Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 270854
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
354 AM CDT Sat May 27 2017

.SHORT TERM...(Today and Tonight)
Issued at 354 AM CDT Sat May 27 2017

Mid level trough continues to dig across central North Dakota into
southeast Wyoming early this morning. This feature will track
eastward through the region today and tonight, before exiting into
the upper Mississippi Valley late tonight. Frontogenetic forcing
developing in south central SD into north central Nebraska is
producing a band of light to moderate rain showers, extending south
to a complex of thunderstorms in Kansas. Dry air remains an obstacle
heading north of the Missouri River, with high cloud bases and dry
low levels preventing much of the activity from reaching the surface
near and north of I-90. Models track the band of showers eastward
through the region, through late morning, with more spotty light
showers activity possible behind the main band this afternoon. Will
leave the highest chances for measurable rain near our southern
border/Missouri Valley and into northwest Iowa with the initial band
of rain this morning. Elevated instability is pretty meager and
largely limited to near the Missouri Valley, so will leave only
isolated mention in our far south. Temperatures will be tricky given
cloud cover concerns. Looks like we could get enough clearing or
scattering of clouds in the afternoon to warm into the upper 60s to
lower 70s.

Tonight, clouds will decrease overall behind the departing wave.
Will need to watch the potential for a secondary shortwave to track
through the northern Plains in the evening and early morning hours.
At this point it looks like the better support for precipitation will
remain north of the forecast area, so will leave the forecast dry.
Lows will be in the upper 40s to lower 50s.

.LONG TERM...(Sunday through Friday)
Issued at 354 AM CDT Sat May 27 2017

On Sunday, the area will generally be between the exiting wave from
Saturday night, and next upstream lobe, with the day filled with
larger-scale subsidence forcing. Will be difficult for most of the
day to find more than a few diurnal clouds, with perhaps enough
destabilization to overcome the forcing by very late day around KMML
area. It will be a breezy and seasonably warm day overall, likely
even considered windy in many spots as mixing become fairly
significant with 25 to 30 knots atop the mixed layer. By evening,
the upstream jet streak will swing southeast into eastern SD and
could see a couple of rogue showers and isolated thunderstorms push
into areas north of I-90 during the evening hours before loss to the
diurnal cycle.

Early week conditions will be courtesy of the influence from closed
low over the western Great Lakes along with various impulses on the
merry-go-round through the Northern Plains. While significant
weather will be absent, a couple of items deserve mention.  First,
temperatures will become cooler than normal once again to start the
week, and have hedged temps a bit lower than climatologically
impacted guidance. Northwest winds will also likely be a bit
stronger each day as deep mixing is favored.  With cool temps aloft,
likely to get a few cyclonic core showers on Monday afternoon mainly
in/near southwest MN, but again appears timing of larger scale waves
is a bit off to get an optimal coupling of forcing.  In fact,
potential with the dynamics along with a subtle wave Monday night
that showers linger somewhat into the evening hours compared to
current forecast. Less depth to any ML instability expected Tuesday
afternoon and early evening, so more on way of diurnal clouds but a
lesser chance for showers.

Troughing relaxes across the region a bit for Wednesday with surface
ridge axis drifting eastward across the area.  Dry and a bit milder
in order. All models indicate a continued progression of upper ridge
eastward through the Northern Plains will begin to allow return flow
by later Wednesday night, and encroachment of some lower- to mid-
level moisture along with gradual arrival a better elevated mixed-
layer. For now, main lower-level synoptic boundary looks to remain
well south of the area, with an occasional incursion of elevated
precip threat mainly through the Missouri River valley, especially
around later Thursday or early Friday.  Certainly will be working
toward/above normal by end of the forecast period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1038 PM CDT Fri May 26 2017

VFR conditions expected through the TAF period. Isolated to
scattered showers will develop late tonight and push across the
area on Saturday, though impacts will be minimal.

&&

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

$$

SHORT TERM...
LONG TERM...Chapman
AVIATION...JM


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