Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 051217 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
617 AM CST Mon Dec 5 2016

Issued at 609 AM CST Mon Dec 5 2016

See below for an aviation forecast discussion for the 12Z TAFs.


.SHORT TERM...(Today through Wednesday Afternoon)
Issued at 445 AM CST Mon Dec 5 2016

Front is now entering into the Western Dakotas, though for the time
being we remain under a modified Pacific airmass. That will change
rapidly today. First, there have been recent changes to the storm
track with the 00/06Z NAM and recent runs of the RUC suggesting a
track now between KRAP - KPIR - KATY and up to KFAR. The shift
south places portions of the CWA within the deformation zone on
the backside of the low. NAM/RUC snow amounts both top out around
3 inches in a narrow band across North Central South Dakota,
however and more importantly is the impact the winds will have
when combined with this snow. With a pressure gradient of 14mb
across the state and pressure rises of 6-9mb, expect advisory
winds across the western half of the CWA. While snowfall from the
most recent storm has been modified due to the mild temperatures,
snowfall that occurs today with these wind conditions will result
in blizzard like conditions. Decided on a Winter Weather Advisory
for north central counties where the likelihood of snow is the
greatest, with just a mention for visibility reductions in a Wind
Advisory for much of the rest of the western/central CWA as cold
air scours out any moisture in the post frontal environment and
results in lighter, more scattered snow shower activity.

The rest of the forecast timeframe consists of winds and falling
temperatures and periods of light snow that wrap around the low as
it moves into the Western Lakes region. Mixed winds in the
Watertown area for Tuesday are in the 30 to 35kt range. Winds for
Wednesday are still in the 20`s, so not only will it be cold but
also will have low wind chills to contend with.

.LONG TERM...(Wednesday Evening through Sunday)
Issued at 445 AM CST Mon Dec 5 2016

Watching temperatures throughout the period running generally below
climo normal, with some of the most anomalously cold air (2-3
standard deviations below normal) forecast to be around Wednesday
night and Thursday. The 00Z GFS deterministic solution was
purporting 925hpa air as cold as -20C to -30C by the middle of next

As for pattern evolution and precipitation potential, there is still
some flurries/small chance pops snow potential Wednesday
night/Thursday. Then conditions go mainly dry through late Friday
night in weak mid-level height rises before the pattern becomes more
active in zonal flow and multiple hard-to-time mid-level shortwaves
potentially sweep quickly eastward through the region. Most of the
00Z deterministic GSM output do show some pretty good waa above
925hpa Friday night into Saturday (tightly packed thermal gradient
means good frontogenesis forcing available for waa banded
precipitation heading into the weekend), so basically kept the pops
that Superblend came up with for days 5 through 7.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 609 AM CST Mon Dec 5 2016

Eventually, sub-vfr cigs will overtake all four terminals
today/tonight, as will strong northwest winds. The strongest
winds will be felt at KMBG and KPIR. KMBG is also expected to
experience some snowfall today. Between the falling snow and
strong winds, KMBG could briefly see considerably reduced
visibility in blowing and/or falling snow. Light snow may also
start up again Tuesday morning at KABR and KATY.


SD...Winter Weather Advisory from noon CST /11 AM MST/ today to 10 PM
     CST /9 PM MST/ this evening for SDZ003-004-009-015.

     Wind Advisory from noon CST /11 AM MST/ today to 10 PM CST /9 PM
     MST/ this evening for SDZ005-010-016-017-033>036.



SHORT TERM...Connelly
AVIATION...Dorn is the U.S. government's official web portal to all federal, state and local government web resources and services.