Area Forecast Discussion
Issued by NWS La Crosse, WI

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522
FXUS63 KARX 162015
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
215 PM CST Tue Jan 16 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 215 PM CST Tue Jan 16 2018

Early afternoon surface analysis indicated broad high pressure
stretching from the upper midwest through the southern plains. Low
stratus stuck underneath an inversion have been slow to erode
today, especially near and west of the Mississippi, but visible
satellite imagery has indicated a fairly rapid breaking up of the
cloud cover early this afternoon. This trend should continue through
the rest of the afternoon with the approach of the ridge axis. Some
mid/high cloud cover will increase overnight in association with
strengthening 850-700 mb warm advection. Temps will fall to around
zero or a bit below zero, but with lighter winds, wind chills will
not be as low tonight, so no wind chill headlines should be needed.
That said, expect one more cold night with wind chills in the 10 to
20 below range.

With the exception of a few mid-high level clouds on Wednesday,
expect mostly sunny skies as the forecast area sits on the
northern periphery of a broad surface high across the southern
plains. That said, the pressure gradient will be strong enough
with roughly 20 to 25 kts in the mixed boundary layer to result
in some southwest breezes, gusting at times up to 25 mph. It will
also be noticeably warmer than today with 925 hPa temperatures
rising about 10 degrees Celsius. Expect afternoon highs in the
lower to mid 20s.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 215 PM CST Tue Jan 16 2018

A compact short-wave drops south across northern MN into WI on
Thursday. Despite strong 500-300 hPa potential vorticity
advection, the system looks moisture starved, so not expecting
much more than some passing mid-high level clouds. Additional
warming at 925 hPa will allow afternoon highs to reach or exceed
the freezing mark for many locations.

Ridging aloft Friday into Saturday will keep the forecast area dry
and warm. Cloud cover will be on the increase, but with afternoon
925 hPa temperatures in the +1 to +3 Celsius range, expect highs
in the mid 30s to lower 40s.

Confidence is increasing that there will be a large storm system
Sunday into Monday somewhere across the Upper Midwest as a Four
Corners trough closes off and ejects northeastward. 16.12Z GEFS
shows a surface low track from near Kansas City to Madison, but
there is a significant spread in individual members, especially to
the north and west of the mean. These track differences translate
to large variations in the thermal profiles as well, so it`s not
possible yet to say whether precipitation falls mainly as rain,
snow, or something in-between. GEFS plumes at La Crosse show a
spread in QPF from just a few hundredths to over an inch. All of
this to say, there is still considerable uncertainty concerning
precipitation amounts, type, and areas of greatest impact. Will
mention storm in HWO, but otherwise refrain from getting too far
into the details at this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1136 AM CST Tue Jan 16 2018

Aviation forecast remains tricky this afternoon, especially
ceilings. Low-level moisture trapped underneath an inversion has
resulted in continued IFR ceilings at KRST with some MVFR ceilings
at KLSE. As surface high pressure continues to build into the
area from the northwest, expect gradual erosion of the lower
clouds, but at this time of year, timing of cloud dissipation is
tough, so confidence is low with cloud trends. Otherwise, winds
will lighten tonight with some increase in clouds before
southwest winds increase and become gusty on Wednesday.

&&

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

$$

SHORT TERM...JM/Rogers
LONG TERM...Rogers
AVIATION...JM



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