Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261713

Area Forecast Discussion
National Weather Service La Crosse WI
1213 PM CDT Wed Apr 26 2017

.SHORT TERM...(Today through Thursday)
Issued at 325 AM CDT Wed Apr 26 2017

The frontal boundary early this morning extends from northern
Wisconsin back into eastern Iowa. Broad low/mid level warm
advection and mid-level frontal forcing has led to areas of
showers early this morning. Expect some showers to continue to
lift northward during the daytime morning hours with the lower to
mid level frontal zone nearby. The GFS/ECMWF continue to remain
in good agreement with a relatively progressive solution, likely
putting an end to the bulk of the precip over much of the area by
later morning/early afternoon. The exception may be areas mainly
east of the Mississippi River, especially far southwest into
central Wisconsin, in closer proximity to the upper wave and
stronger mid/upper forcing lifting northeastward where shower
chances will continue into Thursday. A bit of wintry mix/drizzle
is not out of the question tonight, especially north of I-90,
dependent on surface temps, but with little impact expected. Temps
will be steady or falling as the cold front slides through along
and west of the Mississippi River today, while farther east temps
may have some time to recover before the front slides through.

Behind the front tomorrow will be a stark change from today with
highs reaching no higher than the 40s and low stratus hanging
around under cyclonic flow aloft.

.LONG TERM...(Thursday night through Tuesday)
Issued at 325 AM CDT Wed Apr 26 2017

High pressure does try to build southeastward as the upper trough
continues to slide northeast of the region late in the week. Thursday
night with a chilly air mass in place should see temps down in
the low 30s and possibly 20s, so frost may be a concern. As upper
level energy digs into the Desert Southwest, southwesterly flow
aloft will amplify across the central US. As this occurs, a
shortwave is forecast to eject northeast on Friday out of the
developing trough to the west. The 26.00Z GFS and most of the GEFS
members, along with the NAM/GEM bring some rain into at least
southern parts of the area on Friday as the shortwave interacts
with a mid-level frontal zone. The 26.00Z ECMWF remains weaker
with the wave and keeps the area mainly dry. Kept rain chances
generally along/south of I-90 on Friday.

Behind this wave much of the first half of the weekend may be dry
under the influence of high pressure centered across southern
Canada. However, temps will continue to be below average with
highs on Saturday in the 50s.

However, any dry weather likely will be short-lived as a strong
upper shortwave is forecast to close off as it begins to lift
northeastward out of the southern plains on Sunday. The global
operational models have been in pretty good agreement with this
system over the past few days, with a surface low moving towards the
Upper Mississippi Valley by Sunday night. Chances for precip will
increase late Saturday/Sunday as strong low-level warm/moist
advection pushes north ahead of the wave. With the system becoming
stacked and possibly slowing, precip may linger into Monday.
The track of the system and how much cold air can be wrapped into
system will impact precip type and amounts. There is the
possibility for some snow on the western edge of the system where
cooler low-level thermal profiles are more likely. The 26.00Z GFS
would support some accumulating snow potential into southeast
Minnesota, but it`s too early to have a high degree of confidence
on track/thermal profiles. It will definitely be a system to keep
an eye on late this week. At the least, a chilly and wet period
for the end of the weekend/early next week looks likely, before
the system finally pulls away early next week at some point.


.AVIATION...(For the 18Z TAFS through 18Z Thursday morning)
Issued at 1213 PM CDT Wed Apr 26 2017

Low stratus and patchy drizzle will plague the taf sites thru this
afternoon and tonight as low level moisture remains trapped in and
under a strengthening inversion and under sfc-mid level cyclonic
flow. Cigs thru tonight are expected to remain IFR and lower MVFR as
a seasonably cold airmass spreads in. Drier sfc/boundary layer air
and NW winds 10-15kts will generally keep vsbys in the P6SM range
thru tonight. Some improvement in the cigs expected during the mid-
late morning hours Thu as the sfc-805mb low lifts NE of the area and
the sfc-850mb flow becomes more westerly and pulls in drier low
level air from the plains.




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