Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 072300

Area Forecast Discussion
National Weather Service Sioux Falls SD
500 PM CST Wed Dec 7 2016

.SHORT TERM...(This evening through Thursday)
Issued at 300 PM CST Wed Dec 7 2016

Bare ground, mixing especially during the day, and low level
moisture in the dendritic layer will continue to be the rather
unexciting weather features through tonight and Thursday. Low level
warming and resulting drying had broken up most of the low clouds
this afternoon. Yet, a few paltry flurries continue even under
mostly sunny skies, such as at Marshall MN.

Expect a resurgence of low level moisture from the north under the
still stiff low level and surface flow tonight into Thursday
morning. This should cause the low clouds to increase again later
tonight, with flurries increasing again. As a last weak lobe
rotates around the retreating Ontario upper low, a band of warm
advection and frontogenesis centered around 900mb will approach.
The NAM and ARW forecast this feature to quickly weaken and pass of
to the east by Thursday morning. Therefore, will keep the flurries
just that, except for a little chance of measurable precipitation
far northeast around the Marshall MN area. The flurries will spread
to the south and southwest by Thursday morning, but along with
most of the clouds, should hold short of the Missouri River

By Thursday afternoon, clouds should be decreasing slowly again to
the northeast, although like today, a few flurries are likely to
continue, as remaining clouds will still be in the heart of that
dendritic layer.

The bare ground and mixing will continue to result in warmer
temperatures than we would see with any snow cover in this arctic
air. Winds Thursday, while less strong than today, will be
stronger than model guidance from that mixing, and it will be
breezy. Lows tonight will be in the single digits...above
around 10. Have bumped up highs a bit for Thursday from what we had
before, into the teens to about 20. Could see it getting a bit
warmer than that, though much of the area may have more cloud cover
than today.

.LONG TERM...(Thursday night through Wednesday)
Issued at 300 PM CST Wed Dec 7 2016

On Friday a wave to the north will set up a bit of return flow in
the mid levels Friday afternoon and evening. The forcing and the
moisture are not real concurrent but there does appear to at least
be a threat for a little light snow as this moisture return slides
northeast. Will have a small chance for light snow for areas along
and north of Interstate 90 on Friday afternoon and evening.

By Friday night into Saturday morning the right entrance region of
upper jet will move into Minnesota and should help reinforce mid
level cold air. This is a bit different than yesterdays runs which
allowed the deeper dendritic zone to lift north of the area and not
really settle back southward until later in the event, leaving the
better chances to the east. This is no longer the case as a fairly
deep -10 C to -14 C layer will be in place along and north of
Interstate 90. This of course could fluctuate on future runs just
like it did for the run today, but all indications are that it will
be in place. At this time there are no indications of instability
above the boundary so anticipating a broader less focused band of
snow. With expected precipitation amounts this would hint at a swath
of 2 to 5 inches. The dry slot in the mid and upper levels is also
not real impressive so any help adding some instability through this
process is diminished as well. The Nam, Gem, GFS and ECMWF are
amazingly similar on placement of band of highest qpf with only some
differences on amounts. The 6z GFS was closer to 0.80" liquid but
has backed off to 0.60" which is more in line with the other models.
Will maintain the highest threat for snow along and north of
Interstate 90.

For Sunday through Wednesday not seeing any real threat for snow at
this time. A quick look at the soundings does show the threat for
some flurries or very light snow with a low and occasionally
saturated dendritic zone. Went lower than superblend in locations
with the highest probability of snow cover. Looks like a good chance
for a very cold air mass, likely a touch colder than our current
air mass, so with the snow on the ground suspect temperatures will
be a good 10 to 15 degrees colder than in our current air mass. In
all likelihood we will probably see a couple of days with wind chill
advisories during this time.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 457 PM CST Wed Dec 7 2016

Expecting upper end MVFR stratus to spread back into the area
tonight and linger into Thursday afternoon. Moderate northwesterly
winds will continue across the region, gusting to around 25 kts
through the TAF period.




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