Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 261744
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1144 AM MDT THU MAY 26 2016

.SHORT TERM...(Today Through Friday Night)
Issued at 300 AM MDT Thu May 26 2016

08z surface analysis had boundary boundary from western MN to
eastern CO with low pressure centers over northwest MN and
southeast CO. Water vapour loop had upper low over eastern MT and
another over central AZ. The evolution of these two upper lows and
then the surface low over southeast CO the main concern.

Today, MT upper low shifts into western ND with shortwave energy
rotating through ND/SD border. This will push weak frontal boundary
into CWA this afternoon. AZ upper low ejects into central CO with
deepening surface low over southeast CO. This low will enhance low
level moisture over the southeast half of the CWA. MLCAPE increases
over the CWA through the afternoon peaking around 250J/kg in the
northwest to around 1000J/kg in the southeast. 0-6km bulk shear
sufficient for rotating updrafts with enough instability. MLCIN
erodes midday in the northwest and late this afternoon in the
southeast. Expect TSRA to develop by midday over the Black Hills
and then over the rest of the CWA in the afternoon. Given weak
instability in the northwest, activity should be fairly benign
with better organization in the southeast where instability
greatest. Isolated severe storms possible across south central SD.
Temperatures today will be near guidance.

Tonight, CO upper low moves into western KS with deeper synoptic
forcing wrapping into south central SD and subsequent higher
coverage SHRA/TSRA activity. Ongoing active convection should wane
quickly in the evening. Temperatures will be near guidance.

Friday, upper low over KS weakens and then lifts northeast late.
Should still see SHRA/TSRA over parts of the CWA but instability and
forcing weaker. Temperatures will be near guidance.

.LONG TERM...(Saturday Through Wednesday)
Issued at 300 AM MDT Thu May 26 2016

Persistent upper level trough over the northwest CONUS will keep
active west to southwest flow across the Northern Plains for the
Memorial Day weekend and into the middle of next week. Periodic
shortwave energy will eject out of the trough, keeping a daily
chance of showers and thunderstorms in the forecast through the
extended period. Temperatures will be near seasonal averages, with
highs each day generally in the mid 60s to upper 70s. Lows at
night will be in the 40s to mid 50s.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1143 AM MDT Thu May 26 2016

Showers and thunderstorms will re-develop across the area this
afternoon and evening. Local IFR/LIFR conditions expected in the
vicinity of stronger showers/storms.

&&

.UNR Watches/Warnings/Advisories...
SD...None.
WY...None.
&&

$$

SHORT TERM...Helgeson
LONG TERM...15
AVIATION...13



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