Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 121148
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
548 AM CST Mon Feb 12 2018

.SHORT TERM...(Today and Tonight)
Issued at 322 AM CST Mon Feb 12 2018

Main weather feature in the short term will be the chance for some
light snow this afternoon and evening. A weak shortwave will eject
northeastward from a closed upper low over the southwest and will
provide the region with a bit of lift as warm advection occurs in
the 850-700mb layer. This layer will be marginally within the
dendritic growth zone, so do expect some crystals to form. Main
limiting factor will be the relative lack of low level moisture. Not
thinking enough crystals will survive the trip to the surface for
anything more than flurries or the lightest of accumulations. Kept
accumulations mainly west of the James River as the low levels will
have a bit more moisture there. Kept down high temperatures for
Monday in line with guidance trends and expected widespread
cloudiness. Expecting a bit of a breeze Monday night with continued
mostly cloudy conditions, so bumped lows up a degree or two.

.LONG TERM...(Tuesday through Sunday)
Issued at 322 AM CST Mon Feb 12 2018

Very few highlights in the extended forecast. Several waves pass
across the region Tuesday through Wednesday night but there isn`t
anywhere near enough moisture to result in any additional snowfall.

Midday Tuesday through midday Wednesday see a favorable
southwesterly wind direction and a bit of a surface pressure
gradient set up across southwest Minnesota so have boosted winds
along the Buffalo Ridge during this period. Wednesday looks to be
our warmest day in some time with operational models and their
ensembles in good agreement. Limiting factor will the significant
snow depth across the southeastern half of the CWA - have held back
high temperatures in areas with high current snow depths per NOHRSC
analysis and COOP observations.

Longwave trough arrives from the Pacific Northwest and swings
eastward across the region Thursday bringing a cold frontal passage,
likely early during the day. Should be enough moisture with this
front to induce at least some flurries. Impressive pressure gradient
and CAA aloft in the wake of the frontal passage, so have bumped up
the already breezy consensus winds.

Northwest flow aloft takes over for Friday but the upper pattern
begins to flatten out for Saturday and Sunday, perhaps allowing two
consecutive days with above freezing high temperatures. Operational
model runs continue to be warmer than their ensembles however, so
continue to remain stoic and unexcited about next weekend until
further notice.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 548 AM CST Mon Feb 12 2018

Conditions through the TAF period ending 12Z Tue will be largely
VFR. However, band of mid-level forced lift could bring a brief
period of MVFR visibility snowfall to parts of SE SD during the
evening. Agreement between hi-res solutions and low-res
solutions is fleeting, so have limited both the time and coverage
of non-VFR conditions to KHON. Such conditions could also impact
KFSD after 03z, but trajectory down low is from much drier source
and could easily limit precipitation chance and lowering of
ceiling. For KFSD and KSUX, low-level wind shear conditions will
develop after 09z and linger through around 14-15z.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...Ferguson
LONG TERM...Ferguson
AVIATION...Chapman



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