Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 201655

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1055 AM CST Mon Nov 20 2017

Issued at 1050 AM CST Mon Nov 20 2017

Updated to include 18z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 333 AM CST Mon Nov 20 2017

A fairly benign short term period is expected, with the only
headline being the potential for the warmest temperatures we`ve
seen thus far in November (including possibly hitting 50 degrees
for the first time at KMSP and KEAU). We look to mix to around or
just above 925mb, but will also have a fairly dense layer of
cirrus moving overhead. Think upper 40s to mid 50s will be common,
with the warmest readings along the Buffalo Ridge.

A cold front moves through (dry) tonight, and brings an abrupt
switch to brisk northwest winds by daybreak Tuesday. Lows will
fall into the upper teens to upper 20s, with little warming
expected on Tuesday.

.LONG TERM...(Tuesday through Sunday)
Issued at 333 AM CST Mon Nov 20 2017

The extended still looks to be dominated by a relatively fast and
progressive flow with minimal precipitation chances and pretty
strong temperature swings centered around frontal passages. Model
agreement is still good through about 4 days, which gets us
through Thanksgiving, but diverge thereafter. Only changes made to
the blended forecast were to increase winds Tuesday and warm lows
Friday, highs Friday, and lows Saturday a few degrees.

We will be starting the long term period with temperatures on a
steep downward slide Tuesday in the wake of the cold front moving
through tonight. The windiest portion of the day still looks to be
in the morning. Top of the channel winds off the NAM and GFS get
up into the low 40 kts., so still anticipate some northwest wind
gusts up around 40 mph for our typical windy locations from
western through south central MN. Given how cold our 925 mb temps
are by Tuesday afternoon, not looking for much of a rise in
temperatures during the day, with highs largely remaining in the
20s and in a lot of cases will be 20-25 degrees colder than what
we see today for highs.

For Wednesday, the zonal flow aloft will result in cyclogenesis
over southern Alberta Tuesday night that will track toward
southwest MN by Wednesday evening. There looks to be a WAA band of
precip that develops to the north of this surface low track
across the Dakotas on Wednesday. As this wave and snow move east,
it will be encountering increasingly drier air over MN. To go with
this, all but the ECMWF show the fgen and waa with this wave
getting sheared out as it moves into MN, which is why we decreased
pops further. Can`t rule out some flurries occurring across
western MN as this wave approaches from the Dakotas, but much more
than that looks unlikely.

No significant weather is expected for Thanksgiving. We will see a
weak cold front pass through during the early morning hours, but
by the afternoon we will already be seeing WAA. Looking at model
spread, or current forecast is on the lower end of the guidance
envelope, so wouldn`t be surprised if Thanksgiving ends up being a
couple of degrees warmer than what we currently have.

We`re starting to get better agreement with how Friday will unfold
in the models. The general consensus is that much like today, a
strong surface low will track across southern Canada, placing us
in another mild warm sector, with a good chance at cracking 50
again for areas along and south of I-94. The majority of the
precip looks to be up closer to the surface low, but with surface
dewpoints creeping up to near 40, there will be a better chance
for generating showers locally as the shortwave and associated
vorticity advection move through. Most of the models show a band
of showers developing during the afternoon from eastern MN into
western WI, though temperatures look plenty warm enough to make
this almost all rain, so it will have minimal impacts to travel.
This band of showers will also mark the return of cooler and drier
air as a Canadian high moves back in for Saturday and Sunday.
This looks to knock highs back into the 30s to finish out the
holiday weekend. It looks dry as well, so all-in-all, the weather
looks great from the perspective of driving across the region the
entire holiday weekend.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1050 AM CST Mon Nov 20 2017

VFR conditions expected through this TAF period. High ceilings
will dissipate later this evening but then mid-level ceilings will
approach close to daybreak with the arrival of a cold front. The
duration of mid-level ceilings will be relatively short, roughly
4-6 hours, then high scattered clouds will remain for the rest of
the day tomorrow. Strong NW winds will develop with the frontal
passage and remain in place for much of the day tomorrow with
gusts as high as 35 knots.

KMSP...Only concern will be strong NW winds which will likely
occur during the Tuesday morning push. Ceilings could drop as low
as 4 kft but not expecting anything into MVFR or lower range.

Wed...VFR. Winds SW 5-10 kts.
Thu...VFR. Winds NW 5 kts.
Fri...Mainly VFR. Chance p.m. MVFR/-SHRA. Winds SW 10 kts.




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