Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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593
FXUS63 KFSD 231155
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
655 AM CDT SAT JUL 23 2016

.SHORT TERM...(Today and Tonight)
Issued at 413 AM CDT Sat Jul 23 2016

Lift ahead of mid level wave across western South Dakota has induced
fairly widespread convection in the very early hours of Saturday
across Nebraska and recently nosing into south central South Dakota
in the past hour. Well-defined MCV resides in convection north of
KLXN in south central NE, and this is expected to track consistently
east/northeast and reach near the KSUX area by around 8 am. Increase
in moisture advection ahead of feature is working to displace some
of the deeper off-surface dry layer.  With as warm as the layer is,
would take a pretty significant storm to produce larger hail, and
more apt to find some gusty winds with storms. In fact, some concern
remains that if warm dome aloft works on dissipating storms to a
greater degree, could end up with a heat burst scenario for some
areas through the late night/early morning hours, but for now,
storms remain too intense to feature such an event.  As convective
band works through this morning, surface-layer moisture will likely
be recycled for a while, likely knocking dew point readings into the
upper 60s for a brief period.  Traversing MCV will take majority
threat of precipitation quickly east/northeast with it by mid to
late morning, and in wake should have a quiet period that lasts well
into the afternoon.  Eventually, strong trough pushing out of the
northern Rockies and across North Dakota this afternoon will drive a
cold frontal boundary eastward into the CWA during the mid to late
afternoon hours.  Main dynamic lift will remain generally north of
the CWA, glancing the far north/east perhaps very late afternoon and
early evening, with temps aloft remaining quite toasty the further
southward one works along the frontal boundary.  Scenario following
the morning MCV related convection would suggest perhaps another
organized system developing in ND and pushing east/southeast with
the boundary late afternoon, but questionable if could expand enough
to greatly impact the FSD CWA.  Given the debris from morning
convection and impact on potential destabilization, hard to picture
a very widespread severe threat for much of the area given the
disturbance from the morning convection. Deep-layer shear does
increase to 40-45 knots toward the highway 14 areas to accompany the
frontal push late day, but there remains some question on how great
the cap will remain.  Would not be surprised to see an isolated
severe storm or two with generally a wind threat and a somewhat
lesser chance for hail.

The storms will make a fairly quick exit in the early evening with
tail of organized linear system to the northeast. Following this
will be a welcomed drop in dew point overnight as high pressure
builds into the western plains.

Otherwise, concern continues with excessive heat. At this point, not
considering any increase to the area under the excessive heat
warning, as areas further east will certainly be dealing with a
longer duration of residual cloudiness and impact on eventual
temperatures through the day, despite the eventual return of the
most sultry dewpoints across the area in wake of early day
precipitation. Most likely area to be warmest captured well in
ongoing warning area, but should start to see a strong decrease in
humidity levels behind front to the west of the James River by late
day.

.LONG TERM...(Sunday through Friday)
Issued at 413 AM CDT Sat Jul 23 2016

Sunday: A very pleasant day is expected in the region.  Dew points will
steadily fall into the 50s through the day. Temperatures will climb
into the lower to middle 80s in most locations, with a scattered
afternoon CU field.

Monday: High pressure will slide east of the area, allowing southerly
winds to return.  As a result, temperatures will again climb above
normal in many locations, with middle to upper 80s east of the James
River, and lower 90s in areas to the west.

Monday Night:  The beginning of an unsettled period of weather
begins Monday night.  Several models showing an minor shortwave
entering the Northern Plains. This shortwave will induce an
increasing low level jet across central SD and northern Nebraska.
Decent likelihood of nocturnal convection along a stalled theta-e
gradient, with a potential MCS taking shape by by daybreak Tuesday
diving into Nebraska.  Areas with highest rain potential would
be west of I-29.

Tuesday-Friday: A very unsettled pattern will become established
thanks to quasi-zonal mid-lvl flow. Rather high precipitation
chances will arrive for late Tuesday through Wednesday as at least
one shortwave move through the region.  Rather uncapped afternoon
environments will characterize the mid-week forecast, with
increasing risks for nocturnal MCS.  Shear in general remains on the
lower end of the scale, but would anticipate at least a low end or
isolated severe weather risk for the second half of the week,
and perhaps an increased localized flood risk.

Temperatures from Tuesday onward will fall slightly below seasonal
normals, but will still feature highs in the lower 80s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 655 AM CDT Sat Jul 23 2016

Lingering convection will clutter at least part of first hour or
so for each TAF site, but will be on the way out quickly.
Precipitation has flushed much of the MVFR or IFR ceilings, but
expect that once get some clearing and heating of modified air
pool that will once again see some cumulus development starting
around 2000-2500 ft AGL, and mixing upward toward 4000-4500 ft
AGL by mid to late afternoon. Frontal boundary will push into the
KHON vicinity by 21-22z, and progress through the area through mid
evening. With fairly warm temperatures aloft and the better
dynamic focus north of the area, convective chances would appear
to be fairly small along the frontal boundary for TAF sites late
afternoon and early evening, so have left out for the time being.
Should make note, however, that if storms would manage to develop
later this afternoon, likelihood of severe storms with large hail
and damaging wind would be somewhat high.

&&

.FSD Watches/Warnings/Advisories...
SD...Excessive Heat Warning until 7 PM CDT this evening for SDZ038-
     039-050-052>055-057>071.

MN...None.
IA...Excessive Heat Warning until 7 PM CDT this evening for IAZ001-
     012-020-031.

NE...Excessive Heat Warning until 7 PM CDT this evening for NEZ013-
     014.

&&

$$

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



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