Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 091728

Area Forecast Discussion
National Weather Service La Crosse WI
1128 AM CST Mon Jan 9 2017

.SHORT TERM...(Today and tonight)
Issued at 349 AM CST Mon Jan 9 2017

Latest water vapor satellite imagery shows shortwave trough over the
Great Lakes Region and is producing light snow or flurries across
the forecast area per KARX radar and latest metars.

Main forecast concerns today into Tuesday is snow moves into the
forecast area this afternoon...then snow changes to a wintry mix
over the southern forecast area tonight and possibly for the entire
forecast area Tuesday. The 09.00z GFS/NAM/ECMWF in decent agreement
tracking a strong shortwave trough into the Great Lakes Region today
into Tuesday. Slight differences occur between the deterministic
models in timing of the shortwave trough/surface features and
placement of frontogenetical band over the northern parts of the
forecast area. Lift/forcing increase west to east across the
forecast area after 18z today. Bufkit soundings suggest initial
precipitation this afternoon into this evening will likely be all
snow across the forecast area. Southerly winds aloft/at surface
advects in warmer air across the southern portion of the forecast
area and will change precipitation over to a wintry mix of
sleet/freezing rain/possibly rain mainly after 03z. All snow is
expected along and north of Interstate 94 through 12z
Tuesday...then change over or become a wintry mix of freezing
rain/sleet/snow during the day Tuesday. At this time...light ice
accumulation is expected with up to a tenth of an inch across the
forecast area through Tuesday. Where the frontogenetical band of
snow develops along and north of Interstate 94...snowfall
accumulations of 2 to 4 inches are expected. With the potential of
2 to 4 inches of snow accumulations and possible wintry mix north
of Interstate 94...have issued Winter Weather Advisory for Clark
and Taylor counties in north central Wisconsin late this afternoon
into Tuesday afternoon. Later shifts may expand the advisory
further south based on a wintry mix with light ice accumulation.

.LONG TERM...(Tuesday through Sunday)
Issued at 349 AM CST Mon Jan 9 2017

Upper level trough over southern Manitoba will continue to move
along and north of the International border Tuesday night into
Wednesday. The 09.00z GFS/NAM/ECMWF push surface front associated
with upper level trough across the forecast area during this time
period. The 09.00z deterministic models show significant differences
with placement of frontogenetical band of precipitation with the
cold front. With this...confidence is low with snow chances and have
small chances across the northern parts of the forecast area.

Main forecast concerns Wednesday night into Sunday are mainly
temperatures across the forecast area and precipitation chances
Wednesday night into Thursday. The 09.00z GFS/ECMWF/GEM are in
good agreement in digging/tracking the upper level trough over the
northeast United States through Friday...then push upper level
trough off the North American coast and build shortwave ridge into
the Upper Midwest/Ohio River Valley Saturday into Sunday. The
09.00z GFS/ECMWF/GEM show differences in placement/movement of another
shortwave trough embedded in the southwesterly flow aloft ahead of
upper level trough Wednesday night into Thursday...with the
ECWMF/GEM further south than the GFS. The deterministic models
produce a frontogenetical band of precipitation across parts of
the area Wednesday night into Thursday with this feature. A chance
of precipitation is warranted across much of the forecast area
during this time frame. Then...the deterministic models filter cold
air into the forecast area behind upper level trough/shortwave
trough Thursday night into Friday...with 925mb temperatures
cooling to minus 12 to minus 20 degrees by 12z Friday. Forecast
area will be below normal temperatures...with highs in the single
digits/teens above zero and lows in the single digits/teens below
zero. Southerly flow underneath shortwave ridge will allow
temperatures to warm back into the teens to 20s across the
forecast area Sunday.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1128 AM CST Mon Jan 9 2017

VFR ceilings to start the afternoon will drop to at least MVFR by
09.20-09.21Z as a band of light snow currently from KFAR to KMUT
pushes eastward. IFR restrictions to visibility down to 1SM
possible as well in light snow. It will likely be a quick shot of
snow/lower conditions before briefly rising back to VFR this
evening. Then, expect ceilings to drop to low MVFR/IFR overnight
into Tuesday morning. Precipitation timing/coverage/type less
certain for this period and will depend on available lift and
temperature profile. For now, will keep idea of a freezing
rain/snow/rain mix at both TAF airfields beginning at 10.08Z at
KRST and 10.10Z at KLSE.

South-southeast wind will be the rule through the period,
increasing at KRST this evening and overnight to around 15 kts.
Otherwise, sustained winds 12 kts or less will be commonplace.
Amendments likely over the next several forecast cycles.


WI...Winter Weather Advisory from 4 PM this afternoon to 3 PM CST
     Tuesday for WIZ017-029.



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