Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 030858

Area Forecast Discussion
National Weather Service La Crosse WI
258 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 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 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 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

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 06Z TAFS through 06Z Saturday night)
Issued at 1200 AM CST Sat Dec 3 2016

The area of clearing has edged a little to the northeast this
evening and there is still a concern that this could advected over
the area Saturday as the flow turns more to the southwest.
However, the 03.00Z continues to maintain high levels of moisture
at 925mb underneath the inversion but does show drying just above
this at 850mb. Given that the moisture is under the inversion,
opted to stay pessimistic and keep the MVFR ceilings in place. A
short wave trough and cold front will approach from the west
Saturday evening with light snow. This system does not look like
it will affect either airport until after 04.06Z.




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