Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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790
FXUS63 KFSD 301957
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
257 PM CDT SAT JUL 30 2016

.SHORT TERM...(This evening through Sunday)
Issued at 256 PM CDT Sat Jul 30 2016

It`s another beautiful Saturday afternoon across the local area,
with plenty of sunshine, breezy winds and temperatures only climbing
into the lower 80s.   Much like on Friday, we continue to monitor a
CU field just east of the CWA, but this diurnally based activity
should not impact the CWA and dissipate this evening.

This evening and overnight: Gradual upslope flow will continue across
the Western Plains, and may develop a bit of convection over western
SD, but with increasing mid-lvl ridging visible on water vapor, not
sure what could spark convection closer to home until well after
midnight.  That said, there is a minor shortwave sliding through
southern Idaho at mid-day.  This wave may effectively veer the LLJ
sufficiently to cause scattered showers/storms to develop later
tonight and towards daybreak thanks to a sharp increase in
isentropic lift in the 310K layer. Coverage is the most uncertain
part of the forecast, and will maintain a low end PoPs given the
uncertainty as to just how much development there may be. In fact,
several CAMs indicate little to no precipitation into Sunday
morning.

Sunday:  Will linger a low PoP into the mornings, but most of the
day should remain dry.  Temperatures will climb slightly warmer than
today, into the 80s or even low 90s near the Missouri river. There
may be a marked increase in mid-lvl clouds through the morning.


.LONG TERM...(Sunday night through Saturday)
Issued at 256 PM CDT Sat Jul 30 2016

Strong warming and capping is still evident for the Sunday night
into Wednesday period, but the potential for mainly nighttime storms
still appears to be alive. While stronger to severe storms
associated with an approaching Canadian border wave should be north
and west of the area, boundaries and a low level jet may aid
nighttime storm initiation Sunday and Monday nights. Sunday night
features a weak boundary to the northwest of the area to provide a
focus for storms that may move over the area north of Interstate
90,while another boundary to the south over Nebraska should move
slowly north and could be a focus for scattered storms which
would affect northwest Iowa. For Monday night, the boundary to
the northwest slips across the area and may aid in the nocturnal
storm development, mainly east of the James River. The pattern and
timing are tricky, but there are reasons to keep the storms
mentioned in an environment featuring MUCAPE of 2000-3000 J/kg. A
quick look at model soundings on BUFKIT is all that is needed to
discount significant daytime heating development.

The warming is still on tap, as is the moisture/humidity increase,
although it may take a little more time than we were projecting
yesterday, especially on temperatures. Highs Monday and Tuesday
look to be in the mid 80s east to mid 90s west, perhaps barely
warmer Tuesday than Monday. The presence of the weak boundary to the
south and the projected easterly low level flow will prevent a real
scorching day Tuesday. Also, it will be rather humid, though not
with the near 80 dew points of last week`s heat spell. Low to at
most mid 70s look good for daytime dew points; a bit lower west of
the James River, though not as low as some models, especially the
GFS, are trying to project. Nighttime lows will be mostly around 70.

Ahead of the approaching cold front, Wednesday still looks to be the
hottest day for the forecast area. It will be continued humid as
models are not underdoing dew points as the appeared to be doing
yesterday. Yet we are not looking at the more scorching temperatures
we have had this summer, and a likely eventual heat advisory should
be the strongest highlight needed.

The cold front is projected to move southeast across the area late
Wednesday night and Thursday, somewhat slower than models were
projecting yesterday, and a thunderstorm threat is accordingly
extended to affect more of the area through Thursday. Thursday still
looks cooler with highs in the 80s.

The slower cold front movement corresponds with a weaker drying push
into the upper ridge by the associated wave, and storms may not quite
completely clear out of the Missouri River area before increasing
again by the start of the weekend as a trailing short wave, most
strongly depicted on the GFS, approaches and arrives. Temperatures
still look quite tolerable, with a little more low level/surface
cooling, with highs mostly 80 to 85 by Saturday. POPs are low with
all the uncertainty that far ahead, but the potential suggests that
we do not guarantee against a soggy next Saturday, at least
south of Interstate 90.


&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1152 AM CDT Sat Jul 30 2016

VFR conditions are expected to continue into the overnight hours.
We`ll watch for an increased chance for a few showers or
thunderstorms moving across the terminals after midnight, with the
best chances focused around the daybreak hours.

Coverage may be rather scattered, so will not include any higher
wording than VCTS. Mid-lvl clouds should continue into Sunday
morning with light south to southeast winds.


&&

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

$$

SHORT TERM...Dux
LONG TERM...
AVIATION...Dux



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