Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 290340
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1040 PM CDT Wed Sep 28 2016

.SHORT TERM...(This evening through Thursday)
Issued at 300 PM CDT Wed Sep 28 2016

Large upper-level low pressure continues to spin south of the Great
Lakes, wrapping bands of lower clouds westward.  For the most part,
the South Dakota border has been limiting boundary of clouds during
the midday and afternoon hours, with mixing eroding successive
advancements.  With larger scale ridge axis surface and aloft, the
challenge in the short term is primarily with trends in clouds as
easterly component to low-level flow continues to pull moisture
westward toward the area.

Clouds will be somewhat more perishable through the close of the
afternoon and early evening, but renewed development/push to lower
clouds likely to start up again during the later evening and
overnight. A majority of higher resolution solutions which have
handled clouds decently today indicate stratus coverage will be most
focused in southwest MN and NW IA, and likely to impact temperatures
with lows not as cool as those to the west near the ridge axis.
In proximity to ridge axis, could see a little patchy fog develop
late tonight or very early tomorrow morning, with greatest chance in
the James Valley and northern I-29 corridor, where should see a few
temps dip to the mid to upper 30s overnight.  Would not be shocked
for a couple spots of isolated frost as well.

Ridge will remain nosed in across the area on Thursday. Will again
have to work on eroding/mixing out lower clouds across the eastern
CWA.  Should have mainly sunny to partly cloudy skies by afternoon,
allowing temps to reach mid 60s in parts of southwest Minnesota and
northwest Iowa, to near 70 in south central South Dakota. Overall,
should see less wind, outside where some slightly stronger southeast
return flow initiates in south central SD.

.LONG TERM...(Thursday night through Wednesday)
Issued at 300 PM CDT Wed Sep 28 2016

Not a whole lot going on Friday and Saturday with pleasant weather,
mostly clear to partly cloudy conditions and south to southeast
winds generally around 15 mph or less. Lows will be in the 40s with
highs in the 70s. The only small concern will be a chance for some
patchy fog each morning with the surface ridge axis in place.

In the outer periods (Sunday through Wednesday), Sunday and Monday
will see a strong southerly flow and mild temperatures as low
pressure deepens across the Rockies. This will bring above normal
temperatures, especially overnight lows. Highs will be in the 70s
with lows from the mid 50s to lower 60s. Tuesday into Wednesday
model agreement is marginal. While the models all are hinting at a
deepening trough over the rockies Monday into Tuesday, they diverge
quite a bit on how to eject this energy onto the Plains. Therefore
will continue with chances for showers and thunderstorms Monday into
Wednesday and a gradual cooling without much change to guidance
values.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1037 PM CDT Wed Sep 28 2016

Lower end VFR stratus has cleared out of our forecast area east of
I 29 at this time. However surface dew point depressions are very
small in our far eastern zones east of I 29. So there is a threat
that fog may develop very late tonight and Thursday morning in
those areas. Radiational fog could produce areas of IFR conditions
during that time frame. It appears that the KHON, KFSD and KSUX
TAF sites may be too far west to see a lot of fog. However, at
KHON and KFSD, the dew point depressions are rather small, so
included the mention of at least some possible MVFR fog formation
for a few hours around sunrise Thursday. At KSUX, their air is a
bit drier so did not mention fog at this time.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...Chapman
LONG TERM...08
AVIATION...MJ


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