Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Sioux Falls South Dakota
640 PM CDT Wednesday Oct 1 2014

Short term...(this evening through thursday)
issued at 309 PM CDT Wednesday Oct 1 2014

Main focus for tonight and tomorrow will be another potent shortwave
currently moving through western Wyoming. This wave emerges in the
Central High plains this evening and slowly lifts northeast into the
forecast area on Thursday.

Very slow moving frontal boundary extending north to south near the
South Dakota border with Minnesota and Iowa will finally push east
of the forecast area by midnight. Scattered cumulus field along and
east of this boundary has developed. With some thin middle level
instability and weak lift along the boundary..a few isolated
thunderstorms or showers will be possible near the front middle
afternoon through middle evening. With weak convergence and shear in
this area...not expected any severe storms with this activity.

For the overnight hours...clouds will begin building back into the
region from the southwest. Rain showers will begin spreading into
the Missouri Valley area as some strong middle level frontogenesis
around the 700 mb level begins nosing into south central South Dakota from
central central Nebraska late tonight. This forcing eventually
shifts eastward into extreme southeast South Dakota and northwest
Iowa by midday Thursday. The band of rain is expected to spread
across much of southeast South Dakota Thursday morning and become
likely across our southeastern two thirds of the forecast area
through the rest of the day. Looking at forecast soundings...cape
values are pretty meager at around 200 j/kg or less throughout the will continue to only mention showers with no thunder for
consistency. Most locations should see less than a quarter inch of
rain...with portions of northwest Iowa possibly as high as around a
half inch. With clouds and rain in the picture through the
day...highs will not improve much from overnight readings. Highs
will only reach the 60s.

Long term...(thursday night through wednesday)
issued at 309 PM CDT Wednesday Oct 1 2014

Rain/showers lingering southeast corner of the area will end fairly
quickly Thursday evening and the strong Canadian wave will push the
cold front across the area. Winds are expected to pick up strongly
from the northwest late at night. Winds will be strong...very likely
at Wind Advisory levels...through Thursday then will begin to
decrease Thursday evening. The colder air continues to look moisture
laden at low levels with some middle level moisture northeast. Light
showers still look like a good bet northeast half. The lag in low
level cooling and the light nature of the showers should prevent the
snowflakes that could otherwise result from air this cold.
Temperatures cooling to 40 or so with the cold winds starting up
Thursday night will not warm much Friday...just into the middle 40s to
low 50s.

Clear or clearing skies are expected Friday night and the air looks
cold enough for temperatures to cool to around freezing despite
lingering wind. It is still too early for a freeze advisory or
warning...and frost will not be mentioned because of the lingering
wind and the dryness of the cold air.

Saturday night will start a warming trend as slow but steady ridging
begins behind the cold trough continuing to dig then lift to the
east/northeast. A very weak north northwesterly wave will battle the
ridging Saturday night and Sunday but lift and moisture availability
seem well below the precipitation mention threshold. Monday through
Wednesday will then be dry with continued slow warming.

Temperatures warming to 50 to 60 Saturday will warm a little each
day and should make it into the middle 60s to low 70s for Tuesday and


Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 634 PM CDT Wednesday Oct 1 2014

Clouds will increase tonight into early tomorrow. Expect showers
to also spread northeast across the area through the day. Best
chances will remain along and southeast of a Tyndall to Sioux
Falls to Marshall line. Thus the kfsd and ksux taf sites could be
impacted...mainly from middle morning into early afternoon. Generally
expect conditions to remain VFR in the showers...although could
see visibility and ceiling reductions for a time in the steadier rain
across the southern portion of the region. Not sure it will be
predominate for now will just go with a MVFR tempo
group at ksux.


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


Short term...
long term...

National Weather Service Glossary of Abbreviations