Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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274
FXUS63 KFSD 300812
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
312 AM CDT Fri Sep 30 2016

.SHORT TERM...(Today and Tonight)
Issued at 310 AM CDT Fri Sep 30 2016

In the current upper flow, there will be no real mid level moisture
or lift affecting the area through tonight, so measurable rain
chances are basically zero. A few high clouds may spill over the
upper ridge west of the James River, but today should be basically
sunny with little in the way of cumulus development seen on the
various model BUFKIT soundings after the very shallow early morning
fog is heated out. Temperatures still look to reach 70 or a tad
warmer today.

The low level moisture is shown on all model solutions spreading
from the east at least to the Interstate 29 area during the coming
night. This looks to make skies pretty cloudy over southwest MN and
northwest IA by the end of the night. Current expectations after
coordination are for saturation not to be low enough to produce
significant fog with the stratus and will not include. It is more
tempting to add a mention west of the stratus along the James River
Valley from Huron to Mitchell to Yankton. However, reduction in
visibility in the increasing southeasterly surface flow without fog
advecting west from the stratus area appears to be weak enough to
keep mention out of the public grids and forecast for now.

The stratus could conceivably be deep enough, given projected model
soundings, to yield some patchy drizzle in southwest MN and
northwest IA but the depth is marginal and will not include for now.
Low temperatures tonight will be in the upper 40s west to the lower
50s east.


.LONG TERM...(Saturday through Thursday)
Issued at 310 AM CDT Fri Sep 30 2016

Early morning stratus on Saturday will take quite awhile to clear,
and could potentially have an impact on temperatures in areas east
of the Interstate 29 corridor.  However, by mid-afternoon there
should be enough sun to see temperatures climb either side of 70
degrees.

With a large upper trough digging into the Southwestern CONUs, mid-
lvl ridging will sharpen considerably by Sunday, and surface winds
will turn southerly by daybreak.  Temperatures will respond nicely
to the increase in southerly flow, with highs in the 70s likely.
It may turn quite breezy by Sunday afternoon however, the only fly
in the ointment for an otherwise nice Fall weekend.

As we begin next week, the upper level pattern will break down
allowing the large upper trough over the Western US to pivot
eastward. Deep moisture advection will begin in earnest on Monday,
with showers and thunderstorms within nearly meridional flow focused
over the Central and Western Dakotas on Monday.  This linear band of
rain will slowly crawl eastward on Tuesday, with the most
concentrated period of rain over the CWA from 00Z Wed through 12Z
Wednesday.

While there remains some model differences, a large dry slot will
lift northward into the CWA by Wednesday morning, and should spell a
brief period of dry weather for the first half of the day. Depending
on the track of the upper low, scattered showers or drizzle may
again rotate into the area for Wednesday night. This remains very
uncertain at this time.

Of higher confidence is lowering temperatures a few degrees from
populated guidance on Wednesday, Thursday and Friday.  Most areas
will find themselves in the lower 60s.


&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1044 PM CDT Thu Sep 29 2016

After perusing over the 00Z NAM model data, it still appears the
main thing to watch for is late night and early morning areas of
fog. With an easterly fetch of air tonight, the most organized fog
still looks to be along the upslope side of the Buffalo Ridge in
southwest MN. However, certainly cannot rule out patchy low lying
fog at KHON, KFSD, KSUX, especially since these sites reside at or
near rivers. If the airports receive shallow fog, short term
conditions could be worse then what is reflected in the TAFs.
However due to the nature of shallow radiational fog, it is quite
unpredictable in how long it will last or how much area it will
cover. Therefore do not want to convey any IFR or LIFR conditions
at this time.


&&

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

$$

SHORT TERM...
LONG TERM...Dux
AVIATION...MJ



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