Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 311128
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
628 AM CDT WED AUG 31 2016

.SHORT TERM...(Today and Tonight)
Issued at 318 AM CDT Wed Aug 31 2016

Band of ACCAS developing in very weak warm advection/mid-level
isentropic lift near the James River Valley early this morning. As
of 08Z, a couple of spotty showers have developed as far south as
Highway 14, but general trend is for lift in this region to weaken
and/or shift a little to the west through the pre-dawn hours, so
have not carried any precip chance beyond 12Z for now. Will monitor
closely though, and update if needed. Also watching some patchy fog
in our southern areas, from the Missouri River Valley into northwest
Iowa. Will likely see brief periods of dense fog, but do not expect
it to become widespread enough to warrant any advisories at this
time.

Beyond these early morning concerns, anticipate quiet/comfortable
conditions through the next 24 hours as surface and upper level
ridges linger over the region. Temperatures should be near to just
above normal for this last day of August, with highs from the upper
70s around the Buffalo Ridge/Iowa Great Lakes, to the mid 80s near
and west of the James River. Lows tonight should drop back into the
50s and some models again hinting at some fog potential, primarily
in northwest Iowa/southwest Minnesota. However, confidence in this
is low and will leave out for now.

.LONG TERM...(Thursday through Tuesday)
Issued at 318 AM CDT Wed Aug 31 2016

An upper level ridge swings across the region for Thursday and
Friday. It will be comfortable both days with dew points in the 50s
and highs in the mid/upper 70s east of I-29 to lower/mid 80s west.
With a tightening gradient and winds at the top of the mixed layer
running around 30 to 35 kts, it looks to be windy from the I-29
corridor westward on Friday afternoon.

Saturday will be a transition day to a much more active pattern as
the upper level ridge moves off to the east and a western CONUS
trough shifts slightly eastward - putting our area in a
southwesterly upper level flow. Still looking at highs mid 70s to
mid 80s, and could see some thunderstorm development in our west by
afternoon with increasing theta e advection and instability. It will
again be windy, and with increasing low level moisture it will be a
bit more humid as afternoon dew points rise into the lower to mid
60s.

For the remainder of the extended, it looks to be an unsettled
period as a frontal boundary becomes nearly stationary across our
area for Sunday through Wednesday, and a series of shortwaves eject
northeastward out of the western CONUS trough. This will bring
decent shower and thunderstorm chances to the area through the
period. With that, temperatures will begin to trend downward with
the clouds and precipitation, as highs in the 70s become dominant by
Tuesday and Wednesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 627 AM CDT Wed Aug 31 2016

Areas IFR-LIFR visibility in fog from KYKN into parts of northwest
Iowa to start the period should quickly improve to VFR by 14Z-15Z.
Some models pointing to redevelopment of fog late in TAF period,
again from near KSUX into parts of northwest IA/southwest MN, but
confidence too low to include in forecast at this time.

Could also see an isolated SHRA/TSRA in far northwest corner of
the forecast area near KHON, but this also expected to diminish by
mid morning. Thereafter, VFR conditions and light winds can be
expected into tonight.

&&

.FSD Watches/Warnings/Advisories...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...JH
LONG TERM...JM
AVIATION...JH



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