Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 250016
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
716 PM CDT Sun Sep 24 2017

.SHORT TERM...(This evening through Monday)
Issued at 304 PM CDT Sun Sep 24 2017

Widely scattered showers and isolated thunderstorms will continue
to pop up this afternoon ahead of the cold front over the eastern
Dakotas, where boundary layer heating has resulted in 3-hour
MLCAPE increases of 100-200 J/kg over western Minnesota. This
activity will be possible through sunset. A few stronger storms
cannot be ruled out during this time with a damaging wind threat
given 40-50 knot 850-500 mb flow. Overall, however, the severe
potential is low. The concern for large hail is lower given
relatively poor mid level lapse rates.

After sunset the concentration turns to the main area of post-
frontal precipitation that will advance eastward across the area
overnight and Monday. Have included 70-80 percent precip chances
as the front meanders across the area. This event should provide a
good soaking given precipitable water values are forecast to
increase to around 1.75 inches by 12z Monday, coming close to
setting a record high precipitable water value for the date.

With the bulk of the area socked in with clouds and precip behind
the front on Monday, most areas will see highs in the 50s and 60s,
with the exception of Wisconsin where 70s will be common.

.LONG TERM...(Monday night through Sunday)
Issued at 304 PM CDT Sun Sep 24 2017

Things continue to look similar to how they`ve looked the past
several days. In the big picture, the western upper trough will lift
northeast and work its way across our area through midweek. Ridging
will re-build across the west during that time, with northwest flow
setting up over our area for the second half of the week. The
western ridge will then flatten as it shifts east toward our area
over the upcoming weekend. The numerical guidance is in fairly good
agreement on this overall scenario, with no notable differences
until the tail end of the period.

The frontal boundary will continue to push east tomorrow night
through Tuesday, eventually taking lingering precipitation with it
and out of the eastern portion of the area by Tuesday evening. This
timing could be slightly delayed if the surface wave which develops
along the front on Tuesday winds up stronger than currently
indicated. High pressure will build in from the west and provide
cool and dry weather Tuesday night through Wednesday night. But, a
cold front will drop in from the north on Thursday, with an
accompanying chance for showers. A stronger surface high will build
southeast from Canada behind this front, with seasonably cool and
dry weather Thursday night through Saturday evening. The details are
a bit muddy after that, but the GFS and ECMWF both suggest another
frontal boundary and associated shortwave trough will move toward
the area on Sunday, bringing another chance for precipitation.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 716 PM CDT Sun Sep 24 2017

Broken line of storms and showers early this evening is oriented
nne/ssw from east central into south central mn. These will
progress eastward with a healthy gust front ahead of the line,
with gusts around 40 mph in some locales.

Meanwhile, the main show will take place later this evening and
overnight with concentrated and widespread precipitation over
much of MN into far western WI. Thunder is expected, mainly this
evening. Furthermore, ceilings have already lowered to IFR in west
central MN. Ceilings across the rest of central and southern MN
and far western WI will also lower to IFR or low MVFR tonight,
spreading west to east, then persisting for much of Monday.

KMSP...
Scattered showers and a couple thunderstorms are expected with the
current activity moving in early this evening. The thunder threat
will be brief at times. Steadier rain is anticipated later
tonight, possibly holding off until after 04Z. Then MVFR
ceilings will move in, and may even go IFR late tonight and Monday
morning. Visibility should mostly be MVFR but will not be
surprised if that also goes IFR for short periods of time. Low
clouds will persist most of Monday with the slow moving pattern.

/OUTLOOK FOR KMSP/

Tue...Chc MVFR/TSRA early. Winds NW 5-10 kts.
Wed...VFR. Winds WNW 5-10 kts.
Thu...VFR. Winds W 5 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...LS
LONG TERM...
AVIATION...TDK



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