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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
640 am CDT Friday may 22 2015

Short term...(today and tonight)
issued at 329 am CDT Friday may 22 2015

Short wave energy will lift northeastward toward the Sioux Falls
forecast area today...situating itself pretty close to our MO river
County zones by early this evening. An increase in higher level
clouds will follow suit...but low level moisture is starved with a
large area of high pressure over the MS valley closing the Gulf.
Kept only chance probability of precipitation by middle afternoon primarily in our far
southwest corner toward south central South Dakota...and the precipitation
should be just shower chances with a lack of instability noted.
Overall though it should be a pretty nice to start the Memorial Day
weekend. Due to the increase in cloud cover...highs will likely
remain only in the 60s in our south central South Dakota zones...but 70 to 75
should be widespread elsewhere. Tonight...the true Gulf moisture is
still shutoff as the big area of high pressure drifts closer to the
eastern Seaboard. Surface and boundary layer streamlines are
pointing in a straight east to west direction in the Gulf Coast
states...with the deeper Gulf moisture riding up more across the
Western Plains. In addition...the aforementioned short wave weakens
as it continues to lift northeastward across our forecast area up
and over the downstream ridge. So all told rainfall chances tonight
look fairly skittish with likely or higher probability of precipitation certainly not
warranted yet at this time. Lows are rather tricky because despite
the lack of low level moisture...there will be abundant middle and high
level cloud cover which could hold temperatures up a bit. Therefore
some of the MOS guidance values which were well down into the 40s
looked too cool...and preferred some of the more mild bias corrected
readings which give lows around 50 or the lower 50s.

Long term...(saturday through thursday)
issued at 329 am CDT Friday may 22 2015

Once any potential morning convection rolls through the
area...Saturday looks to be relatively quiet as a lack of moisture
and little forcing promotes little activity. Still can not rule out
an isolated shower...but mainly expect dry conditions to prevail.
Cloud cover will play a large roll in high temperatures....and for
now have sided fairly close to a Canadian/European model (ecmwf) blend.

Saturday night holds potential to be a more active period as
moisture surges northward in the low level jet. Upper level wave
still remains to the west across western South Dakota through the
evening...shifting east after midnight. Have concentrated highest
probability of precipitation in the 06-12z time frame.

Have continued with mention of thunderstorms on Sunday...though the
instability is far from great. At this point...threat for severe
weather looks to be fairly low.

Upper level wave lingers across the region on Monday as low level
cold front swings through the area. Best precipitation chances
appear to be along and ahead of the front...with fairly strong dry
air punch working into the region behind the front.

With drier more stable air working into the region...reduced pop
mention on Tuesday. Another system is expected to move across the
region on Wednesday night into Thursday...creating more muggy
conditions along with the threat of thunderstorms.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 638 am CDT Friday may 22 2015

VFR will prevail across the Sioux Falls forecast area until late
tonight after 06z Saturday...when MVFR ceilings may develop along
with some light rain showers.


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


Short term...mj
long term...

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