Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 150552 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1252 AM CDT Tue Oct 15 2019

Issued at 1238 AM CDT Tue Oct 15 2019

See updated aviation discussion below.

UPDATE Issued at 928 PM CDT Mon Oct 14 2019

Overall the forecast is in fine shape and therefore don`t plan to
make any substantive changes. Pressure rises will usher in beefier
winds late tonight and early on Tuesday. And for the most part if
appears pcpn up in ND will stay mostly out of the CWA.


.SHORT TERM...(This Evening through Tuesday Night)
Issued at 314 PM CDT Mon Oct 14 2019

The forecast challenge is where will any light measurable
precipitation occur tomorrow morning over northeast South Dakota and
west central Minnesota, and what type of precipitation will it be.

Currently, with filtered sun through scattered mid/high clouds
continuing, visible satellite imagery shows daytime heating/mixing
taking a substantial chunk out of the snow field. Temperatures have
warmed into the 40s and 50s throughout the CWA this afternoon on
light east-southeast winds. A cold front is analyzed just off to the
west of the CWA.

Dry weather starts the period, and ends the period, with some low
end precipitation chances in between. Models sweep the
aforementioned cold front through the CWA overnight tonight,
introducing the initial push of low level CAA and winds becoming
northwest and breezy at times by Tuesday morning. This is also
supposed to induce some bkn/ovc low stratus across a good chunk of
the region heading into Tuesday morning. An area of low pressure
churning across far southern Saskatchewan will sweep out it`s waa-
forced cloudiness and precipitation chances tonight, mainly north of
the cwa. But, models support an upper wave rotating down through the
Dakotas on the backside of the upper low early Tuesday morning
through Tuesday afternoon, representing the support for a second
cold frontal/inverted surface trof passage with more reinforcing low
level cold air for Tuesday. This secondary upper wave will bring a
little bit of TROWAL-forced light precipitation potential across
mainly northeast South Dakota and west central Minnesota.

The p-type forecast ends up being rather complex/tricky. Short range
guidance/BUFKIT profiles lend some support to surface wet-bulb
temperatures being warm enough for p-type to be liquid (some very
light rain/sprinkles or some drizzle) when precipitation chances
start to ramp up. But when models indicate enough ice will be
introduced (TROWAL-clouds aloft) into the column (mainly between 7
AM CDT and 4 PM CDT Tuesday) to activate ice, the p-type changes to
either snow or very cold rain (perhaps a rain/snow mix) as the
lowest 1000ft or so of the boundary layer may stay warm enough to
melt the snow into droplets before reaching the ground. Once the
column looses the ice aloft by Tuesday afternoon, the stratus layer
over the eastern forecast area is still probably deep enough and
still probably warm enough to support a few more hours of very light
precipitation (drizzle or very light rain/sprinkles) before the
precipitation potential goes away, leaving at least the eastern half
of the CWA under low stratus clouds heading into Tuesday night.

The temperature forecast from tonight through Tuesday night will
average out much below normal, as low level thermal progs off the
deterministic models, backed by output from the NAEFS S.A. Ensemble
Table, indicate 925hpa thermal progs will be hovering right around
0C across the northeastern third of the forecast area on Tuesday,
and around +3C to +4C across the southwestern portion of the CWA.
Surface high pressure will be building into the CWA Tuesday night,
allowing for breezy/windy northwest winds to relax/go light and
variable Tuesday night.

.LONG TERM...(Wednesday through Monday)
Issued at 314 PM CDT Mon Oct 14 2019

A ridge of high pressure will be building across the northern Plains
as this forecast term gets underway. This will help us to string
together a few dry days along with near normal, if not a bit above
normal temps through the end of the week. High pressure will slide
east of our area on Wednesday followed by an increasing southerly
flow ahead of the next frontal passage that`s progged to move
through dry on Friday. In fact, Wednesday through the daytime
Saturday looks to be dry. High temps will warm from the 40s & 50s on
Wednesday to the 60s Thursday through Saturday. Some places in our
west could top out around 70 on Thursday. Deterministic models
continue to disagree on our next best chance for precip the latter
half of the weekend into Monday. The EC/Canadian continue to track
low pressure farther east through the eastern Dakotas while the GFS
has a much farther south and east track. Will continue to go with in
house chance pops for that time. Somewhat cooler conditions will
possibly return late in the period.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1238 AM CDT Tue Oct 15 2019

An area of MVFR to IFR at times ceilings will work into the area
from the northwest by mid-Tuesday morning, in association with an
area of low pressure. These ceilings may not lift through the
period at ABR and ATY, but could dissipate Tuesday evening for
PIR and MBG. Patchy fog cannot be ruled out Wednesday morning, but
confidence is low at this time.




LONG TERM...Vipond
AVIATION...Lueck is the U.S. government's official web portal to all federal, state and local government web resources and services.