Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261943

Area Forecast Discussion
National Weather Service La Crosse WI
243 PM CDT Sun Mar 26 2017

.SHORT TERM...(This evening through Tuesday night)
Issued at 243 PM CDT Sun Mar 26 2017

Local and regional radars still showing some showers over portions
of Wisconsin and eastern Minnesota this afternoon. These are
wrapping around the surface low that was edging into western
Illinois. This low is expected to pick up some speed overnight as
it tracks northeast across lower Michigan into Ontario. There will
continue to be a chance for some lingering showers east of the
Mississippi River this evening and then mainly northeast of
Interstate 94 overnight.

Water vapor satellite shows another upper level low coming out of
Colorado and into Kansas this afternoon and a northern stream
short wave trough over southern Manitoba. Both of these systems
are expected to generally move east through Monday night. The
upper level low will begin to fill Monday as it tracks into the
Ohio River Valley with the short wave trough staying across
southern Canada and Lake Superior. The forcing from both of these
systems will essentially split the area to the south and north but
could get close enough to produce a few showers. Based on this,
will show just a small 20 percent chance across the southern
sections Monday afternoon and north of Interstate 94 for much of
the day. Any showers that do get into the area are expected to
move off to the east by late afternoon. Once these systems move
past the area, ridging aloft and high pressure at the surface will
build over the region for Monday night through Tuesday night.

.LONG TERM...(Wednesday through Sunday)
Issued at 243 PM CDT Sun Mar 26 2017

The ridging will get pushed east of the Midwest early in this
period as an upper level low comes out of the southern Rockies and
starts to move northeast Wednesday. This low is then expected to
move into the middle Mississippi River Valley through Thursday
before becoming an open wave as it continues to track northeast
toward the eastern Great Lakes. At the same time, another northern
stream short wave trough is expected to ride along the Canadian
border, possibly dipping into the Upper Midwest if the 26.12Z
ECMWF is correct. The surface low will be associated with the
upper level low and is expected to pass through the region well
south of the area. The ECMWF has showed the best continuity with
this system, along with the 26.12Z GEM, while the 26.12Z GFS has
shown a northward jump and is now relatively close to the other
two models. However, since the ECMWF and GEM are still farther
north they allow the precipitation shield to be influenced by the
passing northern stream wave and get drawn much farther north and
over the entire area. The GFS keeps it farther south and indicates
there is a possibility some of the area could remain dry as this
system goes by. Also of concern, with the GFS being farther south
it then has more low level cold air on the northern fringe of the
precipitation shield that could lead to a longer period of a
rain/snow mix into Thursday. For now, since this is the first run
of the GFS coming north, will not adjust the temperatures and
precipitation types for this signal but monitor subsequent runs
to see if this continues.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1239 PM CDT Sun Mar 26 2017

A low pressure system over central Illinois will move northeast
into Lower Michigan tonight. As this occurs, the light rain will
move east of the area. While the rain will be exiting the region,
LIFR/IFR ceilings and IFR/MVFR visibilities will remain across the
region through mid-morning Monday and then both will gradually
improve through the remainder of Monday.

Light north winds will found the TAF period.




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