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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
712 PM CDT Tuesday Jun 2 2015

Short term...(this evening through wednesday)
issued at 312 PM CDT Tuesday Jun 2 2015

19z satellite depicts two areas of concern for the forecast tonight.
The first is an area of growing cumulus across south central South
Dakota. As the cap continues to weaken...expect these storms to
develop into supercells with damaging winds...large hail and even an
isolated tornado or two as threats. Bulk shear in the 0-1 km layer
is a little weak the evening progresses
towards 03z...shear profiles become more supportive and 0-1km cape
increases to around 100 j/kg. Very steep 700-500 mb lapse rates
lead to elevated 1000-2000 j/kg of cape across central South
Dakota...but instability becomes increasingly elevated the further
east you go. If storms are able to get going...they will struggle
to work east with carved vectors pointing south to South West and
environmental parameters becoming increasingly elevated as you work
east. With time...expect storms to become increasingly disorganized
as they struggle to move anywhere of significance.

Second area of concern is currently across eastern Wyoming in an
area of convergence. Area of cumulus is expected to develop into a
complex of storms...and work eastward through the overnight. These
storms would move into central South Dakota after 03z. Models
suggest shear continues to improve through the overnight hours with
increasing speeds. This results in improved bulk shear
values...though instability remains quite limited east of the sames.
Short term high res models suggests these storms would organize into
a Bow echo...shifting south east along the thermal wind. This may
only lead to severe weather in the southwest quadrant if not the
southwest corner of the forecast area....with greater focus across
Nebraska. With dry air in the middle levels of the atmosphere leading
to good downdraft cape...think the main threat is is winds to 75 miles per hour
across south central South Dakota...and large hail.

Tricky forecast for tomorrow as a large part depends on how far the
front is propelled south by convection tonight. Expect arms
ahead of the front to re-destabilize throughout the day on
Wednesday...potentially leading to another round of severe weather
for the southeast quadrant of our forecast area tomorrow. Main
threats are going to be hail and damaging winds.

Long term...(wednesday night through tuesday)
issued at 311 PM CDT Tuesday Jun 2 2015

The problem Wednesday night is the apparent lack of lift and
dynamics as the Wednesday impulse moves further east of the area...
combining with the opposite effect of increasing
moisture...instability...and thermal support ahead of Central Plains
ridging into the area. The consensus seems to be a minimum of
showers and storms much of the night with what there is continuing
across the southern part of the area...but an increase beginning to
surge north/northeast by the end of the night into Thursday
morning...with a peak threat Thursday afternoon into the night
especially south. This is the time period also when parameters
should combine to produce the most rainfall over the area.

Temperatures look close to normal on highs and above normal on
lows with highs mainly in the 70s.

Another minimum in convection looks targeted for Friday and Friday
night behind a passing weak wave...then an increase seems likely
early in the weekend with another wave or two climbing over the
plains ridge. A Canadian short wave seems timed to force a brief
turn to a northwesterly upper flow and a dry or drier period Sunday
night and Monday...then an increase in showers and storms again by
next Tuesday as the upper flow again turns southwesterly and short
waves advance up the ridge. Temperatures look to turn a little
warmer by early next week with a stronger advance of warm and humid
air associated with the southwesterly flow up the Southern Plains

Timing on all these wet dry or wet/less wet oscillations is tricky
with Faith in models solutions low as myriad detains keep changing.
What seems sure is no cool or scorching hot strong
drying...and at most one decent dry day at a time

Considering the detail uncertainty would not put much stock in this
for now...but the GFS does want to bring an eastern Pacific tropical
system and its moisture all the way from southeastern Baja California up toward
the central and northern plains by the end of the forecast period
next Tuesday.


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 705 PM CDT Tuesday Jun 2 2015

Tricky aviation forecast tonight with thunderstorm chances
developing late evening through the overnight hours. Lots of
uncertainty in where these storms will develop and track...with
some models showing convection tracking east across the entire
forecast area while others keep storms primarily near the Missouri
Valley. Given this uncertainty...removed thunder mention from kfsd
but will leave storms in the ksux taf where the potential seems
highest. Models hint at scattered MVFR clouds developing with the
convection. A cold front sags across the area Wednesday morning
shifting southerly winds to the north.


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


Short term...
long term...

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