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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
611 am CDT Sat may 30 2015

Short term...(today and tonight)
issued at 337 am CDT Sat may 30 2015

Water vapor imagery shows a middle-level disturbance continuing to rotate
southeast across the area this morning. Scattered showers or
sprinkles will persist over the southeastern third of the County Warning Area
through a dry layer of air at or above 5k feet above ground level advects
southward into the area. A breezy and cool Saturday is expected for
most...with high temperatures nearly 10 degrees below normal.
Soundings suggest cumulus development by early afternoon...and could not
rule out a few sprinkles.

Otherwise...a very chilly overnight period is expected tonight as
skies remain clear. Will need to watch for a bit of stratus trying
to advect westward across northern Iowa overnight. Temperatures
will fall into the 40s in many areas.

Long term...(sunday through friday)
issued at 337 am CDT Sat may 30 2015

On Sunday...middle and clouds will increase fairly quickly from the
northwest with approach of the upper level wave/weak jet out of
the northern rockies...with a little stratus brushing across the
south. Dry air mass in place to the east...which will resist the
initial effects of middle level isentropic lift for much of the
morning. Eventually...persistence and support of the deeper lift
circulation should result in coverage of scattered light showers
across mainly eastern South Dakota especially during the afternoon
and early evening. Wave really seems to outrun the middle level
boundary/warm advection going through the afternoon and evening
hours...and will likely find the dry air to the east and the
disjointed system making for a difficult precipitation progression
into southwest Minnesota. Soundings quite stable as
thunder not anticipated. Eventually...get low level jet bringing
some increased off surface moisture toward southeast South Dakota
during Sunday night...and a very small elevated cape could be
enough for an isolated rumble or two heading into Sunday night
west of I- 29. In terms of temperatures...nudged temperatures down just a touch
for Sunday especially through middle James Valley toward east central
South Dakota...given the degree of cloudiness and impact of evaporative
cooling on stable southeast flow. With southeast gradient
remaining overnight...will keep temperatures milder in upper 40s to middle
50s on Sunday night.

Middle level boundary hanging around on Monday...while heights continue
to build through the plains...diverting the better of weak forcing
around the region. Spells likelihood that precipitation threat will
be fairly small...even given the moisture transport into the area.
Worked on trending existing low probability of precipitation by Monday morning downward...
and mainly a dry afternoon and evening. Western areas under impact
of greater ridging and out of the better low level moisture
transport could warm up nicely toward 80 degrees...while threat for
more clouds east will mean below to near normal upper 60s to middle
70s. Weak signature of low level synoptic boundary looks to remain
across areas well south and west...which concerns that better threat
for convective development overnight Monday will remain south of the
area. Assuming low level jet does not get diverted too much...and
with weak wave moving into the Western Plains...will keep a lower
late night chance mainly across southeastern South Dakota.

For the longer range /Tuesday through Friday/...look to be dealing
with large scale ridge and the myriad of smaller scale disturbances
which push across/through the feature. Persistent southeast to
south flow will increase the moisture through the period...and will
probably feel a great deal more humid this week than has been of
late. Diurnal ranges are also likely to be somewhat restrained with
potential greater cloud cover and increased low level moisture. Probability of precipitation
are a real will generally be broad brushed a bit at
this range given the uncertainty in feature timing and boundary
location. Message of this period of the forecast is not one of a
total washout...but numerous chances for precipitation through the
week. Some indication that a more coherent system will move into
the mean ridge around Wednesday night and early Thursday. Prospects
for a bit better convergence and location of lower level boundaries
also increases certainty in this period for convection...but much
will depend on activity from earlier in the week. Would also have
to say that a couple episodes of severe storms would also not be
unreasonable for the latter half of the week...especially if can get
stronger low level boundary into the area along with an increase in
middle level winds as indicated by several models by Wednesday night/Thu/Fri.


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 609 am CDT Sat may 30 2015

MVFR deck will gradually shift south of ksux this morning...with
VFR conditions likely over the entire area into Sunday morning.

Winds will remain from the northeast today...with occasional
gusting upwards of 20 knots at times. Winds will turn light
overnight...with middle-upper clouds increasing by Sunday morning.


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


Short term...dux
long term...Chapman

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