Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 180938

Area Forecast Discussion
National Weather Service La Crosse WI
338 AM CST Sat Nov 18 2017

.SHORT TERM...(Today and tonight)
Issued at 337 AM CST Sat Nov 18 2017

At 3 AM, a band of strong 700 to 500 mb frontogenesis was
producing rain from southeast Nebraska northeast through northeast
Iowa, extreme southeast Minnesota, and southwest and central
Wisconsin. Hourly rainfall amounts range from a trace to 0.05

The 18.08Z RAP shows that this band of frontogenesis will continue
to move southeast this morning and moves out of the area by
18.16z. As this occurs, the precipitation will end across the
area. Soundings suggest as the boundary layer cools that there
will be a mix of rain and snow. There may be a brief period of all
snow as the precipitation ends. Snow amounts across southwest
Wisconsin and a small portion of northeast Iowa will range from a
trace to maybe a few tenths of an inch.

In the wake of this system, the combination of a tight surface
pressure gradient and steep 950-900 mb lapse rates will result in
northwest wind gusts of 20 to 30 mph. These wind gusts will
gradually diminish this evening as the low level lapse rates
weaken. Wind chills this afternoon will range from the teens to
mid 20s.

Another short wave trough will move through the region tonight.
This system will produce mostly cloudy skies along and north of
the Interstate 94 corridor.

.LONG TERM...(Sunday through Friday)
Issued at 337 AM CST Sat Nov 18 2017

On Monday, 18.00z models continue to show that 925 mb temperatures
will warm into the 6 to 9C in the ECMWF and from 4 to 9C in the
GFS. With quite a bit of sunshine, the high temperatures will
likely range from the mid 40s in north central Wisconsin to
around 50 in southeast Minnesota and northeast Iowa.

On Monday night, a strong Canadian cold front will move southeast
through the region. 925 mb temperatures will dramatically cool and
by Tuesday afternoon they will range from -5 to -8C in the GFS
and -6 and -9C in the ECMWF. High temperatures will range from
the upper 20s to mid 30s on Tuesday and from the mid 20s to mid
30s on Wednesday.

On Friday, 925 mb warm dramatically ahead of an approaching
shortwave trough. The ECMWF has these temperatures warming into
the 9 to 12C range. Meanwhile, in the GFS, these temperatures
range from 9 to 14C. The NAEFS 850 mb temperature anomalies are 1
to 2 standard deviations just to the west and southwest of the
forecast area. The ECMWF has high temperatures ranging from the
upper 40s to lower 60s. Meanwhile, the GFS has its high
temperatures ranging from the lower 40s to mid 50s. In both cases,
the warmest temperatures are along and west of the Mississippi
River. Since this warmth has been a consistent signal in the
models, raised the maximum temperatures 5 to 10F above the model


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1135 PM CST Fri Nov 17 2017

The front has pushed through both airports late this evening and
once it did, it allowed the lower visibilities from the fog to
improve. The fog is continuing to reduce the visibility into the
2 to 4 mile range and this will slowly improve through the night
as slightly drier filters and as the north winds increase to
around 10 knots. By early to mid morning Saturday look for the fog
to be completely dissipated. Ceilings will also slowly improve
with MVFR expected by mid morning and then going to VFR as the
clouds scatter out. It will be a little gusty Saturday afternoon,
especially at KRST, as steep low level lapse rates allow some mid
20 knot gusts to mix down to the surface.




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