Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 232314
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
515 PM CST Fri Feb 23 2018

.SHORT TERM...(This evening through Saturday night)
Issued at 321 PM CST Fri Feb 23 2018

At 3 PM, the low pressure system that brought a wintry mix to the
area was located over Lake Superior. Meanwhile, a 1032 mb surface
high was located over central South Dakota. A weak to moderate
surface pressure gradient was found between these 2 systems. It
was producing 10 to 20 mph winds. Under partly sunny to mostly
cloudy, temperatures ranged from the upper 20s to upper 30s.

For tonight, expect some patchy fog to continue across parts of
southeast Minnesota, northeast Iowa, and west-central Wisconsin.
Elsewhere skies will be mostly cloudy. Temperatures will fall into
the teens where it snowed last night and be in the lower and mid
20s elsewhere.

From Saturday afternoon into Saturday night, the 23.12z models are
showing that a negatively tilted shortwave trough will move
through the region. This will help to wrap warm air into
southwest and central Wisconsin for Saturday afternoon and
evening. This along with a dry slot will result in the loss of
ice for this area. This will result in the precipitation being
mainly in the form of rain and maybe a brief period of freezing
rain at the onset during the afternoon and as the precipitation
ends on Saturday night. The western and northern extent of this
warm nose in southeast Minnesota and northeast Iowa is still in
question. The 18z NAM is a bit further west than its 12z solution.
The GFS has also trended this way too, but it is still much
cooler than the NAM. Considering the tilt of this system, still
thinking that going warmer in these areas is the best way to go.

Meanwhile, further west, the deformation band of snow was located
across parts of southeast Minnesota, northeast Iowa, and north-
central Wisconsin. These areas will likely see 3 to 5 inches of
snow with some locally higher amounts up to 6 inches. Due to this,
a Winter Weather Advisory has been issued for this area. If this
band happens to shift a bit further east, there is still a
possibility that some of these counties may have to be upgraded to
a Winter Storm Warning.

.LONG TERM...(Sunday through Friday)
Issued at 321 PM CST Fri Feb 23 2018

On Sunday, a tight surface pressure gradient may result in some
patchy blowing snow across southeast Minnesota and north central
Wisconsin.

From Tuesday night into Wednesday, the models continue to show
that a baroclinic zone will be located south of Interstate 90.
This will be the focus for some rain and snow during this time
period.

From Wednesday night into Thursday night, the models continue to
differ of the track of a low pressure system through the region.
Due to this, just stayed with the blend for now.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 515 PM CST Fri Feb 23 2018

Cigs: challenging forecast with high pressure building overhead,
light wind field, and models holding onto low level saturation.
Suggestion is stratus/fog would develop in the clear areas later
tonight - likely ifr. Tough call on how extensive and where -
although current setup supports a higher threat for KRST. Some
improvement in cigs on Sat, but low clouds quickly return toward 00z
Sun as the next storm system approaches the region from the
southwest.

WX/vsby: with the stratus tonight should comes some br/fg. Like for
the cigs, confidence shaky in where and how low the vsbys will go.
Will continue to favor KRST with the worse conditions. Will likely
need refinement to the forecast later tonight as scenario plays out.
Snow/wintry mix/rain will start to spread in from the southwest by
00z. Looks like mainly snow for KRST, but could see a wintry mix
from time to time Sat night. Warmer air aloft/sfc puts KLSE squarely
in the rain/wintry mix at this time.

Track of the storm and warm air placement is still not certain, so
some changes in types (and accompanying vsby and other impacts) are
possible.

Winds: becoming light east/vrb as high works overhead tonight, then
strengthening from the east/southeast by Sat afternoon as the storm
system nears from the southwest. Will swing to the west overnight
Sat with the passage of the low.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 3 PM Saturday to 6 AM CST Sunday
     for WIZ032>034.

     Winter Weather Advisory from 6 PM Saturday to 6 AM CST Sunday
     for WIZ017-029.

MN...Winter Weather Advisory from 3 PM Saturday to 6 AM CST Sunday
     for MNZ079-086>088-094-095.

IA...Winter Weather Advisory from 3 PM Saturday to 6 AM CST Sunday
     for IAZ008-009-018-019.

&&

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Wetenkamp



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