Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 222046

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
346 PM CDT Fri Sep 22 2017

.SHORT TERM...(This evening through Saturday)
Issued at 346 PM CDT Fri Sep 22 2017

The surface cold front is knocking on our doorstep late this
afternoon, with the thermal ridge ahead of it producing near-
record temps/dewpoints and attendant widespread heat indices in
the upper 90s to lower 100s across central/southern MN into west
central WI. As the low level jet re-intensifies tonight, expect
showers and thunderstorms to develop over far western Minnesota in
the vicinity of the front. As the front meanders slowly eastward
on Saturday, precipitation chances will inch toward central MN
throughout the day. With precipitable water values also nearing
record values, heavy rainfall will be of concern over western MN
given the front will be nearly stationary. Given east/south
central MN into west central WI will go most of the diurnal
heating period precip-free with decent mixing, expect highs in
the upper 80s to lower 90s. Meanwhile, temps over the western
forecast area will likely only moderate about 5 degrees (into the
mid 60s to lower 70s).

There will also be a small threat for severe storms Saturday
afternoon and early eve given the abundant moisture combined with
deep layer shear progged around 30 knots, although the fact that
the stronger flow aloft is displaced from the frontal boundary,
expect the threat to remain marginal in nature.

.LONG TERM...(Saturday night through Friday)
Issued at 346 PM CDT Fri Sep 22 2017

In the big picture, we`ll see the western trough ever so slowly
shift eastward over the weekend, with its associated frontal
boundary grudgingly moving along with it. With the heart of the
thermal ridge a bit farther east and more in the way of cloud cover,
we will be a bit cooler (but still well above normal) on Sunday. The
upper trough will work into the area for the first half of the week,
then we`ll start to shift into northwest flow by the end of the week
as ridging starts to develop over the western US.

Most of the precipitation with the frontal boundary to our west
looks to occur along and west of the front, meaning it will mainly
be the western and northwest portion of the area that will be
impacted through the weekend. We could see some activity as far east
as the Twin Cities metro, but it would be limited, with most of the
weekend looking dry from near I-35 eastward. The front will finally
move eastward Sunday night and Monday, bringing its shield of
showers and some embedded thunder along with it. We should see
precipitation end from west to east Monday night and Tuesday as the
frontal boundary moves into the eastern Great Lakes and high
pressure works into our area. Things look mainly dry through the
remainder of the week with temperatures near or slightly below
normal. The main chance of any precipitation after Tuesday looks to
be Thursday into Friday when we`ll see a cold front bring a
reinforcing shot of cold air, then wind up beneath the upper cold
pool while cyclonic flow lingers over the area.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 110 PM CDT Fri Sep 22 2017

We should be shower & thunderstorm-free through this eve now that
the nocturnally-driven activity has ended and the low/mid level
temperatures are building. Sct-bkn mid level clouds will be
around through most of the period. South/southeast winds will
become gusty this afternoon, then lose the gustiness this eve with
low level wind shear becoming a concern into the overnight hours
(for KSTC/KMSP/KRNH/KEAU). The cold front will be entering western
MN at 06z tonight. Showers and thunderstorms may develop along the
front late tonight into the early morning hours. Have maintained a
PROB30 at KAXN, but confidence/potential is too low to include at
other sites at this point. MVFR level cigs behind the front will
also be possible on Saturday, primarily at KAXN/KSTC during this
TAF period.

VFR expected through tomorrow morning with the potential for low-
end VFR clouds by 18z Saturday. Low level wind shear tonight is
the only other concern, with TS/SHRA activity expected to stay to
the west through Saturday afternoon.

Sun...Mainly VFR. Slight chance MVFR/TSRA. Winds SW 5-10 kts.
Mon...MVFR/TSRA. Winds S 5-10 kts.
Tue...Chc MVFR/TSRA early. Winds NW 5-10 kts.


WI...Heat Advisory until 7 PM CDT this evening for WIZ023>026-028.

MN...Heat Advisory until 7 PM CDT this evening for MNZ054-056>070-



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