384
FXUS63 KFSD 150855
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
255 AM CST Fri Nov 15 2024

.KEY MESSAGES...

- Dense fog through mid-late morning of Friday.

- Dry with above normal temperatures today through Sunday.

- Widespread rain likely Monday afternoon into Tuesday.
  Conditions likely become cold enough for mostly snow Tuesday
  night into Thursday. Better chances for accumulating snow will
  be west of I-29 and north of I-90, but the latest trends are
  going down with any snowfall amounts Wednesday into Thursday.

&&

.DISCUSSION...
Issued at 254 AM CST Fri Nov 15 2024

Fog may be slow to erode this morning as a strong inversion above
the surface does not allow for any mixing of drier air aloft. There
are some indications that in downslope areas the fog is scouring out
which could change things a bit. The moist layer is very shallow
which may allow coverage of dense fog to be a little less than
expected. Increasing southerly flow late this morning into the
afternoon should essentially break up any remaining fog as the
inversion weakens. Even with the increasing southerly flow and
warming in the low levels the model soundings hint at fog potential
again tonight, especially east of I-29. Will be something to watch
as a shorter lived dense fog advisory might be needed there.

Otherwise temperatures will warm a bit today with some limit in the
east as the area waits for fog to dissipate. Expect highs from near
60 in south central SD to 45 to 50 under areas that hold on to fog
the longest. The southerly gradient increases further tonight with
mild temperatures aloft. Could be a night when lows do not fall much
below 45 in some areas, but upstream dew points are still in the 30s
so there will be room to drop if winds diminish at times.

Saturday should prove to be the warmest day for the next several as
southwest flow ahead of the low pressure tracking to the north
across the western Dakotas brings a mild mixing environment. Expect
highs mainly in the 50s with a few lower 60s near and south of I-90.

The wave moves by to the northeast and leaves the area in mild
westerly flow. While not as warm as Saturday, most locations should
top out in the 50s, or at least upper 40s.

Monday will see a rapid increase in cloud cover as a strong wave to
the south lifts north. By afternoon some rain will begin to develop
and by Monday night most locations will see rainfall. Latest EC
Ensemble showing a 100 percent chance for a half an inch or more
near and east of I-29 with a 60-70 percent chance for an inch or
more in the same area. The GEFS is a little farther east with these
higher probabilities but only running about 20 percent less than the
EC Ensemble output.

Tuesday will likely see rainfall lift quickly north with only a very
small chance for any of the rain to change to snow. Highs Tuesday
should mostly be in the lower to mid 40s.

Models still trying to come to grips with the energy mid week. The
latest GEFS and GFS wrap up the low well to the east, which would
not allow a trowal to develop and wrap moisture back into the area
Tuesday night into Wednesday. Thus the latest GEFS only showing
about a 10 percent chance for 1 inch or more of snow close to
highway 14.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1024 PM CST Thu Nov 14 2024

Dense fog continues to develop in areas along and east of the
James River valley late this evening. Fog will continue to
overspread the area, lowering visibility near zero at times with
ceilings between 100 and 400 ft AGL.

With a lack of flow and steep inversion overhead, it will be
difficult for fog to mix out on Friday. Thus will keep lower
visibility in most locations through almost mid-day.

VFR conditions eventually return in the afternoon, but areas
along the Buffalo ridge may see lingering stratus in the late
afternoon. If this happens, then a repeat of dense fog formation
could take place over SW Minnesota and NC Iowa after sunset.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until 10 AM CST this morning for SDZ038>040-
     052>056-058>062-065>067.
MN...Dense Fog Advisory until 10 AM CST this morning for MNZ071-072-
     080-081-089-090-097-098.
IA...Dense Fog Advisory until 10 AM CST this morning for IAZ001>003-
     012>014-021-022.
NE...None.

&&

$$

UPDATE...Dux
DISCUSSION...08
AVIATION...Dux