Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 110427
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1027 PM CST Wed Jan 10 2018

.UPDATE...
Issued at 955 PM CST Wed Jan 10 2018

Latest HRRR, RAP, and NAM are suggesting the heaviest band of snow
may be shifting slightly east by a county or two. Higher snow
totals are possible further east so have expanded the winter
weather advisory into La Crosse, Houston, and Winneshiek Counties.
Further adjustments are possible as we continue to review
mesoscale model output tonight. Have tweaked snow totals up a bit
across these counties, more into the 2-3 inch range.

&&

.SHORT TERM...(Tonight through Thursday)
Issued at 320 PM CST Wed Jan 10 2018

Winter storm for the region with accumulating snows, blowing and
drifting, and the potential for a brief period of wintry mix - some
icing?

Drizzle and fog will spread across the local area tonight. Fog could
become locally dense at times before a warm front moves in from the
south and/or a cold front sweeps in from the west. Some potential
for a few hours of Dense Fog Adv. Will monitor.

The precipitation will quickly transition to snow, but about a 1-3
hour wintry mix period is possible. During the transition, the cold
air could lead to a "flash freeze" of standing water on untreated
roads and sidewalks. Unexpected slippery travel conditions could
result ahead of the main snow band.

As of the snow, latest model runs have shifted where the narrow band
is favored - currently now running mostly from central IA, through
southeast MN, and across northwest WI. Ratios from 10:14 to 1 with
qpf upwards of 1/2" would lay down 4 to 6 inches in the narrow band.

Meanwhile, tight pressure gradient will result in northwest wind
gusts upward of 35 mph in open and unsheltered areas, blowing and
drifting what snow falls. Southeast MN and northeast IA will have
the higher impacts.

With all this in mind, have issued Winter Storm Warnings and
Advisories based on anticipated impacts from the snow, icing threat,
and blowing/drifting concerns. Amounts may not reach warning
criteria, but the results will be impactful given the entire
scenario.

All said, still not 100% certain in where this narrow band sets up
and there could still be some adjustments on where, and how much.

.LONG TERM...(Thursday night through Wednesday)
Issued at 320 PM CST Wed Jan 10 2018

Cold air returns for the upcoming weekend, post the departing cold
front/storm system, and looks to hang around for the early part of
the new work week. Single digit highs above and lows in the single
digits to teens below zero will be common. See the potential for
another round of Wind Chill Advisories for the night time/early
morning hours during this period - mostly in the favored wind areas
of southeast MN/northeast IA.

The GFS and EC are in pretty good agreement with dropping an upper
level shortwave trough out of northern Canada and across the Great
Lakes Sun afternoon/night. Pretty good slug of QG convergence
through the layers along with a slug of low level warm air
advection. Plenty of saturation to work with - per RH fields and
bufkit soundings. If scenario bares out, should see a prolonged
period of snow with a few inches of accumulation possible. Has a
Winter Weather Adv potential.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1027 PM CST Wed Jan 10 2018

LIFR to VLIFR conditions will continue in fog and low stratus
through the overnight hours. IFR to LIFR conditions are then
expected in periods of snow and possibly some blowing snow on
Thursday. Look for rain to move into the region after 08Z with a
switch over to snow mainly after 11Z at KRST and after 13Z at
KLSE. Conditions should improve to MVFR late Thursday afternoon
into Thursday evening as high pressure builds in from the west.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 3 AM to 6 PM CST Thursday for
     WIZ029-033-034.

     Dense Fog Advisory until 2 AM CST Thursday for WIZ053-054-061.

     Winter Weather Advisory from 7 AM to 6 PM CST Thursday for
     WIZ041.

     Winter Storm Warning from 3 AM to 6 PM CST Thursday for WIZ017-
     032.

MN...Winter Weather Advisory from 3 AM to 6 PM CST Thursday for
     MNZ088-095.

     Dense Fog Advisory until 2 AM CST Thursday for MNZ095-096.

     Winter Weather Advisory from 7 AM to 6 PM CST Thursday for
     MNZ096.

     Winter Storm Warning from 3 AM to 6 PM CST Thursday for MNZ079-
     086-087-094.

IA...Winter Weather Advisory from 3 AM to 6 PM CST Thursday for
     IAZ009-018-019.

     Dense Fog Advisory until 2 AM CST Thursday for IAZ008>011-018-
     019-029-030.

     Winter Weather Advisory from 7 AM to 6 PM CST Thursday for
     IAZ010.

     Winter Storm Warning from 3 AM to 6 PM CST Thursday for IAZ008.

&&

$$

UPDATE...Wetenkamp
SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...Wetenkamp



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