Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 152317 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
617 PM CDT Tue Aug 15 2017

.SHORT TERM...(This Evening through Wednesday Afternoon)
Issued at 334 PM CDT Tue Aug 15 2017

A large 500mb trough was set up across the western half of the
nation, with a ridge across MN and down through IL, leaving us in
southwesterly flow aloft. An initial embedded trough currently over
western WY will swing over western SD Wednesday morning, and exit
across the eastern half of the state through the afternoon hours.

We are currently stuck between exiting high pressure across
the Great Lakes region, and low pressure nearing from western SD/NE.
The sfc low will slowly shift from far southwestern SD and western
NE this afternoon to eastern SD by the end of the day Wednesday. The
Canadian was the quickest with the eastward progression, over west
central MN by 15Z Wednesday, while the consensus is to keep it
across the eastern SD until at least 18Z. Will generally go with a
non-Canadian solution as it overdid the initial showers from Redfield
and east this morning. Storms in NE are also having an impact,
limiting the northward extent to additional showers to southeastern
SD. Also the line of showers/storms from MBG to PIR are not well
done in most models, as they are much slower to progress

Another round of fog is expected tonight, especially east of a line
from Redfield to Aberdeen around daybreak. Slowed down the exit of
showers and thunderstorms by a couple of hours Wednesday, and will
need to see if this trend continues, allowing for additional rounds
of moderate rain to fall across our southeastern counties. Have the
best chance of 0.25-0.50in or greater over our eastern 3 tiers of
counties 06-09Z Monday.

.LONG TERM...(Wednesday Evening through Tuesday)
Issued at 334 PM CDT Tue Aug 15 2017

The models show very good agreement during the long term period from
Wednesday night through Tuesday. One short wave trough will be
leaving the far eastern part of the CWA Wednesday evening taking any
leftover showers/storms with it. Surface high pressure will build in
behind it bringing a short dry period before the next well agreed
upon short wave trough/surface front move through Thursday night and
Friday bringing chances of showers/storms. The models then all show
a large upper level low pressure area/trough moving into western
Canada and across central Canada from Friday night through Monday.
This will push a Canadian frontal boundary slowly across our region
from Saturday night through Sunday night. At this time, have in
chances of showers/storms in for Sunday night. The models vary some
on this timing and thus may have to adjust the weather and pops some
later on.

As for temperatures, Thursday and Friday are expected to be near
normal across the cwa in the upper 70s to the mid 80s. Warm south
winds for most of Saturday and Sunday, depending on the speed of the
cool front, will bring temperatures to slightly above normal in the
80s and lower 90s. These may be bumped up some in later forecasts.
Monday and Tuesday will cool down a bit with Canadian high pressure
pushing in with temperatures near to slightly below normal. At this
time with the frontal zone expected to be south of our region,
Monday and Tuesday look to be mostly dry at this point.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 616 PM CDT Tue Aug 15 2017

The current vfr conditions across the region should gradually
transition to mvfr/ifr cigs overnight as rain become more
widespread. Occasional mvfr vsbys are also possible due to late
fog. Vsbys could become ifr for brief periods of time during any




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