Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 202344

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
644 PM CDT SAT AUG 20 2016

.UPDATE...for 00z Aviation discussion below


.SHORT TERM...(This evening through Sunday)
Issued at 342 PM CDT Sat Aug 20 2016

Early afternoon satellite imagery together with radar and surface
obs showed a large synoptic system across the Upper Midwest with
deformation rainfall over northern Wisconsin. Meanwhile a few
scattered showers and thunderstorms developed behind the surface
cold front as the cool air aloft together with mid-August sun
promoted instability and shallow convection.

These showers and thunderstorms will continue through the early
evening hours before dissipating. Clouds will dissipate as well, but
forecast soundings show the potential for redevelopment again by
late morning Sunday, so increased the clouds in the sky grids
slightly and decreased temperatures across eastern MN and western
WI. At this time it does not appear that the cumulus will be deep
enough to produce precipitation. Back to tonight, northwest winds
should keep the boundary layer mixed enough to prevent fog formation
despite the widespread rainfall today.

.LONG TERM...(Sunday night through Saturday)
Issued at 342 PM CDT Sat Aug 20 2016

High pressure over the Missouri Valley will slide east early next
week with strong warm air advection taking over by Monday. Gusty
south winds ahead of the approaching trough and mixing to 875 mb
will allow us to reach the mid 80s to lower 90s both Monday and
Tuesday, warmer day being Tuesday. Coordination with surrounding
offices led to increasing highs a few degrees above the standard
blend due to the good mixing. GFS and NAM forecast soundings show
potential for gusts of 30-35 mph.

Low pressure associated with the trough will track eastward across
the Dakotas into northern Minnesota Tuesday night. A trailing cold
front may spark off some thunderstorm activity across western MN
Tuesday evening. However, a developing low along the southern end
of the front over Kansas, with a surface warm front extending to
the east along the IA/MO border, may produce a cluster of storms
or an organized MCS along I-80 which could prematurely steer the
healthy 45-55 kt low level jet to the east. If that were to
happen, it would be tough to get widespread storms across MN and
WI, particularly being in the entrance region of a secondary LLJ
centered over northern MN. Kept PoPs around 50 percent for now.

Cooler and drier weather follows for Wednesday night through
Friday before the next system approaches Saturday.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 645 PM CDT Sat Aug 20 2016

Scattered showers and isolated thunderstorms will wane toward
sunset, with clearing anticipated to ensue and persist through the
remainder of the period. Gusty northwest winds will subside this
evening, but should stay up enough (around 6-8kts) to hinder fog
development overnight.

The thunder threat should be gone at the site, with scattered
showers ending by 02z. Clearing ensues, with VFR conditions then
expected through Sunday.

Mon...VFR. Winds SSW 15-17G25 kts.
Tue...VFR. -TSRA possible late. Winds SSW 15-17G25 kts.
Wed...VFR with -TSRA/MVFR possible. Wind SW 10G15 kts becoming W.


.MPX Watches/Warnings/Advisories...


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