Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 261049

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
549 AM CDT Mon Jun 26 2017

.UPDATE...For 12z Aviation discussion below


.SHORT TERM...(Today and tonight)
Issued at 342 AM CDT Mon Jun 26 2017

Today marks the last day with area weather influenced by cyclonic
flow on the periphery of the mid/upper trough dominating the eastern
half of the CONUS, although the effects will be less notable than
they were over the weekend. Skies will be mostly clear to start the
day, with patchy fog burning off quickly. We will see diurnally-
driven cumulus cloud development, primarily over west central
Wisconsin. Said area will also be prone to scattered showers and
isolated afternoon thunderstorms, but areas west of I-35 are
expected to be dry. At the surface, high pressure will be sliding
into MN from the Dakotas. This will make for much lighter winds than
experienced the last couple of days, with speeds generally around 10
kts or less (with west central WI on the higher end of the range).

Despite more sun today, temperatures will still be around 10 degrees
below late-June normals. Highs will top out from the mid 60s to
lower 70s. Lows tonight will generally range from 45 to 55 degrees,
which is also below normal by about 5-10 degrees.

.LONG TERM...(Tuesday through Sunday)
Issued at 342 AM CDT Mon Jun 26 2017

The primary concern during the latter portion of the forecast is
the system that will impact the area from late Tuesday night
into Wednesday night. Guidance is in fairly decent agreement on
this system in terms of general location and timing, although
there are certainly some differences in frontal positions, the
degree of instability and capping, and shear profiles. By the
latter portion of the week and the weekend, the guidance starts to
exhibit more spread in the large scale pattern, although there is
some basic agreement on a low amplitude west/east ridge/trough
pattern, with our area seeing some weaker shortwave troughs moving
through on west or northwest flow helping to keep things somewhat

High pressure will be centered over the area on Tuesday before
shifting east Tuesday night as low pressure takes shape over the
Northern Plains. Convection should develop in the High Plains
late Tuesday afternoon then work east Tuesday night, assisted by a
stout low-level jet and feeding on MUCAPE values of 1000-2500
J/Kg. Some of that instability, and what is left of convection,
should work into the western portion of the area overnight Tuesday
night, and perhaps as far east as I-35 Wednesday morning. The
warm front looks to quickly push through the area Wednesday
morning, with the cold front moving through during the late
afternoon and evening. We could certainly be dealing with cloud
cover issues lingering from earlier convection when the cold front
makes its way across the area, and the new day 2 and day 3
outlooks from SPC do a nice job of highlighting the potential for
some severe weather with both the instability/moisture surge late
Tuesday night and the possibility of additional activity with the
cold front Wednesday afternoon/evening. The GFS suggests MLCAPE
values of 1000-2000 J/Kg across much of the area ahead of the cold
front, although MLCIN values would keep much from re-developing
until late afternoon. Deep layer (0-6 km) bulk shear is not
forecast to be overly impressive, generally around 30 kt, but 0-3
km bulk shear is progged around 25 kt, so could certainly see a
wind threat with any storms that develop.

Weak cold advection and drier air look to work in late Wednesday
night and Thursday, with mainly dry weather expected across the
area. The guidance continues to show a weak surface low moving by
to our south on Friday, with an inverted trough extending north
through our area. Pattern would certainly support chance PoPs at
this point on Friday into Friday night. For the weekend it appears
we`ll have a mid-level cold pool (not as significant as the
current one) over the area with a few weak upper waves swinging
through the region. So, will unfortunately need to litter that
time frame with some chance PoPs as well for what should mainly be
diurnal activity.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 550 AM CDT Mon Jun 26 2017

VFR conditions will likely prevail through the TAF period. Few-
scatter cumulus clouds are epected to develop by this afternoon,
along with scattered showers, with the highest coverage in WI.

High onfidence in VFR through the period.


Tue...VFR. SHRA/TSRA late, with MVFR cigs. Winds S 5-10 kts.
Wed...VFR/MVFR. Periods of SHRA/TSRA early. Winds SSW 10-15 bcmg W.
Thu...VFR/MVFR. Winds W 5-10 kts.




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