Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 232012

Area Forecast Discussion
National Weather Service La Crosse WI
212 PM CST Thu Nov 23 2017

.SHORT TERM...(This evening through Friday)
Issued at 212 PM CST Thu Nov 23 2017

The main concern is where and how much precipitation there will be
across the area Friday afternoon. The main short wave trough will
swing across the Upper Midwest during the afternoon with the 23.12Z
NAM showing this producing a band of moderate pv advection in the
500-300 mb layer. As the cold front moves in with the short wave
trough, there should be a band of weak to moderate frontogenesis in
the 1000-500 mb layer. Decent up glide should occur as well, with 2
to 5 ubar/s expected on the 290K isentropic surface right along and
a little behind the surface front. With this good forcing, the main
question is just where will there be enough moisture to allow
saturation to occur. The NAM would suggest the best chances for
saturation and precipitation would be well to the north of the area
across northern Minnesota and over Lake Superior. The 23.12Z GFS is
a little farther south but still mainly across central Minnesota
into northern Wisconsin, or generally north of Interstate 94. With
these signals, have trended the area of precipitation chances a bit
farther north with the highest chances across Taylor County. For
now, have kept the chances no higher than 50 percent, but could see
the need to possibly have these bumped up some if the forcing
signals remain consistent. Temperatures ahead of the front will warm
well into the 40s and 50s, so the precipitation Friday will be all

.LONG TERM...(Friday night through Thursday)
Issued at 212 PM CST Thu Nov 23 2017

The end of November is shaping up to be very quiet weather-wise
across the region. Surface high pressure will drift across the
region through the weekend providing dry conditions with plenty of
sunshine save for some patches of high clouds at times. Even
behind the cold front, temps will remain seasonable, with highs
near or above 40 in most locales on Saturday, except for north
central Wisconsin. 925 mb temps do warm several degrees from
Saturday to Sunday as the surface high passes to the southeast,
supporting warmer highs well into the 40s, with even some 50s

Heading into the coming work week, upper ridging will spread over
the area on Monday ahead of an upper level trough approaching from
the Rockies. Some mid/high clouds may move across the area, but with
a very mild airmass (925 mb temps of 7-11C), well above average
highs back near or above 50 appear likely in most areas.

There are some model differences persisting among the various
model solutions with the upper trough passage on Tuesday and
subsequent evolution of the upper air pattern. 12Z models suggest
a stronger shortwave will pass well north, while another wave
ejecting into the southern plains may eventually close off to the
south over the course of the week. As a result, much of the deep
forcing remains north and south of the area, so will maintain a
dry forecast into mid-week. Temps will cool down behind a cold
frontal passage Monday night into Tuesday, but temps are expected
to remain at least near seasonal norms through the next week.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1058 AM CST Thu Nov 23 2017

Quiet VFR conditions expected through Friday morning. A short wave
trough moving across southern Canada tonight may bring a few mid
level clouds to the area, but not expecting there to be enough
moisture for these to produce a ceiling. Another short wave
trough will be right behind the one for tonight with an area of
low pressure to be along the North Dakota/Canada border. This will
turn the winds more to the south with an increase to 10 knots or
just above this evening into Friday morning. As the short wave
trough and surface low move east Friday morning, a cold front will
approach from the west with a gradual increase in the cloud cover,
but do not look for any ceilings or precipitation to form until
Friday afternoon.




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