Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 252342

Area Forecast Discussion
National Weather Service La Crosse WI
642 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 00Z TAFS through 00Z Wednesday evening)
Issued at 642 PM CDT Tue Apr 25 2017

Low pressure continues to advance toward the region, and will
cross the area through midday Wednesday. A few rounds of showers
are expected at both LSE and RST, mainly between 00Z and 09Z,
before precipitation chances quickly dwindle. However, much colder
air advancing into the area should result in a quick lowering of
ceilings to LIFR levels at RST and mainly lower end MVFR levels at
LSE later tonight, with ceilings very slowly lifting into
Wednesday afternoon as winds become a bit gusty from the




LONG TERM....Rieck
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