Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 270454

Area Forecast Discussion
National Weather Service Sioux Falls SD
1054 PM CST Sat Nov 26 2016

.SHORT TERM...(This evening through Sunday)
Issued at 254 PM CST Sat Nov 26 2016

Very light flow across the area will continue through the early
evening hours.  Easterly flow will develop and strengthen towards
06Z. Nam, RAP and HRRR all show low level saturation developing, and
the potential of fog along and east of the James.  GFS is much drier
in the low levels, and fails to saturate.  Cross over temperature is
in the mid and upper 30s across the region, and with forecasted lows
in the upper 20s and lower 30s, the technique would suggest fog
potential, so have discounted GFS. HRRR and RAP to an extent have
delayed the onset of fog through the afternoon, but still are
forecasting widespread dense fog by early Sunday morning.  If this
occurs, will be difficult to get rid of the stratus tomorrow morning
as easterly flow strengthens and moisture flux increases ahead of an
approaching wave from the southwest.

As the initial wave of the upper trough lifts northeast through the
area, expect a band of showers to lift from the southwest to the
northeast.  A minor amount of CAPE exists along and east of the
James River, so could see a lightning strike or two. High
temperatures in the east could be held down some on Sunday by
lingering fog and stratus and by shower activity in the afternoon.

.LONG TERM...(Sunday night through Saturday)
Issued at 254 PM CST Sat Nov 26 2016

The cold front aloft swings north quickly on Sunday night and still
indications for enough instability that we could here a few rumbles
of thunder. The dry slot races north through the evening which
should shut down precipitation coverage and may introduce a little
drizzle. Lowest levels not saturated enough to introduce but
something that may need to be added. Overall should be pretty much
rain with some small threat for light snow along and west of the
James River Valley.

Monday will be mild as westerly flow develops, and this will
actually be the pattern that develops through mid week. The only
difference will be a very gradually shift to a more northwesterly
flow and slightly cooler low level air building in. But overall
Monday through Wednesday will see breezy west to northwest winds,
temperatures in the 30s, a little warmer Monday, and scattered
showers with the cold pocket aloft. On monday a few of these showers
will likely remain rain showers, but Monday night into Wednesday
evening the most likely precipitation type will be snow as the warm
layer is very shallow.

Thursday through Saturday looks dry with a sustained chilly period.
Northwest winds will diminish through this period but highs will
remain in the 30s with lows in the 20s.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1047 PM CST Sat Nov 26 2016

Areas of fog will continue to expand across the area through the
next few hours, with the best potential to the east of the James
River. Locally dense fog will be possible, especially across
southwest MN into east central SD, but not enough confidence to go
lower than 2SM at TAF sites. Will need to monitor for development.
Expect low ceilings to become more widespread beginning late
tonight into midday Sunday, as the next system lifts northward
into the region. Do not expect much ceiling improvement Sunday
morning. As the rain showers become more widespread midday Sunday,
expect lower visibility and ceilings to become widespread MVFR to
IFR. Some isolated thunder will also be possible mainly in the
afternoon Sunday, but coverage is too low for mention in the TAF.




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