Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 101129

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
629 AM CDT Thu Aug 10 2017

.UPDATE...For 12z Aviation discussion below


.SHORT TERM...(Today and tonight)
Issued at 411 AM CDT Thu Aug 10 2017

A cool and cloudy day is expected today, with cyclonic flow
fostering scattered showers, along with a potential for isolated
thunderstorms given relatively steep lapse rates during the
afternoon. In the meantime, patches of dense fog will be possible
prior to and shortly after daybreak in locations that cleared out
temporarily near the front. Highs will top out 10 to 15 degrees
below normal, which translates to upper 60s to mid 70s.

Clearing ensues across the Minnesota portion of the area tonight,
which will bring the potential for fog development as lows dip into
the mid to upper 50s.

.LONG TERM...(Friday through Wednesday)
Issued at 411 AM CDT Thu Aug 10 2017

Again no huge concerns in the extended with some rain possible in
west central/southwest MN Saturday night/Sunday with no other
systems of significance that may bring more widespread rains until
the middle of next week. Temperatures will run on the cool side
through the weekend with highs only in the 70s, but we will start to
warm next week, with 80s becoming more common by the middle of the

Concerns in the long term don`t really start until the
second half of the weekend, with a surface high keeping us mild and
dry Friday and Saturday. This weekend, we`ll see another shortwave
work around the upper low centered near Hudson Bay. This wave will
be rather diffuse with a positive tilt, working south across the
Canadian Prairies Friday, east across the Dakotas on Saturday, then
across southern MN for Sunday. Forcing with the upper wave looks
weak, with no surface reflection of the wave expected. In addition,
mid level lapse rates around 6 C/km and surface dewpoints in the 50s
will limit instability build up. It all adds up to it looking dry
this weekend, with a cloudy Sunday as mid/upper level clouds work
across the area with the shortwave.

Next week, upper level shortwave energy will begin pouring into
western Canada, which will work to flatten and push the western
ridge east. That ridge will be working across the upper MS valley
during the first half of next week, keeping us dry. As we make the
transition to the west side of the ridge and more zonal flow, models
continue to indicate a boundary working across the region
Wednesday/Thursday. Although all of the guidance shows a boundary
working through this period, there is still a good deal of spread in
terms of timing, strength of forcing, and the degree of moisture
return ahead of it, but with dewpoints looking to return to the 60s
and temperatures into the 80s, we`ll have the potential to have a
bit more instability to work with for this go around.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 630 AM CDT Thu Aug 10 2017

Primary concerns are related to the fog and stratus this morning,
followed by scattered shower and thunderstorm potential.

The main area of showers and thunderstorms has exited to the east
early this morning. Fog developed in its wake, especially in
central MN. Stratus clouds will continue to overspread the area
this morning with MVFR/IFR ceilings becoming common. Ceilings
should improve to VFR during the afternoon, but rain showers and
an isolated thunderstorm or two will occur with a weak disturbance
aloft. Skies clear out tonight with patchy fog possible toward
daybreak Friday.

Cigs around 1000 ft will persist through the morning, with
improvement to VFR anticipated during the afternoon. A few SHRA
are also possible today, primarily during the afternoon. There is
an isolated thunder threat as well, but probability is too to
warrant inclusion in the TAF. West winds will become northwest
this morning and persist through the day at speeds below 9 knots.

Fri...VFR. Wind N 5-10 kts.
Sat...VFR. Wind NE 5 kts.
Sun...VFR. Slight Chc SHRA/TSRA afternoon. Wind ESE 5 kts.




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