Scientific Forecaster Discussion
fxus63 kfsd 141154
Area forecast discussion
National Weather Service Sioux Falls South Dakota
654 am CDT Mon Oct 14 2019
Short term...(today and tonight)
issued at 420 am CDT Mon Oct 14 2019
Under a sprawling surface ridge early this morning, a quiet and cool
morning underway across the area, with just a few dissipating shards
of stratocumulus remaining northeast of kmml. Potentially a bit of
shallow fog in the lower Missouri River valley and other lower spots
near the surface ridge axis through around 8 am. Otherwise, it will
remain quiet as a weak ridge of high pressure aloft shifts across
the area today, with sunshine fading behind some periods of high-
level clouds already showing force streaming across the central and
northern rockies. Southerly winds already revealed this morning will
increase and actually become quite breezy by midday west of I-29 and
across most of the area during the afternoon. Will continue to work
away any of the remaining snow cover in parts of east central South Dakota as
temperatures make a climb toward just shy of normal readings in the
mid 50s to mid 60s.
By evening, a sharp wave/jet sliding through Montana early this morning
will push into the western Dakotas. A wind shift will move into
areas west of the James River as early as very late afternoon, and
will move at a good clip eastward tonight to enter Minnesota and Iowa before
midnight. Likely that temps could do some funny things tonight
depending on windows for decoupling ahead of the boundary and the
likelihood of a pulse of mixing behind the front before tailing off
with the cold advection further into the night as northwest winds
reach a gusty 20-30 mph. Will likely be a close call, but any spotty
precipitation within the strong pv advection in the warm advection
Wing should tend to form just east of the area across
southern/central Minnesota. Later into the night, expect lower clouds to
sweep in behind the exiting front/low pressure, but likely without
precip through daybreak.
Long term...(tuesday through sunday)
issued at 420 am CDT Mon Oct 14 2019
Moving through Tuesday, the quick moving and digging trough will
shift toward the western/southern Great Lakes with cold advection
and widespread stratocumulus spilling through the northern plains.
For the most part, appears as would not be surprised to end up
adding in a few sprinkles or even some drizzle (depending on
variable moisture depth) during the later morning through at least
mid afternoon before larger scale subsidence really takes over.
Thermodynamic profiles suggest getting much in the way of ice
processes involved would be difficult, again having precip
efficiency take a hit, and thus will not mention any
sprinkles/drizzle at this point. The main issue will again be
winds, which look to have potential to be just shy of advisory
levels with 33 to 38 knots atop the mixed layer. Could easily see
temps reach a nearly steady state by later morning/midday, and
will be much cooler than today, from 40 to 50, but it sure will
not feel that way with the clouds/wind.
More dry weather through the week as a stronger ridge aloft over the
western U.S builds eastward. With stronger southerly flow returning
Thursday, highs which should be in the mid 40s to lower 50s
Wednesday will make way for upper 50s and 60s Thursday and Friday,
even as another dry front pushes through the area.
A deeper trough moving into the western U.S. Will set up
southwesterly flow aloft over the area for the weekend, which
appears to be the next chance for meaningful precipitation.
As the jet entrance region from the wave spreads across the area
later Saturday night into Sunday (timing still up for grabs amongst
the models/ensembles), should have a fairly decent mid-level
boundary across the area to focus a better chance for precipitation.
The European model (ecmwf) keeps the trough a bit more southern focused into Sunday,
whereas as the GFS exhibits more influence of the northern branch,
with some difference in how far northward any elevated instability
spreads. For now, have introduced a low thunder chance mainly south
of a ksux-kspw line by later Sat night, and as far north as ktkc-
konl on Sunday.
Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 654 am CDT Mon Oct 14 2019
The lower Missouri River near ksux will have potential for some
shallow fog through around 14z. However, VFR conditions are
expected for the remainder of the sites and period, with the
exception of the threat for some MVFR ceilings dropping southward
behind a cold front after 09z. Just ahead of the cold front for a
few hours this evening, there will be low-level wind shear
conditions for ksux and kfsd, starting after 01z and continuing
through the frontal wind shift.