Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261128
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
628 AM CDT Thu Apr 26 2018

.SHORT TERM...(Today through Sunday)
Issued at 300 AM CDT Thu Apr 26 2018

Upper level shortwave trough slated to drop southeast across the
region this afternoon, quickly slipping east/southeast later in the
evening. Decent amount of frontogenetic lift along the front,
although relatively narrow and mostly confined to the 900:800 mb
layer. Favorable lapse rates from 900 to 700 mb to promote upward
motion, with perhaps some aid from a 300 mb jet streak left exit
region (northern WI early afternoon). Saturation is generally
confined around the front and best in the 500-800 mb layer.
Meanwhile, bufkit soundings also pointing to a rather dry sub cloud
layer, roughly 5 kft worth. So, while there looks to be enough lift
and saturation to fire a thin, broken like of showers, fighting
though the dry layer could be a challenge where lift/saturation is
weaker/shallower. Will continue small shower chances this afternoon,
but not put a thunder mention with no CAPE to speak of.

Another shortwave progged to drive across northern parts of the
region overnight thu/fri. Models have this feature stronger than the
first shortwave, and looks to pack a little bigger punch. Good
frontogenetic lift on the leading edge of the shortwave, with deeper
saturation also evident. Expect an area of showers to spark across
northern/eastern WI given the current track of the shortwave. A
little instability (500 j/kg mucape in the gfs) could be enough to
trigger an isolated storm or two. Best rain/thunder chances look to
hold east of I-94 right now.

A surface high builds across the region for the weekend, with an
upper level ridge gradually creeping in later Sunday. Sunshine
should be plentiful, but it will be a bit cooler compared to today.
Passage of a secondary cold front early Friday will usher in cooler
air, with 850 mb temps dropping from +4/6C Fri morning to around -5
by 12z Sat. Highs Sat will be in the 50s for most. Should see a
rebound back into the low/mid 60s for Sunday as winds swing to the
south.

.LONG TERM...(Monday through Wednesday)
Issued at 300 AM CDT Thu Apr 26 2018

A more active weather pattern to kick off the new work week as the
upper level ridge slides off to the east and a trough starts to
approach from the west. The region comes under southwest flow with
various pieces of upper level energy kicking out of the mean trough.
Southerly fetch to gulf moisture with a pretty good low level jet to
feed into the trough, associated shortwaves and sfc boundaries.
Showers and storms should fire in response - although the
where`s/when`s aren/t clear with some differences between the GFS
and EC continuing. Will let consensus dictate pcpn chances for now.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 628 AM CDT Thu Apr 26 2018

A cold front across northern Minnesota will slide southeast and
across both airports during the mid to late afternoon. Lots of
high level clouds over the area already for VFR ceilings and these
will remain until early evening. The ceilings may come down to
around 10k feet with the passage of the front with some scattered
lower clouds possible along with some sprinkles. The winds will
swing around to the northwest behind the front and could get a
little bit gusty for a couple of hours at KRST. The winds will
settle down and the clouds will clear out early this evening.

&&

.FIRE WEATHER...
Issued at 300 AM CDT Thu Apr 26 2018

Drier air will likely result in lower RHs this afternoon and again
Sat and Sun. Today, mixing will play the main role while a turn to
north/northeast flow Sat/Sun will push drier air across
northern/eastern WI. Afternoon humidities will near 20 percent
across central/northern WI Sat afternoon.

Winds look fairly light this weekend as sfc high pressure meanders
slowly through. Today though, if showers are realized, some enhanced
gustiness would be possible, with some increase in wind speeds as
they become westerly behind a passing cold front.

Monday could be of interest too as highs are expected to top into
the low/mid 70s. If frontal system expected to impact for the start
of the new work week is slower, there is the potential for lower RHs
combined with southerly winds in the 10 to 20 mph range.

&&

.HYDROLOGY...
Issued at 138 PM CDT Wed Apr 25 2018

Flood warnings are in effect for portions of the Mississippi River
and the Yellow River at Necedah. Minor to possibly moderate flooding
is expected into the first week of May. See the latest flood
statements for more detailed information.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...04
FIRE WEATHER...Rieck
HYDROLOGY....DAS



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