sd discuss
Office: FSD
FXUS63 KFSD 201751
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
1151 AM CST Thu Nov 20 2025
.KEY MESSAGES...
- Areas of fog may impact this morning's commute, but general
improvement is expected from northwest to southeast through
mid-morning. Lingering clouds will limit high temperatures to
the 40s for many areas today.
- A warm-up is expected for the weekend, with highs in the 50s
to possibly lower 60s. This would be a good time to wrap up
outdoor winter or holiday preparations.
- Much colder air arrives for the Thanksgiving travel period,
with the chance for below average temperatures increasing by
Tuesday night.
- Low-moderate (20-40%) chances for light rain early next week
(Monday-Tuesday). Some uncertainty in timing/location, but
high confidence that rain will be the dominant precipitation
type.
&&
.UPDATE...
Issued at 1144 AM CST Thu Nov 20 2025
The Dense Fog Advisory will be allowed to expire at the top of
the hour (12 PM CST) as conditions continue to improve.
Visibilities may still be locally down to around one mile for
next hour mainly over Buena Vista County and Ida County, IA.
&&
.DISCUSSION...
Issued at 331 AM CST Thu Nov 20 2025
Light winds and an area of clear skies ahead of a cool front
has led to areas of fog early this morning. While pockets of
dense fog have been observed, a relatively short-lived duration
of lowest visibility along with expected improving conditions
with the passage of the front preclude issuance of a Dense Fog
Advisory. Have issued a Special Weather Statement to highlight
the potential for changing visibility which could linger into
the morning commute for portions of northwest Iowa.
While the lowest stratus currently over the area may thin/clear,
a broad area of somewhat higher stratus is poised upstream and
expect this to sag southeast into the area today. As we have
seen the past couple of days, NBM temperature forecast has been
overly-optimistic in areas of more persistent clouds and have
again trended toward cooler end of guidance for highs today.
Moving into tonight and Friday, a surface ridge will provide
limited mixing. May see areas of fog and/or stratus linger into
the morning. However, models do generally show a thinning of
the low-level moisture, so modest optimism for more sunshine and
will stick closer to NBM high temperatures in the mid 40s-near
50.
The weekend ahead will feature warmer temperatures building
into the northern Plains ahead of a southern stream trough that
may bring chances of rain to parts of the northern Plains early
next week. Saturday should be the warmer day of the weekend and
the better chance to see highs in the 60s for some areas south
of I-90, though both Saturday and Sunday will see temperatures
10-20F above normal and dry conditions. If you have remaining
outdoor yard work or holiday decorating, this weekend would be
a great time to finish up those tasks as a sharp cool-down is
coming by the middle of next week.
The aforementioned southern stream trough has trended northward
in its trek through the Plains early next week compared to this
time yesterday, bringing low-moderate (20-40%) chances for rain
to parts of the forecast area sometime in the Monday-Tuesday
timeframe. While there is still low confidence in the exact
track and timing of this system, confidence is currently much
higher that temperatures will remain warm enough for rain to be
the dominant precipitation type.
Big changes on the way by the end of this forecast period with
regard to temperatures, as our extended stretch of mild weather
comes to an abrupt end. Timing of a stronger northern stream
wave and associated arctic cold front varies more in the latest
model solutions. Some now bring the front through as early as
Tuesday morning, while others hold off until later Tuesday into
Tuesday night. This is leading to low confidence in highs for
Tuesday, with a 10th-90th percentile spread in the NBM of over
15F. In either case, temperatures take a sharp downward turn
by Wednesday with even the warmest guidance indicating highs
in the lower-mid 30s. Increased northwest winds will accompany
the arctic blast, so those with holiday travel plans should be
prepared for the cold and wind.
While confidence is high that below normal temperatures will
dominate the latter half of the holiday week (highs only in the
20s and 30s and nighttime lows in the teens), there is still
uncertainty in whether wintry precipitation could further
impact holiday travel.
&&
.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1144 AM CST Thu Nov 20 2025
IFR to MVFR stratus continues to impact the area this afternoon,
with two distinct decks over us. The southern deck is located south
of I-90, and the leading edge of the second deck is moving across
the Highway-14 corridor and drifting southwards. In between, there
is a mix of clear skies and newly developing low clouds near the I-
29 corridor from KMDS to KFSD. All this will lead to mainly MVFR
conditions across the area through the rest of the afternoon into
the evening, with occasional breaks in the clouds. All these low
clouds will slowly drift southward through the period, clearing KHON
just before sunset, clearing KFSD after midnight, and sticking
around KSUX through the period (though there looks to be a break in
between the two stratus decks for a few hours this evening at KSUX).
Some fog may develop where skies clear out tonight, but confidence
was not high enough to include in the TAFs at this time. Guidance
currently indicates the best chance of fog develops where skies
clear along the Missouri River Valley in south-central South Dakota.
Winds will be mainly out of the northwest this afternoon around 5-10
kts, turning light and variable to calm overnight.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...Dense Fog Advisory until noon CST today for IAZ014-021-022-032.
NE...None.
&&
$$
UPDATE...Samet
DISCUSSION...JH
AVIATION...Samet
Office: UNR
FXUS63 KUNR 202022
AFDUNR
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
122 PM MST Thu Nov 20 2025
.KEY MESSAGES...
-Seasonally mild and dry through the weekend
-Turning colder next week with some light snow possible
&&
.DISCUSSION...(This Evening Through Thursday)
Issued at 117 PM MST Thu Nov 20 2025
Mild Pac flow will continue into early next week as split flow
persists. Sfc front has stalled over the SW third. This supported
an area of low clouds and fog this morning with a large portion
of the fog and clouds having since burned off. The same area
across the SW third to half will likely see low clouds and patchy
fog once again tonight as LL moisture will remain in place with
ESE upslope flow. WAA will ensue overnight into Fri allowing for
mild conds most areas Fri, with mild conds most places persisting
through the weekend as zonal Pac flow continues over the northern
CONUS Rockies. Any morning clouds and fog will dissipate Fri
morning as dry air mixes down from aloft. Expect highs mainly in
the 50s and 60s through Monday, with some 40s over northeast areas
Friday. Pattern change will ensue next week as a large ridge of
high pressure in the north Pac dislodges a CP airmass into the
northern CONUS. This will ensue via a stronger cold front Mon
night into Tue, with breezy NW winds expected Tue. Some light snow
will be possible Tue into Wed across the western third, mainly
northeast WY and the northern BH. Additional precip chances later
in the week will depend on where the frontal boundary sets up next
week as impulses ride SE along the baroclinic zone.
&&
.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 958 AM MST Thu Nov 20 2025
Local MVFR and IFR conditions in low clouds and fog will persist
this afternoon across portions of northeastern Wyoming and
southwestern South Dakota. VFR conditions are expected across
northwestern and south central South Dakota. Areas MVFR/IFR/LIFR
conditions will redevelop this evening and continue through Friday
morning.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...JC
AVIATION...Smith
Office: ABR
FXUS63 KABR 201946
AFDABR
Area Forecast Discussion
National Weather Service Aberdeen SD
146 PM CST Thu Nov 20 2025
.KEY MESSAGES...
- High temperatures will be in the 40s and 50s through next
Tuesday, which is around 5 to 15 degrees above normal. Warmest
temperatures will be this weekend.
- Turning markedly colder starting next Wednesday, as temperatures
tumble into the teens at night and 20s and 30s during the day.
- There is a 20-40 percent chance of precipitation centered mainly
on Monday night and Tuesday of next week.
&&
.DISCUSSION...
Issued at 143 PM CST Thu Nov 20 2025
At 1 PM CST, skies were becoming mostly sunny across the forecast
area. Temperatures have warmed into the 40s for most localities on
northwest winds around 5 to 15 mph.
Surface high pressure over the region does not look to be in a hurry
to depart, forecast to stick around tonight into Friday before
finally being deposed by a surface warm front moving into the
northern plains. The weak low level CAA that has been happening
looks to be replaced by neutral air advection tonight. On Friday,
starting to see the beginnings of low level WAA that continues into
Friday night. Portions of central and north central South Dakota
should begin to feel the effects of WAA Friday afternoon. As the WAA
continues Friday night, extending over into west central Minnesota,
expecting to see, at least, a mild downslope wind event developing
in the lee-of-the-Prairie-Coteau as a result. There could be a
resurgence of low clouds into, at least, the west river counties of
the CWA on Friday, as the low level wind field sets up somewhere
between southerly and westerly in response to the shifting surface
high pressure system over the region. This may, somewhat, hamper
Friday's warm up out west.
The long term period is a split flow pattern through Monday, as a
low amplitude upper level ridge pattern builds out the northern
branch jet-stream over the northwest/north central CONUS. Beyond
that, the jet-stream appears to consolidate as a longwave trof works
across southern Canada and the northern plains, knocking down the
upper ridge from Monday night through Wednesday. At the same time
this international border system is occurring, model camps now appear
to be introducing a new wrinkle, namely, bringing an upper level
closed low drifting out of the desert southwest into the deep south
Saturday through Sunday, and then up into the central plains/western
Great Lakes region Monday and Tuesday. Ensemble PoPs are now
showcasing a 20 to 40 percent chance of WAA-forced precipitation
(over this CWA) between these two northern and southern branch
systems from mainly Monday afternoon through Tuesday night. Right
now, the far northeast corner of the CWA holds a 20-35 percent
chance of receiving a tenth of an inch or more of precipitation
between 00Z Tuesday and 00Z Wednesday.
The southern Canada/northern plains upper level trof is expected to
sweep a potent cold front through the CWA somewhere between 00Z
Tuesday and 00Z Wednesday. The change in airmasses with this cold
fropa next week will be quite noticeable. Instead of high
temperatures being in the 40s and 50s, highs will only be in the 20s
and 30s starting next Tuesday. Low temperatures are expected to
transition from 20s and 30s down into the teens (possibly single
digits) above zero.
&&
.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1136 AM CST Thu Nov 20 2025
Terminals KABR,KATY,KPIR,KMBG
KMBG is coming out of MVFR conditions, and should be VFR for the
rest of the TAF valid period. MVFR conditions at KPIR, KABR and
KATY will start transitioning from MVFR to VFR here between 18Z
and 00Z.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
DISCUSSION...10
AVIATION...10
