Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 140820
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
320 AM CDT Fri Jul 14 2017

.SHORT TERM...(Today and Tonight)
Issued at 319 AM CDT Fri Jul 14 2017

Not much to talk about other than the heat building back into the
Tri-State area. As high pressure continues to pull off to the
east, winds will become more south to southeast this afternoon.
The southerly winds will begin to bring more moisture back into
the area causing the heat indices to approach the century mark out
west. No change to the fire danger despite the drier conditions
due to the light winds.

Clear skies overnight tonight will allow temperatures to drop
once again tonight, but not near as low as the past couple.
However areas of northwest Iowa will fall into the lower 60s once
again due to the continued influence of the ridge of high
pressure.


.LONG TERM...(Saturday through Thursday)
Issued at 319 AM CDT Fri Jul 14 2017

Return of heat and humidity will be primary focus to start this
period as upper ridge builds eastward across the Northern Plains.
Low level thermal ridge pivots west-east Saturday ahead of weak
southward-moving boundary which approaches Highway 14 late in the
day. Despite relatively light wind flow, anticipate decent mixing in
southwesterly flow ahead of the boundary, so will hedge toward the
warmer end of guidance, especially west where ground conditions are
much drier. Should see some triple-digit readings along/west of the
James Valley Saturday afternoon, but with the mixing in a fairly dry
air mass, dew points should mix lower through the afternoon. Perhaps
not quite as low as GFS indicates, but did blend in that direction
in our west where grasses are driest. This should limit heat index
values, although could still see some readings reach 100F, and later
shifts may need to consider a heat advisory for Saturday afternoon.
Mid-level wave topping the ridge is expected to remain far enough
northeast of the area at this time to maintain a dry forecast for
Saturday.

Boundary continues to sag southward Saturday night, and Sunday cools
a bit, especially across our east with east-northeast flow north of
the boundary. Western locations will see less cooling, though, with
temperatures and heat index values again pushing into the mid-upper
90s. Upper ridge moves farther east Sunday night, with the boundary
lifting back northward as a warm front. This allows southerly flow
to increase Sunday night/Monday, with low-level heat expanding back
to the east. Similar to the weekend, could see temperatures climb
well into the 90s across the west, and southerly flow could bring a
little deeper moisture northward, so could see heat indices again
approach 100F near/west of the James Valley on Monday.

As the upper ridge axis shifts into the Upper Mississippi Valley
Monday, modest mid-upper level wave tracks through the Dakotas,
dragging a cool front to central South Dakota by Monday evening.
This wave/front could trigger spotty storms across the area late
Monday/Monday night, primarily across western/northern parts of the
forecast area. Coverage could be limited by extensive warm air
aloft, and shear is quite weak, so would not anticipate severe
storms at this time.

Ridging breaks down further toward mid-week, and looks a little
more unsettled Tuesday-Thursday. Heat/humidity may linger across
southern areas, especially Tuesday, but confidence decreases as we
progress further through the week, as temperatures could be impacted
by any storms that affect the area.


&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1028 PM CDT Thu Jul 13 2017

VFR conditions expected through the TAF period. There could be
some patchy fog development late tonight over portions of east
central SD, southwestern MN, and northwestern IA, though is not
expected to affect TAF sites.


&&

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

$$

SHORT TERM...Heitkamp
LONG TERM...JH
AVIATION...JM



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