Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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446
FXUS63 KFSD 230825
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
325 AM CDT FRI SEP 23 2016

.SHORT TERM...(Today and Tonight)
Issued at 325 AM CDT Fri Sep 23 2016

Seeing a narrow band of thunderstorms developing from the central
Interstate 90 corridor into northwestern IA very early this morning.
This activity is collocated with midlevel theta e advection and a
instability axis lifting northward through the area. Hi res models
have this activity continuing to lift northward through the mid
morning hours, possibly filling in to the west on the nose of a
developing low level jet situated through central NE. Otherwise,
much of the area is socked in with stratus, though visibilities
remain good overall. While there could be some patchy fog
development through the early morning hours, think it should remain
in check with winds running 10 to 15 mph across the area.

At the present time a surface warm front is located just to the south
of our CWA. This boundary will lift slowly northward through the
day, with thunderstorms and stratus eventually pushing north of our
CWA by mid afternoon. Low level warm air advection behind the front
will result in much above normal temperatures for most of the area
this afternoon, with trickiest temperatures residing in the north,
dependent on how quickly precipitation/clouds clear. At this point,
think that highs will top out in the upper 80s through the Missouri
River corridor, then taper downward to the north and east to mid 70s
through east central SD into portions of southwestern MN where
clouds may hang on. Tonight looks mostly clear during the early part
of the night, with the exception of the Buffalo Ridge area where low
level moisture may linger. It appears to remain fairly breezy
overnight with southeasterly winds of 15 to 20 mph, and it will be a
very mild night with lows in the mid and upper 60s. Later at night a
cold front begins to approach from the west, and could see some
thunderstorm development through south central SD toward 12z on
Saturday.


.LONG TERM...(Saturday through Thursday)
Issued at 325 AM CDT Fri Sep 23 2016

Unsettled weather pattern expected in the mid range as a large upper
level low slowly barrels northeast across the central and northern
Plains Saturday and Sunday. Modest agreement amongst the various
model solutions brings reasonable confidence in the timing.  Frontal
boundary sets up across western South Dakota and Nebraska Saturday
morning. With a tight pressure gradient developing, southerly winds
increase across the forecast area ahead of the front. With plenty of
moisture feeding into the region, scattered showers and storms
across southeast South Dakota will become more numerous by midday
and spread eastward as the front advances Saturday afternoon.
Precipitation tapers off from west to east Saturday evening into
early morning Sunday. With ample cloud cover and ongoing
precipitation early in the day, severe risk looks marginal at best.
Think CAPE values will be pretty low/modest while shear is good. Not
overly excited for severe potential.

Cold air advection arrives late Saturday night into Sunday, with
gusty northwest winds developing by Sunday afternoon. Winds will be
strongest in south central SD where sustained 20 to 30 mph with
gusts to 40 mph are possible. Models also suggest that stratus will
also filter into the region on Sunday and help hold afternoon
temperatures in the 60s.

The slow moving upper low exits the region into the western Great
Lakes on Monday, leaving the northern Plains under cool northwest
flow. While we should see sunshine return on Monday, cooler
temperatures in the 60s persist into Tuesday. Flattened ridging
arrives midweek, ushering in a warming trend. We see some larger
difference pop up between the GFS and ECMWF on Thursday and beyond.
The ECMWF brings a wave through the region on Thursday while the GFS
holds onto the ridge. Followed the blend pops which keeps this time
frame dry for now.


&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1044 PM CDT Thu Sep 22 2016

Main concerns through the TAF period are stratus and potential
fog overnight through Friday morning. Stratus will bring IFR
ceilings to HON, FSD, and SUX with LIFR ceilings possible at HON.
Showers and storms are possible, but low confidence precluded a
mention in the TAF. Conditions will improve following sunrise as
southerly winds clear the region out by early afternoon.


&&

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

$$

SHORT TERM...JM
LONG TERM...
AVIATION...08



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