Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 262328
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
628 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 00Z TAFS through 00Z Saturday evening)
Issued at 628 PM CDT Fri May 26 2017

A weak cold front continues to work east early this evening, and
is expected to make it to about LSE later tonight before stalling
and dissipating. A couple of isolated showers have developed along
that front, but should steer clear or LSE or RST to the north
through 02Z, with VFR conditions expected for much of the night.
However, where that front ends up stalling may prove difficult, as
there is an increasing risk for some fog and/or stratus
development to the east of the front, where higher moisture levels
will remain present. At this time, it appears the greatest risk
for IFR stratus and/or fog will exist just to the east and south
of LSE, but trends will need to be monitored closely, as the risk
for a several hour window of lowered ceilings does exist.
Otherwise, a gradual increase and lowering of ceilings is expected
from west to east through the day on Saturday as our next system
approaches, with only a very limited risk for an isolated shower
prior to 00Z. The greater risk for rain and potential reduced
ceilings will hold off until Saturday evening and night.

&&

.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...Lawrence
HYDROLOGY....DAS



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