Area Forecast Discussion
Issued by NWS La Crosse, WI

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483
FXUS63 KARX 261130
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
630 AM CDT Sun Mar 26 2017

.UPDATE...
Issued at 630 AM CDT Sun Mar 26 2017

It`s a very soupy morning with low stratus, patches of fog, and
showers. Some lower visibilities have developed over far SW WI/NE
IA into SE MN, with the more widespread low visibilities so far
remaining just to the south. Will continue to monitor for any
northward development of dense fog over the next few hours.

Otherwise, with little overall change in conditions expected
today, will trend highs down a few degrees, as temps likely will
struggle to rise with the low cloud cover/showers.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 220 AM CDT Sun Mar 26 2017

Upper level trough/500 mb low spinning over the mid mississippi
river valley early this morning, per latest water vapor satellite
imagery. The trough will continue to lift northeast today-tonight,
with the low filling as it moves over the eastern great lakes.
Spokes of energy will fragment and slip across the forecast area
today into tonight, with some weak reflection frontogenetically on a
few pressure sfcs. Most of the saturation is confined under 600 mb -
per time/height x-sections and bufkit soundings. The combo of
lift/moisture should be enough to keep scattered, light showers
going today into tonight.

GFS/NAM then favor bringing a weak ripple along the 500 mb flow from
the northern plains to across northern portions of the upper
mississippi river valley tue. Decent frontogenetic response in the
800-600 mb layer, and with enough saturation present, expect a few
more showers to develop across central MN and northern WI.

Farther south, models want to slip a shortwave in the southern
branch of the flow from the southern plains to across the oh/tn
river valleys. Some variances with how far north this shortwave
makes, and the potential for rain chances across the far south. At
this time, most models trend keeping the bulk of any pcpn chances
just south...although with small chances across the far south. Looks
reasonable at this time.

.LONG TERM...(Wednesday through Saturday)
Issued at 220 AM CDT Sun Mar 26 2017

Forecast confidence remains shaky for the mid to later part of the
new week as the GFS and EC remain at odds with their handling of the
various upper level shortwaves that could (would?) impact the local
area.

First point of contention is with a shortwave trough slated to roll
out of the desert southwest Wed, tracking east north-east toward the
oh river valley and eastern great lakes. The EC takes a more
northeast track with the trough, with a large swath of associated
pcpn (low level warming, deformation region) ahead and north of its
associated sfc low. This has been a consistent signal in the EC over
its past several runs. The GFS has the same trough, but holds it
farther south, with little if any pcpn threat locally. This has been
a consistent signal in the GFS. Meanwhile, the latest Canadian is
more on board with the EC, giving that solution a bit more weight.
With this in mind, will lean toward the wetter solution in Thu-Fri
time frame.

The second point would be a shortwave in the northern stream slated
to drop across the Upper Mississippi River Valley Sunday...at least
if you believe the GFS. A swath of pcpn would accompany the trough.
A consistent signal in the GFS. Meanwhile the EC is slower and not
as strong with this feature. Rather, it eventually merges it with
another trough moving out of the southwest that would bring another
round of pcpn Mon (ala what the EC expects for Thu-Fri). With
confidence low, going to let consensus blend detail any pcpn chances.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 630 AM CDT Sun Mar 26 2017

Mainly IFR/LIFR conditions expected through the next 24 hours.
Widespread low stratus/fog will persist through today with
occasional light showers. Ceilings are expected to remain
IFR/LIFR, although KLSE may approach MVFR at times. Some gradual
improvement in visibility through the day is expected at KRST, but
visibilities may decrease again tonight, with winds remaining
quite light.

&&

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

$$

UPDATE...JM
SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...JM



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