Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 212346 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
646 PM CDT SUN AUG 21 2016

Issued at 646 PM CDT SUN AUG 21 2016

00z aviation discussion updated below.


.SHORT TERM...(This Evening through Tuesday Afternoon)
Issued at 252 PM CDT SUN AUG 21 2016

Surface high pressure continues to slide south and east this
afternoon and a dry southwesterly flow and warm air advection
pattern has returned to the region. This dry air will persist into
Monday as well and fire weather becomes the main concern. 850 MB
temp/dewpoint spreads across the southwest CWA will be in excess of
20 degrees. The current forecast MinRH for this area bottoms out in
the low 20s...perhaps dropping into the teens. Didn`t adjust the
high temperature forecast much from previous forecasts either, still
maintaining highs near or at 100 degrees. The surface low will
approach from the west during the afternoon hours, tightening up the
pressure gradient, especially across the eastern CWA. Winds are a
little more difficult to forecast across the western CWA however,
since they may slacken as the center of surface low approaches.
Winds across the eastern CWA will be gusty through the day. So
probably bordering on Red Flag criteria for fire weather zones 267
and 270. No headlines out at this point, but something to consider
with subsequent updates.

The surface low and associated cold front continue to track east on
Tuesday. Meanwhile the upper level low skirts the MT/international
border area, allowing more of a southwest flow over SD. A pretty
significant wave of energy tracks up from the southwest and will
provide forcing for thunderstorm initiation Tuesday afternoon/night.
Big question will be timing of storms and how far west they will
develop. The ECMWF/NAM have trended slightly further to the west
with the surface trough/instability axis, whereas the GFS remains
slightly faster/further east. As with any north/south oriented cold
front type event, the best bulk shear will lag behind the front,
however models still show up to 20 kts of 0-6km shear across the
eastern CWA by 00z. SPC has placed us in a marginal risk for now.

.LONG TERM...(Tuesday Evening through Sunday)
Issued at 252 PM CDT SUN AUG 21 2016

An upper trough will linger over the region until Saturday when
temps will begin the climb back close to average. Temps will rebound
to above average (highs in the 80s) on Sunday as upper ridging
builds in.

Sfc high pressure will keep the region dry on Wed and Thu. However,
as one high exits on Thursday night, some shortwave energy will ride
through the trough. Coupled with what could be the nose of a llj
nudging into the southwestern cwa, the potential for showers and
thunderstorms comes back into the forecast. Southerly flow ahead of
an approaching sfc low will return moisture to the region on Friday,
keeping chance pops in the forecast through Saturday. As the sfc low
then moves over the plains, there will be off and on precip chances
into Sunday.


.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 646 PM CDT SUN AUG 21 2016

Vfr conditions are expected at all locations through tonight and
Monday. As the sun sets and the inversion forms this evening,
some llws is expected at pir, aty, and abr for a time tonight.


.ABR Watches/Warnings/Advisories...


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