressure system from
the Dakotas moves across the region Wednesday afternoon and


.ARX Watches/Warnings/Advisories...


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