Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 210007

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
707 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 00Z TAFS through 00Z Sunday evening)
Issued at 707 PM CDT Sat May 20 2017

The dry slot is firmly implanted over the area. Steady precip is
likely done for night, though we expect drizzle to continue, along
with IFR cigs that will likely go LIFR after 6z as the low over NW
IA moves up across the Twin Cities. We have seen a line of
shra/tsra develop east of DSM, the HRRR has been showing this line
of convection and associated instability working north with the
occluded front, moving through the EAU area around 8z, hence why
we briefly brought shra with a vcts into EAU. Expect gradual
improvement in CIGS Sunday as the low moves off to Lake Superior.
Based on obs down by Omaha, we could certainly see conditions
improve a bit faster and go a bit higher than what we currently
have. For precip, expect drizzle to cut off as winds become more
westerly late tonight into Sunday morning, with some iso/sct shra
possible Sunday afternoon.

KMSP...It`s drizzle/-ra the rest of the night for MSP. NAM
soundings do not show omega in the cloud layer going away until
about 15z Sunday, so certainly possible we don`t end the dz/-ra
until mid Sunday morning. Surface low will go overhead at 9z, and
confidence in wind direction around that time is low. Think if
anything, cigs will improve faster and be higher than what we
currently have for Sunday.

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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