Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 110923

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
423 AM 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 cooldown
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 06Z TAFS through 06Z Friday night)
Issued at 1237 AM CDT Fri Aug 11 2017

Expect stratus out by EAU to remain in place through the rest of
tonight, but will quickly dissipate between 12z and 15z this
morning. Just west of this stratus, winds will begin to drop
overnight and there is potential for fairly widespread dense fog
along the MN/WI border, which could be an issue for RNH. Also for
fog, we are already seeing br/fg in central MN and this may
become an issue at STC, where some vsbys between 1sm and 3sm are
expected in the morning. Also went a bit above guidance for winds
east, as forecast soundings at EAU show some winds in the 15-20kt
range getting mixed down this afternoon. Otherwise, no additional
concerns this period, with a few-sct cu field expected in the 5k-
6k ft range.

KMSP...There will likely be fog in the MN River Valley this
morning, but this is not expected to directly impact the field.

Sat...VFR. Wind light/variable.
Sun...VFR. Wind SE 5 kts.
Mon...VFR. Wind SE at 5 kts.




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