Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261915
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
215 PM CDT Fri May 26 2017

.SHORT TERM...(Tonight through Saturday Night)
Issued at 215 PM CDT Fri May 26 2017

Current water vapor/mid-level analysis has a shortwave trough
progressing eastward across eastern IA while another trough was
pushing across MN. Radar had showers brushing northeast IA into far
southwest WI associated with the southern wave while northern wave
was generating fairly widespread mid/high cloud cover across the
rest of the area. Otherwise, temperatures across the area ranged
from the middle/upper 60s in the thicker cloud cover across the
south, to the lower/middle 70s along the I-90/94 corridors.

Going into this evening, we will be watching that mid-level trough
over MN push a weak cold front into the area. All the CAMs show a
narrow line of showers/thunderstorms developing along the front,
then rapidly diminishing in intensity as they move into northern WI
by early this evening with loss of surface heating. Look for this
wave/front to push through the area by midnight with skies becoming
partly cloudy overnight. Diminished cloud cover and fairly light
winds will likely lead to some fog formation. Will have to keep an
eye on how dense this fog gets toward morning.

For Saturday...another mid-level wave ejects northeast from the
Plains, combining with increasing mid-level frontogenesis and
lingering surface boundary/convergence. This will produce a chance
of showers and thunderstorms in the afternon during peak surface
heating. Will have to watch for the potential of a few
stronger/possibly severe storms across southern WI into northeast IA
late in the afternoon as the NAM develops a narrow corridor of 1500-
2500J/kg of 0-6km MUCAPE along with increasing 0-6km bulk shear in
the 35-50kt range after 21z. This is probably the extreme of all the
models, but certainly bears watching for the possibility of strong
to severe storms if this higher-end CAPE and Shear is realized.

Scattered showers expected to continue into Saturday night as a
strong mid-level trough/associated cyclonic flow rotates in
from the Northern Plains.

.LONG TERM...(Sunday through Friday)
Issued at 215 PM CDT Fri May 26 2017

Long wave trough sets up across the area Sunday through Wednesday as
a closed low moves through southern Canada. This will set up on/off
shower chances through the period along with the possibility of a
few afternoon storms in peak heating/steepening lapse rates. Look
for highs Sunday in the upper 60s to middle 70s, cooling into the
60s Memorial Day through Wednesday.

Could still see a slight chance of showers Thursday and Friday as
area remains in northwest flow on the backside of the departing
closed low.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1135 AM CDT Fri May 26 2017

Cigs: upper level shortwave slipping east across the region
currently, bringing some showers to the south, but mostly just mid
level clouds to KRST/KLSE. Expecting skc/sct conditions tonight into
Sat morning, with more increasing mid level clouds from the
southwest as another shortwave spits out of the mean trough to the
west. Some potential for30 mvfr cigs by Sat evening.

WX/vsby: meso models continue to hint at a thin line of shra/ts
developing along a north-south running sfc front across
northeast/eastern MN by late afternoon - diminishing with the loss
of daytime heating. Trends favor keeping any threat north of the taf
sites, and will keep forecast dry as a result. Better chances return
by Sat evening with that next shortwave.

With a mostly light wind field/baggy pressure gradient and moist
boundary layer, some fog could develop overnight into Sat morning.
Winds just off the deck via bufkit soundings are breezy though,
which will help hinder widespread/thick fog. Going to leave "clean"
for now, but its a scenario that will have to be monitored.

Winds: winds become mostly light/variable tonight, eventually moving
more to the north but staying light Sat afternoon.

&&

.HYDROLOGY...
Issued at 215 PM CDT Fri May 26 2017

Elevated river levels/minor flooding will continue along the
Mississippi River through the weekend into early next week. Those
with interests along or on the Mississippi River should monitor the
latest river forecasts and statements closely. If you are planning
any recreational activities/boating be aware of these elevated river
levels and watch out for objects in the water that may pose a threat
to watercraft.

&&

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

$$

SHORT TERM...DAS
LONG TERM....DAS
AVIATION.....Rieck
HYDROLOGY....DAS


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