Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 060101 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
701 PM CST Tue Dec 5 2017

Issued at 700 PM CST Tue Dec 5 2017

Allowed the wind advisory to expire. Northwest winds continue to
diminish this evening.

UPDATE Issued at 528 PM CST Tue Dec 5 2017

Made a couple of adjustments to precip type this evening as
temperatures have risen into the upper 30s around Pierre. Any
showers should be all rain over the next couple of hours across
south central SD.


.SHORT TERM...(This Evening through Wednesday)
Issued at 130 PM CST Tue Dec 5 2017

Through Wednesday the main forecast challenge will be pcpn. One
wave/jet streak appears to be moving across the region this
afternoon with light snow up and down the Missouri River valley.
That activity will probably wane by late afternoon and early
evening. However, another wave is fast on the heals of the first,
and should spread more light snow across mainly the central part of
South Dakota later this evening and overnight. Quite a number of CAM
solutions are indicating upwards of a couple inches over north
central South Dakota overnight.  The GFS has slightly less snow, but
keeps about the same areal axis as the other models. So feel perhaps
a bit more confidence in the snow forecast now that the models are
somewhat in agreement. For Wednesday a sfc front moves through and
begins scouring out the moisture, thus brining an end to any snow.

Lows tonight are likely to range from about 10 above in the far
east, to the mid 20s south central. Wednesday should be a bit cooler
than today behind cold front.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 130 PM CST Tue Dec 5 2017

Will start off Wednesday night with a slow moving large 500mb trough
over the eastern half to two-thirds of North America, and a ridge
over the west coast up through British Columbia and Yukon/Northwest
Territories. This overall pattern will remain through the forecast
period, with the 500mb low meandering around Hudson Bay and James

As a result of this nearly stagnant weather pattern, daytime highs
will only range from the low 20s to upper 40s. The warmest readings
will likely be from Saturday on, over our southwestern counties.
Otherwise, lows will generally be in the teens to mid 20s. The
exception looks to be Wednesday night, with single digit lows
possible across much of the area.

Taking a look at the sfc weather pattern, we`ll start off Wednesday
evening with the main low over eastern Hudson Bay/northern Quebec,
and high pressure over British Columbia/WA/ID. A ridge looks to
extend into the western half of South Dakota, and across NE during
the day Thursday. In its place, a trough over ND and western SD late
Thursday morning will sink across the forecast area through Thursday
evening. Otherwise, we will just be stuck in north to northwesterly
flow in between high pressure to the west, and low pressure east.

Expect the western ridge to again push a ridge into South Dakota
Saturday night. Another feature of note will be a sfc low developing
across central Canada over the weekend, that could push into Hudson
Bay on Sunday. Will exclude the output from the Canadian from Monday
on, the 00Z and 12Z solutions creates a stronger secondary low over
central Canada Monday, which swings across northern MN Monday night.
They were also much deeper with the main low over Hudson Bay. So,
the only precipitation mention in the extended period is Sunday
night through Monday. The operational GFS and ECMWF are in pretty
good agreement in timing and intensity at 150-170 hours, boosting
confidence in the current forecast.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 528 PM CST Tue Dec 5 2017

Most of the area will remain VFR through the period. However,
brief periods of snow this evening near KMBG could cause vsby or
cigs to fall to MVFR. KPIR could also see a brief period of MVFR
fog/stratus Wed morning.




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