Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 150218 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
818 PM CST Sat Jan 14 2017

Issued at 816 PM CST Sat Jan 14 2017

Have made a few changes this evening. Over the deeper snowpack of
NC/NE SD, temperatures are falling a little faster than
anticipated and thus have had to lower temps a notch. Not much in
the way of clouds or wind thus snow cover will rule overnight.
Rest of forecast fine for now.


.SHORT TERM...(This Evening through Monday Night)
Issued at 344 PM CST Sat Jan 14 2017

Temperatures have struggled to reach highs today, mainly from the
James valley westward into central SD. This is especially noticeable
in north central SD where MBG is still a good 10 degrees away from
previously forecast high. Just too much snow on the ground and no
mixing. This will be the biggest concern in the short term,
determining temperatures in a weakly mixed atmosphere with deep snow
cover. First challenge comes tonight when clear skies and light
winds will dominate. After falling short with highs today, just how
far do temps tank tonight? Dropped lows several degrees in some
areas, undercutting SuperBlend quite a bit in places. Leaned towards
some of the colder guidance numbers, but there are some out there
that are even colder yet. Something to monitor into the evening
hours as lows may need to be adjusted.

Heading into tomorrow, temps at 925/850 mb really do not rise much,
only a couple degrees. But again, there is very little mixing over a
deep snow field. Fear the same situation will occur again tomorrow,
with highs falling short of forecast. Have therefore dropped lows a
handful of degrees once again, but feel it may not even be enough in
places, particularly over north central SD where snow is the
deepest. As is the case in these situations though, it takes a day
or two to get a feel for how temperatures respond to "warming
trends" and to figure out just how much the snowpack affects
readings in certain areas.

Of course, the other story is the storm system moving across the
Plains on Monday. Models continue to keep the system mainly south of
the CWA, with just the northern fringe affecting the CWA border area
with FSD. Increased POPs a bit along the borders with FSD and MPX,
mainly for collab purposes. BUFKIT soundings still show a threat for
freezing rain for a couple hours late Sunday night into Monday
morning. Snow and ice amounts continue to be forecast on the low
side due to the brunt of the system remaining south of the area.

.LONG TERM...(Tuesday through Saturday)
Issued at 344 PM CST Sat Jan 14 2017

Once the Mon/Tues system departs, an upper level ridge builds across
the region. While a warm-up is certain, just how much is still up
for debate. Superblend warms high temps into the upper 30s and lower
40s across the CWA. Persistent/deep snowpack has proven a
formidable cooling influence over recent days however, and these
values could be overdone. Something to keep an eye on a little
further down the road. Regardless above average temperatures will
likely last through the weekend, and at least some snow melt
should occur.

The ridge begins to break down as a broad trough begins advancing
from the west. A couple pieces of energy eject northeastward from
its base, the first of which impacts the area by Friday morning.
POPs have been introduced from this time in the form of mainly snow
through the end of the period Saturday afternoon. Will need more
time for models to hone in before confidence can increase on exact
timing and placement of this precipitation.


.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 512 PM CST Sat Jan 14 2017

VFR conditions are expected through the period.




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