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Area forecast discussion
National Weather Service Sioux Falls South Dakota
345 am CST Tue Jan 23 2018

Short term...(today and tonight)
issued at 344 am CST Tue Jan 23 2018

Much quieter weather expected across the region for today, with
widespread low stratus to start the day. The strong low pressure
responsible for our blizzard on Monday has moved into the Great
Lakes, with subtle surface ridging expected to provide much lighter
winds across the region today. Sky cover a little tricky as models
not doing a great job with the existing stratus. However, both GFS
and NAM hold onto higher relative humidity values over central and eastern portions
of the forecast area through the day, and even if stratus does break
up as the lower relative humidity thins, high clouds now over the western Dakotas
will move in ahead of a weak upper wave. So, overall expect clouds
to be prevalent east of the James River throughout the day, with
some increase in sunshine across our western areas this afternoon.
Will have to watch for areas of fog across the west early at the
back edge of the stratus, but at this time do not expect widespread
dense fog to develop into our forecast area. Highs today will be
impacted by clouds and fresh snow, especially across our southeast
where reports of 8-10 inches or more were common. Clouds may allow
for slightly warmer temperatures than full sunshine given the high
albedo of the deep snowpack. However, even with that in mind, hedged
toward the cooler end of guidance over the deepest snow, with highs
from the mid 20s east to mid 30s west of the James River Valley.

Tonight, the weak ridge moves east across the region, while clouds
gradually decrease. While not expected completely calm winds nor a
Crystal clear sky, conditions should still support good radiational
cooling over the fresh snow, and like highs, have favored some of
the cooler guidance for lows tonight.



Long term...(wednesday through monday)
issued at 344 am CST Tue Jan 23 2018

Relatively quiet pattern will continue for our forecast area through
this forecast period. Upper ridging will dominate through Thursday
night, shifting east into the Great Lakes Friday as a broad trough
tracks east out of The Rockies across the northern plains. Appears
as though moisture will be hard to come by across our forecast area
with this trough and its associated cool front, so anticipate little
more than a modest increase in clouds and shift in wind direction to
mark its passage. Will have to watch wind speeds Thursday night into
Friday, as GFS/European model (ecmwf) depicting 35-40kt southerly flow at 925mg ahead
of the front Thursday night/early Friday, and 25-30kt Post-frontal
flow at this level later in the day Friday. Although yesterday's
snow was overall a little wetter than our recent Arctic events,
stronger winds could impact roads with drifting snow. Consensus
blends not really capturing the stronger winds due to differences in
timing of the front, but will be something to monitor and possibly
adjust as we move through the week.

Low level temperatures warm nicely with the upper ridging and
southwest flow ahead of friday's trough. If we still had fairly bare
ground, would likely have to bump highs up several degrees over the
given consensus numbers. However, with the fresh snow, did not make
any such adjustments. In fact, actually lowered blends a few degrees
Wednesday-Thursday over the deepest of the new snow from Yukon/sux to
spw/mjq.

Secondary trough develops over the Canadian prairies toward next
weekend, though models differ in handling this wave, ranging from
progressive GFS which has little impact on our area, to the slower
00z European model (ecmwf) which digs the wave southward across the eastern Dakotas
and Minnesota Sunday. The latter results in a chance of light precip
over the northeast half of the forecast area, while other solutions
remain dry. Given the European model (ecmwf) is a relative outlier, did not alter the
dry consensus forecast at this time. Overall, temperatures should
remain near to above seasonal normals for the last week in January,
with many days seeing a potential for highs at or above freezing.



&&

Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1021 PM CST Mon Jan 22 2018

Northwesterly winds will continue to slowly taper down through the
night, with patchy blowing snow over northwestern Iowa through 09z.
There could be some patchy fog development through the western
James River Valley during the night, though not expecting it to
get into khon. Otherwise, IFR/MVFR ceilings will linger into
Tuesday afternoon.



&&

Fsd watches/warnings/advisories...
South Dakota...none.
Minnesota...none.
Iowa...none.
NE...none.
&&

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