Area Forecast Discussion
Issued by NWS Rapid City, SD

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296
FXUS63 KUNR 250837
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
237 AM MDT Sat Mar 25 2017

.SHORT TERM...(Today Through Sunday Night)
Issued at 234 AM MDT Sat Mar 25 2017

08z surface analysis had low over southern AB with trough/warm
front into western NE and cold front into ID. 2-3mb/3hr pressure
falls noted along warm front, which was supporting gusty southerly
winds over northeast WY into far northwest SD. Latest water
vapour loop had weak ridge over the northern plains and trough
kissing the west coast. This feature will be the main concern in
the short term.

Today, upper ridge shifts east as upper trough moves into the
Rockies. Thermal ridge peaks over the CWA today as warm front moves
east of CWA, but won`t be fully realized given upstream mid/high
cloud cover. Ascent ahead of trough may bring some precipitation
to the far western reaches of the CWA late with a few showers
possible over the Black Hills given steep lapse rates.
Temperatures will be near guidance.

Tonight through Sunday morning, cold front drops into the CWA as
surface low travels across south central Canada. Cold front links up
with secondary low over eastern WY. Well-defined 850-700mb
frontogenesis foreseen with band of lift supporting a 3-6 hour
period of -RA moving across the CWA through Sunday morning. Thermal
profiles suggest -SN possible over northeast WY and the higher
elevations of the Black Hills, but accumulations will be minor. Kept
categorical pops going just behind cold front given model
consistency.

Sunday afternoon and night, transient upper ridge moves into the
northern plains with surface high building into the Dakotas. Return
flow starts up rather quickly Sunday night ahead of next upper
trough entering the west coast. Temperatures will be near guidance.

.LONG TERM...(Monday Through Friday)
Issued at 234 AM MDT Sat Mar 25 2017

Unsettled progressive flow is expected next week with a series of
upper troughs moving through the CWA. First system moves through
Monday night and Tuesday with mainly -RA, but some -SN possible
over the higher elevations. Next main system rolls in next Friday.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 234 AM MDT Sat Mar 25 2017

IFR CIGS/VSBYS due to stratus/BR over central SD will mix out by
17z. Otherwise, VFR conditions expected through this afternoon.
Gusty southerly winds over the west will shift east today. A storm
system and frontal boundary will bring deteriorating conditions
tonight with areas of MVFR CIGS/VSBYS developing. Local IFR
conditions expected over the higher terrain.

&&

.FIRE WEATHER...
Issued At 234 AM MDT Sat Mar 25 2017

Drier and warmer weather is expected today. Gusty southerly winds
at times with minimum relative humidities dipping to around 20
percent are expected east of the Black Hills. Very high grassland
fire danger is expected for these areas.

&&

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

$$

SHORT TERM...Helgeson
LONG TERM...Helgeson
AVIATION...Helgeson
FIRE WEATHER...Helgeson



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