Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KFSD 060442

Area Forecast Discussion
National Weather Service Sioux Falls SD
1042 PM CST Mon Dec 5 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 243 PM CST Mon Dec 5 2016

Strong cold front moving through the area this evening. Wind gusts
in the mixed layer from all models quite a bit higher than anything
the raw model and climatological mos data kicks out. Other than
possibly touching wind advisory criteria for a short period the main
concern will be IF any light snow can develop, which should be along
and west of the James River this evening, will there be any reduced
visibility. At this time do not believe it will occur for long
enough to be a concern, if it can develop at all. Otherwise quickly
falling temperatures this evening and become cold. By late tonight
most locations will see wind chill values close to zero with about
10 above in northwest Iowa.

Did add a chance for light snow and flurries to areas along and
north of Interstate 90 on Tuesday as the dendritic layer is fairly
low, fairly deep and occasionally saturates so through it was at
least worth a threat for a tenth or two of light snowfall.
Temperatures will be fairly steady or only slightly rise Tuesday
with highs in the 20s.

.LONG TERM...(Tuesday night through Monday)
Issued at 243 PM CST Mon Dec 5 2016

The Tuesday night through Monday period will feature a simple
temperature trend. The coldest weather will prevail at first in the
arctic regime, with highs in the teens to lower 20s, and lows
mostly in the single digits. A lack of snow cover will prevent more
frigid readings. Still, strong winds producing subzero wind chills
will continue to make this turn to colder weather the main weather
feature of the week into Thursday.

By the weekend, increasing westerlies over the area will bring
readings a little closer to normal, with highs in the 20s to lower
30s, and lows mostly in the teens. At the surface, strong arctic
ridging will be replaced by a weaker and variable pattern, as a
series of weak westerly waves move across in the strengthening upper

A weak lobe rotating around the cold Ontario upper low seems poised
to bring a few flurries Wednesday night into Thursday to the area
roughly from Huron to Sioux Falls to Spencer IA and northeast. Low
and mid level moisture with this lobe will bring increasing clouds
Wednesday. The low level moisture will be in the dendritic zone in
this cold air mass, so it will be very easy for some flakes to
precipitate out. Some barely measurable snow amounts are conceivable
in part of southwest MN, as weakening northerly warm advection and
frontogenesis around H900 brushes that area. For now, will go with
the loaded guidance and keep mention mostly at flurries. At least,
the timing, weak strength, and potential area affected does not
seem in much doubt.

The weak waves arriving in the Friday through Monday period are
more of a problem on both timing and area affected, although models
do depict them as fairly weak. Currently, the first appears timed
for Friday night into Saturday night, and in fact could consist of
two successive and rapidly moving waves. The light snow threat
appears to be mostly Interstate 90 and north at this time. Two to
three days ago, most models were depicting a stronger and more
general system. The second has appeared timed for Monday, mainly in
northwest Iowa by some models, but there seems even more doubt on
this one, as it is a week away, and the new EC has backed off on
this timing. Fortunately, the weak nature of these waves also appear
to insure little or no threat of snow approaching advisory levels.
Neither does there appear to be enough warming aloft for any threat
of freezing precipitation.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1035 PM CST Mon Dec 5 2016

MVFR are beginning to break up from the west, and guidance is
suggesting these clouds to scatter out through the night, though
returning around KHON after 10z. There could be light snow in
areas through the northern Highway 14 corridor on Tuesday.
Northwesterly winds will continue to be strong, gusting to 30 to
35 kts through late Tuesday afternoon.




AVIATION...JM is the U.S. government's official web portal to all federal, state and local government web resources and services.