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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
221 PM CDT Wednesday Jul 29 2015

Short term...(this evening through thursday)
issued at 221 PM CDT Wednesday Jul 29 2015

Early afternoon satellite imagery showed an impressive cyclone in
eastern Ontario...with 90 degree temperatures in the warm sector reaching
as far north as the shores of James Bay. Cold air continued to wrap
around the southern side of this cyclone...and this Canadian
airmass was responsible for the seasonably dry dewpoints over the
upper Midwest.

Later this evening the westerly wind gusts will subside...and
overnight lows will fall to near 60 across the region which is right
around climatology for late July. On Thursday the wind gust will
pick up again...but have a slight northerly component. No chance of
rain is expected within the next 36 hours.

Long term...(thursday night through wednesday)
issued at 221 PM CDT Wednesday Jul 29 2015

The longer term still looks relatively quiet... with the most
interesting period in terms of precipitation looking to be over the
weekend. In the big picture... northwest upper flow still looks to
predominate through the period... with the extended guidance all
in basic agreement on that. So... chances for precipitation will be mainly
tied to shortwaves dropping southeast through the area and their
attendant weather surfaces lows/waves. None of these appear to
have sufficient moisture/instability to do anything until the
Saturday/Sunday time frame. The GFS and European model (ecmwf) both show one such
feature moving through the region late Saturday
afternoon/evening... with the southwest portion of the area likely
having the best shot of seeing precipitation develop and/or an upstream mesoscale convective system
move through the area. However... chance probability of precipitation do include all of
the area given uncertainty in where the shortwave will track and
how far north elevated instability will extend. Currently...
Sunday is pop-free... with chance probability of precipitation advertised once again for
Sunday night. This is with another northwest flow wave dropping
through the area. The GFS has a more substantial surface feature
than the European model (ecmwf) Sunday afternoon/evening... but both manage to
develop some precipitation over the region by Sunday night. Timing changes
could certainly lead to probability of precipitation being included a bit earlier on
Sunday in subsequent forecasts... so it will bear watching. In
addition... the GFS manages to bring MLCAPE values at or above 2000 j/kg
into most of the area ahead of this feature... and with decent
middle-upper level northwest flow the deep layer shear is at or above 40kt.
So... at the current time if we/re going to have any time period
for more robust convection across the area it may be with the
system moving through later on Sunday. Cwasp values from the GFS
Sunday evening are in the 50-70 range... so although not
overwhelming do at least suggest some potential for stronger
storms should things develop. After that.... we look to see some
ridging and dry weather on Monday before chances for precipitation return
later Tuesday into Wednesday as the upper ridge starts to flatten
and shift a bit eastward and we see better low level moisture work
into the region.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 108 PM CDT Wednesday Jul 29 2015

VFR conditions throughout. Wind gusts will decrease
overnight...but increase again Thursday morning.

Kmsp...
VFR conditions throughout. Wind gusts will decrease
overnight...but increase again Thursday morning.

/Outlook for kmsp/
Friday...VFR. Wind northwest 10 knots.
Sat...VFR with MVFR/thunderstorms and rain possible late. Wind SW at 5-10 knots.
Sun...VFR. Wind S at 5 knots.



&&

Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&

$$

Short term...jrb
long term...
aviation...jrb

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