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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
637 PM CDT Tuesday Oct 21 2014

Short term...(this evening through wednesday)
issued at 355 PM CDT Tuesday Oct 21 2014

Very warm and breezy this afternoon with the fairly strong winds
continuing through the overnight hours. This will keep temperatures
very mild through the overnight hours with lows ranging from the middle
40s east to the middle 50s west. Low pressure currently moving through
the north and central rockies will spread eastward through tomorrow
bringing decent upper level support for rainfall. Almost more
importantly is some deeper moisture moving north through western
Nebraska into south central South Dakota. Expect these dew points to show
themselves much more once our deep mixing abates around sunset.
Suspect that this will cause stratus to develop and shift eastward
overnight as well. Some limited elevated instability and fairly
strong moisture convergence may be enough to initiate an isolated
shower or thunderstorm during the overnight hours into early
Wednesday morning.

Farther west the deeper middle level moisture and upper level support
will spread from west to east from middle Wednesday morning into
Wednesday evening. Will maintain likely to categorical
probability of precipitation...especially in the east late afternoon. Some marginal
instability may support a couple of rumbles of thunder with the
better chances in the south and east. Temperatures will be a bit
variable with the passing clouds/showers but highs will mainly be in
the 60s.

Long term...(wednesday night through tuesday)
issued at 355 PM CDT Tuesday Oct 21 2014

Back edge of rain band will likely be just west of a kmml to kfsd
to kykn line at 00z...which would be a fairly strong consensus
without the latest edition of a slowing European model (ecmwf). Larger scales not
very siding closer to the consensus...which should
result in a fairly distinct back edge to west of middle level trough
axis. The threat for a couple of isolated storms in the broader
precipitation zone will likely be limited to I 90 and south east
of the kfsd area...where residual of elevated instability and weak
near surface based instability may develop ahead of band of
precipitation. Progression of system will mean that most
precipitation should be ended by 06z with exception of the extreme
southeast. Some lower clouds may linger back toward surface
frontal location...but overall should find a strong clearing trend
and with weak cooler push and decreasing gradient...have nudged
lows a bit lower in more decoupled western zones.

Following the trough and associated precipitation...ridge will
rebuild across the northern plains...interrupted only by a wave
and associated cirrus pulse peaking the ridge on Friday...pushing
a cold front southward into the area late day. With thermal ridge
across the area and decent mixing...Friday looks to be quite
warm...well into the 70s...if not approaching 80 in Lower Brule
locations. A bit of lower level moisture ahead of pre frontal
trough could impact warming along with period of weaker flow
across northwest Iowa. Larger diurnal range likely heading through
Saturday as well...weak surface ridge axis parking across the area
Saturday morning...but mixing not quite as strong on Saturday with
more stable profile and more generous easterly component to lower
level winds...mainly middle to upper 60s lower 70s
Missouri Valley.

Ridge will finally begin to break down again by later Sunday with
strong jet punching through the northern and central rockies. Cold
front will shift through the region...but looks to be a mainly dry
feature through Sunday night. Better chance for rainfall suggested
to evolve with trailing southern trough energy Monday into Monday no problem maintaining lower end chance probability of precipitation during
this period...and with quite a bit of qg forcing straddling the
00z period...was hesitant to drop chances off too early.

Potential again for a very warm prefrontal day on Sunday...but
will perhaps have a little more challenge by clouds/low level
moisture streaming up in more stable environment on Saturday
night. Temperatures for early next week will settle back to closer to


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 632 PM CDT Tuesday Oct 21 2014

Primary concerns in the next 24 hours deal with stratus
development towards daybreak...along with rain chances Wednesday
afternoon. Isentropic lift increases after midnight as a band of
middle-level moisture moves through the area. Already an ac field over
south central South Dakota at 6pm...and would not rule out an
isolated shower or thunderstorm as this band moves through prior
to daybreak. However...models remain consistent in producing
MVFR stratus towards daybreak as moisture tries to stream into
the area. Cannot rule out a bit of drizzle scattered in the low
ceiling through middle- morning. The frontal boundary and rain showers/rain
activity will move through the region by middle-Thursday afternoon.


Fsd watches/warnings/advisories...
South Dakota...none.


Short term...08
long term...Chapman

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