Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 250005

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
705 PM CDT Sun Jun 24 2018

Issued at 629 PM CDT Sun Jun 24 2018

Updated to include 00z aviation discussion below.


.SHORT TERM...(This evening through Tuesday)
Issued at 212 PM CDT Sun Jun 24 2018

Current radar imagery shows some scattered showers/thunderstorms
across the area, with the main activity focused from southwest
into south central Minnesota, and secondary activity northeast of
the Twin Cities metro. The larger scale activity from earlier in
the day dissipated as it moved toward the metro and into an area
of reduced deep layer moisture along the leading edge of the 850
mb theta-e gradient. However, activity was able to develop in the
north/east metro where convergence was enhanced due to northeast
flow that worked its way down from Lake Superior. Expect to see
more widespread convection develop to our west/southwest this
evening/tonight which will try to move across the forecast area
again on Monday, but once again it looks like it will tend to fade
as it moves east into drier air. However, we will eventually see
the shortwave over the eastern Rockies work its way eastward,
which will bring a more widespread area of showers/thunderstorms
across the forecast area Monday night into Tuesday morning as its
associated surface low moves east along the Minnesota/Iowa border.
This could certainly exacerbate ongoing flooding issues and delay
cessation or increase the crests of river levels. The better
juxtaposition of instability and shear still looks to be to our
south, so the main potential of any severe weather still looks to
be in that area, although a few severe storms can`t be ruled out.

.LONG TERM...(Tuesday night through Sunday)
Issued at 212 PM CDT Sun Jun 24 2018

Once the Tuesday shortwave trough kicks east it still appears we
will see ridging build across the central CONUS with troughing
setting up over the western CONUS by the end of the week. This
should lead to some active weather in the region from Thursday
night into the weekend with southwest upper flow initially west of
the region slowly pushing east with time. However, the guidance
still shows a fair amount of spread with where/when MCS activity
will develop and move, so the forecast will still have some chance
PoPs for a greater period of time than there will likely be
precipitation in the area. The are also some significant
differences on when the strong upper ridge will be displaced
eastward, which will obviously impact the forecast as we head
through the weekend. The ECMWF and Canadian are more progressive
than the GFS and FV3 solutions. At this point, don`t have too much
confidence to favor one over the other, although upper ridges of
this forecast magnitude at this time of year are often more
stubborn than guidance would like them to be.

Any precipitation with the Monday night/Tuesday system should
shift east Tuesday night, with a weak ridge of high pressure
bringing warm and dry weather for Tuesday night and most of
Wednesday (a weak shortwave trough passing by to our north could
bring some shower/thunderstorm activity through late Wednesday).
Warm advection and moisture return will dramatically increase on
Thursday as low pressure sets up in the lee of Rockies. The
guidance currently suggests this will lead to widespread
convection (MCS activity) across the Dakotas on Thursday that will
lift northeast through northern Minnesota Thursday night into
Friday, while we remain hot, humid, and capped. After that the
guidance has much more spread due to differences with how quickly
they bring the western trough east and push the cold frontal
boundary through our area. The ECMWF and Canadian would bring it
through Friday night and early Saturday, while the GFS would delay
it by at least 24 hours (the FV3 from 06Z was somewhat between
these solutions). Our main chance for precipitation currently
looks tied to this frontal passage and forcing from the
association shortwave trough. So, will need to carry PoPs for much
of the time period from late Friday into Sunday to account for the
differences in timing and evolution.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 629 PM CDT Sun Jun 24 2018

The bulk of the precip ongoing at the 25/00z initialization time
over SW MN will gradually dissipate and shift further W and S thru
the late evening and overnight hours. As an upper low to the west
of southern MN shifts eastward during the day tomorrow, rain will
slowly return from the west and gradually spread east across
southern MN into western WI. As for timing, am not looking for
rain to reach eastern MN (let alone western WI) by 00z tomorrow
evening. Still, ceilings may drop to MVFR for brief periods
overnight into tomorrow morning. Should any heavy shower directly
impact a terminal, IFR visibilities cannot be ruled out.

KMSP...Went with a more optimistic approach and kept precip out of
MSP thru 00z tomorrow. Small chance that the precip over
southwestern MN reaches MSP this evening with high confidence of
dry overnight thru the first half of tomorrow, then chances slowly
increase with showers likely tomorrow evening.

Tue...MVFR/-SHRA/-TSRA likely. Winds E bcmg NW 5-10 kts.
Wed...Chc morning MVFR. Winds NW 5-10 kts.
Thu...VFR. Winds SE 10G20 kts.




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