Scientific Forecaster Discussion
fxus63 kmpx 262358
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
658 PM CDT Mon Jun 26 2017
Short term...(this evening through tuesday)
issued at 300 PM CDT Mon Jun 26 2017
Surface high pressure continues to build into western Minnesota 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 Minnesota 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. South-southwest winds of 10 to 20 with gusts up to 25 miles per hour 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 Minnesota to account for warm air advection 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
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 Storm Prediction Center 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 00z tafs through 00z Tuesday evening)
issued at 658 PM CDT Mon Jun 26 2017
Western Wisconsin will have a couple broken lines of showers and
an isolated thunderstorm early this evening, but these should
dissipate by sunset. For Minnesota, only some cu, which will dissipate
by sunset. Only other item of concern will be the wind gradually
shifting from the northwest this evening to southwest late
tonight, then increasing Tuesday morning as gradient tightens
associated with next incoming system.
isolated showers this evening viewable from kmsp but are off to
the east in Wisconsin. Otherwise cu will dissipate this evening
with wind gradually becoming SW late tonight at less than 5 kts.
South wind will increase mid morning Tuesday with some gusts over
20 kts tomorrow afternoon as gradient strengthens.
/Outlook for kmsp/
Tue night...VFR. Rain showers/thunderstorms and rain late, with MVFR cigs. Winds S 5-10 kts.
Wed...VFR/MVFR. Morning thunderstorms and rain likely. Chance afternoon thunderstorms and rain.
Winds S 10-15 bcmg west.
Thu...VFR. Winds northwest 5-10 kts.
Fri...VFR. Chance thunderstorms and rain. Winds north-NE 5-10 kts.