Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KMPX 200908

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
408 AM CDT Mon Mar 20 2017

.SHORT TERM...(Today and tonight)
Issued at 310 AM CDT Mon Mar 20 2017

Surface analysis early this morning shows high pressure centered
over the Appalachians with a weak low pressure center near KOMA.
Its associated cold front stretches nearly due westward into
central Wyoming with an east-west oriented area of high pressure
to the north of the cold front into southern Canada. Aloft, the
pattern is very much zonal with troughs offshore each CONUS coast.
As the day progresses today, the low pressure system over the
central Plains will shift southeast to near KSTL by midday while
the cooler high pressure to the northwest sags into the upper
Mississippi River Valley. This will result in mainly high clouds
for much of the day but also enact cold air advection to the
region. Another cold front in southern Canada will drop southeast
this evening but will contain limited moisture. The lack of upper
air support combined with deeper moisture well to the southwest of
the WFO MPX coverage area will mean that any precipitation
associated with the cold front will also remain off to the
southwest. The front will cross the coverage area during the early
morning hours Tuesday, resulting in nothing more than a
reinforcing shot of colder air which will last into midweek. While
max temperatures today attempt to climb into the lower 50s, highs
will only reach the 35-40 degree range on Tuesday.

.LONG TERM...(Tuesday through Sunday)
Issued at 310 AM CDT Mon Mar 20 2017

The mean pattern will change significantly over the next few days
as a series of storm systems move inland across the west coast.
This will lead to the weak quasi-zonal flow aloft, to a more west-
southwest flow. This change will also cause the relatively dry
weather we have been experiencing, to a more wet and active

As always, models usually try to change long wave (persistent)
patterns too fast and lead to timing issues for the onset and
duration of precipitation. In addition, there remains
inconsistency on the evolution of the mean long wave trough
moving across the CONUS, and how short waves develop over the
plains. This continues today as the EC/GFS/GEM have different
scenarios of where/when the upper low moves out into the plains
late this week.

Another aspect to this pattern change is how will the influence of
an upstream upper trough in eastern Canada, and an upper ridge off
the southeast coast, play a role in the speed/evolution of this
weeks storm system. Even a blended forecast of all the
deterministic models doesn`t support the timing/speed of this
weeks system. Although once the pattern does change, a period of
wet weather is likely. As for QPF/rainfall amounts... do to the
increase surge of gulf moisture by Thursday/Thursday night, QPF
amounts could be conservative from the models, especially
considering the higher PWAT values expected above one inch.
Although there could be some light snow as the pattern changes
late Wednesday, early Thursday, anything that falls should be
little if any.

Once this system leaves the region early in the weekend, another
storm is expected to form in the plains early next week. Thermal
profiles still remain warm enough to support rain/snow mix.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1101 PM CDT Sun Mar 19 2017

Few changes needed for the TAF with cold front expected to be
moving though the Twin Cities to start the TAF. Winds have have
gone calm ahead of the boundary, but switch to the NW at 5-10 kts
in its wake. Orientation of the pressure gradient between low
pressure moving from the Missouri into the Ohio River valley and
high pressure over the Dakotas will all winds to eventually veer
over to the NNE Monday morning, but directions will drift back to
the west later in the day as a secondary cold front slips through.
Still anticipating nothing more than virga with plentiful
mid/upper clouds.

KMSP...high confidence in TAFs with no differences from what was
mentioned above.

Tue...VFR. Wind N 5-10 kt.
Wed...VFR. Wind SE 5-10 kt.
Thu...MVFR with -RA likely in afternoon. Wind SSE 10 kt.




AVIATION...MPG is the U.S. government's official web portal to all federal, state and local government web resources and services.