Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 172119

Area Forecast Discussion
National Weather Service Aberdeen SD
319 PM CST Sat Feb 17 2018

.SHORT TERM...(This Evening through Sunday)
Issued at 319 PM CST Sat Feb 17 2018

The tighter pressure gradient overhead this afternoon will weaken
late this afternoon/this evening as the ridge of high pressure that
has been over western SD glides across eastern SD and western MN by
00Z Sunday. The lighter winds will be short lived as low pressure
nears from the west and we start of experience increased southeast
winds after 06Z bring gusts nearing 15-20kts that will quickly slide
to eastern SD (mainly Coteau area) by 12Z Sunday.

Still expecting lows to spin down into the teens, with a few low 20s
sneaking in mainly southwest of PIR. While the potential still
exists for light snow (less than 1in) and freezing drizzle (around a
trace), the threat has shifted mainly north of the ND/SD border.
Have still included a mention for our northern counties in the HWO,
but the threat continues to diminish. Otherwise for Sunday, expect a
mostly cloudy sky with temperatures ranging from the 20s over north
central SD, behind the exiting sfc low that will be shifting from
western SD at daybreak to our southwestern counties at 15Z, and to
our east by 21Z. Given the late arrival of the low/cold front,
temperatures could still rise into the 40s over east central SD
Sunday afternoon.

.LONG TERM...(Sunday Night through Saturday)
Issued at 319 PM CST Sat Feb 17 2018

The main time period of interest in the long term will be Sunday
night through Tuesday morning. The region will be situated between
low pressure over the Central Plains and high pressure to the
northwest, with much of the state in the prime area for accumulating
snow. The models are in fairly good agreement with this, just differ
on where a couple of potential snow bands may set and produce higher
amounts of snow. Cold temperatures will unfortunately limit the
amount of moisture in the snow to just one quarter to one half inch
or so. The snow looks to begin across the western CWA between 03Z
and 06Z Monday, then will spread eastward and continue through early
Tuesday morning. Current indications are that the southwestern and
south central part of the CWA will see the best potential for higher
amounts of snow, generally in the 7 to 9 inch range over about a 36
to 42 hour period. Due to the prolonged nature of the event, it does
not meet criteria for a winter storm per se, but with the amounts
expected, will go ahead and issue a Winter Storm Watch for areas
where amounts of 8 inches or more look possible, which is mainly the
five southwesternmost counties.

High pressure moves in on Tuesday bringing a return to dry
conditions. May see a little light snow across the southeastern CWA
on Friday as a system tracks from northern Texas to the eastern
Great Lakes, then another high pressure system will bring dry
conditions on Saturday.

Below normal temperatures will be the rule during the first half of
the period, with highs in the single digits and lower teens Monday,
Tuesday and Wednesday. The latter half of the period will see a
return to near to above normal temperatures, with highs in the mid
20s to lower 30s Thursday, Friday and Saturday.


.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1123 AM CST Sat Feb 17 2018

VFR ceilings and vis anticipated at all terminals. The main
concern will be the wind sheer starting 06-11Z, and continuing
through much of the forecast period. Stronger winds just above
the surface will be changing direction and speed as the fast
moving sfc low along the WY/SD border at 09Z Sunday shifts across
our southwest counties by 15Z, and near or east of ATY by 18Z.


SD...Winter Storm Watch from Sunday evening through late Monday night
     for SDZ033>035-045-048.



LONG TERM...Parkin
AVIATION...KF is the U.S. government's official web portal to all federal, state and local government web resources and services.