Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 210403

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1103 PM CDT Sat May 20 2017

.SHORT TERM...(This evening through Sunday)
Issued at 234 PM CDT Sat May 20 2017

Main issue in the short term will be continuation of larger scale
precipitation on the northwest side of the surface low moving by
to our southeast. The warm advection and DPVA forced precipitation
earlier today is transitioning more into deformation zone
precipitation forced by upper level divergence and mid-level
frontogenesis. It will start to focus more to our northwest as the
night progresses, although some light precipitation will likely
continue over much of the area through the night. Some sleet has
mixed in at times just to our northwest this afternoon, and
wouldn`t be shocked to see a little of that in the far northwest
for a time this evening, although the majority will be in liquid
form. The surface low looks to lift north toward Lake Superior on
Sunday, but some cyclonic flow and the upper level trough will
linger over our area, keeping some shower activity going at time.

.LONG TERM...(Sunday night through Saturday)
Issued at 234 PM CDT Sat May 20 2017

A few lingering showers may persist into Sunday night, but mainly
over the northern part of the area. Otherwise, we await Monday,
when things look at least marginally interesting. A surface trough
will extend from the departed surface low southwest through the
southern portion of our area, as a secondary short wave trough
rotates around the main upper low, and looks to help generate some
shower activity during the afternoon and into the evening, with
the best combination of forcing and moisture looking to be over
the southwest. Forecast soundings show some instability during the
afternoon and evening which isn`t surprising given the cold pool
aloft, so thunder can`t be ruled out. If storms are able to
develop some hail could certainly be possible with the very low
freezing levels and cold temperatures aloft.

Some showers could linger into Tuesday with the upper trough
remaining in the region. However, we should see improvement after
that as ridging begins to work in from the west, with dry weather
and a warming trend expected from Tuesday night into Friday. The
guidance is all in fairly good agreement on this large scale
evolution of things, with the next chance for precipitation
looking to arrive from west to east on Friday. The ECMWF and MPAS
are quicker than the GFS and Canadian solutions with the frontal
boundary leading to those precipitation chances, and at this point
it would be tough to say which is more likely. As a result, will
wind up with some chance PoPs blanketing the time frame from
Friday through Saturday as the system moves through the region.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1103 PM CDT Sat May 20 2017

Surface low near Fairmont will move across the Twin Cities
tonight. Have high confidence in conditions ahead of the low and
occluded front...drizzle with IFR/MVFR vis and LIFR/IFR cigs.
Behind the low and front though, conditions in Iowa are a mix of
MVFR/VFR. For now, kept the TAFs relatively unchanged outside of
EAU. EAU will be in line to get into the warmer air associated
with the VFR conditions over Iowa, so have them going VFR for a
bit late tonight/early Sunday morning, in line with CIG forecast
from the HRRR. Though a period of VFR will be possible at MSP and
RNH as well. Looking at forecast soundings, we have enough lift
(omega) in the cloud layer to keep -dz/-ra going through mid
morning, but after that expect mainly dry conditions, with
afternoon shower activity confined more to the eastern Dakotas
where some sun and destabilization will be possible.

KMSP...HRRR continues to indicate a period of VFR conditions being
possible as the surface low works through between 9z and 13z,
which isn`t unreasonable when looking at obs down in IA. Think CIG
forecast is pessimistic if anything on Sunday when looking at the
mainly MVFR/VFR obs to the south of the low across ern Neb/wrn IA.

Mon...VFR. Chc MVFR/-shra. Wind NW at 5-10 kts.
Tue...VFR. Chc MVFR/-shra. Wind N 10-15 kts.
Wed...VFR. Wind NE 5-10 kts.




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