Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 251133
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
633 AM CDT MON JUL 25 2016

.SHORT TERM...(Today and Tonight)
Issued at 340 AM CDT Mon Jul 25 2016

High pressure will provide a splendid late July day to the area,
with abundant sunshine, fairly light winds, and lower humidity.
Southerly winds will pick up through the day west of the James, but
should not exceed 10 to 20 mph during the afternoon.  With drier
air, should warm fairly efficiently despite lack of mechanical
support for most, and expect highs from the mid 80s in southwest
Minnesota and northwest Iowa, to lower 90s from the James valley
westward.  Tonight, will have to monitor progression of storms
expected to develop late day in the far western plains troughing.
Low-level jet will strengthen to 35 to 40 knots through the central
Dakotas by 06z-09z.  As weak wave traverses the upper ridge by late
tonight, support exists for convection to spread perhaps as far east
as the James Valley along the instability gradient aloft, but should
struggle further eastward with residual dry air at lower levels.
This drier air and weaker gradient may allow some temps into the
lower 60s, while mainly mid to upper 60s expected elsewhere. Could
see a bit of an elevation wind enhancement toward the Buffalo Ridge
very late night as low level jet veers.

.LONG TERM...(Tuesday through Sunday)
Issued at 340 AM CDT Mon Jul 25 2016

Scattered convection may be ongoing early Tuesday morning along the
Missouri River valley, as the low-lvl convergence focuses in the
region. We should gradually see this activity diminish through the
morning, as the LLJ focuses back to the west. The questions in the
afternoon are really focused on the northward positioning of a warm
front and the northward expansion of the warm sector. The NAM/EC
bring the warm front into north central SD, with the GFS much
further north.  Strong convection should develop along this boundary
in the afternoon, with several clusters of storms dropping southeast
into Nebraska through the MO River valley.  The local storm chances
appear to increase more substantially further east after dark as a
secondary shortwave moves through and nocturnal convection breaks
out. This activity should slide southeast into NW Iowa by daybreak
Wednesday.

There remains a great deal of uncertainty for Wednesday and
Thursday, but the overall synoptic pattern would suggest very
unsettled weather. A myriad of shortwaves will move through the
northwesterly flow aloft during the day. The biggest question will
be the impacts of overnight convection, and potential stabilization
of the environment for the day on Wednesday. Presently, the greatest
severe weather risk has shifted slightly further south for Wednesday
and Wednesday night.

Thursday and Friday will see yet another shortwave move towards the
local area.  As alluded to in previous discussions, flow aloft is
generally very weak, and focal mechanisms hard to determine at this
time distance.  That said, pattern would suggest that it is prudent
to keep at least scattered precipitation wording in the forecast.
With temperatures cooling into the upper 70s to lower 80s, general
severe weather risk is low.

The pattern as we move into next weekend has shown some signs of
trending drier.  Shortwave ridging potential has increased for
Saturday and Sunday, as broad scale ridging also increases.  Will
remove PoPs at this point.  The developing ridge does not appear to
be as strong as in previous weeks, but given a persistence of
southerly flow and return of higher sfc moisture, heat index values
may again climb towards 100 degrees by Sunday and Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 631 AM CDT Mon Jul 25 2016

VFR conditions are expected to persist through 12z Tue. A small
chance for thunderstorms reaching KHON after 08z remains too minor
to mention in TAF.

&&

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

$$

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


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