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fxus63 kabr 142015 

Area forecast discussion
National Weather Service Aberdeen South Dakota
315 PM CDT Mon Oct 14 2019

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 County Warning Area this afternoon on
light east-southeast winds. A cold front is analyzed just off to the
west of the County Warning Area.

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 County Warning Area overnight tonight,
introducing the initial push of low level cold air advection 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 County Warning Area 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 County Warning Area.
Surface high pressure will be building into the County Warning Area 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 18z tafs through 18z Tuesday afternoon)
issued at 1239 PM CDT Mon Oct 14 2019

VFR conditions will prevail across the area into this evening.
After 06z, look for sub-VFR stratus cigs, associated with low
level caa developing behind a frontal passage, to develop mainly
over the kmbg/kabr/Katy terminals. VFR/MVFR cigs could eventually
reach as far south in the region at kpir during the day on
Tuesday. Breezy/windy northwest winds are also expected by late
tonight/Tuesday morning behind the frontal passage.


Abr watches/warnings/advisories...
South Dakota...none.


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