Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 141718
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1119 AM CST Tue Nov 14 2017

.SHORT TERM...(Today and tonight)
Issued at 314 AM CST Tue Nov 14 2017

Main forecast concerns through tonight are on drizzle and rain. A
little freezing drizzle is possible over north-central Wisconsin
early this morning before temperatures warm above freezing.

Areas of drizzle and patchy fog will continue across the region
today as low level moisture continues to stream across the
region. A cold front approaches late this afternoon from the west
and will move through during the overnight hours into Wednesday
morning. Look for the light rain to become more widespread as the
front moves in and isentropic lift increases on the 290-300K
surfaces. Patchy fog will continue across the area today and may
become locally dense over portions of north central Wisconsin
tonight. Mesoscale models and SREF visibility probabilities are
showing a fairly strong signal for dense fog tonight north of the
Interstate 94 corridor. Will have to keep a very close eye on this
possibility.

.LONG TERM...(Wednesday through Monday)
Issued at 314 AM CST Tue Nov 14 2017

Main forecast concerns in the long term are on the potential for
some snow showers over north-central Wisconsin Wednesday afternoon
into Wednesday night and a period of gusty winds during this same
timeframe across the entire area. Then focus turns to rain/snow
chances late Thursday night into Saturday. Colder temperatures are
expected Saturday night into Sunday.

The front pushes east of the area by early Wednesday afternoon then
a compact shortwave trough pushes through and this is when the
colder air arrives along with gusty northwest Winds. Lapse rates
really steepen late Wednesday afternoon into Wednesday evening so
we may see some rain and and snow showers, especially over north-
central Wisconsin. We could see wind gusts of 35 mph in open
areas late Wednesday afternoon into the early evening hours.

The next chance for rain and perhaps a wintry mix arrives late
Thursday night into early Friday as a broad upper trough and surface
low approach from the west. Warmer air moves into the region ahead
of this system so after the initial wintry mix possibility, the
main precipitation type should switch over to all rain by late
Friday morning across the local area. There could be some light
ice accumulations Friday morning across north-central Wisconsin.
As the low moves to the east of the area, colder air moves into
the region so we could see a switch over to snow late Friday
night into Saturday morning. Much cooler air then moves into the
region during the day on Saturday with temperatures falling
through the day. The coldest air arrives Saturday night when lows
will fall into the teens to around 20. Persistent northwest winds
will drive wind chill values into the single digits above zero
Sunday morning. Forecast confidence really falls off going into
next week with the forecast models showing large differences in
the overall pattern across the CONUS.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday noon)
Issued at 1119 AM CST Tue Nov 14 2017

A very moist lower level airmass, trapped under an inversion near
900mb, will remain over the area this afternoon into Wed morning.
The present MVFR/IFR and lcl LIFR cigs with areas of MVFR/IFR vsbys
in BR are going to persist thru the afternoon. Deeper moisture and a
a round of lift will spread across the area tonight. Periods of -RA
are expected at the taf sites, mainly 00-08z at KRST and 02-10z at
KLSE. The -RA should help keep cigs/vsbys from dropping to VLIFR at
sites like KRST and LIFR at sites like KLSE during the later evening
and overnight hours. A cold front is set to push across the area
later tonight, moving thru KRST around 09z and KLSE around 12z.
Behind front will be a switch to brisk/gusty NW winds and an influx
of drier air.

Cigs/vsbys will improve behind the front and thru Wed morning, but
question remains how long will bkn/ovc MVFR cloud decks hold on.
Model soundings/x-sections showing plenty of lower level moisture to
remain trapped under the inversion well into Wed afternoon. For now
trended a bit optimistic with the lower cloud decks becoming sct
around 15 at both sites, but confidence not overly high with this.

&&

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

$$

SHORT TERM...Wetenkamp
LONG TERM....Wetenkamp
AVIATION.....RRS



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