Area Forecast Discussion
Issued by NWS Rapid City, SD

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755
FXUS63 KUNR 190807
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
207 AM MDT Sat May 19 2018

.DISCUSSION...(Today Through Friday)
Issued at 205 AM MDT Sat May 19 2018

08z surface analysis had wiggly frontal boundary from northern UT
into the central Plains into the upper Midwest. High pressure
over south central Canada nosing into the northern Plains with low
level upslope northeast boundary layer flow over the CWA. This
flow assisting some DZ/FG that has developed recently, noted on
KUDX radar. Upstairs, water vapour had upper low over northeast
CO. Convection associated with upper low decreasing as instability
wanes. Short term concern is the upper low.

Today, upper low meanders into central NE as it weakens and upper
ridge moves into the northern Rockies. Surface high continues to
build in with drier air increasingly pulled into the CWA. Result
will be decreasing chances for precipitation as well as fog. Have
trimmed pops significantly this afternoon, except near the NE
border. Temperatures will be warmest across the north where best
sunshine occurs.

Tonight, any leftover precipitation ends early as surface high
becomes dominate. Temperatures will be near guidance.

Sunday, surface high shifts east with return flow and warm air
advection. Southwest flow aloft develops as another upper
trough/low deepens across the far western CONUS. Temperatures
will be near guidance.

Monday through Wednesday, upper trough spins a series of shortwaves
into the CWA under southwest flow aloft. TSRA chances warranted
given low level moisture return. Temperatures will be 5-10F above
normal.

Thursday into Friday, uncertainty increases as upper low ejects
into south central Canada and then moves away as upper ridge
builds over the Rockies. PoPs continue with slightly above normal
temperatures.


&&

.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1034 PM MDT Fri May 18 2018

Widespread MVFR-IFR (local LIFR) conds can expected across the SW
2/3 tonight with rain slowly trending south. Drier air will move
into the area Sat with flight conds improving NE-SW.

&&

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

$$

DISCUSSION...Helgeson
AVIATION...JC



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