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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
630 PM CDT Sat Aug 1 2015

Short term...(this evening through sunday)
issued at 253 PM CDT Sat Aug 1 2015

Nebraska convection has put a damper on both temperatures and
convection chances over much of the forecast area today. A stronger
than anticipated shortwave and a slow to wane low level jet has kept
convection ongoing nearly all day to our south...with a persistent
feed of middle-upper level clouds into areas south of I-90 today.

12z GFS/NAM/ECMWF not very much help today at all...with only models
that seemed to have a clue being the 00z arw/nmm with more recent
runs of the hrrr/hopwrf capturing the trends reasonably well.

That said...a secondary shortwave continues to track southeast
through North Dakota this afternoon...developing a weak surface low east
of Bismarck and sending an elongated warm front southeast into areas
near the Minnesota River Valley early this afternoon. Dew points
have been a sticking point in model guidance the past few days...but
at this with lower forecast values have seemed to do
better. Southwest of this warm front over the northeastern half of
the County Warning Area...temperatures have been slow to rise...and dew points are
now mixing down into the upper 50s to lower 60s. Given the remnant
capping inversion aloft at or above 700mb...we may be hard pressed to
sustain any convection that does develop given the poor heating.

Will continue to monitor elevated showers and isolated thunderstorms
over eastern South Dakota and far western Minnesota...which seem to be rooted
above this elevated mixed layer. Should sufficient moisture pool
along the warm is possible to have a few storms develop
further and become surface based into the late afternoon hours. Stronger
activity may stay fairly isolated...with best forcing ahead of the
surface low in eastern ND and northwest Minnesota this evening and along a secondary
frontal boundary in northern South Dakota behind the surface low. Highest
instability and severe weather risks will be found along these
aforementioned boundaries.

By Sunday...a secondary frontal boundary will slide through the
region early in the day...bringing gusty northwest winds and much
drier air. Temperatures will still reach above normal but no rain
is anticipated.

Long term...(sunday night through saturday)
issued at 253 PM CDT Sat Aug 1 2015

Sunday night and Monday should be dry and mild. The tone for the
rest of the week is for a flattening upper ridge..temperatures going
to a little below normal...and periodic hard to time shower and
thunderstorm activity with a increase in moisture and the passage of
short waves. The moisture return from the south will not be quite as
fast as earlier figured and have held of the precipitation chance
over the southern edge of the area until Monday night. The influx of
moisture will take time to get to the northeastern corner of the
area with Wednesday the first period we will have some precipitation
mention over all of the area. Mainly due to the timing
difficulties...probability of precipitation will be chance at most. Will go with the
extended guidance on a mention each period from Wednesday on for the
same reason as above...timing is too uncertain to pin down any dry
periods although a couple or three seem likely for the area.

As hinted at above...temperatures for the coming week will be
trending toward the opposite of our recent warm days and cool nights
with the change to overall near normal nights and below normal
daytime highs.


Aviation...(for the 00z tafs through 00z Sunday evening)
issued at 630 PM CDT Sat Aug 1 2015

Isolated convection possible in northern parts of the forecast
area this evening...possibly moving into parts of southwest Minnesota and
northwest Iowa after 06z. Due to expected limited coverage of any
storms...opted to not include in tafs at this time...though will
be watching khon area closely as potential appears greater there
through the first 2-3 hours of the taf period than any other
location. Aside from convective threat...which may produce brief
MVFR visibility...expect VFR conditions to dominate.

Lingering wind gusts from the southwest expected to diminish by
sunset. Increasing southwest-west low level jet above 800ft could
produce a period of low level wind shear after 02/06z. While this
could briefly impact kfsd taf location...appears to be more likely
east/northeast of kfsd and have not included in the kfsd taf at
this time.


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


Short term...dux
long term...

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