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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
1053 PM CST Tuesday Nov 24 2015

Short term...(this evening through wednesday)
issued at 239 PM CST Tuesday Nov 24 2015

Main concerns tonight into tomorrow mostly centered around
fog/drizzle threat. Dew points in the middle 30s across eastern
Nebraska into eastern Kansas this afternoon will continue to advect
northward tonight. With an inversion in place and snow cover this
should lead towards widespread stratus and fog. Drizzle will also be
likely...especially ahead of the incoming cold front. Expecting to
see stratus and fog expand in coverage from about 2z through 9z with
most locations under stratus or fog by 12z Wednesday. For now no
concerns with freezing drizzle as it appears that any drizzle should
occur with temperatures mainly 34 or warmer. The one area to watch
may be around the James Valley or just east of there where
temperatures could sneak down to 31 or 32 by sunrise and cause a
little freezing on exposed surfaces and untreated roads. Confidence
too low to include at this time and believe the threat will be east
of the colder temperatures. Will have early evening lows in the
eastern County Warning Area with rising temperatures but more Standard lows in the
western County Warning Area.

Removed any mention of rainfall for Wednesday as dry air aloft will
keep the threat to drizzle or fog. Do still have some 20 probability of precipitation over
parts of northwest Iowa as there is a chance some of this drizzle
could produce a hundredth or two tomorrow afternoon. Otherwise highs
mainly in the upper 30s to middle 40s.

Long term...(wednesday night through tuesday)
issued at 239 PM CST Tuesday Nov 24 2015

Wednesday night will see some spread of light rain and drizzle north
across northwest Iowa and southwest Minnesota as the low level moisture flow
gets deeper. Some frontal lift of this moisture is likely and have
kept a chance of light precipitation...tending to snow with the
cooling...over the Missouri River area all the way to Chamberlain.
Some mixed freezing rain and sleet also possible in the transition
area as cooling behind the front progresses and gets deeper.

Thanksgiving day will bring continued steady cooling with light
precipitation mainly southeast half. The precipitation will continue
to trend to snow with a mixture preceding. The precipitation threat
should peak around the middle of the day then begin to decrease from
the west. Given the positive tilt nature of the system and fairly
quick drying coming in behind the front...likely to unqualified probability of precipitation
will be in the forecast only for northwest Iowa into the southeast
corner of southwest Minnesota including Jackson. At this time the
snowfall outlook is around 2 inches in this area with less to the
west and north. Winds will get just a bit on the stiff side but not
seen strong enough at this time to justify a mention of blowing snow
with these limited amounts. The problem with getting more is that
the short wave coming up the east side of the southwestern upper low
is going to run into ridging forced by the northern stream wave
which helps bring in the colder the wave will be dampened
out as it approaches and the decent frontal banding will not have
much to work on it.

Snow should move out to the northeast or simply dissipate over the
area Thursday night and a couple days of dry and cold weather will
arrive. It looks like the main upper low will approach by late in
the weekend. Models differ greatly not only among each other but
from run to run on handling this system. A decent wave coming up
toward the area may tend to rap back around the upper low. In any
event thermal contrast looks fair to poor in this
despite the considerable uncertainty in model not
look for a big storm threat at this time. The GFS seems to serve up
the best potential of a few inches of snow with its positioning of
the wave by Monday.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1047 PM CST Tuesday Nov 24 2015

Main change was to slow down the arrival of MVFR visibility and
low stratus overnight. With temperatures staying up so far this
evening and a more substantial dewpoint depression this
evening...fog is slow to develop. A band of low end VFR stratus is
lifting northward into northwest Iowa...while high clouds are
filtering into the western forecast area. While models are split
on the fog and stratus potential think that there
is enough of a potential later tonight with increasing leave mention of lower visibility in fsd and sux
around 10 to 12z. With increasing moisture...some lower stratus is
also likely to form late tonight/Wednesday morning. Still a lot of
uncertainty in timing for the lower ceilings and how long
IFR/MVFR conditions will persist Wednesday.


Fsd watches/warnings/advisories...
South Dakota...none.


Short term...08
long term...

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