Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 131721

Area Forecast Discussion
National Weather Service Sioux Falls SD
1221 PM CDT Wed Sep 13 2017

.SHORT TERM...(Today and Tonight)
Issued at 321 AM CDT Wed Sep 13 2017

Weak shortwave pivoting southeast across central SD and northern NE
may continue to produce occasional showers or sprinkles through
daybreak.  This wave is running into an increasingly dry airmass the
further SE it travels, so really only expecting a cloud cover impact
into mid-morning. A bit of patchy fog is anticipated to remain
focused over NW Iowa and MN. This fog appears to be relatively thin
as satellite tools have yet to pick it up yet. Would anticipate a
fairly quick dissipation after sunrise.

Otherwise, Wednesday continues to look dry and seasonally warm.
Southwesterly flow at the surface and aloft, combined with a
seasonally warm thermal ridge should result in temperatures 10 or
more degrees above normal in many areas. Lower 90s are likely in
central SD with highs in the middle and upper 80s further east
towards MN/IA.

Model guidance hinting at decent instability buildup by the
afternoon hours, but soundings again showing capping inversion and
general lack of forcing which should prohibit diurnal based
convection over the CWA.

Slightly better opportunity for showers and a few thunderstorms moves
in around or after midnight as a subtle 700 mb wave moves into the
Dakotas. This convection should be able to sustain itself a bit
better, given stronger forcing from the LLJ. Nevertheless, it will
again struggle to move east of the James River valley with such dry
air lingering in the area.

.LONG TERM...(Thursday through Tuesday)
Issued at 321 AM CDT Wed Sep 13 2017

Warm & breezy conditions are expected on Thursday and Friday ahead
of a developing trough across the western US.  The strong southerly
flow is expected to push 925 hpa temps into the upper 20s, which
would result in highs in the upper 80s to lower 90. Raised highs and
winds over the blend on both days.

Series of waves associated with the upper trough begin to lift from
southwest to northeast across the region on Friday night into
Saturday creating the potential for showers and storms. Near the
surface, a convectively driven front will move across the region
Friday night into Saturday.  With CAPE values in the 1-2K range and
0-6 bulk shear of 30-40 knots could see a few severe storms
producing large hail and damaging winds.

Cooler air works into the region behind the front on Saturday and
continues into Sunday.

Warmer air quickly returns early next week and continues through the
better portion of the week. There are a few upper level disturbances
that move through the area resulting in the potential for showers
and thunderstorms, but should be more sporadic than Friday night-


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1212 PM CDT Wed Sep 13 2017

A few isolated high based sprinkles or light rain showers continue
to move through the area and may linger around KSUX over the next
few hours, but shouldn`t have much of an impact. Ceilings are
expected to remain VFR at all TAF sites. Another small chance of
showers or thunderstorms exists later tonight, largely west of the
James River.




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