Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 201459

Area Forecast Discussion
National Weather Service Aberdeen SD
859 AM CST Sat Jan 20 2018

Issued at 858 AM CST Sat Jan 20 2018

An early analysis of the 12Z NAM shows a southern trend in some of
the higher precipitation through Sunday night (06Z was on the high
end when compared to a majority of the solutions). This lines up
better with our ongoing forecast. Will continue to monitor model
trends today, for potential adjustments to the current headlines.


.SHORT TERM...(Today through Monday Afternoon)
Issued at 343 AM CST Sat Jan 20 2018

While models have been consistent with bringing a significant winter
storm into the region, they differ in timing an placement of the
heaviest snowfall amounts.

As of 9Z, the regional radar shows light pcpn moving across western
SD. With a substantial dry layer to overcome, little pcpn is
expected east of the Missouri River today. Another west/east band of
pcpn should develop tonight with accumulating snow possible across
the southern half of the CWA. While the eastern extent of the band
may diminish Sunday morning, locations along I-90 could see snow
continue through Sunday with 1-3 inches possible by 0z Monday. As
the surface low intensifies over eastern Nebraska, we`ll see
moderate snowfall over south central and southeastern South Dakota
Sunday night through into Monday. With an additional 1-3 inches of
snow possible along I-90 Sunday night, will issue a winter storm
watch for Jones, Lyman, and Buffalo Counties for the potential of
3 to 6 inches.

A few models are suggesting a slightly further north track Sunday
night into Monday with moderate to heavy snow possible in Deuel
County. Based on the current storm total snowfall forecast, will
issue a winter storm watch for Deuel County from 0Z Monday through
0Z Tuesday.

.LONG TERM...(Monday Evening through Friday)
Issued at 343 AM CST Sat Jan 20 2018

A brief shot of "relatively" cooler air will proceed the low
pressure system exiting the region on Tuesday morning. 925 mb
temperatures drop into the upper single digits to low teens, which
translates to a Tuesday morning low temperature forecast in the
teens, although would not be surprised to see the forecast trend
slightly cooler given MOS guidance remains cooler than most
deterministic models. This shot of cooler air is very short lived
however. The upper level pattern over the northern plains shifts to
a weak northwest flow followed by a ridge, and temperatures bounce
back to the 5 to 10 degree above normal range for the remainder of
the work week. The next shot at precipitation will be the
Friday/Saturday time frame. Models somewhat agree on a weak to
moderately forced, but very quick moving system tracking across the
northern plains.


.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 523 AM CST Sat Jan 20 2018

VFR conditions can be expected through this evening for all
terminals. A storm system southwest of the region will bring low
end VFR cigs by the late afternoon hours for the terminal of KPIR.
Light rain, changing over to snow will be possible for KPIR after
0Z Saturday. Light snow could impact the terminal of KATY toward
the end of the valid TAF period.


SD...Winter Storm Watch from late tonight through late Sunday night
     for SDZ045-048-051.

     Winter Storm Watch from Sunday evening through Monday afternoon
     for SDZ023.



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