Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 140351

Area Forecast Discussion
National Weather Service Sioux Falls SD
1051 PM CDT Thu Oct 13 2016

.SHORT TERM...(This evening through Friday)
Issued at 300 PM CDT Thu Oct 13 2016

The primary forecast  concerns are the winds tonight and then the
potential fire weather impacts tomorrow.

Overnight tonight all models show a strong low level jet developing
across the area. This will keep winds around 10 kts in most
locations tonight which will help keep lows in the lower to middle
40s. The exception will be east of the Buffalo Ridge in southwest
Minnesota. With an inversion setting up overnight, hi-res models,
especially the WRF-ARW, are showing strong winds east of the ridge
axis in parts of Lincoln, Lyon and Cottonwood counties in
southwestern Minnesota. Have winds gusting to 30 mph overnight and
35 mph early Friday morning.

On Friday, with southwesterly flow, the atmosphere will be well-
mixed. The GFS and ECMWF were favored showing a more well-mixed
atmosphere than the NAM.  Temperatures look to rise well into the
80s around Chamberlain and to 80 degrees as far east as the James
River...with 70s in most other areas in southeast South Dakota,
southwest Minnesota and northwest Iowa. Winds will pick up to 20 to
30 mph east of the James River with gusts approaching 40 mph around
the Buffalo ridge in the afternoon.

One concern tomorrow afternoon will be fire weather potential. At
this point, winds look light enough that really dry air aloft is not
expected to mix down and this will keep the afternoon relative
humidity around 25%. However, if mixing is more efficient and dew
points fall to around 40 instead of staying the mid 40s, then the
relative humidity could be at or even below 20%.

.LONG TERM...(Friday night through Thursday)
Issued at 300 PM CDT Thu Oct 13 2016

The weekend will see quite a bit of dense high and some middle cloud
cover in a developing rapid west southwesterly upper flow with
Pacific moisture coming quickly across. Moisture levels generally
look insufficient for any precipitation with weak short waves coming
across, though an area of mid level moisture brushing the northern
edge of the area, from Huron to Brookings to Marshall, may be enough
to generate a few light showers about Sunday, so will mention with
minimal pops. A bigger problem is a fetch of low level moisture and
potential stratus spreading across northwest Iowa Friday night into
Saturday. The NAM suite seems to overdo this potential as usual,
though even the GFS brings some across the corner. After
coordination will mention some patchy drizzle late friday night and
a slight chance of showers Saturday, the latter possibly being
drizzle again, or it could indeed be low topped light rain from the
lower clouds. With the low level flow remaining southerly or south
southwesterly, it seems possible that most of the stratus could
stay southeast of our area.

Temperatures will certainly be mild, with lows close to 60 Friday
night and around 50 saturday night, and highs up into the 70s. How
far into the 70s will depend on the thickness of the cloud cover.

Stiff southerly winds will slowly decrease from the west Friday
night, but will still be somewhat strong part of the night int he
east. This will be especially true northeast along the Buffalo Ridge
area, where a nocturnal LLJ will keep winds up longer. At least, for
now, we will not of course have any snow cover to bring blowing snow
concerns, as we will likely have a few times with this type of
pattern during the coming winter. Winds will continue to fade
Saturday as a weak surface trough brings a shift to northwesterly.
This will aid in clearing stratus out of northwest Iowa, if it is
there. A steady but modest southeasterly breeze looks to develop for

Monday through Thursday look to bring mild temperatures then a
cooling trend, as a broad Pacific trough forces its way east. A
strong southern plains upper ridge will limit amplitude, and, for
now, the shower potential, mainly with the first wave and cold front
Monday and Monday night, looks low enough to keep out mention. A
little more amplitude than forecast could change that a little, but
in such a rapidly progressing pattern, timing difficulties present
problems trying to pin down spotty light precipitation, at least
unless the potential becomes greater. Meanwhile, the cooling trend
looks to bring down daytime highs modestly to mid 50s to lower 60s
by Thursday, not far from normal.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1044 PM CDT Thu Oct 13 2016

VFR will prevail for the rest of tonight and Friday. During Friday
evening, MVFR stratus will begin to nudge in from the southeast
first into the Storm Lake Iowa area, then likely lower through the
evening into possibly the upper end IFR category as it moves
northwestward. At this time, it looks like the NAM model is a bit
aggressive in bringing the stratus northward compared to other
models. Therefore left it out of the KFSD TAF site Friday evening.
However, there is a chance that the stratus could get into KSUX
very late in the 06Z TAF period. Therefore hedged and included an
MVFR group for KSUX late evening Friday. Concerning winds, the
surface winds will likely be too strong tonight and Friday to
warrant the mention of any non convective low level wind shear.




SHORT TERM...Schumacher
AVIATION...MJ is the U.S. government's official web portal to all federal, state and local government web resources and services.