Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 122102
AFDMPX

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

.SHORT TERM...(This evening through Monday)
Issued at 300 PM CST Sun Nov 12 2017

As surface ridging builds in from the west, we have been slowly
eroding away the clouds. Question for this evening with these clouds
is where does the west edge set up. The HRRR had been showing the
west edge setting up from Mille Lacs to the west of Eau Claire
through the night, but current satellite trends would support these
clouds getting east of the MPX area, meaning mainly clear skies for
us tonight. That may sound great, but with the surface ridge axis
overhead and dewpoints this afternoon in the upper 20s, we will have
to watch for the threat of seeing fog/low stratus develop tonight
across eastern MN into western WI. Though skies will be clear, lows
should not get too carried away tonight for a couple of reasons. For
one, dewpoints currently in the mid/upper 20s will help keep lows
from falling much below the mid 20s, while return flow will be
getting going tonight in western MN, where temperatures will likely
start rising before sunrise.

Monday, no precip is expected, though a weak short wave passing in
zonal flow will result in a mostly cloudy day thanks to its
associated mid/upper clouds. As the high moving through tonight
moves into the Great Lakes, increasing southeast winds through the
day will help push highs back up into the upper 30s in northwest WI
to near 50 out in southwest MN, which is pretty close to normal for
the time of year.

.LONG TERM...(Monday night through Sunday)
Issued at 300 PM CST Sun Nov 12 2017

Not much has changed in the general thinking for the extended,
with systems passing through Tuesday evening and again
Friday/Friday night. Tuesday will be the warmest day before the
cold front comes through, with a brief cool down Wednesday before
getting back into WAA Thursday. System for the end of the week
looks to deepen significantly into a "Gales of November" type
system for the Great Lakes this weekend, but locally looks to
bring mainly rain on Friday, followed by strong northwest winds
Friday night into Saturday. We will see a quick cool down behind
this system for next weekend, but temperatures look to moderate
again as we head toward Thanksgiving.

Though our warmest day, Tuesday won`t exactly be the nicest day of
the week. Both the GFS and NAM support dense low stratus the
entire day, while even through Tuesday night they lack moisture
above about 5k feet, which means any precip we see starting late
Monday night and lasting through the fronts passage would be in
the form of drizzle. Greatest moisture feed and threat for
drizzle/light rain still looks to be found across eastern MN into
WI, which is where highest PoPs continue, especially Tuesday
night, when we will finally get a little added lift from shortwave
coming across the northern Plains that will be catching up to the
front as it is heading out the east end of the MPX area. Tuesday
still looks to very well be the Twin Cities last chance this month
at cracking 50, though if we do it, it will be based purely on
advection, with overcast conditions expected all day. Blended
current SuperBlend with going forecast to pull a degree or two off
our highs for Tuesday, though still be warmer than blended
guidance.

For the end of the end of week system, models agree on a general
idea for large scale evolution, but still differ significantly on
timing of one of those features. Where there is good agreement is
that we will see a northern stream wave go off to our northwest
on Thursday night, which will help push a front into the upper
Midwest. Where differences lie in timing is with a much stronger
southern stream wave that will ride up along this boundary from
the central Plains into the Great Lakes. Our precip chances look
to be tied to the developing baroclinic leaf on the northwest side
of the southern stream wave. The ECMWF is a good 12 hours behind
the GFS with this wave. With either solution we look to get
precip, especially from south central MN up toward northern WI,
but it`s a question of does it come Friday morning/afternoon (GFS)
or Friday night (ECMWF). Though timing differences exist, both
solutions show it being warm enough to where the majority of
precip we see will be rain. Only change made to the SuperBlend was
to boost winds for the whole Thursday through Saturday period.
Saturday looks to have the greatest wind potential with strong
CAA. It`s not out of the question that we see gusts Saturday
between 40 and 50 mph before an approaching high finally knocks
winds down for Sunday.

As we get on to the backside of the low, we will see a quick hit
of cold air, with h85 temps dropping to around -15c Saturday into
Sunday, but with zonal flow/flat ridging building back in for next
week, we will quickly see temps moderate back near to a little
above normal as we work into the week of Thanksgiving.

&&

.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.

/OUTLOOK FOR KMSP/
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.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...MPG
LONG TERM...MPG
AVIATION...MPG



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