Area Forecast Discussion
Issued by NWS Twin Cities, MN

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248
FXUS63 KMPX 150432
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1132 PM CDT Mon Aug 14 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 331 PM CDT Mon Aug 14 2017

Early afternoon satellite imagery together with surface obs and
500mb heights showed an upper level ridge over the Dakotas, with a
shortwave trough over Wisconsin. Beneath these two features was an
area of surface high pressure characterized by light winds, but
boundary layer moisture remained in place which led to overcast
skies. A few breaks in the clouds have started to form over the last
few hours, and this trend should slowly continue into the evening
and overnight. Given the light winds, should see radiation fog
quickly develop in those areas that manage to clear out.

On Tuesday an upper level trough currently located over the Idaho
panhandle will move eastward and develop an area of convection
over the high plains. This precip will reach western MN Tuesday
afternoon. Any storms that develop late Tuesday into Tuesday night
will have the potential to produce heavy rain. Tropopause heights
are still above 150mb with PWATS near 2 inches. It does appear
that the forcing will be distributed over a large area, meaning
not expecting a focused area for ascent which should limit the
flooding potential. Regardless will have to watch the HiRes models
and see if any higher totals appear as they begin to capture this
event.

.LONG TERM...(Tuesday night through Monday)
Issued at 331 PM CDT Mon Aug 14 2017

Main focus of the long term period continues to be the expected
rainfall for late Tuesday night through the day Wednesday, and even
lingering Wednesday night across the eastern portion of the area.

By tomorrow evening, a strengthening shortwave will be advancing
northeast across the high plains and pulling in plentiful moisture
from the south, indicated by PWATs increasing to around 2 inches and
surface dewpoints around 70 degrees.  This system does not look to
be much of a severe weather producer, but instead a widespread
moderate rain produces with sub-severe embedded thunderstorms.  So,
main concern with it is potential for heavy rainfall, which lines
up with the slight risk outlook for excessive rain by WPC. Expect
healthy rainfall amounts, with many locations in the 1-3" range,
but over a prolonged period in general as opposed to falling very
quickly. However, there were a few places that received a couple
inches of rainfall last night, making them a little more at risk
for seeing surface runoff develop quickly.

Conditions look to dry out Thursday into Friday, with another
shortwave expected to move in Friday night.  This wave will come
down from our northwest and looks much more meager than the
Wednesday system.  Still, could see some scattered showers and
storms.

After that, conditions should be dry with southerly flow developing,
leading to a gradually warming pattern through the end of the
weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1132 PM CDT Mon Aug 14 2017

Concern remains the development of low clouds and fog tonight,
with widespread MVFR and IFR. This looks most favorable for
southern MN into the KEAU area, where lingering moisture is most
prevalent, but areas of central MN to WI will also have some dense
radiational fog with light winds. This should persist to 13Z-14Z,
then gradual improvement through the morning.

KMSP...
Mostly clear skies and light northeast winds will continue
tonight. There is some potential for radiational fog, but it is
uncertain how dense it will be. This is due to light ne winds
persisting with a little bit of a gradient. Therefore kept a
period of MVFR visibility, but left the clouds as low scattered.
Then for Tuesday, some midday cu are likely, and mid/high clouds
should spread across the area later Tuesday.

/OUTLOOK FOR KMSP/
Wed...MVFR/IFR with -TSRA. Wind S-SE at 5-10 kts.
Thu...VFR. Wind N-NW 5-10 kts.
Fri...VFR. Wind W 5 kts.

&&

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

$$

SHORT TERM...JRB
LONG TERM...SPD
AVIATION...TDK



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