Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 222257

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
557 PM CDT Tue Aug 22 2017

Issued at 539 PM CDT Tue Aug 22 2017

Updated to include 00z aviation discussion below.


.SHORT TERM...(This evening through Wednesday)
Issued at 359 PM CDT Tue Aug 22 2017

Early afternoon water vapor together with GFS 500 mb heights and
winds showed confluent northwest flow across the region which
meant subsidence and surface high pressure. Seasonably cool air
aloft led to a few clouds and rain showers across northeast MN
and northern WI, but most of the area was mostly sunny this
afternoon with northwest winds around 10 to 20 mph.

Expect clear skies again tonight and much of Wednesday, but a
quick-moving upper level shortwave trough will move approach the
region late Wednesday and be the focus for a few rain showers.
HiRes models show the best chance for rain north of I-94, so tried
to mirror that in the precip chances. May be a little too quick
with pops, so would not be surprised to see the timing slowed a
bit if that trend continues.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 359 PM CDT Tue Aug 22 2017

In the longer term, we`ll briefly see northern stream upper
ridging build over the center of the Continent from Thursday
into the start of the weekend, although the main upper ridge and
warm temperatures associated with it stay well to our south/west.
After that we will once again see redevelopment of a more full
latitude western ridge during the first half of next week, setting
us up for more somewhat cool and mainly dry northwest flow. The
main period of interest in terms of weather across our area will
be during the first part of the weekend as we see a period of some
warm advection and moisture return over the region.

We will see a few showers and perhaps isolated thunder drop
through the area tomorrow night as a compact shortwave trough
drops southeast through the area. Thursday should be dry with high
pressure and subsidence re-asserting itself over the region.
However, chances for showers/thunderstorms will start to increase
from west to east Friday into Saturday as low pressure develops
over the northern Plains and return flow works into our area. This
system will make slow eastward progress, eventually moving
through our area Saturday night and Sunday. The period looking to
have the best combination of forcing and deep moisture looks to be
Saturday afternoon/evening, when we could see fairly widespread
precipitation of a half inch or more, with locally higher amounts
associated with more persistent convection. The surface low
weakens and essentially washes out over the area Sunday and
Monday, with some spotty chances for precipitation lingering as we
don`t see a strong push of drier air until perhaps Tuesday.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 539 PM CDT Tue Aug 22 2017

VFR conditions throughout. Expect light northwest winds overnight
picking up from the north tomorrow afternoon close to 10 knots.
Skies will clear out this evening then clouds will return tomorrow
afternoon in the 6-10 kft range, potentially developing a ceiling
tomorrow evening as a quick moving system possibly brings a few
showers down from the northwest. Chances are too low at this point
for inclusion in the TAF.

KMSP...No significant weather impacts expected over the next 24
hours. Small chance of some isolated/scattered showers moving
close to MSP by 00Z Thursday but confidence at this time is too
low to include mention in the TAF.

Thu...VFR with MVFR possible. Wind SE at 10 kts.
Fri...VFR with MVFR/-SHRA possible. Wind SE at 10 kts.
Sat...VFR with MVFR/-SHRA possible. Wind S at 10G20 kts.




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