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266
FXUS63 KFSD 231105
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
605 AM CDT Fri Jun 23 2017

.SHORT TERM...(Today and Tonight)
Issued at 414 AM CDT Fri Jun 23 2017

The primary concern for today and tonight is cloud cover and winds.

All models are in good agreement over the evolution the next 24 h.
A fairly strong wave will move from eastern Wyoming into Nebraska
this morning. There is a lot of mid level clouds which have spread
into south central South Dakota. There is also light rain into
southwestern SD and the Nebraska panhandle. At the same time, very
dry air is moving southeastward behind the cold front with dew
points in the mid 30s in PHP at 07Z. At best could see a sprinkle or
two around Gregory County early this morning but given evolution of
system and very dry low levels, more likely that precipitation to
evaporate before reaching the ground and decided against adding
sprinkles into the forecast through 15Z.

What is more certain is that clouds will really increase this
morning with mostly cloudy skies this afternoon. The unseasonably
cool air aloft combined with strong heating this morning will allow
cumulus to rapidly develop by mid morning and then only gradually
dissipate later this afternoon. This will also promote efficient
mixing with wind gusts between 25 and 35 mph over most of the area
from late this morning through early evening. Despite the cool air
aloft, there is a capping inversion in place which is expected to
keep the entire cloud above freezing. This should prevent any
showers from develop this afternoon - even in southwestern Minnesota
where the coldest air aloft will be situated.  Overnight tonight,
winds will rapidly decrease and skies will clear allowing
temperatures to fall below normal. Highs today will range from the
upper 60s in southwestern MN into the mid 70s in the Missouri
Valley. Lows tonight will be in the 40s.

.LONG TERM...(Saturday through Thursday)
Issued at 414 AM CDT Fri Jun 23 2017

Sharp trough will be dropping southeast across Minnesota early on
Saturday. Main dynamic support for lift brushes through southwest
Minnesota from mid-morning to early afternoon, and just enough
MLCAPE to suspect existence of a few light showers drifting east
of a MML to SPW line. Further west, expect development of a few
more stable cumulus, but not enough depth for enough cooling to
make for precipitation generating processes. As wave swings by,
mixing will refresh along with breezy conditions.

Winds will diminish with diurnal cycle, but maintain some better
coupling near/east of I-29 ahead of low-level ridge axis through the
Dakotas in area of cold advection. Depending on the degree of
coupling maintained west of I-29, especially the James River valley,
temps could get quite cool. In fact, could be looking at a few
record to near-record low temperatures Sunday morning, with a
majority of standing records from 1958.  Will not take long for the
winds to freshen again on Sunday, but overall should see even a bit
more sunshine than Saturday, with a few flat cumulus favoring east
of I-29 over west.

With surface ridge over the area on Sunday night, again will see
temps fall mainly into the 40s. Would likely have dipped temps even
a few more degrees near/east of I-29 from guidance, however, will
see encroachment of some mid-level warm advection toward the lower
Missouri River valley by late night. This looks to be enough at a
minimum to produce some mid clouds, and if can overcome the wedge of
drier air at low levels, perhaps even a couple of showers. Models
quite uncertain as to how aggressive to generate precip, but main
question appears to be more on moisture than dynamics, as most have
a subtle wave late Sunday night into Monday morning.

Overall, precip chances will be fairly skittish until Tuesday night,
when ridge which builds through the area on Monday into Tuesday is
flattened by a decent jet punch from the Rockies.  Will have
somewhat a limited moisture return until this time, with perhaps
enough to risk an isolated shower or storm on Tuesday toward south
central SD on leading push of elevated mixed layer. Temps Monday and
Tuesday gradually moderating to - and just above - normal. Strong
low-level jet developing Tuesday into Tuesday night, with eventual
moisture return increasing instability and enhancement of deep layer
shear. Will have to watch the progression of warm temps
aloft/capping on Tue night, but will generally carry scattered level
PoPs for thunder as this feature advances eastward overnight.

Wednesday likely the warmest day of the week as frontal zone pushes
into the area from the west, but will have to keep consideration of
potential residual cloudiness and convection to restrict readings.
Could see another round of late day convection along the boundary,
but much remains to see how any intervening convection may impact
location and timing. ECMWF more aggressive with pushing boundary
southward on Thursday and limiting any precip chances, while GFS
lingers a bit more across northwest Iowa. Current thinking follows
more closely with ECMWF/Canadian, with a generally drier and
seasonable day.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 605 AM CDT Fri Jun 23 2017

Main aviation concerns are clouds through today. Currently
satellite picture shows 2500-4000 ft ceilings now south of KABR
and approaching KPIR. Current projections put these clouds to HON
by 13Z and to FSD by 1430Z. These clouds would reach KSUX around
16Z. Initially, model soundings support ceilings from 2500-3000
and have MVFR ceilings at KHON and KFSD for a period this morning.
With daytime heating, ceilings are expected to rise above 3000 by
noon. Therefore expect ceilings will be above 3000 ft all day at
KSUX and rising above 3000 feet and KFSD and KHON by noon CDT.
Clouds will clear from west to east through the afternoon with any
residual clouds quickly dissipating by sunset leaving clear skies
the remainder of the night. The other concern will be gusty
northwest winds. Expect gusts between 25 and 30 kts from late this
morning into early this evening. Winds will fall to less than 10
mph shortly after sunset.

No precipitation is expected through 12Z Saturday

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...Schumacher
LONG TERM...Chapman
AVIATION...Schumacher