Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 281711
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1111 AM CST Mon Nov 28 2016

.SHORT TERM...(Today and Tonight)
Issued at 315 AM CST Mon Nov 28 2016

Surface low located just south of Watertown as of 09Z this
morning, and is forecast to lift slowly northward into the lower
Red River Valley by the end of today. Fairly broad area of rain
showers around the south side of the low, covering much of
southeast South Dakota/southwest Minnesota at the present time.
Abundant moisture and lift will continue to wrap around the low,
keeping precipitation wrapping into areas mainly north of I-90 as
the system lifts to the north through the day. Dry slot punching
northward through Iowa into southern Minnesota should also limit
eastward extent to around I-29 or US Hwy 75 corridor near the
SD/MN border.

Temperatures aloft become cool enough to support snow by daybreak
today, so precip type through today will depend on lingering surface
based shallow warm layer. Temperatures really not expected to move
too far from daybreak readings in most areas, thanks to widespread
thick cloud cover and neutral-weak cool advection aloft. This
results in surface temperatures holding in the mid 30s through the
Highway 14 corridor, with coolest temperatures and greater potential
for light snow accumulations in the higher elevations of western
Jerauld/far western Beadle Counties, as well as the plateau across
Kingsbury County between the James and Big Sioux Valleys. Could see
around an inch of wet snow accumulations in these areas by the end
of today, with little if any accumulation expected elsewhere.

System moves very little through tonight as the upper level low
becomes cutoff over the lower Red River Valley. Expect off and on
precipitation to continue wrapping into southeast South Dakota, and
with only very shallow surface layer near/above freezing, expect any
lingering rain/snow mix to change to light snow through the evening.
Moisture/lift appear to be more limited this far removed from the
system, though, and thus only light snow accumulations generally
less than a half inch are expected tonight, again mainly near/north
of I-90.

.LONG TERM...(Tuesday through Sunday)
Issued at 315 AM CST Mon Nov 28 2016

A cool upper low, with not very much thermal contrast, will begin to
slowly move east from the eastern Dakotas and Minnesota Tuesday and
Wednesday. Low to mid level moisture locked in over the northern
plains by this low will result in light precipitation over the area,
concentrated more to the north of Interstate 90. Precipitation will
show some diurnal rain/snow variation, with an overall tendency for
the light precipitation to become snow, under the influence of
general slow cooling. One wave rotating around this low appears to
come across late Tuesday and Tuesday night. This would appear to
target Tuesday night as the best time for light snow accumulations,
perhaps on the order of an inch or two in a few places north.
Dynamic lift, perhaps aided by a little warm advection around 850mb,
would contribute to the modest precipitation increase.

On Thursday, while clouds should still be plentiful, light
precipitation should abate as the low moves further east of the
area. Am leaving some morning mention only in southwest MN for that
day.

Have increased winds a little from model blends for the daytime hours
Tuesday through Thursday, because model soundings show the lowest
layers becoming fairly well mixed, even when the gradient will be
slowly decreasing on Thursday.

The weather Friday through Sunday looks dry, under initial broad
ridging left behind the departed upper low, followed by a very weak
upper trough as a strong upper low digs well south of the area.
Temperatures overall should be close to seasonal, with daytime highs
warming slightly from a little below freezing Friday to the 30s and
lower 40s by Sunday. This should take place with little or no snow
cover.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1105 AM CST Mon Nov 28 2016

IFR Conditions expected along and north of I90 today as low
pressure system moves from northeast South Dakota into eastern
North Dakota. Could see some scattered shower activity in this
area as well, temporarily reducing visibility at times. Northwest
winds will be gusty through the period, especially in shower
activity and during the daylight hours. VFR conditions further to
the south will gradually transition to MVFR as another lobe of
energy rotates around the upper low. This will result in MVFR
conditions developing around KSUX on Tuesday morning.

&&

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

$$

SHORT TERM...JH
LONG TERM...
AVIATION...BT



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