Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 062018

Area Forecast Discussion
National Weather Service La Crosse WI
220 PM CST Tue Dec 6 2016

.SHORT TERM...(Tonight through Thursday)
Issued at 220 PM CST Tue Dec 6 2016

Concerns in the short term:

1) Cold air
2) Light snow chances north

1) A blast of cold, winter air on tap for the region - and probably
about time considering the rather mild late fall/early start to
winter. 850 mb temps still set to take a tumble with the passage of
the cold front from this morning...dropping from around -4 C at 12z
to -14 C by 12z Friday. Highs near 20 with lows in the teens Wed-Fri
still looking good. With persistent cyclonic flow suggesting more
clouds then not, it should keep overnight temps up a bit. That said,
if there is a night where more clearing takes place, lows would
probably be 5 to even 10 degrees colder - especially for areas with
snow pack.

In addition...its going to be blustery. Pressure gradient tightens
up for Wed-Thu...15-25 mph with higher gusts, especially open areas
west of the Mississippi. Wind chills in the single digits above and
below zero will result. Brr.

2) Cyclonic flow, cold air a loft and decent low/mid level lapse
rates will promote light snow chances for the next few days. The
better chances will surround a westward hanging trough (extending
off the departing low pressure system) which slowly sinks southward
to across the local area by 00z Fri. Locally, most of the light snow
chances will hold along/north of I-94. Amounts will
minimal...perhaps 1/2 to 1 inch of fluff through the period.
Expect scattered flurries south of these light snow chances.

.LONG TERM...(Friday through Tuesday)
Issued at 220 PM CST Tue Dec 6 2016

Main concern in this time period is the potential snow maker over
the weekend.

GFS/EC still on track with bringing and upper level shortwave west-
east across the Upper Mississippi River Valley this weekend. The
models also remain at odds with each other: placement, timing and
strength. Also, not a lot of continuity from run to run within the
models. Confidence moderate/high that snow will fall across the
region this weekend...but low in the details on where/when/how much.
GFS continues to lean stronger and thus more snow compared to the
EC. Some recent EC runs would keep the bulk of the accumulating snows
north of the local area. It certainly is a time period to watch.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1116 AM CST Tue Dec 6 2016

Main aviation concerns are extent of low clouds on back side of
large upper low slowing working across far northern Minnesota late
this morning. Initial cold front has moved through and moved bulk of
precipitation off to the east. This has allowed some VFR conditions
to return for a time, but in cold air advection zone, starting to
see mainly MVFR ceilings wrap back into the area.

Looks like ceilings will likely sit about Interstate 90 and points
north into Wednesday, with some gradual improvement in the MVFR to
VFR range. Held clouds in longer than guidance given pace that upper
low will progress east, and also bumped up winds somewhat.

Speaking of winds, with fresh snow cover and peak winds exceeding 30
kts at KRST, introduced some minor restrictions to visibility, but
this shouldn`t last too long.




LONG TERM....Rieck
AVIATION.....Shea is the U.S. government's official web portal to all federal, state and local government web resources and services.