Area Forecast Discussion
Issued by NWS La Crosse, WI

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923
FXUS63 KARX 100407
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1007 PM CST Fri Dec 9 2016

.SHORT TERM...(Tonight through Sunday Night)
Issued at 233 PM CST Fri Dec 9 2016

Long duration snow event set for Saturday afternoon through
Sunday.

Current water vapor/500mb analysis shows an energetic mid-level
trough making it`s way into the Pacific Northwest. Models in good
agreement, bringing this wave across the Plains and across the Upper
Mississippi River Valley Saturday through Sunday evening. Push of
isentropic lift combined with mid-level frontogenesis will produce
widespread 3+ inch accumulating snow across the area from Saturday
afternoon through Sunday evening. As of right now, still looks like
heaviest snow will be along and south of a line from Rochester MN to
Viroqua WI...or generally south of I-90 where 6-8 inches is
expected. A few pockets of even higher amounts are possible if we
can get into some convective/heavier snow rates. Currently have a
Winter Weather Advisory out for most of the area from Saturday
afternoon through Sunday evening to cover this long 30-hr duration
event. May have to watch for the potential of heavier convective
snow band which may warrant an upgrade to Winter Storm Warning for
portions of the area mainly south of I-90.

Otherwise...plan on lows tonight in the single digits above zero and
highs Saturday in the teens/lower 20s. A bit warmer on Sunday with
highs in the middle/upper 20s.

.LONG TERM...(Monday through Friday)
Issued at 233 PM CST Fri Dec 9 2016

Main story for this next week will be the invasion of Arctic air and
much below normal temperatures. After a quiet Monday, an Arctic cold
front plunges through the area on Tuesday. Plan on falling
temperatures through the day Tuesday after early morning highs in
the single digits above zero. A few snow showers may accompany this
front Monday night ahead of the front but more impactful will be
temperatures falling into the single digits above and below zero by
Tuesday afternoon.  Wind chills Tuesday are expected to be in the
single digits/teens below zero.

Arctic airmass hangs over the area Wednesday into Thursday with highs
expected to be only in the zero to 10 above range and overnight lows
Wednesday night in the minus 5 to minus 10 range.

GFS/ECMWF a bit at odds for next Friday. ECMWF brings a fairly
strong low out of the Rockies which spreads snow into the area
whereas the GFS is much slower with the low and actually hangs high
pressure over us for dry conditions. Will take a model consensus for
now which yields 20-40 percent chance of snow. Otherwise, remaining
cold with highs in the 5 to 10 above range.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1007 PM CST Fri Dec 9 2016

Mid level clouds continue to work through the region, along with
occasional flurries. That will continue for another few hours,
before clouds scatter for a brief time Saturday morning. However,
look for clouds to thicken and lower from west to east into the
afternoon and evening, with light snow breaking out across the
region as conditions dip to IFR levels. Still looking like the
heaviest snow from this upcoming winter storm will occur roughly
06Z through 18Z (after the current TAF period), with total
accumulation of 4 to 8 inches. Winds will remain light from the
northwest overnight, gradually shifting southeast at 6-12 knots
later Friday afternoon and evening.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 2 PM Saturday to 6 PM CST Sunday
     for WIZ054-061.

     Winter Weather Advisory from 4 PM Saturday to 9 PM CST Sunday
     for WIZ032>034-041>044-053-055.

MN...Winter Weather Advisory from 2 PM Saturday to 6 PM CST Sunday
     for MNZ079-086>088-094>096.

IA...Winter Weather Advisory from 2 PM Saturday to 6 PM CST Sunday
     for IAZ008>011-018-019-029-030.

&&

$$

SHORT TERM...DAS
LONG TERM....DAS
AVIATION...Lawrence



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