Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 161723
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1123 AM CST Tue Jan 16 2018

.UPDATED for 18z taf discussion below...

&&

.SHORT TERM...(Today and tonight)
Issued at 403 AM CST Tue Jan 16 2018

Widespread stratus clouds have kept temperatures from getting too
bitterly cold overnight. This means wind chills are not quite as
low as previously anticipated. Therefore have shaved 1-2 tiers off
the eastern edge of the Wind Chill Advisory area given values
will mostly stay in the mid teens to lower 20s below zero range
this morning. The warning in western MN is somewhat borderline as
well, but given we are near -35 right now, will not make any
changes to it at this point.

The stratus deck will become more straggly but linger through the
morning hours, with flurries possible. Highs will top out in the
single digits. Flow turns to the southwest tonight, so lows will
be somewhat higher than on prior nights. Wind chill headlines
should not be needed.

.LONG TERM...(Wednesday through Monday)
Issued at 403 AM CST Tue Jan 16 2018

First the good news, the extended portion of the forecast now
contains no arctic air!  In fact looking at the GEFS mean h5
forecast through the next 2 weeks, there do not appear to be any
weather patterns conducive to sending arctic air like we have seen
frequently since Christmas our direction. The two main concerns
though this forecast period are how warm do we get Wednesday
through Saturday, followed by the track of a potential major winter
storm Sunday/Monday.

This morning, a classic omega high shows up on water vapor imagery
centered over Alberta and Saskatchewan. Over the next couple of
days, this will break down, but the warm air associated with it will
travel southeast toward us, resulting in a rapid modification of our
temperatures. Yes, we will be getting the ever popular WAA in
northwest flow at the start of the period! Our initializing model
blend continued it`s trend of being a degree or two warm than the
previous forecast and we are likely pretty close to where highs will
end up. The warmest day still looks to be Friday as we get into a
warm sector of a surface low going across southern Canada. We should
see plenty of 40s that day across western and southern MN, with a 40
not out of the question as far northeast as the Twin Cities.

Over the weekend, we will see an h5 wave deepen over the 4-corners
region that will eject out across the central Plains Sunday and into
the Great Lakes Monday. Still a good deal of spread in the
deterministic models and ensembles, but the vast majority of
guidance still points to a major winter storm tracking across the
central CONUS. Our current forecast is pretty close to a blend of
the 16.00 GFS and 15.12 ECMWF, which means we saw a continued shift
in the higher PoPs toward the southeast. GEFS probabilities also
point to higher snow potential existing from central Iowa into
southern WI, but there is a secondary axis of higher snow
probabilities farther northwest, more in line with the 16.00 ECMWF,
which jumped northwest quite a bit from its 15.12 run. At either
rate though, it`s still too early to get bogged down in the
specifics of a wave that is currently a weak short wave that is
cresting a ridge between the Kamchatka Peninsula and the Aleutian
Islands and still needs to undergo a strengthening phase as it
merges with and then gets ejected by an upper low currently over
the Gulf of Alaska.

Behind this wave we will cool down, but as alluded to in the first
paragraph, it won`t be with arctic air. Instead, we look to go from
10 to 15 degrees above normal ahead of it, back down to near
to slightly below normal behind it.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1125 AM CST Tue Jan 16 2018

Satellite trends indicate lower clouds/IFR/MVFR eroding around
east central MN and dropping slowly south. Still have a Lake
Superior enhanced band trailing south toward KRNH as well. This is
thinning but may linger a couple hours yet. VFR trend through late
afternoon for the rest of the period with some patchy mid and fair
amount high level clouds into the night. NW winds diminishing
becoming S-SW tonight and increasing into Wednesday late morning.

KMSP...
Looking like VFR trend through the period.Some patchy stratus
remains east and west of the airport but is eroding across the
interior city. NW-W winds into the afternoon becoming light SW-S
into tonight and increasing later Wednesday morning.

/OUTLOOK FOR KMSP/
Wed Night-Fri...VFR. Wind SW at 5-10 kts.

&&

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

$$

SHORT TERM...LS
LONG TERM...MPG
AVIATION...DWE



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