Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 120534
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1135 PM CST Sat Nov 11 2017

.SHORT TERM...(Tonight through Sunday Night)
Issued at 243 PM CST Sat Nov 11 2017

At 2 PM, a vigorous short wave trough was moving into the eastern
South Dakota.  A band of moderate 700 to 500 mb frontogenesis
extended east across southern South Dakota and northern Iowa.
Patches of light drizzle continues along and south of the Interstate
90 corridor.

The 11.12z models are in agreement that as the short wave trough
will move east southeast through Iowa tonight.  As this occurs, a
band precipitation will develop south of Interstate 90.  With
limited ice aloft and temperatures at or above freezing at the
surface, the precipitation will be mainly in the form of rain
However, on the north edge of this band will have to be watched for
a wintry mix.  With all of this said, the NAM does have more ice
aloft and does indicate the potential of snow.  It even has 1.3
inches in its Cobb data at Dubuque.  This will have to watched
tonight.  Another thing that will have to be watched is that the dew
points are still below freezing, so will have to watch for the
potential of freezing rain too.

On Sunday morning, the short wave will move quickly southeast away
from the region.  Other than a brief wintry mix in southwest
Wisconsin and northeast Iowa, the day will be dry across the region.

High pressure settles overhead Sunday night with mostly clear skies
and light winds resulting. Good radiational cooling is expected to
produce overnight lows in the teens and lower 20s.

.LONG TERM...(Monday through Saturday)
Issued at 243 PM CST Sat Nov 11 2017

Monday looking like a decent day with partly sunny skies and slight
moderation in temperature. Plan on highs in the middle 30s to lower
40s.

Increasing warm air advection/isentropic lift set for Monday night
into Tuesday ahead of low pressure pushing east out of the Northern
Plains. This is expected to result in increasing/thickening cloud
cover and patchy light rain or a wintry mix (at least through
Tuesday morning where temperatures will be in the upper 20s/lower
30s). Should be all rain chances by afternoon as temperatures warm
into the upper 30s to middle 40s. Rain will be likely Tuesday night,
tapering off my late morning as that Northern Plains cold front
passes through the region.  Otherwise, looks like near normal
temperatures Wednesday with highs in the 40-50 degree range.

Next precipitation chance rolls in Thursday afternoon into Friday as
low pressure tracks out of the Plains and across our region. Looks
like mostly rain with this system although could see some light snow
at times mainly across the north where cooler temperatures will
reside.

Saturday looks dry and cooler behind the departed low with expected
highs in the upper 20s to upper 30s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1135 PM CST Sat Nov 11 2017

Cigs: tricky forecast. Northern edge of the current cloud deck sits
nearly on top of KRST/KLSE per latest fog/stratus satellite imagery.
Sfc obs point to sites mostly sub 3 kft. Meso models suggest the
edge will slip slowly south overnight, resulting in sct-bkn vfr
conditions. Given the southeast tack of the responsible shortwave
trough, that still seems reasonable - although it might take until
12z for KLSE.

Next concern is the mass of low clouds across eastern ND/northern
MN. Fog/Stratus satellite imagery shows it making very slow progress
south-southeast, not nearing the TAF sites (if it holds together and
keeps current direction) until early Sun afternoon. NAM/RAP low
level RH still favoring bringing this mass across the TAF sites -
especially KLSE - pulling east late in the evening. The GFS keeps it
just north/east, with minimal impact (especially KRST). Conundrum.
Low level ridge building in from the west could serve to shunt the
cloud mass far enough east by the afternoon to avoid any impact at
KRST...maybe even KLSE. Confidence not high in how this will play
out. If you like one set of models, there will be several hours of
MVFR for the afternoon. If you like another, its VFR through much of
the day.

For now, going to play some cig impacts at KLSE for the afternoon.
Will continue to monitor at update as needed.

Clouds will clear (if around) Sunday evening as high pressure builds
in.

WX/vsby: see some threat for mvfr br at KRST with weaker gradient
building in, although some high clouds to contend with. Will add a
tempo group in with vsby restrictions showing just to their west at
late evening.

Winds: light south/vrb winds tonight should become more
northwesterly Sunday, still staying relatively light.

&&

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

&&

$$

SHORT TERM...JSB/DAS
LONG TERM...DAS
AVIATION...Rieck



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