Area Forecast Discussion
Issued by NWS Rapid City, SD

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171
FXUS63 KUNR 240510
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1110 PM MDT Sun Jul 23 2017

.DISCUSSION...(This Evening Through Sunday)
Issued at 148 PM MDT Sun Jul 23 2017

Latest upper analysis shows a ridge over much of the western CONUS
with and upper trough digging southward into the Pacific
Northwest. A weak shortwave moving through the upper ridge will
combine with a developing low level jet to create a chance of
showers and thunderstorms, moving from southwest to northeast over
the forecast area tonight. There may be some isolated showers or
thunderstorms lingering into Monday morning over the northeastern
part of the forecast area.

On Monday, the upper ridge will build eastward over the high
plains with the thermal ridge peaking over the forecast area ahead
of an upper low and associated trough crossing the Canadian
prairie provinces. A surface front will move into the forecast
area early, but its southward advancement will slow as the
boundary becomes parallel to upper flow near the Nebraska border.
Hot temperatures will occur across the region with high on the
plains generally ranging from around 95-105F. MLCAPE will rise to
1.2-1.8KJ/kg along boundary, but MLCIN will be pretty stout so
any convection should be rather isolated with lack of organized
forcing. Isolated strong/marginally severe storms are possible
given 15m/s 0-6km bulk shear. Temperatures will be near guidance
in the west and above guidance to the east of the sfc boundary.

Tuesday through Saturday, guidance now pushes frontal boundary much
further south which suggests drier weather than previously
thought through the week although isolated thunderstorms will
still be possible. Flat upper ridge Tuesday and Wednesday will
bring cooler temperatures, but temperatures will be on the rise
for the end of the week into next weekend.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1109 PM MDT Sun Jul 23 2017

Scattered thunderstorms will move across northeast Wyoming into
the Black Hills and northwest South Dakota overnight into early
Monday morning. Local MVFR conditions and gusty winds with the
thunderstorms, otherwise VFR conditions expected.

&&

.FIRE WEATHER...
Issued at 148 PM MDT Sun Jul 23 2017

Warm temperatures will support deep mixing on Monday with minimum
relative humidity dropping to 12-24 percent on Monday afternoon.
Breezy areas are likely over south central SD, but this is where
the relative humidity should be the highest.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION...10
AVIATION...7
FIRE WEATHER...10



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