Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 172333

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
633 PM CDT Sat Jun 17 2017

.SHORT TERM...(This evening through Sunday)
Issued at 319 PM CDT Sat Jun 17 2017

Clusters of showers and embedded thunderstorms are developing
across northern and western Minnesota and the Dakotas this
afternoon. Expect this activity to shift eastward this evening. A
vort max rotating across southern Minnesota will likely serve as
a focus for more concentrated/robust showers and storms across
central MN and western WI early to mid evening, with some heavy
rainfall possible in spots. GFS and NAM show this potential well,
although their rainfall totals may be a bit high - particularly
the two inches in the metro with the NAM. Nonetheless, high
coverage of showers necessitated the increase of PoPs into the
80-90 percent range this evening before a stabilizing atmosphere
allows activity to wane overnight.

Another couple weak waves in the northwest flow will bring a
chance for additional scattered showers and storms Sunday
afternoon across northern and central WI, and the eastern Dakotas
and far western MN. That should be more hit and miss than today.

.LONG TERM...(Sunday night through Saturday)
Issued at 319 PM CDT Sat Jun 17 2017

The main item of interest/concern in the longer term will be a
shortwave trough and associated surface low and frontal features
which look to impact the area on Wednesday. Otherwise, things are
generally similar looking as they have appeared the past few days,
with northwest flow expected during the first half of the week,
transitioning to more of a zonal flow for the second half. The
guidance remains in reasonable agreement on the large scale pattern
and its evolution, but there are certainly some differences in the
details, which will impact how interesting Wednesday`s system winds
up being for us.

We should see any lingering showers/thunderstorms quickly fade
Sunday evening as the boundary layer cools. However, with the
cold pool still over the area, we`ll likely see some
shower/thunderstorm activity again Monday into Tuesday. On
Tuesday, a weak shortwave trough dropping southeast around the
main upper trough may help to enhance some of the activity during
the evening hours, particularly over the north/east portion of the
forecast area. After that, the main upper trough will start to
lift out of the eastern CONUS and we`ll see a shortwave ridge move
in from the west, with good warm advection suggested by Wednesday
afternoon. The guidance differs in some of the details on
Wednesday, with the GFS, Canadian, and MPAS all bringing a good
shortwave trough into the Northern Plains by Evening, with our
area in the warm sector of a surface low near the
Minnesota/Ontario border. The ECMWF is slower with this feature,
and although it would have some warm advection precipitation over
our area on Wednesday, it doesn`t bring a cold front through until
Thursday. Needless to say, things are a bit uncertain at this
point, so will have a period of somewhat higher PoPs from
Wednesday into Thursday. Depending on the timing of things, there
could be some severe weather concerns, with MLCAPE ahead of the
eventual cold front looking to be in the 1500-2000 J/Kg range, and
deep layer shear AOA 45 kt. So, will certainly need to keep an
eye on this system in terms of an eventual severe weather threat.
After that we`ll be in fairly quick zonal flow and could see a few
shower/thunderstorm chances as quick moving disturbances move
through the flow and across our area.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 630 PM CDT Sat Jun 17 2017

Initial band of SHRAs have caused a few high wind gusts of 20-25
kts early this evening. This will be included in the tafs for the
next few hours as the SHRA/VCTS continue to move across Minnesota,
and into western Wisconsin. Although the TSRAs are very isolated,
will continue with VCTS in all tafs, but coverage is likely to
diminish this evening, unless the main wave of energy across the
eastern Dakotas holds on. This will affect the taf sites
overnight, and not during the busy evening commutes. Otherwise, I
did speed up the onset of MVFR cigs in west central
Wisconsin/eastern Minnesota as LCLs and abundant boundary layer
moisture should result in these lower cigs developing. Kept the
MVFR cigs thru the morning before slowly lifting them to low end
VFR in the afternoon.


Main change to the first 6 hours of the taf was to increase wind
speeds from the northwest. Otherwise, VCTSs through the evening,
but coverage will diminish. Kept the MVFR cigs in the taf but
started the beginning of the cigs a few hours earlier.


Mon...VFR/Chc TSRA. Wind NW 10 kts.
Tue...VFR. Wind NW 10 kts.
Wed...VFR. Wind S 10 kts.




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