Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 031700
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1100 AM CST Sat Dec 3 2016

.SHORT TERM...(Today)
Issued at 258 AM CST Sat Dec 3 2016

Latest water vapor satellite imagery shows west to east zonal flow
across the northern tier states with a shortwave trough embedded
in the flow over eastern Wyoming and southern Montana. Latest 08z
surface analysis indicates high pressure over much of Minnesota
into Iowa. The forecast area remains on the eastern fringe of the
surface ridge and cyclonic flow continues to wrap stratus deck
into the forecast area.

Surface ridge axis builds into Wisconsin and Illinois today. With
the surface ridge axis building over the forecast area...the 03.00z
GFS/NAM try to erode the low level moisture in association with
stratus deck over the forecast area. Some parts of the forecast area
could see a hint of sunshine this afternoon...however confidence is
low...as the deterministic models stream mid level clouds in advance
of shortwave trough over the High Plains.

.LONG TERM...(Tonight through Friday)
Issued at 258 AM CST Sat Dec 3 2016

Next concern is shortwave trough spreading snow into the forecast
area tonight into Sunday. The 03.00z GFS/NAM/ECMWF suggest decent
lift/QG forcing and saturation of atmosphere column with shortwave
trough. The 03.00z GFS/NAM bufkit soundings indicate atmosphere
column remains below freezing and saturated through the minus 10 to
minus 20 degree celsius layer. At this time...much of the
precipitation will fall as snow late tonight into Sunday. Rain may
mix in with the snow Sunday afternoon on the backside of the
precipitation...as temperatures near the surface warm above
freezing. For right now...snowfall amounts of 1 to 3 inches are
expected across much of the forecast area.

Monday will be dry across the forecast area...as shortwave ridge
builds into the Upper Great Lakes Region. High temperatures will be
in the middle 30s to lower 40s with the 03.00z GFS/NAM/ECMWF
indicate 925mb temperatures warming to 0 to plus 2 degrees
celsius.

Main forecast concerns Tuesday through Friday are small
precipitation chances and temperatures through the period. The
03.00z GFS/GEM/ECMWF are in slightly better agreement in
movement/placement of upper level trough digging over the
central/eastern United States through the period. The
deterministic models show weak lift/forcing in association with
pieces of energy embedded in the upper level trough to produce
periodic small chances of precipitation across much of the
forecast area through the period. The 03.00z GFS/ECMWF/GEM
indicate on the backside of the first impulse embedded in the
upper level trough to advect in a cooler airmass...with the 03.00z
GFS/ECMWF suggesting 925mb temperatures cooling to minus 10 to
minus 15 degrees celsius by 00z Thursday. Expect high temperatures
by middle of next week to be in the 20s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1100 AM CST Sat Dec 3 2016

Cigs: low clouds look to give us a break as the current mass shifts
to the north/northeast this afternoon...per latest satellite trends.
The low cigs quickly return later this evening as an upper level
disturbance approaches from the west. Expect ifr/mvfr cigs to then
hold through the better part of Sunday.

WX: a couple upper level shortwave troughs to bring snow to the
region tonight through Sunday afternoon. First shortwave will bring
light snow/flurries, with the second/stronger wave bringing the main
area of accumulating snows/impacts in for Sunday morning. Should get
a few hours of 1-2sm with these snows...and while the bulk of the
accumulations will be on grassy surfaces...expect some on pavement
as well. KLSE at risk for a bit more compared to KRST...generally 1-
3.

Winds: light/variable wilnd becomes south/southeast this evening,
gradually increasing overnight as the sfc pressure gradient
tightens.

&&

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

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...Rieck



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