Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

212
FXUS63 KFSD 220339
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1039 PM CDT SAT MAY 21 2016

.SHORT TERM...(This evening through Monday afternoon)
Issued at 245 PM CDT Sat May 21 2016

A few lingering showers are rapidly dissipating this afternoon,
and despite the rather breezy conditions, Saturday is turning out
to be very pleasant. These pleasant conditions will continue into
the overnight hours, with the main focus of the forecast on the
severe weather risks late Sunday and Monday.

Tonight: Upper troughing over the Rockies will continue to keep
moisture transport pushing northwest into western Nebraska and the
western Dakotas overnight. We`ll again see a return of low level
stratus into central SD/NE tonight, and as the LLJ begins to veer
after midnight, this stratus will begin to advect into the Missouri
River valley. Further east, winds will gradually settle, but remain
elevated enough to keep temperatures in the lower 50s.

Sunday:  The slow and gradual advection of quality sfc moisture will
continue through the day, with moisture trying to pool ahead of an
eastward advancing frontal boundary nosing into the western
Dakotas/Nebraska by afternoon.  Soundings continue to both a
continuation of stratus west of the James river into the afternoon,
but also the arrival of an capping inversion around 750mb. As mid-
lvl energy begins to edge into the Plains should see an erosion of
this stratus ahead of the boundary, allowing an area of MLCAPE
approaching 2000-2500 J/KG by late afternoon. While effective
shear is marginal (25-35 KTS), CAMS suggest relatively discrete
cells forming ahead of the frontal boundary along a line near
Pierre to Valentine late in the afternoon.

Sunday night: Given the marginal shear profiles, the discrete nature
of the activity should be limited with storm interactions and cold
pool development allowing for several clusters of storms to form as
they try to push east towards the Missouri River valley. Further
east towards Mitchell and Yankton, soundings continue hold onto
capping inversion until the LLJ develops later in the evening.
The main risks continue to be focused on damaging winds with some
potential for hail in the initial stages of convection. DCAPE
values to push 1000 J/KG during the evening, and with mid-lvl dry
air, would feel potential for marginally severe winds. Hail
potential should be limited by the lack of effective shear. The
fairly unidirectional flow aloft should promote a slow eastward
progression to storms through the night. CIPS analogs continue to
support the idea of isolated to scattered severe weather reports
Sunday evening and early Sunday night, but that severe weather
risk will greatly diminish eastward with time.

Monday: With no strong push eastward of the storms, and rather weak
frontal boundary , rain may linger well through the day on Monday
over the eastern half of the CWA. Temperatures behind this cloud
shield may climb back into the 80s.  Very uncertain chance for
redevelopment of convection Monday afternoon remains with the main
concerns focused on forcing.

.LONG TERM...(Monday evening through Saturday)
Issued at 245 PM CDT Sat May 21 2016

Looks like unsettled weather pattern will continue throughout the
week with upper level flow becoming more southwesterly increasing
the shear a little, especially on Tuesday.  Will have to keep on
Tuesday as we may have a little sleeper severe weather event, but
confidence remains low at this point.  Very muddied pattern so was
very difficult to pin down exact timing of precip events.  Looking
ahead at Holiday weekend looks to be even more unsettled as models
bring a pretty strong short wave over the area keeping a pretty good
chance for storms beginning on Thursday and continuing through
Saturday.

Highs look to be in the 70s throughout the extended period, but will
be heavily influenced by the cloud cover throughout the period.
However, having said that I think the surface flow should allow
temps to warm to seasonal normals.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1031 PM CDT Sat May 21 2016

For the remainder of tonight, the primary concern will be low
level wind shear. With a low level jet around 40 kts at 1500 ft
AGL, we are expecting low level wind shear to develop at Huron
around 06z and continue through 12z with winds aloft increasing
around Sioux Falls and Sioux City around 10Z leading to low level
wind shear around sunrise. The winds will pick up near the surface
shortly after sunrise ending the risk of low level wind shear by
13z. The low level jet will bring stratus northward as well and
with ceilings at or below 3000 ft in parts of central Nebraska and
South Dakota, expect MVFR ceilings to slowly spread northeast
through the night. The MVFR ceilings may reach Huron by mid
morning before ceilings lift back above 3000 ft over most of the
area. Thunderstorms look to reach Huron around midnight on Sunday
night which may result in MVFR or IFR conditions. Did add
thunderstorms to TAF at HON but did not lower ceilings below 3000
ft. While current forecast has VFR conditions at KSUX and KFSD
through the period, stratus moving north and lowering Sunday
evening could produce MVFR ceilings after 03z. While not in TAF at
this time, the possibility will be monitored.

&&

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

$$

SHORT TERM...Dux
LONG TERM...Heitkamp
AVIATION...Schumacher



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.