Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 251944
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
245 PM CDT Tue Apr 25 2017

.SHORT TERM...(Tonight through Friday)
Issued at 245 PM CDT Tue Apr 25 2017

Band of showers associated with a warm front lifting northward
across the region this afternoon, and should slide north of the
local area by 00z or so. Meanwhile, a cold front lies just to the
west, and should make its way to the Mississippi river by 12-15z
Wed. An upper level shortwave will lift northeast out of the Plains,
working on the cold front, and triggering a broad area of showers
across MN and northwest WI tonight. Should see some activity farther
south of the cold front, although the bulk of the pcpn looks tied to
the shortwave.

The cold front works into eastern wi/central ill by 00z thu, just in
time for another 500 mb through (currently swinging across the
desert southwest) to lift northeast toward the Great Lakes. Another
more enhanced area of showers (and storms) will result from the
front-shortwave interaction (with some upper level jet support
thrown into the mix). However, latest model trends has this activity
shifted to the east, with the system a bit faster then in some
previous model runs. Good news locally for many with soggy grounds
and high running rivers.

Thu into Friday morning looking dry right now, but some threat for
returning showers Fri afternoon-evening across the south. The GFS
and Canadian would spin a 500 mb shortwave trough into northern IL,
bringing shower chances to locations mostly along/south of I-90. NAM
and the EC are a bit farther south, keeping the area just outside
the pcpn chances. Going to hold with some small chances across the
south for now.

.LONG TERM...(Saturday through Tuesday)
Issued at 245 PM CDT Tue Apr 25 2017

The GFS and EC are both wanting to wind up a storm system for
Sunday, carving out an upper level trough over the desert SW,
developing a closed low as they drive it northeast to across the
local area by 12z Mon. Deepening (and nearly vertically stacked sfc
low by this time) - with some differences in placement between the
EC/GFS. Not unexpected this far out. Big push of low level warm air
advection ahead of the low and riding the accompanying warm front -
with good sloping frontogenetic lift north-south. Both models bring
a large expanse of pcpn into the region sat night/sun - associated
with the thermodynamic/frontogenetic forcing. Current model runs
keep the sfc low just to the southeast, essentially keep us under
the deformation region through Monday.

While most of what falls looks like rain at this time (with minimal
if any thunder threat), there is a surge of cold air post the low
that wraps into the system, which could bring some snow into the
pcpn type question. GFS bufkit soundings point to a prolonged period
of snow Sunday at KRST. Can`t rule out the potential for some
accumulating snows right now, but obviously too far away to put a
lot of stock into that...yet. Certainly a storm system to watch.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1158 AM CDT Tue Apr 25 2017

Conditions expected to deteriorate over the next 24 hours as low
pressure moves out of the Plains into our region. Currently watching
a band of scattered shra on radar in advance of this low moving into
northeast IA/southern MN. Most of this was falling out of higher/VFR
cloud base so some of it was evaporating before hitting the ground
per surface observations under the radar echo.
More widespread shra activity expected to overtake the area tonight
through Wednesday as the low moves over the region. Plan on MVFR
cloud moving into KRST after 02z, lowering further into LIFR after
midnight. KLSE expected to stay VFR this evening, lowering into MVFR
after 06z.

&&

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

$$

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



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