Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200255

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
955 PM CDT WED OCT 19 2016

Issued at 955 PM CDT Wed Oct 19 2016

Updated to include 06Z aviation discussion below.


.SHORT TERM...(This evening through Thursday)
Issued at 339 PM CDT Wed Oct 19 2016

A low level inversion was trapping boundary layer moisture and as
a result stratus continued across the region for most of the day.
Visible satellite as of early Wednesday afternoon showed clouds
starting to transition from stable gravity waves to more turbulent
driven cloud streets which is a sign that clouds will continue to
dissipate this evening. Forecast models continue to show clearing
skies overnight and through the day on Thursday, but will remain
cautiously optimistic that will indeed be the case on Wednesday.

As for temperatures, cold air advection will lead to cooler temps on
Thursday, with afternoon highs struggling to reach 50 at most
locations. No precipitation is executed.

.LONG TERM...(Thursday night through Wednesday)
Issued at 339 PM CDT Wed Oct 19 2016

Dry weather continues to dominate the forecast through Monday as
the flow becomes more amplified and we get stuck between troughs
that will be developing on either side of the continent. Eventually,
the eastern trough will begin to fill and weaken, allowing the upper
ridge to head east, allowing energy from the western trough to come
out into the Plains. However, there continues to be disagreements
with when this ridge shifts to the east, allowing precip to start
falling again. Per usual, it`s the GFS running about 12 hours ahead
of the ECMWF.

For Friday through Monday, not much is happening outside of a couple
of dry fropas that will have minor impacts on temperatures. We will
be starting Friday off on a cool note with a surface ridge overhead,
but by the afternoon that ridge will be off into the Great Lakes,
with waa and return flow setting up for us. There`s no LLJ, upper
level support, or moisture for precip with the WAA advection on
Friday and expect nothing more than a N-S band of mid level clouds
to announce the arrival of the warmer air. We will see a surface
trough work across the area Sat/Sat night, but the biggest impact it
would have is that depending on the timing of the warm sector with
respect to peak daytime heating, we could see highs Saturday a few
degrees warmer than what we currently have. In fact, blended
forecast used already tacked on a couple of degrees to highs
Saturday from the previous forecast. With southwest flow aloft, we
will maintain the mild airmass Sunday and Monday, with highs again
getting up into that 5-10 degrees above normal range.

Precip chances appear again Monday night in the forecast, with 30
pops across eastern MN/western WI Monday night.  This is a GFS
centric forecast, as this is when the GFS brings in its first surge
of isentropically forced precip. The ECMWF gets into similar type
precip, but about 12 hours later. There are also differences in the
strength of the wave, with the ECMWF being the stronger of the two,
with a surface low forecast to come across MN Wednesday, whereas the
GFS keeps more of an open surface wave and trough going through. The
ECMWF solution would bring rain farther west across MN, whereas the
GFS would keep the heavy rain down from IA into the U.P. of
Michigan. Whatever solution you take, unstable air is heading this
direction, so continued to keep a thunder mention in the grids as
well. Lastly, both the ECMWF and GFS show an anomalously strong
subtropical ridge developing next week across the southeast
US/western Atlantic, which is often a key feature seen for heavy
precip events up this way, so it should be no so surprise that
although the GFS/ECMWF may differ on the location of the heaviest
QPF, they both are hinting at the potential for another round of
fairly widespread 1 to 3 inch type rainfall amounts.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 955 PM CDT Wed Oct 19 2016

Some marginal MVFR ceilings will continue to flirt with the
northern TAF sites for the first few hours of the TAF, but should
continue to slowly erode and move east as high pressure builds
into the area. After that, ridging will prevail through the
remainder of the forecast, with light northerly winds. Return flow
doesn`t look to arrive until after the current forecast period as
the surface high shifts eastward.

KMSP...Only item of concern will be the nearby MVFR ceilings at
the current time, and how long they will remain in the area, which
could differ from an hour or two from current estimate.

Friday and Friday night...VFR. Southeast wind 10 kt or less.
Saturday...VFR. Variable wind around 5 kt.
Saturday night...VFR. Southeast wind 5 to 10 kt.
Sunday...MVFR ceilings possible. South Wind 5 to 15 kt shifting


.MPX Watches/Warnings/Advisories...


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