Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 111759

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1259 PM CDT Fri Aug 11 2017

.SHORT TERM...(Today and tonight)
Issued at 334 AM CDT Fri Aug 11 2017

Surface high pressure over the eastern Dakotas will slide east
today across the upper MS Valley, resulting in a beautiful day
today, with highs in the mid 70s and dewpoints in the 50s. Main
concerns during the short term are all found this morning with
cloud trends and fog, both of which will be a thing of the past by
mid morning. Fog is becoming fairly dense across central MN,
though it`s extent at 4am is about as far as we expect it to get
this morning. Along the MN/WI border, its a batch of stratus that
came down off of Lake Superior that is leading to some
uncertainties on the aviation side of the house. Will continue to
keep it just east of MSP, but it will be close. Like the fog
though, expect the stratus over eastern MN and western WI to mix
out pretty quick, with nothing more than a few-sct cu field
expected today. Only part of the forecast we deviated some from
the blends on was with winds. Momentum transfer in BUFKIT shows
some 15-20kt winds a couple thousand feet off the ground through
the day out in WI, so did go above guidance with wind speeds there
once we get a little mixing going.

Tonight high pressure will remain in control. Not expecting as
much fog though, as low level moisture profiles look drier than
what we are seeing this morning. Moisture return on the back side
of the high will be out in the central Dakotas, so the MPX area
will be remaining dry. With mainly clear skies expected tonight
and dewpoints in the 50s this afternoon, we should again have no
problem dropping back down into the 50s for lows area wide.

.LONG TERM...(Saturday through Thursday)
Issued at 334 AM CDT Fri Aug 11 2017

Saturday and Sunday...Surface high pressure along with northwest
flow aloft will prevail for Saturday, which will keep a wobbling
quasi-stationary front over the lee of the Rockies in place and a
surface cold front in central Canada from dropping into the
region. However, these influences will wane going into Sunday as
the trough over the eastern CONUS becomes a bit sharper and
stronger southerly flow develops on the backside of the departing
high pressure area. While no surface fronts are expected to pass
through the region, a weak baroclinic zone will develop over the
eastern Dakotas through western Minnesota which will make these
areas susceptible to isolated/scattered shower and thunderstorm
development late Saturday night through Sunday morning. There is
evidence of a weak shortwave trough axis aloft rotating around the
western periphery of the longwave eastern CONUS trough which could
work within an atmosphere of slightly deeper moisture, thus have
highlighted best chances for precip in the mid-high chance
category for western Minnesota with chances dropping off going
east. These precip-making features will lose their influence by
late Sunday night as high pressure regains control, thus allowing
precipitation chances to diminish late Sunday night. Temperatures
will remain near to below normal over the weekend, particularly
below normal on Sunday with the cloud/rain complications. Still,
no airmass change is expected which would produce any strong
variations in temperature aside from the nondescript cool down
Saturday into Sunday.

Monday through Thursday...The early portion of the week will be
dominated by surface high pressure and a sharp ridge axis aloft,
making for mainly clear conditions and slightly warmer
temperatures with the greater H5 heights. This ridge will be
short-lived, passing to the east of the area by daybreak Wednesday
morning. A fairly well-organized frontal system crossing the
Rockies Tuesday and the Dakotas Wednesday will move across
Minnesota/Wisconsin Thursday, setting the stage for a few rounds
of showers/thunderstorms Wednesday into Thursday. An accompanying
trough aloft over western Canada will help usher the low pressure
system east and give it modest upper level support for better
coverage of precipitation than the Saturday-Sunday system. That
said, there is still no strong airmass change thus temperatures in
the 70s to around 80 will persist through at least the middle of
next week.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1259 PM CDT Fri Aug 11 2017

Plenty of cu have developed, and these will persist into the
early evening. They are most widespread in central MN and western
WI, but will spread into southern MN.

Satellite imagery shows that some of the cu have some decent
vertical development. There are some of the latest short term
models that develop isolated showers this afternoon. That is
certainly possible, but not certain enough to add anything yet to
the tafs.

Late tonight, doubt there will be as much fog as Friday morning,
as moisture is projected to be in a much shallower layer. But that
will be something to watch.

KMSP...Healthy field of cu have developed, and there may be a
shower near the airfield this afternoon. Not confident enough yet
to add anything, but it does need to be watched. Otherwise, doubt
there will be any late night fog tonight, as there is less low
level moisture.

Sat PM...VFR. Wind light/variable.
Sun...VFR. Slight Chc SHRA/TSRA afternoon. Wind SE 5 kts.
Mon...VFR. Wind SE at 5 kts.




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