Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 271911
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
211 PM CDT TUE SEP 27 2016

.UPDATED for 18Z Aviation Discussion...
Issued at 151 PM CDT Tue Sep 27 2016

&&

.SHORT TERM...(Today and tonight)
Issued at 330 AM CDT Tue Sep 27 2016

Surface analysis this morning shows deep stacked low over
northern Lake Superior. MSLP in the center is down to 994mb while
the upper low, nearly atop the surface low, is down to about
5400m (compared to heights in the 5700m-5850m range from central
MN through the Dakotas). The stacked low is forecast to drift to
the south through tonight, taking a position over the southern tip
of Lake Michigan by daybreak Wednesday morning. As the low moves
south, a noticeable trough axis will rotate around the western
fringes of the upper low, sweeping across the MN international
border around 21z then through southern MN by around 00z and into
far southern WI and northern IA by 03z. The system will still
contain plenty of moisture, obtained over the weekend from a
tropical plume originating over Mexico. Putting the timing of
these features together along with the timing of the arriving
trough axis, the window from 18z-03z looks good for having
scattered to numerous showers over eastern MN into western WI
today. Not looking for much in the way of QPF, although far
eastern portions of the WFO MPX coverage area (specifically the 3
Wisconsin counties of Rusk/Chippewa/Eau Claire) could receive up
to one quarter inch of rain.

The deep low will take on a more easterly component close to
daybreak Wednesday morning, thus ending the precipitation chance
by then (although precipitation is expected to largely end earlier
than daybreak, closer to around 06z). However, clouds will hold
strong over the area through daybreak Wednesday due to the close
proximity of the large deep low. With additional and prolonged
cloud cover over the area today through tonight, temperatures will
run some 5-8 degrees cooler than seasonal normals for highs today
and close to normal tonight. Highs will range from the mid 50s in
northern and eastern portions of the WFO MPX coverage area with
mid 60s in western and far southern portions. Tonight, lows will
drop to the 40s.

.LONG TERM...(Wednesday through Monday)
Issued at 330 AM CDT Tue Sep 27 2016

The extended period can be characterized as dry and mild as a
blocking type pattern keeps this region uneventful through the
weekend.

The aforementioned storm system in the short term will likely hold
in the Ohio Valley through Friday/Saturday, and possibly longer
depending upon the strength of an upper level ridge building
across southeastern Canada. The latest NAEFS mean of all three
500/700/850 MB heights are outside climatological normals (Maximum
Mean Heights) across southeastern Canada by the end of this week.
This anomalous ridge will keep the storm system across the Ohio
Valley from moving very little. Therefore, the mean upper flow
over the Upper Midwest will be persistent (Weak - North-
Northeast) once the storm system over the Great Lakes moves
southward. Not until the Upper Ridge breaks down or weakens
considerably will our weather change. I would not be surprised to
see models trending toward the stagnate pattern continuing through
early next week. Once the pattern changes and the upper ridge
moves overhead, will the weather pattern change to more unsettled.
The best scenario is to hold off on precipitation chances until
late Monday/Tuesday.

Past the 7 day period, longer range models (GFS/EC) are showing
the mild conditions becoming cooler and more unsettled past
October 5-6.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 151 PM CDT Tue Sep 27 2016

VFR conditions will give way to MVFR and possible IFR at the
Wisconsin sites as an upper level low rotates over the Great Lakes
and brings low clouds and showers across the Upper Midwest.
Northwest winds will gradually become northerly overnight with a
slight easterly component expected on Wednesday morning.

KMSP...
Rain showers are located just to the northeast of KMSP, but should
impact KMSP later this afternoon. Visbys should stay above 6
miles. The main concern is the low clouds which are forecast to
dip below 3000 ft, but they should remain above 1800 ft tonight.
VFR conditions will return Wednesday morning.

/OUTLOOK FOR KMSP/
Thu...VFR. Wind NE at 10kt
Fri...VFR. Wind NE at 05kt
Sat...VFR. Wind NE at 05kt.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...None.
&&

$$

SHORT TERM...JPC
LONG TERM...JLT
AVIATION...JRB



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