Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 031137 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
537 AM CST Sat Dec 3 2016

Issued at 519 AM CST Sat Dec 3 2016

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


.SHORT TERM...(Today through Monday Afternoon)
Issued at 337 AM CST Sat Dec 3 2016

Stratus continues the rather rapid retreat with 925mb winds shifting
to the south/southwest. Clearing has resulted in localized pockets
of dense fog, mainly downwind of the Missouri river. A surface
trough will move across the western Dakotas today, with a warm
advection push that will result in increasing low to mid clouds,
with weak lift of 3-5 microbars generating light snow/sprinkles.
There will also be some light precipitation that follows the upper
trough as it moves overhead Saturday night, and mid level
temperatures cool slightly.

The post frontal airmass will be milder than ahead of the trough as
a modified Pacific airmass moves into the Dakotas. Westerly winds
will also enhance mixing - with mixed temps around 40F. Snow cover
will probably have less impact on these readings due to the
favorable mixing direction and ample sunshine compared to the
readings expected for Today. Mild air will remain across the area
early Monday though a surface low is expected to develop and track
across the forecast area during the day. While the cold front will
move across the area during the morning, 925mb readings start
quite mild, from -1 to +4C at 15Z, resulting in highs above
average for the day but likely falling in the afternoon as 925mb
readings drop to 0 to -6C by 00Z Tuesday. Also anticipate
precipitation on the northwest side of the surface low as
temperatures within the profile cool.

.LONG TERM...(Monday Evening through Friday)
Issued at 337 AM CST Sat Dec 3 2016

Not a lot of change to speak of in the out periods this morning,
compared to yesterday morning. Still dealing with a low pressure
system early next week that, arguably, could be producing a decent
band of snow in some strong wind somewhere over the northern plains.
Available deterministic/ensemble guidance still seems to be pinging
North Dakota for placement of most of the precipitation potential
Monday/Monday night with this system, but this system is still being
watched closely. A shift of just 50 miles to the south, and this
band of snow is creating hazardous traveling conditions across, at
least, north central South Dakota!

The rest of the 7-day is dry except for Thursday and Saturday. For
two consecutive mornings, the ECMWF brings a slug of saturated
conditions between 850-700hpa southward through the eastern Dakotas
and much of Minnesota, when SnowRatios are quite possibly between 18
and 23:1 over the region. There could be up to an inch of light
fluffy snow falling over the region east of the James River valley.
The 00Z GFS/ECMWF are also still highlighting some waa-forced
precipitation chances on Saturday as another Pac-NW shortwave sweeps
through the Dakotas.

Lastly, given past run-ins with 925hpa thermal progs as low as
-20C, and 0.5km wind progs as high as 25 to 30 knots, considering
whether wind chill values will be lower than advertised -10F to -20F
w.c. values currently showing up in the forecast database between
Tuesday and Friday. Perhaps a target of opportunity for refinement
over the next few days.


.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 519 AM CST Sat Dec 3 2016

KPIR is currently VFR, but sits right on the edge of IFR/LIFR fog
and low stratus streaming off of Lake Oahe this morning. There is
also a mid-level VFR deck of clouds working into the picture as
well. Overall, expecting VFR conditions to prevail over the next
24 hours at KPIR. KMBG is in the IFR/LIFR fog and low stratus that
has been advecting north through the Missouri River valley all
night. However, these conditions are not expected to persist for
very long this morning, especially once the mid-level deck of VFR
clouds makes it to KMBG. By mid-day, KMBG should be into
prevailing VFR conditions as well. The low-stratus clearing line
is at KABR and KATY. However, VFR conditions and morning sunshine
may become self-destructive at these two terminals, resulting in
potential sct-bkn MVFR cigs through late this afternoon. By the
time the mid-level cloud deck reaches the KATY terminal this
afternoon, sufficient saturation through a deep enough layer may
occur to support a few hours of light precipitation there.
Otherwise, short-range guidance suggests KABR/KATY may be bouncing
back and forth between sct-bkn VFR/MVFR cigs during much of the 24
hour valid period.




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.