Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 161406

Area Forecast Discussion
National Weather Service Aberdeen SD
906 AM CDT Sat Sep 16 2017

Issued at 858 AM CDT Sat Sep 16 2017

Just minor updates to pops/TAFs to fine tune the forecast. Area
of rain extends along a line from KMBG to KATY. While it continues
to move northeast, we are seeing some weakening. As the previous
forecaster mentioned - not much instability over our area - so
removed mention of thunder for locations west of the western half
of the Coteau. Still, there are a few weak convective elements
near KATY and KMHE so will continue mention of thunder for the
eastern Coteau and Minnesota counties. As for temps, its a tough
call as stratus covers most of the region. Decided on lowering
highs just a few degrees though I do realize that any sunshine
this time of year will easily cause temps to jump. Guidance
suggest the most likely areas that won`t break out are the James
valley and our northern tier counties.


.SHORT TERM...(Today through Monday Afternoon)
Issued at 405 AM CDT Sat Sep 16 2017

Continue to watch the next approaching upper level wave which is
moving northeast out of NE and into SD. Large area of showers and
thunderstorms associated with this wave across western NE and now
moving northward through south central and southwest SD. With
limited instability over our region, much of the thunderstorm
activity over NE has diminish to plain light to moderate rain as it
moves into SD, with just an occasional lightning strike. Re-adjusted
POPs to better match current situation and expected trends over the
next several hours. Again, it seems the CONSSHORT/HRRR/ECAM flavor
of POPs has a decent handle on the situation so closely followed
them for today`s forecast. Limited instability today so just
expecting showers with embedded thundershowers, but any threat for
strong to severe storms will be well east of the area.

Cold air advection continues today, and with clouds remaining in
place, do not expect temps to rise that much. In fact, have shaved a
few degrees off the previous forecast, which now keeps the CWA in
the mid to upper 50s for today.

For tonight, system exits the area as surface high pressure begins
building in. Models suggest the clouds will clear out as well,
especially for the southern half of SD - something to watch though
because cloud cover will have a huge impact on lows tonight. Winds
do become light tonight, mainly along and west of the James River -
especially over central SD where the high center will reside. Feel
slightly higher elevations will keep a slight breeze overnight,
which will prevent a total free-fall in temps. But, valleys
certainly can tank if skies clear. Dropped lows a few degrees from
previous forecast and now have plenty of mid and upper 30s showing
up across central SD eastward into the James valley. Did insert some
patchy frost across central SD where winds are expected to be
lightest under the high center.

Sunday will be a quiet day with the dry and stable surface high
still largely in control. Highs will rebound into the 60s. As we
head into Monday, the surface high moves east and we will get back
into warm and moist southerly flow. Temps will warm back into the
70s and 80s. A weak mid-level impulse moves east across the Dakotas
as well and models indicate the possibility for a few showers and
thunderstorms with its passage.

.LONG TERM...(Monday Evening through Friday)
Issued at 405 AM CDT Sat Sep 16 2017

An active pattern is in store for the extended period. Models have
not had much run to run consistency on timing of precip in the out
periods. But, the general trend is for temperatures at or above
normal with a few systems bringing chances for precip.

A frontal system will move through the Dakotas on Tuesday bringing
the first round of showers and thunderstorms. The upper trough will
follow and usher in slightly cooler air (highs in the 70s) for the
remainder of the week. Shortwave energy will eject out of a deep
longwave trough starting on Thursday night. These waves will bring
off and on chances for showers that will intensify as another sfc
front moves through Friday.


.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 627 AM CDT Sat Sep 16 2017

A mix of MVFR and IFR cigs this morning will gradually improve to
VFR this afternoon in the west and this evening in the east. Rain
showers will move over the region this morning. Vsby may fall to
MVFR in heavier showers.




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