Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
FXUS63 KFSD 151202

Area Forecast Discussion
National Weather Service Sioux Falls SD
702 AM CDT Sat Oct 15 2016

.SHORT TERM...(Today and Tonight)
Issued at 411 AM CDT Sat Oct 15 2016

Larger scale flow for non-resident pheasant opener today finds a
wave moving just north of the international border through a
slightly ridgy zonal pattern. Ahead of the wave, strong low level
jet continues across the CWA with strong winds especially along
higher terrain which has shown gusts from 35 to nearly 45 mph at
times. Frontal zone associated with the upper level wave has now
pushed to just west of the James river valley by 08z. Main
challenge today will be dealing with mass of stratus field
evolving at the present (08Z) across eastern Nebraska, northwest
Iowa and into southwest Minnesota.

See no reason that low level jet will not continue to drive stratus
north/northeast through the CWA early this morning. Challenge will
be to determine how far west stratus can spread before a greater and
greater westerly component begins to shunt the area to the east. NAM
is outlier on the western extent of which it has been quite
incorrect on through the current time.  If one ensembles several
runs of the HRRR/experimental HRRR/RAP and WRF, this would suggest a
western boundary somewhere near I-29, a bit more westward through
the Missouri valley. So far there has not been a hint of any
visibility drop nor drizzle signature on radars under the stratus
canopy, but given the shear would not be shocked to get patches of
drizzle or fog develop toward daybreak with a favor shown toward the
Buffalo ridge and extension through parts of northwest Iowa.
Progression of weak frontal boundary across the CWA will
increasingly push the stratus more and more into areas toward the
eastern tier of Iowa counties from the Iowa Great Lakes to Storm
Lake by early afternoon, and out of the CWA in the afternoon. While
winds will not be terribly strong behind the front, it will set up a
good mixing environment with weak cold advection, which should drive
temps mostly into the 70s today.  One area to watch is how much the
stratus period impacts readings across northwest Iowa, but even
there, temps and dewpoints are in the lower 60s at present, and can
only work upward from there.

Tonight, weak high pressure will drop winds, and will not take long
for weak flow to pick up a south to east component. A bit of lower
level moisture hangs on around southern portions of northwest Iowa,
and with weak flow could be prime for redevelopment of lower clouds
and fog later in the night, so have added in areas of fog,
especially for highway 20 into the lower Missouri valley.

.LONG TERM...(Sunday through Friday)
Issued at 411 AM CDT Sat Oct 15 2016

Sunday will be warm and breezy as low pressure aloft moves across
the North Dakota/Canadian border. This will bring the increasing
southerly flow as well as increasing high clouds. The nam and GFS
are indicating that stratus may be a problem, especially across
southwest Minnesota and northwest Iowa as southeast flow in the low
levels increases. Will generally have 70s in most locations.

Sunday night upper level support swings by to the north and could
spark a shower east of the Buffalo Ridge on Sunday evening but
chances will be minimal. With a warm air mass in place lows will be
mild and in the 50s.

Monday a tough call on temperatures and small precipitation chances
as models not very agreeable on location and strength of jet max
moving through. Lowered highs just a touch along and north of
Interstate 90 as the potential to remain in easterly flow appears to
have increased which will limit mixing. Highs 70 to 75 north of I-90
and 75 to 80 south. Will keep a small chance for showers north of I-
90 Monday night as forcing along and ahead of the wave may allow fro
development of showers.+

Tuesday through Friday will see a trough of low pressure move from
the Rockies onto the plains by Wednesday night. After the passage of
the trough drier northerly flow sets up so no precipitation chances
Thursday or Friday. However there will be a chance for showers south
of I-90 Wednesday and Wednesday night as the main upper level
support passes by to the south. Temperatures will generally be
pretty cool with highs in the 60s Tuesday then 50s Wednesday through


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 702 AM CDT Sat Oct 15 2016

MVFR stratus continues to be a challenge for the 12Z TAF set.
Western edge currently east of I-29, but surge moving up through
eastern Nebraska should push as far west as KYKN and may brush
around the KFSD areas around 14-15z. Have yet to see visibility
drop anywhere, and have eliminated any mention of fog and/or
drizzle in KSUX and KFSD, and most area to the east. With boundary
slowing to the south and some low-level moisture hanging up, have
brought back potential for some lower MVFR ceilings and some
visibilities into the IFR range for KSUX after 08z.




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