Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Sioux Falls South Dakota
332 PM CDT sun may 24 2015

Short term...(this evening through monday)
issued at 331 PM CDT sun may 24 2015

Been entertaining watching the radar today with two modes of
precipitation...the deeper showers working northward...and the
shallow drizzle processes pushing westward. All has spelled a pretty
moist afternoon for most locations. As we progress through the
remainder of the afternoon...widespread lower clouds will prevent
creation of any meaningful surface based instability...even as dry
slot wraps into the far west early this evening. Will maintain a
slight chance mention for thunder in Lower Brule areas...but remains
is much too stable. Most of the fsd County Warning Area looks like it will fall
between the two upper systems tonight...with one upper center
wobbling around northern Colorado and southern Wyoming...and
Southern Plains wave lifting rapidly northeast toward Iowa. Despite
a great deal of atmospheric moisture...meaningful advections become
absent for the most part. Kept in some marginally higher likely
probability of precipitation later in the evening and early overnight across the far
southeast to account for a close brush by of the Southern Plains
energy/MCV...but in general other than a drizzle threat as fog
develops overnight...there may be a distinct lack of precipitation
over the rest of the County Warning Area after the late afternoon and early evening
batch works gradually northward.

As the western low wobbles eastward on Memorial Day afternoon...
boundary will be induced to work northward toward the far southern
County Warning Area. Convection would look to initiate further west along the
boundary toward south central areas midday or early afternoon...
spreading eastward through the day as upper wave slips east. If can
break out of lower clouds...would be set up to generate on the order
of 1000 j/kg cape...with shear perhaps a bit better than previous
days. Not much at 0-1 km level...but middle level winds suggest 25-35
knots would be possible...fairly unidirectional. Given all these
conditional occurrences...may be able to scrape up an isolated near
severe storm south of a Jackson Minnesota to Vermillion line. Much
will depend on diabatic support...and for now am looking at
potential of lower to middle 70s near/south of boundary.

Long term...(monday night through sunday)
issued at 331 PM CDT sun may 24 2015

Upper trough continues to slowly pull away to the northeast on
Monday night and Tuesday. Once again...the most recent model runs
have slowed the progression of the upper low...hanging back the
trough over north central Nebraska Monday evening and slowly lifting
it across our eastern forecast area through Tuesday afternoon.
Expect the greatest potential for rain showers and storms across our
southeastern half Monday evening with scattered showers lingering in
Iowa and adjacent areas into Tuesday. Mostly cloudy skies hang on
for much of the day...but will gradually scatter out from west to
east Tuesday afternoon and evening.

Not much of a break expected in the precipitation as the active
weather pattern resumes later this week. Large scale upper trough
digs across the intermountain west...placing the Central Plains
under moist southwest upper flow. Models in good agreement that an
initial shortwave emerges from The Rockies Wednesday night...with
thunderstorms becoming likely mainly west of i29 overnight. Once the
wave swings through the area on Thursday...models begin diverging
rather significantly with respect to the more active southern or
northern streams. The common denominator is that the weather looks
active with high chance probability of precipitation through Friday night. The European model (ecmwf) and GFS
swing the main trough through the area Friday night...however the
Gem keeps the northern stream trough hung up over the northern
plains into Saturday. Temperatures will be seasonally warm Wednesday
and Thursday in the upper 70s and lower 80s...but cool back into the
60s by Saturday.


Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1153 am CDT sun may 24 2015

Abundant low level moisture leading to fairly widespread IFR
conditions this morning...which will slowly climb into the MVFR
range during the afternoon. Degraded ceilings and areas of lower
visibilities in fog and light precipitation will continue to be a
feature through 18z Monday.


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


Short term...Chapman
long term...

National Weather Service Glossary of Abbreviations