Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 170407

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1107 PM CDT Fri Jun 16 2017

.SHORT TERM...(This evening through Saturday)
Issued at 245 PM CDT Fri Jun 16 2017

Two disturbances will be impacting our weather for the next 24
hours. The first, now over South Dakota will continue on its
east-southeast trajectory, tracking across southern Minnesota and
Iowa this evening. Extensive cloudiness across western Minnesota
has limited the degree of destabilization this afternoon, but
MLCAPE has recently increased to 1000-2000 J/kg across Iowa extending
up into southern Minnesota. As the vort max rotates eastward late
this afternoon toward this destabilizing airmass, expecting
scattered showers and thunderstorms to develop, a few of which may
be severe south of a line from Fairmont to Eau Claire. This
activity will shift east of the CWA by mid evening.

After a break overnight into Saturday morning, a stronger trough
will rotate eastward to Minnesota during peak heating mid
afternoon. This wave, in combination with a moist and modestly
unstable airmass should get numerous showers and scattered
thunderstorms to develop. A couple stronger cells are possible,
but the low CAPE/shear profiles should limit this potential
significantly. Instead, relatively brief heavy rainfall rates are
the biggest issue. Increased PoPs to categorical across many areas
west of I-35 and likely east. Widespread cloud cover and rain by
afternoon will keep highs in the 70s.

.LONG TERM...(Saturday night through Friday)
Issued at 245 PM CDT Fri Jun 16 2017

The medium range guidance is in fairly good agreement on the overall
evolution of the large scale upper air pattern over the upcoming
week. The shortwave trough impacting the region tomorrow and
tomorrow night will work to carve out a larger scale trough over the
eastern part of the CONUS, which will put help put us in northwest
flow with ridging over the western CONUS. This looks to break down
some by the middle of the week, with fairly zonal flow for the
second half of the week. We`ll have some showers/thunderstorms
lingering into tomorrow night as a surface low lifts northeast from
Iowa into the Upper Great Lakes. Some showers, mainly diurnally
driven given the cold pool aloft, can be expected on Sunday. A few
could manage to produce lightning, mainly across the northeast
forecast area where mid-level temperatures look coolest, and across
the southwest where better boundary layer moisture will be present.
A shortwave trough looks to drop southeast with the upper flow and
pass through the region late Monday into Tuesday, so should see some
showers and a few thunderstorms with that. In addition, the
baroclinic zone to our southwest will periodically work to generate
some showers and thunder during that period. A more predominantly
dry period looks to occur later Tuesday into Wednesday as a decent
surface ridge takes hold over the area. However, return flow and
warm advection Wednesday should help generate showers/thunderstorms
as we see the 850 mb theta-e ridge work into the area. After that,
with the flow becoming more zonal, the guidance diverges a bit more
in terms of the forecast details. Overall, it looks to be more of a
typical summertime pattern, so will need to mention at least some
PoPs for most of the period from late Wednesday into Friday until
timing and placement of features can be hammered out better.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1105 PM CDT Fri Jun 16 2017

VFR conditions thru 18z with a general light west/southwest wind.
After 18z, chance of SHRA/TSRA develops as a sharp weather
disturbance moves across Minnesota, and into western Wisconsin.
Timing and areal coverage remains the main challenge of SHRA/TSRA
but did adjust timing to more mid/late afternoon as this system
has slowed some. Winds will become more west/northwest by the end
of the taf period. There is an increasing chance of MVFR cigs
developing across central Minnesota Saturday evening and moving
southward during the overnight hours. Later shifts will need to
redefine how much coverage these lower cigs become.


No aviation concerns through 18z with timing of SHRA/TSRA mainly
after 21z. Cigs could begin to lower to MVFR after 6z/18.


Sun...VFR. Chc -SHRA. Wind NW 10-15 kts.
Mon/Tue...VFR. Wind NW 5-10 kts.




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