Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 240341

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1041 PM CDT Wed Aug 23 2017

Issued at 1031 PM CDT Wed Aug 23 2017

Updated to include 06z aviation discussion below.


.SHORT TERM...(This evening through Thursday)
Issued at 354 PM CDT Wed Aug 23 2017

A pleasant late-summer day this afternoon across the Upper Midwest
today with highs topping out in the mid-70s & dewpoints in the
upper 40s to low 50s. This drier air at the surface will be a
limiting factor in our precipitation tonight, associated with a
shortwave trough diving south from Manitoba. PW values remain
fairly low with the lack of moisture so despite fairly organized
isentropic ascent & divergence aloft, really not expecting
anything more than 0.25" of precipitation tonight across central
MN & west- central WI. Additionally, we`re looking at little to no
CAPE with this system so expecting tonight`s precipitation to be
light & showery with no thunder forecasted.

This area of showers will clear out of the area around sunrise
tomorrow with broken cloud cover holding on into the afternoon.
Held off on any fog mention across the northern CWA tomorrow
morning despite the damp ground & calming winds, as cloud coverage
should be enough Thursday AM to put a damper on peak radiational
cooling. Winds become southerly tomorrow as an area of high
pressure at the surface slides off to the southeast. This warm
advection aloft & moisture return at the surface looks to be
enough to generate some scattered showers towards Thursday
evening, as another shortwave trough approaches from the west.
Cloud cover Thursday will keep temperatures close to 10 degrees
below normal, with highs remaining in the low 70s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 354 PM CDT Wed Aug 23 2017

The long term period remains rather unsettled looking, really not
a lot has changed from the previous forecast. All in all, cooler
than normal temperatures are expected, along with showers and
periodic thunderstorms.

Thursday night through Thursday night, the longwave
trough will be centered over the Great Lakes as the wave that is
expected to move through our region tonight will end up near
Detroit by Thursday evening. Our cool northwesterly flow aloft
will continue, whereas at the surface we expect southeasterly
winds by Friday. Low pressure will be developing to our west by
Friday with a warm frontal boundary extending eastward. We could
see some light precip during the day Friday to the north of the
front, and with mostly cloudy skies as well expect temperatures to
be held in the 60s for much of the area.

Friday night through Sunday...The next system to watch will be a
developing shortwave across the Dakotas on Friday, which will move
east through our are this weekend. Precip will begin spreading
into western MN ahead of this wave overnight Friday night most
likely. Instability is not impressive, but there could be some
embedded thunderstorms in this activity. Increased POPs to 60% for
much of west central MN through the metro during this period. The
trough will continue to move through Saturday with the surface
front across portions of southern MN, a good bet for continued
showers and storms to move through. At this point, the threat for
severe weather is low. As we get to Sunday, we`ll see the winds
turn northwesterly as the system passes to the east, and the main
slug of moisture goes with it. But, showers are still possible
during the day with the cold air aloft in place on the back side
of the upper trough, leading to sufficient lapse rates for showers
to develop. Meanwhile, Harvey will be slowing moving through the
Gulf Coast of Texas, which could limit the southern extent of our
northern stream trough and ultimately dictate the large scale
weather pattern to some degree.

Monday through Tuesday...after the weekend system finally departs
the area, conditions should dry out and improve. Again, will have
to watch how the long range pattern may be altered by the
acitivity of Harvey; hence a lower than normal confidence forecast
at this time range.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1031 PM CDT Wed Aug 23 2017

VFR conditions expected throughout this TAF set. Clouds will
increase aloft through the rest of this evening then will look
for ceilings to lower into the mid-levels during the early morning
hours. A few showers are expected mainly from KSTC-KMSP eastward
but nothing that should bring conditions lower than VFR. Showers
will shift off to the southeast shortly after daybreak then
partial clearing is expected through midday tomorrow.

KMSP...VFR expected throughout. Main window for showers looks to
be in the 06z-10z timeframe and only intermittent at best with
minimal impacts expected.

Fri...Mainly VFR. Chance MVFR/-TSRA. Wind SE 5-10 kts.
Sat...Mainly VFR. Chance MVFR/-TSRA. Wind SE 5-10 kts.
Sun...Mainly VFR. Chance MVFR/-TSRA. Wind SW 5 kts becoming NW.




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