Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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581
FXUS63 KFSD 300812
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
312 AM CDT SAT JUL 30 2016

.SHORT TERM...(Today and Tonight)
Issued at 312 AM CDT Sat Jul 30 2016

Seeing a band of thunderstorms trying to graze our far south central
SD zones very early this morning. short term models show these
showers and storms possibly continuing over that area through mid
morning, then waning after that. Otherwise, surface ridging shifts
off to the east today. With an increasing southerly flow on the
backside of the high, thermal profiles will begin to warm, and
looking at highs a couple of degrees warmer than yesterday. This
will play out to afternoon readings in the upper 70s to mid 80s.

For tonight, models indicating convective development over central
SD in the evening with increasing theta e advection as a 30 to 35 kt
low level jet develops over the region. These showers and storms are
then portrayed as tracking eastward across portions of our area
overnight. Severe storms look to be unlikely in our area with the
better instability being confined to the western portions of SD. It
will be a milder night with lows in the lower to mid 60s.


.LONG TERM...(Sunday through Friday)
Issued at 312 AM CDT Sat Jul 30 2016

Early portion of next week will feature increasing heat and humidity
accompanied by sporadic thunderstorm chances as various waves slide
overtop broad upper ridge covering much of the southern CONUS. More
organized upper forcing remains well north of our area with upper
trough over the Canadian Prairies, but the quasi-zonal upper flow
pattern is favorable for weaker convective waves to track east over
the Northern Plains. This brings potential for occasional scattered
storms moving through the region, mainly confined to nighttime hours
as diurnally-driven storms drift east out of the High Plains, though
ultimate timing/location could depend largely on placement of any
outflow boundaries generated by convection to our northwest. The
increasing heat and humidity should result in moderate instability.
However, with faster upper flow positioned near the Canadian border
and our forecast area in closer proximity to the upper ridge, deep
layer shear is on the weak side and this should limit severe threat
across the area through Monday night. As far as heat headlines, the
latest forecast keeps heat indices just shy of advisory levels in
most areas through Tuesday, though ultimately could depend on how
well we recover from any overnight convective debris on these days.
Highest readings generally in 95 to 100 degree range look to remain
concentrated southwest of a line from De Smet-Sioux Falls-Spencer
Iowa.

Tuesday through Wednesday appear to be a more extended dry period as
models are trending a bit slower with the progression of cold front
expected to push into the region mid-late week. Although still some
discrepancies in timing among the longer range models, consensus is
pointing to front/better convective chances moving into southeast
South Dakota later Wednesday night. Slower front should allow for
better mixing/heating in more southerly flow ahead of the boundary
on Wednesday, and should again see heat indices approach triple
digits in some areas.

Second upper trough will continue to move east across the Canadian
Prairies Thursday, dragging northern end of the cold front eastward
through the Northern Plains. However, southern end of the front gets
hung up over eastern Colorado/western Kansas as strong upper ridge
over southeast CONUS limits progression. This will keep lingering
chance of storms in areas south of Interstate 90 Thursday night,
while drier air works into northwest portions of the area. By Friday
the surface boundary should be well south of the area. Operational
GFS an outlier in showing a stronger wave tracking into the area in
southwest flow aloft Friday/Friday night, while ECMWF shows a more
dominant upper ridge helping to keep the area dry. With the front
located in the central Plains and surface ridge from the Red River
Valley into eastern South Dakota, will lean toward drier ECMWF
solution at this time.


&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1029 PM CDT Fri Jul 29 2016

Generally VFR through the period. Will need to watch parts of
mainly northwest Iowa late tonight and early Saturday morning for
the potential for MVFR fog. This area is on the back edge of the
low level moisture which may allow for fog development as
temperatures and winds drop tonight.


&&

.FSD Watches/Warnings/Advisories...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...JM
LONG TERM...JH
AVIATION...08



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