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094
FXUS63 KMPX 271218
AFDMPX

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

.UPDATE...
Issued at 641 AM CDT Tue Sep 27 2016

Updated to include 12z aviation discussion below.

&&

.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 12Z TAFS through 12Z Wednesday morning)
Issued at 641 AM CDT Tue Sep 27 2016

Deep low over Lake Superior will slowly drift south into Lake
Michigan through tomorrow morning, making this feature the main
player over the next 24 hours. Light rain showers over NE MN will
also gradually drift south due to this system, likely impacting
KMSP eastward. A few showers may reach KSTC but chances are low
while both KAXN-KRWF are too far removed from the reaches of this
system to see any precipitation. KRNH-KEAU may even have some
stronger showers, possibly enough to reduce visibility down to
MVFR levels. However, the main threat for MVFR will come from
lowering ceilings associated with this system. The low ceilings
look to move in later this morning into the early afternoon and
remain there into the early morning hours before VFR returns along
with high pressure.

KMSP...Best window for showers into KMSP looks to be roughly
21z-03z. Not expecting anything heavy, no worse than 6SM
visibility, but ceilings are likely to drop into MVFR this
afternoon into the mid-evening hours. Breezy northwest winds can
again be expected (but not quite as high as yesterday). Speeds
will increase to around 15G25kt later this morning through this
afternoon.

/OUTLOOK FOR KMSP/
Thu through Sat...VFR. NE wind less than 10 kt.

&&

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

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...JLT
AVIATION...JPC