Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 131746
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1146 AM CST Fri Jan 13 2017

.SHORT TERM...(Today thru Saturday)
Issued at 230 AM CST Fri Jan 13 2017

Fairly stout surface high (1040+ mb) building into MN early this
morning and is slated to meander eastward later today/start of
weekend. Meanwhile a weak ripple in the upper level flow on the
MT/WY border is progged to zip east...moving across the region
tonight. Another wave shifts out of CO mirroring the northern wave
in timing...just a bit farther south. Similar systems have been able
to drop a narrow band of an inch or two of snow. That said, these
shortwaves are going to have battle the dry air associated with the
sfc high. NAM/GFS/RAP bufkit soundings want to saturate this several
hundred mb moisture deprived surface layer as the day wears on,
suggesting enough saturation in the evening for some light snow
chances. Might be a tad optimistic in such rapid saturation given
the amount of forcing, which isn`t robust. That said, enough for at
least flurries and/or light snow chances and will continue mention
in the forecast. Any accums look minor at this time.

.LONG TERM...(Sunday through Thursday)
Issued at 230 AM CST Fri Jan 13 2017

Main weather concern over the next week is the storm system progged
to roll out of the southwest and drive across the eastern Great
Lakes by 00z Wed...with impacts from late Sunday night through Tue.

The GFS and EC both lift a ball of upper level energy northeast out
of the desert southwest Sunday, spinning it into the region by 12z
tue. Models keep the wave open with some cyclogenesis as the system
approaches the area, but the frontogenetic response is somewhat
meager - at least at this time. Strong push of moisture northward
into the system though. NAEFS pw anomalies from +1 to +3 with the
GFS pointing to a 30-40 kt 850 mb jet nosing into northeast IA
(thunder anyone?).

Big push of warm air ahead of the trough/low...with the EC around +8
C at 850mb by 12z Tue across the south. The GFS is half that, but
still quite warm. Obvious pcpn type implications with such a warm
layer. Sfc temps are currently expected to warm into the mid/upper
30s, but road temps likely below freezing for a portion of the
period. In addition, models also suggest that ice in cloud could be
an issue from time to time. Yet another consideration for what
falls.

As it sits...some of everything could fall...snow, sleet, freezing
rain, rain. A lot of uncertainty on placement, timing, and
what/where the most likely pcpn types will fall. It`s a mess, plain
and simple. And could be a very hazardous one.

Current setup favors two distinct "main" areas of pcpn. 1) with the
shortwave/deformation region of the sfc low. This sweeps in from the
south late Sunday night, moving northeast across the forecast area
on Monday. Mixed bag of pcpn with this, perhaps favoring freezing
more than snow or rain. 2) Sfc low/low level jet-moisture transport
influences. Current placement would drive this pcpn region into
northeast IA and southwest WI Mon night-Tue morning. This could be
mostly rain, aside from any cold road considerations.

Headlines? Probably. Advisories seems more likely right now, but
can`t rule out warnings. Watch could proceed either adv/warning.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1146 AM CST Fri Jan 13 2017

The band of light snow across northwest Iowa into southwest
Minnesota is expected to have a hard time surviving as it move
east this afternoon. High pressure was still centered over western
Wisconsin late this morning and was keeping dry low level air in
place. In addition, the short wave trough was moving into
confluent flow aloft, which will cause it to weaken and diminish
the forcing to keep the snow going. If any snow does survive, it
will likely go south of both airports and will continue with a dry
forecast. The VFR ceilings will remain into this evening and the
early overnight before moving east allowing skies to scatter out.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...04


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