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

937
FXUS63 KFSD 250431
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1031 PM CST Fri Feb 24 2017

.SHORT TERM...(This evening through Saturday)
Issued at 352 PM CST Fri Feb 24 2017

Last bit of snow slowly pivoting southward and out of the CWA as we
approach mid-afternoon.  Winds are slowly weakening as well, as the
surface pressure gradient relaxes. Will leave the far row of
counties in a blizzard warning based on camera views from a few of
the plow trucks in the area.  However, it`s possible the warning
could be ended rather quickly later this afternoon or early evening.

Tonight: Surface ridge axis will glide eastwards overnight, and
we`ll have one of the coldest nights since February 9th as
temperatures fall into the single digits over the snow to the teens
along the highway 14 corridor.

Light winds and a great deal of sunshine should prevail on Saturday.
The warmest readings will end up along the snowless areas in the
Highway 14 corridor. Further south, anticipating a high impact from
snow cover and temperatures holding in the 20s.

.LONG TERM...(Saturday night through Friday)
Issued at 352 PM CST Fri Feb 24 2017

Main forecast concern from Saturday night through Monday is
temperatures and the impact of snow cover. On Saturday night, all
models show a very weak wave moving across the Dakotas. Moisture
is limited and the primary lift is north of the forecast area.
While there could be some very light snow north of Highway 14 in
South Dakota, am expecting it to remain dry.

On Sunday and Monday, westerly flow and somewhat warmer air move
over the area. The winds are not very strong so mixing will be
limited. Also with fresh snow cover south of a line from Windom
to Chamberlain, a lot of the sun`s energy will be reflected back
rather than used to warm the surface. North of I90 am expecting
more mixing due to bare ground. Temperatures along Hwy 14 will be
in the upper 30s to lower 40s. However, south of I-90, highs will
only be in the lower to middle 30s. Monday will have a similar set
up except temperatures aloft will be 2 to 3 degrees warmer so
that highs will range from the lower to middle 40s along Hwy 14 to
the mid to upper 30s south of I90. Meanwhile, on Sunday night,
light winds across northwest Iowa will allow temperatures to fall
into the lower teens.

In the extended, Tuesday through Friday, all models agree that an
upper level wave and associated jet streak will move across the
northern Plains. There is some mid-level frontogenesis coupled
with large scale ascent from the approaching short-wave. However,
there is disagreement on where and when the wave will move.
Generally the upper level wave/PV anomaly moves from north central
Nebraska into southern Minnesota but all models keep the greatest
precipitation closer to the surface front across northern Iowa.
With uncertainty associated with the location of the upper wave,
have generally kept PoPs around 50% although east of I-29, it is
becoming more certain that precipitation will occur. The system
does bring up fairly warm air. For now kept precipitation rain or
snow but there is some concern that if precipitation is on Monday
night or early Tuesday morning, there could be a little freezing
rain...especially south of I90 where temperatures aloft are more
likely to be above freezing. High temperatures will also be
impacted by timing of precipitation. Temperatures aloft favor
highs in the mid to upper 30s. However, there is the potential
that evaporative cooling of precipitation could keep temperatures
in the lower to middle 30s resulting in more of a mix of rain and
snow rather than a change to all rain during the day on Tuesday.

Northwest flow sets up in the middle of the week with a
baroclinic zone across the eastern Dakotas. By the end of the week
there is fairly large differences between the ECMWF/Canadian and
GFS. The GFS shows warmer air moving into the area by Friday while
the EC and Canadian keep colder air in place. Prior to Friday,
temperatures will be fairly close to normal. On Friday, did warm
temperatures a couple of degrees given the trend toward warmer
temperatures. However, with the large discrepancies in
temperatures, only raised highs into the mid 30s near Hwy 71 to
the mid 40s in the Missouri Valley rather than 40s to near 50 that
the GFS would suggest.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1029 PM CST Fri Feb 24 2017

Northwesterly winds will continue to decrease overnight.
Otherwise, VFR conditions are expected through the TAF period.

&&

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

$$

SHORT TERM...Dux
LONG TERM...Schumacher
AVIATION...JM



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