Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sioux Falls South Dakota
525 am CST Wednesday Nov 26 2014
Short term...(today and tonight)
issued at 333 am CST Wednesday Nov 26 2014
Back end of snow system will be dropping southeast across the
area this morning and should weaken slowly as it does. Winds will
continue to pick up from the west and north. The current advisory
looks good with this second surge moving across and the winds due to
pick up. Have considered adding the northern counties from Hon to
bkx but with Hon having almost no snow so far and bkx a little slower
on the wind pickup...have elected to leave out. Even bkx has
less snow than fsd...we have an inch...and the winds will pick
up a little slower than at Hon. Will keep some blowing snow in the
forecast and continue to monitor. The second surge has dictated more
snow mention and a little higher amounts over this stretch from now
through middle or late morning...but it will still move out to the
southeast rapidly later in the morning. Some snow will hang on in
the advisory area into the afternoon and will continue some blowing
snow in that area past the noon advisory expiration.
Skies may partially clear from the northwest for a while over the
area west of the James River but an assortment of middle and low clouds
should increase again later today and tonight. Better clearing
should take place further east...especially northeast...this
afternoon with skies remaining clear to partly cloudy there tonight.
The cloud increase to the southwest will be from warm advection
upstairs starting in already. Will keep a few flurries far southwest
late tonight but that should be it with little upper support to
accompany the warm advection.
The strongest winds through early afternoon should be in the west
and south where there will not be much snow to blow...and am
currently projecting these winds to stay a little below Wind
Advisory levels. Further east...the slightly less strong winds plus
the later pickup should prevent too many problems once the falling
snow ends...thus keeping the advisory expiration at noon.
Temperatures will be dropping most of today...maybe briefly
leveling off early afternoon before resuming a drop tonight.
Readings will drop below zero late tonight north central and
northeast. The wind dropoff should keep wind chills dropping to the
minus 20 and colder zone which is our advisory criteria for
that...but the far northeast with the coldest temperatures may get
Long term...(thursday through tuesday)
issued at 333 am CST Wednesday Nov 26 2014
A rather progressive flow pattern will become established over the
Continental U.S. As we move through the Holiday weekend. High pressure will
cross the region for Thanksgiving as middle-level heights build through
the day. Low-level warm air advection will commence quickly by
Thursday morning and cannot rule out a few flurries through the day
as this middle-level band of moisture/lift crosses the area.
Temperatures will be well below normal...with an exception across
south central South Dakota where warmer temperature will begin to creep
northeast. Shortwave energy and a Stout upper level jet will produce
a band of snow to the north and northeast of the County Warning Area late Thursday
into Thursday night.
Warm westerly flow will bring above normal temperatures to the
region for Friday and even into Saturday. Would not be surprised
to see upper 40s in the southern zones...with a rather warm Friday
A blast of cold air will race through the region Saturday night into
Sunday and drop temperatures back below normal. This progressive
pattern will likely not support sustained long-duration cold
spells...as signs point to a quick rebound back towards normal by
the very end of the extended forecast.
Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 525 am CST Wednesday Nov 26 2014
Ceilings 1-3k feet visibilities 3-5sm in snow with areas of
ceilings below 1k feet and visibilities below 3sm in snow at 12z.
Conditions will improve from the northwest 12z-18z to ceilings
2-4k feet and visibilities p6sm except very local visibilities
3-5sm in blsn will continue through 21z. Further improvement to
VFR expected by 27/00z with VFR continuing through 27/12z. Surface
gusts 25-35 knots from the north to northwest until 22z.
Minnesota...Winter Weather Advisory until noon CST today for mnz071-072-080-
Iowa...Winter Weather Advisory until noon CST today for iaz003.