Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 121739

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1139 AM CST Sun Nov 12 2017

.SHORT TERM...(Today and tonight)
Issued at 416 AM CST Sun Nov 12 2017

Clouds will continue to spread southeast across southern and eastern
Minnesota, and into west central Wisconsin during the pre dawn
hours. These clouds will linger through the morning before winds
become more westerly in western Minnesota, allowing for drier air
and clouds to clear. The clouds will likely linger in eastern
Minnesota until sunset, with clouds remaining in western Wisconsin
through the evening. Temperatures will reflect the cloud cover as
readings will slowly rise into the 30s. Out west, more sunshine this
afternoon will lead to highs in the 40s.

Overnight, skies will remain clear to partly cloudy with patchy fog
likely. Winds will back to the south as the next storm system
approaches from the west.

.LONG TERM...(Monday through Saturday)
Issued at 416 AM CST Sun Nov 12 2017

Mild and moist air will flow northward early week ahead of a cold
front set to push through Tuesday evening. Negative omega
throughout a shallow but saturated lower level airmass should
allow patchy/areas of drizzle to develop Monday evening and
continue through Tuesday, mainly across eastern MN and western WI.
The boundary layer itself may be a bit drier if it can warm as
much as the GFS/ECMWF indicate. That would limit the overall
extent of the drizzle, especially Tuesday. There could be some
freezing drizzle in western WI Monday evening before warmer air
continues to advect in overnight. Not expecting any impacts given
the very light/patchy nature of any drizzle. Increased highs
Monday and Tuesday despite the cloud cover closer to the GFS/ECMWF
and their MOS products. Advection matters more than the weak
sunshine of this time of year for daytime temperatures.

Steadier rain may develop as the front passes through, but it
should be short-lived with drier already moving in late Tuesday
evening. High pressure dropping southeast across the region Wednesday
night may allow temperatures to drop into the teens.

Models are showing more consistency for the late week system.
Details are still murky, but what appears to be one constant is
the system will begin with a northern stream short wave traversing
southern Canada and a southern stream wave rounding the central
Rockies Thursday night. The two will phase somewhere over the
Upper Midwest or the Great Lakes and generate a strong cyclone to
the east of the Great Lakes this weekend. Impacts locally appear
low in this scenario with cold air likely arriving during the tail
end of the precip when the system becomes more negatively tilted.
If the northern stream system slows then things may get a little
more interesting.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1138 AM CST Sun Nov 12 2017

Trend of MVFR cigs is biggest issue this TAF period. It is
starting to erode from the west, but at a slower pace than the 12z
TAFs had. Bumped out timing a few hours between what we had and
what is probably a little slow RAP/HRRR. Followed the idea of the
RAP/HRRR as well with this stratus stalling out through the night
from northeast MN through western WI, with it remaining in place,
possibly through Monday morning at RNH/EAU. Tonight, the question
becomes do we see fog/stratus return. There will be a favorable
zone for fog/stratus from Little Falls through STC/MSP/MKT down
into southeast MN. The end of the HRRR run shows dense fog/low
stratus developing within this strip, though was hesitant to get
too carried away with it at this point, with forecast soundings
showing upper clouds thickening tonight as well, which may limit
that development. Still, this will need to be watched closely as
it could easily drop STC and MKT below airport minimums Monday
morning, with MSP seeing significant issues with low cigs/vis.

KMSP...Window for going back to VFR is 20z to 00z. With the slower
trend in the clearing west, started pushing us toward the later
end of that window. Tonight, MSP will have a treat for seeing fog
and/or cigs under 500 feet that would last into Monday morning.
Still low confidence on if/where such conditions would form, but
would be high impact if MSP gets into it, so this threat will
need to be watched closely this evening.

Tue...IFR/MVFR cigs. Chc -dz. Wind S 5-10 kts.
Wed...Chc MVFR. Wind NW 10-15 kts.
Thu...VFR. Wind SE 5-10 kts.




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