Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 270933

Area Forecast Discussion
National Weather Service Sioux Falls SD
333 AM CST Sun Nov 27 2016

.SHORT TERM...(Today and Tonight)
Issued at 331 AM CST Sun Nov 27 2016

First issue in the short term is dense fog, particularly over
southwest MN. Have issued a dense fog advisory for southwest MN and
then Minnehaha county until 9 am.  Calls to county sheriff offices
in southwest MN, souteast SD and into northwest Iowa found that the
extent of widespread dense fog was mostly confined to southwest MN
and into the Sioux Falls area so have confined the advisory for
those areas where more widespread dense fog was confirmed.
Calm/light wind, clear skies and available low level moisture have
allowed visibility to drop to 1/4 mile or less in the advisory
area. Expect that as the sun comes up and wind picks up,
visibility will improve. Hi res models also show a break in low
visibility between fog this morning and onset of rain this

Next issue in the short term is timing of onset of rain.  Shortwave
coming out of southern California will combine with a PacNW low and
help push a band of showers into the area from southwest to
northeast this afternoon.  Models are in pretty good agreement on
timing of rain starting and keeping rain in all day long.  Model
soundings do show a thin area of CAPE later this afternoon
and evening so have kept in isolated thunder.

As the short wave digs deeper and becomes more of a long trough, a
surface low develops and squeezes up against high pressure over the
southeast US, which will strengthen the gradient over the plains,
resulting in increased wind this afternoon.  As the surface low
moves northeast then more north from NE into ND expect rain and
gusty wind to continue into tonight, then start tapering off from
south to north after midnight.

Colder air on the back side of the low may cause rain to mix with
some snow in whatever precip is left by dawn on Monday morning.

Temps today will be above normal again with highs in the mid 40`s to
low 50`s.

.LONG TERM...(Monday through Saturday)
Issued at 331 AM CST Sun Nov 27 2016

The Monday through Wednesday time will be marked by the upper low
meandering from eastern ND and northeastern SD into MN. A moderate
low level flow will gradually veer from southwesterly to
northwesterly and bring general cooling. Weak waves circulating
around the low will enhance lift and bring areas of light rain and
snow. Models agree on timing of the greatest light precipitation
coverage being Tuesday and Tuesday night, with most precipitation
north of Interstate 90. Warm advection and a weak TROWAL pattern
will have pulled just north of the area by the start of Monday, and
should stay north and northeast of HON/BKX/MML. Precipitation will
slowly decrease Wednesday as the low begins to drift east.

The overall cooling will slowly cause a swing in the mixed
precipitation from rain to snow being the dominant type. Diurnal
temperature patterns will cause rain/snow swings from day to night
within the overall cooling pattern. Greater nocturnal snow ratios
will cause most of the light accumulations to be at night. Even
then, nobody should get as much as an inch in any 12 hour period.

Slow low level cooling and resulting mixing should keep the
strongest winds over the Chamberlain to Pickstown part of the
Missouri River area Monday and Tuesday. Northwest winds Wednesday
will be marginally breezy over the area. The cooling will take high
temperatures down from mostly 40s Monday to the lower and middle 30s
by Wednesday. Diurnal temperature variation will be small, with lows
cooling only to the 20s.

As the upper low moves further east of the area Thursday and Friday,
the weather will be mainly dry, but a lingering weak upper trough
may provide lift and moisture for a little light snow to linger in
southwest MN. Ridging should bring dry weather everywhere Saturday.
Clouds, which will be plentiful this week, may start to decrease
Saturday. High temperatures are expected to remain in the lower to
middle 30s Thursday through Saturday, or close to normal for the
start of December.


.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.


SD...Dense Fog Advisory until 9 AM CST this morning for SDZ062.

MN...Dense Fog Advisory until 9 AM CST this morning for MNZ071-072-



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