Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 100942
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
342 AM CST Tue Jan 10 2017

.SHORT TERM...(Today and tonight)
Issued at 342 AM CST Tue Jan 10 2017

Latest 08z surface analysis shows low pressure developing over
southern Nebraska and northern Kansas with warm front extending into
southern Iowa and northern Missouri. Light wintry mix of
precipitation has developed across southern Minnesota...northern
Iowa and western Wisconsin per mosaic radar.

As surface low deepens and associated forcing/lift increases across
the Upper Midwest Region...precipitation will become more
widespread across the forecast area this morning. Differences
occur between the 10.00z deterministic models with temperature
profiles today...as the NAM much colder than the GFS/ECMWF. This
would have impacts on precipitation type...hence the NAM
suggesting more snow across parts of the forecast area...than the
GFS/ECMWF a more wintry mix solution. With current
observation/reports indicating a wintry mix...will be trending
toward a warmer solution. This would result in a wintry mix of
freezing rain/sleet/snow across the southern forecast area this
morning. As colder air filters in behind the shortwave
trough/surface low the wintry mix will transition to all snow late
this morning into the afternoon hours. Along and north of
Interstate 94...expect precipitation to be all snow. Ice
accumulation of up to a tenth of an inch can be expected across
the southern half of the forecast area. Snowfall accumulations of
2 to 6 inches is expected north of Interstate 90 with up to 2
inches elsewhere. Locally higher snowfall amounts are possible
north of Interstate 94 today. On the backside of the surface
low...pressure gradient tightens and may cause some blowing and
drifting snow in the afternoon hours...especially in the higher
terrain and open areas. A Winter Weather Advisory is in effect for
the entire forecast area through 00z Wednesday.

Precipitation/snow will diminish rapidly across the forecast area
around 00z Wednesday...as the surface low/shortwave trough pushes
into southern Ontario.

.LONG TERM...(Wednesday through Monday)
Issued at 342 AM CST Tue Jan 10 2017

Shortwave trough moves quickly east of the forecast area and
upper level trough digs over southern Manitoba Wednesday. This
will allow west to east zonal flow over the northern tier states
to develop. The 10.00z GFS/NAM/ECMWF tracks a weak shortwave
trough embedded in the west to east zonal flow and produces a
frontogenetical band across parts of the northern forecast area
Wednesday. Have increased precipitation chances across the northern
parts of the forecast area Wednesday. As surface front slowly
pushes south into Illinois and northern Missouri...precipitation
chances will be focus over the southern forecast area Wednesday
night into Thursday.

Main forecast concerns Thursday night through Monday are
precipitation chances Sunday into Monday. The 10.00z GFS/ECMWF/GEM
are in good agreement pushing upper level trough over the
northeast United States and eastern Canada and build shortwave
ridge into the central United States through Saturday.
Then...differences occur between the deterministic 10.00z models
with movement of the upper level low over the southwest United
States. The 10.00z ECMWF is slower in lifting upper level low
into the Upper Midwest than the GFS. With the shortwave ridge
building into the central United States...weak shortwave troughs
embedded in the flow will allow for the possibility of
precipitation across the southern forecast area Friday night into
Saturday. Confidence is low Sunday into Monday...based on
differences in timing of the upper level low. The higher
precipitation chances will be over the southern forecast area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1113 PM CST Mon Jan 9 2017

As the weak short wave trough and mid level frontogenesis continue
to move east, the band of precipitation has as well. This looks
like it will past both airports by or shortly after 06Z. The break
in the precipitation is not expected to last long as the forcing
starts to increase again late tonight ahead of the next short wave
trough and surface low. Based on the latest model guidance, expect
this next band to be all snow for KRST but enough warm air aloft
could get brought in over KLSE for a period of a wintry mix late
tonight into Tuesday morning. This warm air aloft should cool
enough to then support all snow from about late morning through
the afternoon. The heaviest snow in the deformation zone looks to
have a chance to impact both airport and will show the visibility
going down to less than a mile in this. The VFR conditions will
quickly go down to MVFR and then IFR late tonight as the
precipitation starts. Improvement back to VFR is expected to occur
fairly quickly once the snow ends Tuesday afternoon. Some concern
for additional visibility restrictions in blowing snow at KRST
Tuesday afternoon and evening as the winds switch to the west and
gust to around 25 knots on the back side of the surface low.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 PM CST this evening for WIZ017-
     029-032>034-041>044-053>055-061.

MN...Winter Weather Advisory until 6 PM CST this evening for MNZ079-
     086>088-094>096.

IA...Winter Weather Advisory until 6 PM CST this evening for
     IAZ008>011-018-019-029-030.

&&

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...04



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