Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 262135
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
335 PM CST Sat Nov 26 2016

.SHORT TERM...(This Evening through Sunday)
Issued at 328 PM CST Sat Nov 26 2016

We will see the breakdown of the 500mb ridge overnight into early
Sunday as the large Pacific Coast trough moves east and stretches
from Alberta down through eastern WY and the 4-corners region by
late Sunday.

The weak pressure gradient overhead, and very light winds will be on
the way out as low pressure becomes better organized by daybreak
Sunday. In the meantime, fog over much of central MN will be
nearing our eastern counties, and may remain in place through the
overnight hours. Expect the low to be set up from MT through eastern
CO at 12Z Sunday and shift over the southern SD border by the end of
the day. Expect 6 hour pressure falls of 4-6mb Sunday afternoon.
Precipitation will edge northward, and mainly impact our central and
eastern counties shortly after 18Z as southerly low level winds
increase. 850mb winds get up to 30-35kts Sunday afternoon. Did not
put a lot of weight into the 12Z NAM qpf, wrapping more into our
western counties. Kept the higher precip over our south and east for
now. Did keep the potential for thunder over the southeastern cwa
as MUCAPE values peak in that region.

.LONG TERM...(Sunday night through Saturday)
Issued at 328 PM CST Sat Nov 26 2016

Not a lot of change now in the deterministic solutions regarding
this early week anomalously deep surface low/large upper system.
GFS/ECMWF/Canadian 12Z runs have all converged on an upper low track
through South Dakota into southeast North Dakota on Monday where it
stops and spins for appx 24 hours before shifting south and east out
of the region Tuesday/Tuesday night.

700-500hpa layer rh disappears for a time across the eastern
forecast zones after 06Z Monday, so lowered ForecastBuilder qpf
amounts some across the eastern zones Monday morning. There`s still
some smallish CAPE showing up in the BUFKIT output at
KABR/KATY/KAQP, so continued with the thunder mention across the
southeastern zones Sunday night. Highest pops continue to be focused
across the western half of the CWA, where either snow or a rain/snow
mix is expected to persist for much of the Monday through Tuesday
forecast period.

StormTotalprecipitation continues to be appx 0.25 to 0.75inches less
than national guidance qpf, but hopefully as this event continues to
draw closer, ForecastBuilder and the addition of CAM output can fine
tune these amounts. Likewise, given how warm it is in the boundary
layer, despite low level caa ramping up late Sunday night into
Monday morning, and how low the snow-ratios are on Monday (less than
10:1), StormTotalSnow remains less than 6 inches across portions of
north central/northeast South Dakota with the highest amounts
currently nestled between the MO River and the James River. Still
looks windy across central South Dakota Monday through Tuesday where
falling snow is expected to be occurring.

After one final vort-max rotates all the way around the upper low
and sweeps south-southeastward through the Red River valley on
Wednesday, precipitation chances pretty much dry up for the rest of
the week as surface high pressure sits down over the region. There
may be another upper wave starting to enter the northern plains
region from the northwest by Saturday, but for now will leave
Saturday dry.

Like yesterday, 925hpa temperatures do not fluctuate wildly during
the period, but the coldest air appears to be set up over the CWA by
Wednesday evening and remains over the region through Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1136 AM CST Sat Nov 26 2016

VFR ceilings and vis will remain through the day today. Patchy
fog will be possible tonight, mainly over our east for ABR and ATY
where the light winds remain. Rain will be approaching from the
south Sunday, by stay mainly south of the TAF sites through 18Z.

&&

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

$$

SHORT TERM...KF
LONG TERM...Dorn
AVIATION...KF



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