Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 222328

Area Forecast Discussion
National Weather Service La Crosse WI
628 PM CDT Fri Sep 22 2017

.SHORT TERM...(Late This Afternoon through Saturday)
Issued at 233 PM CDT Fri Sep 22 2017

Latest upper-air analysis shows our area on the western edge of
strong ridging over the eastern CONUS, while a closed low was
spinning over the Intermountain West. A cluster of strong to severe
thunderstorms attached to a mid-level wave has stayed just off to
our north, moving along a west-east oriented stationary front.
Underneath the ridge, strong southerly flow has brought unseasonably
warm and humid air into the region. Temperatures have already risen
into the 90s, and combined with dewpoints around 70F, heat indices
are approaching 100. A Heat Advisory is in effect until 7 PM this
evening for much of the area.

Not much change in the upper-air pattern heading into Saturday as
the western trough very slowly begins to make its way east. 925 mb
temperatures are progged to be around 1-2C cooler than today, which
will still give us highs in the upper 80s and lower 90s.

.LONG TERM...(Saturday Night through Friday)
Issued at 233 PM CDT Fri Sep 22 2017

The season may officially be autumn now, but the weather won`t
reflect it for a few more days. Stubborn blocked-up flow regime over
much of the CONUS will remain through the weekend, with broad (and
impressive) upper ridging in place across much of the eastern
states, courtesy of tropical cyclones Jose and Maria meandering off
the East Coast. Meanwhile, deeper troughing over the western CONUS
will remain intact, with the "battle ground" centered over the
Plains where a nearly stationary frontal boundary will maintain
periods of precipitation to our west. While today`s highs are likely
to be the warmest, Sunday still looks quite mild with highs pushing
the low 90s once again in spots as 925mb temps hold around 20-25C
during peak heating.

Big changes still on track to arrive into much of next week with
persistent hints the past few days that the western CONUS trough
will finally break through the eastern ridge. During the time of
transition toward the early work week, a slow advancing cold front
should bring at least some risk for rainfall to the area, especially
later Monday into Tuesday per current trends, before things dry out
and cool down significantly into late week as upper troughing and
low level ridging dominate the region. With that said, there is some
small risk that a few showers could be realized during the late week
with any smaller hard-to-time shortwaves dropping through the mean
trough, but by far the bigger impact will be a return to much more
fall-like conditions through the work week.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 628 PM CDT Fri Sep 22 2017

Region will remain along the western periphery of a large high
pressure system through the period. Primary aviation concern will
be low-level wind shear as winds in the 1500 to 2000 ft agl layer
once again increase to between 40 and 45 kts overnight. Wind shear
will diminish late tonight into Saturday morning with increasing
southerly surface winds, gusting at times in the afternoon to 20
kts at KRST. Skies will be mostly clear/sunny through the period
with perhaps some thermal cumulus Saturday afternoon in the 4000
to 5000 ft agl layer.


WI...Heat Advisory until 7 PM CDT this evening for WIZ032>034-041>044-

MN...Heat Advisory until 7 PM CDT this evening for MNZ079-086>088-

IA...Heat Advisory until 7 PM CDT this evening for IAZ008>011-018-019-



LONG TERM...Lawrence
AVIATION...Rogers is the U.S. government's official web portal to all federal, state and local government web resources and services.