Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Sioux Falls South Dakota
305 PM CST Friday Mar 6 2015

Short term...(this evening through saturday)
issued at 303 PM CST Friday Mar 6 2015

Subtle wave dropping southeast through the forecast area has
ushered in some thicker cirrus clouds and turned winds northwest.
Later this evening winds should briefly turn west southwest again
ahead of a cold front which will drop through the forecast area
overnight. Models hinting at the potential for some stratus to drop
into the region behind the front...with the NAM being the most
aggressive with this push. Looks like the best potential for stratus
development will be for areas north of Interstate 90 - mainly in the
Highway 14 corridor. Forecast soundings suggest that this stratus
layer will be relatively thin and without a lot of lift...so will
keep the going forecast precipitation free. A few spotty areas of
drizzle may become possible but potential is too low to mention
right now. Lows tonight will be quite mild in the middle 20s to near
freezing.

Stratus cloud deck will linger into the morning before thinning
during midday. Middle level temperatures cool only slightly behind the
exiting shortwave...keeping surface temperatures seasonally mild.
Even with partly to mostly cloudy skies...highs should warm into the
upper 30s to lower 40s.

Long term...(saturday night through friday)
issued at 303 PM CST Friday Mar 6 2015

Tough forecast across the area on Saturday night as wave drops down
in northwest flow. Atmosphere suffer from saturation issues above
2000 feet Saturday night including the dendritic layer. This brings
precipitation type into question...but mainly appears to be a freezing
drizzle/light freezing rain event if it precips at all.
Frontogenetic band moving through the area with kissing jets
providing added lift. The question is whether these middle and upper
level dynamics will be utilized with all the saturation occurring in
the near surface layer. At the surface...weak cold front moving
through the area with slight cold air advection behind the front
through the morning hours on Sunday. Clearing skies and warming
temperatures aloft should melt any precipitation that falls on
Sunday. Expect to see rebound in temperatures across central South
Dakota...especially along and west of the James River. Further to
the east...expect less of a temperature recovery.

Split jet flow across the US with northern stream buckled up to the
north of the forecast area with second branch of the jet across the
southern edge of the forecast area. With jet focused to the
north...have continued to warm forecast temperatures through the
extended but am still shy of full mixout by 5-7 degrees. Models
show a weak boundary coming down on Thursday...with substantial
warming ahead of the boundary. GFS is more aggressive than the
European model (ecmwf) with boundary- but continued to trend upwards ahead of the
front. If today/S warming is any indication...will have a nice
taste of Spring next week.

&&

Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1143 am CST Friday Mar 6 2015

VFR conditions expected across the area through around 12z
Saturday. MVFR or low end VFR stratus will begin working into the
region from the northeast behind a cold front...and should spread
into all areas except the Missouri Valley through 18z Saturday.
NAM...GFS and sref indicate that both khon and kfsd will likely
see MVFR conditions after around 15z but ksux may remain just
outside of the stratus area.



&&

Fsd watches/warnings/advisories...
South Dakota...none.
Minnesota...none.
Iowa...none.
NE...none.
&&

$$

Short term...
long term...
aviation...

National Weather Service Glossary of Abbreviations