Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 141201 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
701 AM CDT Thu Sep 14 2017

Issued at 622 AM CDT Thu Sep 14 2017

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


.SHORT TERM...(Today through Saturday Afternoon)
Issued at 407 AM CDT Thu Sep 14 2017

Frontal boundary is stalled out across the CWA, stretching from west
central MN southwest to around PIR. A wave of low pressure is moving
northeast along the front early this morning with upper level
support as well. Area of showers and isolated storms continues to
move eastward across the central Dakotas. Have been adjusting POPs
to account for this activity as it pushes eastward towards the James
valley over the next few hours.

For later this afternoon, focus will shift to potential shower and
thunderstorm development along the front across the eastern CWA.
MLCAPE does increase to around 1500 J/KG, but with generally weak
vertical shear. It would seem multicell storm structures are
possible with perhaps some instances of locally strong winds and
marginally severe hail.

Frontal boundary will begin sliding south tonight through Friday as
cold air advection takes over. Will also see a stratus deck begin to
move south through the area, probably sometime tonight. Cooler
temperatures will move in on Friday as more widespread precipitation
and upper level shortwave energy moves into the Dakotas.

The heart of the cool air will move through on Saturday and have
dropped lows a few degrees below SuperBlend based on chilly 925/850
mb temps and abundant cloud cover. Seemed like a good target of
opportunity to decrease temperatures closer to what the raw ECE/MEX
guidance numbers are showing. Much of north central SD eastward into
the northern James River valley may not make it out of the 50s on
Saturday. A taste of fall for sure to start off the weekend.

.LONG TERM...(Saturday Evening through Wednesday)
Issued at 407 AM CDT Thu Sep 14 2017

The main forecast trends continue this morning. Precipitation
chances dwindle for the most part from Saturday night through
Wednesday, as mid/upper level ridging is forecast to set up over the
region while a western CONUS upper level longwave trof reloads with
more energy. There could be a couple of low-end measurable precip
events (not widespread) influencing portions of the cwa between
Saturday night and Wednesday, but by and large, the period looks
dry. Late next week looks a little bit more interesting for a return
to more widespread moderate to potentially heavy rainfall. The
question is timing, as is typical of swrn CONUS large upper low
pressure systems, which tend to end up moving through this region
often 24 hours or more later than initially depicted/forecasted by
the models.

Cooler than climo normal airmass is in place over the region
Saturday night/Sunday, but moderation looks to begin on Sunday into
Monday before low level waa takes over, and high temperatures
Tuesday/Wednesday end up climbing back to or above climo normal


.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 622 AM CDT Thu Sep 14 2017

Still dealing with the effects of western U.S. wildfire smoke
across the region, particularly at KMBG and KABR. This may cause
drops below "VFR" flying weather visibility. There may be a few
more difficult to time showers or weak thunderstorms
developing/moving across South Dakota today/tonight, before the
more widespread round(s) of precipitation move in on Friday. Also,
there is a growing consensus amongst short-range models/guidance
that VFR conditions today/this evening will be replaced by
IFR/MVFR stratus by Friday morning. For this reason, stratus has
been introduced into the TAFs late tonight.




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