Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 140241 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
841 PM CST Sat Jan 13 2018

.UPDATE...
Issued at 836 PM CST Sat Jan 13 2018

The forecast for tonight looks okay. Clouds slowly spreading east.
Light snow in parts of central/south central South Dakota moving
south. A slow gradual warming trend setting up. Did receive a
report of some patchy freezing drizzle underneath these low clouds
in the Missouri River valley, so adjusted the wx grids to include
some freezing drizzle mention.

UPDATE Issued at 527 PM CST Sat Jan 13 2018

See below for an aviation forecast discussion for the 00Z TAFs.

&&

.SHORT TERM...(This Evening through Sunday Afternoon)
Issued at 321 PM CST Sat Jan 13 2018

Continue to watch area of light snow move southeast across western
SD, with PHP having recently reported -SN. Web cams across the
southwest corner of the CWA still do not seem to show any snow, but
will maintain chances into the early evening as we continue to see
the activity slide southeast and potentially affect the far western
and southwestern parts of the CWA. Any accums will be very light and
remain under a half inch.

For the overnight, will see south breezes and warm air advection as
clouds increase as well. This will all lead to steady or slowly
rising temps through much of the night after lows are reached this
evening. Hourly temp grids reflect this trend. There appears to be a
bit of a downslope wind event tonight as well, but should be rather
weak to moderate as 925mb winds are only around 25 to 30 knots out
of the southwest.

On Sunday, the brief shot of milder air spread over the area as
northwest winds gradually increase. Highs will reach the 20s and 30s
for most areas. Will be watching the next arctic front moving south
through the area by late afternoon. The stronger push of cold air
advection begins between 21Z and 00Z. Still expecting areas of light
snow to accompany the front, along with gusty north/northwest winds
and patchy blowing snow. Any blowing snow is highly dependent on
snowfall rates and amounts as there isn`t much at all on the ground
to blow around. Overall accumulations look to be around a half inch
or so for the eastern CWA.

.LONG TERM...(Sunday Evening through Saturday)
Issued at 321 PM CST Sat Jan 13 2018

The period starts off with a deep upper level trough just east of
the plains states. A secondary lobe of the trough will swing across
the Northern Plains Sunday night through the day Monday. Ridging
will build over the Rockies on Tuesday, but gets de-amplified before
it reaches the center part of the country by a shortwave trough
tracking from the Pacific Northwest to the Southern Plains, leaving
a more zonal flow pattern to the north. On Friday, will see the flow
switch back to the southwest as another trough tracks across the
western part of the country and to the Central Plains on Saturday.

At the surface, the frontal boundary will be well east of the area
Sunday evening, with maybe just some lingering light snow over the
far southern CWA. Strong high pressure then begins to work its way
toward the region from the northwest. Breezy conditions will be
possible Sunday night ahead of it, then looks like the high will be
centered over the CWA by Tuesday morning. This high will usher much
colder air back into the area as well beginning Sunday night and
lingering through Tuesday night. As the high pushes off to the east
after that, will see a big moderation in temperatures for the
remainder of the period. Models hinting at a potential system moving
somewhere across the plains at the very tail end of the period, but
do not agree on the location, with the GFS currently much further
south than the ECMWF.

The cold air will begin to settle in Sunday night, with lows in the
single digits and teens below zero. With the breezy conditions in
place, expect to see wind chills in the -25 to -40 degree range.
Highs will only reach the single digits above and below zero on
Monday, then will plummet again Monday night under the center of
the high, generally into the -15 to -25 degree range. Bitter wind
chills will again be a factor that night. After one more cold day
with highs in the 0 to 15 degree range on Tuesday, will then see the
temperatures moderate, with highs in the 20s and 30s Wednesday, and
in the 30s and 40s Thursday, Friday and Saturday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 527 PM CST Sat Jan 13 2018

MVFR conditions (cigs) appear to have set up now at KMBG and KPIR.
Expecting much of the next 24 hours to be sub-VFR there.

VFR conditions persist early this evening at KABR/KATY. But
guidance and satellite imagery seem to agree, that sub-VFR (cigs)
conditions will be overspreading these two terminals with the next
12 to 15 hours as well.

The weather`s gonna get rather snotty at all four terminals by
Sunday afternoon when the next arctic cold frontal boundary
blasts southward through the region. The front is going to induce
scattered snow showers/snow squalls Sunday afternoon/evening as
strong and blustery northerly winds will develop, post-frontal
Sunday afternoon and persist through Sunday night.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Dorn
SHORT TERM...TMT
LONG TERM...Parkin
AVIATION...Dorn



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