Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 270521

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1221 AM CDT Tue Jun 27 2017

.UPDATE...For 06z Aviation discussion below


.SHORT TERM...(This evening through Tuesday)
Issued at 300 PM CDT Mon Jun 26 2017

Surface high pressure continues to build into western MN this
afternoon and the center of the high is expected to slide to our
south tonight.  In the meantime, upper level cyclonic flow remains
across eastern MN and western WI with a diurnally driven cumulus
field once again.  Isolated showers and even a stray thunderstorm
will continue across western WI until this evening.  Expect the
cumulus field to dissipate this evening with mostly clear conditions
overnight.  With the cool airmass still in place, overnight lows
will be able to fall into the 40s once again.

For tomorrow, we finally see the winds become southerly on the west
side of the aforementioned surface high, with warm air advection
ongoing as the upper ridge to the west pushes in and the trough
that`s been in place for the last several days progresses to our
east.  SSW winds of 10 to 20 with gusts up to 25 MPH are expected
tomorrow afternoon as we find ourselves between an approaching low
and the departing high.  The precip associated with the approaching
system looks to primarily hold off until tomorrow night, but did
include a slight chance during the late afternoon timeframe in far
western MN to account for WAA induced precip ahead of the main

.LONG TERM...(Tuesday night through Monday)
Issued at 340 PM CDT Mon Jun 26 2017

There is high confidence that the beginning of the extended
period will be wet and stormy as a strong short wave, and
associated deep moisture regime, develops across the Northern
Plains, and Upper Midwest Tuesday evening. The main concern is
placement of the low level jet and orientation of the strong
theta-e ridge /85h- 70h/, which may displace the core of the
convection either north or south of MPX forecast area.

Both the EC/GFS have similar forecasts in their surface features
and short wave energy which yields a broad area of heavy rainfall
across Iowa and southern Minnesota. The GEM or Canadian model
focuses the heaviest rainfall across Iowa and separates the energy
of the two short waves across Minnesota. This would leave a gap
of the heaviest rainfall to the north and/or south of the MPX
forecast area.

As for the main forecast, it will still rain across
southern/central Minnesota starting Tuesday night, the main
concern is to pinpoint the strongest convection, and potentially
heaviest rainfall in the Upper Midwest for Tuesday night, and into
Wednesday. Later shifts need to focus on the development of the
low level jet and how it sets up in the increasing unstable
atmosphere. Severe weather parameters /see SPC latest outlook/
still support some isolated severe storms Tuesday evening as both
wind shear and ample CAPE remain, especially in southwest/south
central Minnesota. As for Wednesday, this is all dependent on
whether the atmosphere can recover from morning/afternoon
convection. The best potential of recovery and severe weather
parameters are in south central/southeast Minnesota during the

No major changes past Wednesday as the Upper Midwest remains in a
quasi-stationary zonal flow aloft. There will be a period of
rainfall sometime next weekend, but timing in these type of fast
zonal flow regimes is problematic in weather models.

For those still looking for more heat and humidity... the longer
range models are favoring for a warm-up after the 4TH of July.
The EC and somewhat of the latest GFS does show an upper ridge
beginning to build across the center of the country. 85h
temperatures begin to rise significantly east of the Rockies
early next week. This outlook still needs to be monitored and some
modifications of this increasing warm air are likely, but the
main emphasis is to highlight the potential and wait.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1220 AM CDT Tue Jun 27 2017

High confidence in VFR conditions through Tuesday evening. High
clouds will be on the increase Tuesday afternoon/eve as the next
system approaches. Associated showers and thunderstorms will
spread eastward across the area after 06z Wednesday.
South/southwest winds will increase for Tuesday afternoon ahead of
the system, generally reaching 15g25kt speeds between 17-18z
(with the exception of KEAU where gusts are not expected).

No concerns.

Wed...VFR/MVFR. Morning TSRA likely. Chance afternoon TSRA. Winds
S 10-15 bcmg W.
Thu...VFR. Winds NW 5-10 kts.
Fri...VFR. Chance TSRA. Winds N-NE 5-10 kts.




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