Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 061941

Area Forecast Discussion
National Weather Service Aberdeen SD
141 PM CST Wed Dec 6 2017

.SHORT TERM...(This Evening through Thursday Afternoon)
Issued at 140 PM CST Wed Dec 6 2017

The forecast challenge is temperature.

Currently, under a partly cloudy sky, winds are from the northwest
at 20 to 30 mph with some higher gusts thrown in. An area of low
pressure over MN embedded in northerly flow aloft is helping to
generate some scattered flurries over the northeast corner of the
South Dakota over into west central MN. Temperatures are struggling
to warm through the upper teens and lower 20s.

Tonight...the clouds over the east should go away, leaving the whole
cwa pretty much cloud-free (except for maybe some higher jet-level
cirrus). Surface high pressure glances the region to the south and
west, so expecting winds overnight to switch over to more of a
westerly direction. In theory, that should work against temperature
free-fall overnight under clear skies.

Thursday...the westerly component surface wind persists, and along
with expected more sun than clouds, temperatures should rebound into
the 20s (eastern zones) and 30s (western zones). The Rapid Refresh
model has been indicating a north-south band of clouds rolling into
the western zones by Thursday afternoon, and a few of the CAM
solutions have continued to generate some light returns over the
west, so did collaborate some small pops across parts of western
South Dakota Thursday afternoon.

.LONG TERM...(Thursday Evening through Wednesday)
Issued at 140 PM CST Wed Dec 6 2017

North to northwesterly flow remains at 500mb, with a large trough
extending from north central Canada through Hudson Bay, the Great
Lakes, and into the south central U.S. At the same time a high
amplitude ridge is over the western U.S. up through northwestern
Canada. This overall pattern will continue through at least early
next week.

Will begin with a sfc trough sinking southeast across the Northern
Plains Friday night. The best chance of seeing any snow looks to be
over the eastern half of the forecast area. Actual moisture profiles
are pretty varied for this time, but do show at least a small
potential for a couple of hours of freezing drizzle for Brown/Spink
Counties as precipitation ends around daybreak Friday. Confidence is
low, and little to no precipitation is expected.

The pressure gradient will increase Friday afternoon-Friday night as
the trough exits across the Great Lakes and southeastern Canada, and
large high pressure dominates the intermountain west. Can`t rule out
patchy blowing snow for some of our northern areas Friday night,
where they still have snow on the ground.

Otherwise, dry weather will be the rule through Sunday, along with
warmer conditions. A weak trough will slide across the Dakotas
Saturday night, with clouds and a wind change being the main
results. 850mb temps will rise to near 10C Sunday afternoon, with
sfc highs jumping to around 15F above normal for this time of year.

The next embedded 500mb wave looks to slide in from the northwest
Sunday night, with a slight chance of rain or snow possible. The
operational GFS and ECMWF were more in line with timing and location
of light precipitation then their 12Z/06 counterparts, but both
still show some. Farther out, dry weather will continue, with highs
in the 30s and 40s.


.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1224 PM CST Wed Dec 6 2017

KPIR and KMBG have returned to VFR flying weather, while KABR and
KATY have gradually fallen into some MVFR cigs and light snow
flurries. VFR will prevail for the rest of today and tonight at
KPIR and KMBG, but by mid-Thursday morning, some sub-VFR cigs may
be approaching the KPIR/KMBG terminals from the west. Will
continue to monitor. KABR and KATY should expect the bkn-ovc MVFR
cigs and light snow flurries to persist until around sundown,
before cloudiness begins to clear off for the overnight across
northeast South Dakota. Currently, expecting a return to VFR by
00Z-03Z timeframe, with continued VFR conditions through the
middle of Thursday at KABR/KATY.




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