Area Forecast Discussion
Issued by NWS Rapid City, SD

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166
FXUS63 KUNR 291602
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1002 AM MDT Wed Mar 29 2017

.UPDATE...
Issued at 1000 AM MDT Wed Mar 29 2017

Current surface analysis shows low pressure system that brought
the recent rains is centered over southeast KS. Upper level
analysis shows slow moving low over central OK, with near zonal
flow across the western US. Strong jet remains mostly northwest of
the region. Lingering light rain early this morning across far
southern SD has ended. Sat imagery shows low clouds persisting across
parts of northeast WY and western SD, but fog has mostly lifted.
Clouds remain across south central SD, with some clearing
elsewhere. Temps are in the 40s with light winds.

Have updated to make adjustments to cloud cover, remove pops and
fog, and tweak temps for the afternoon. Will keep highs mostly in
the 50s, with some areas near 60 over northeast WY and the far
western SD plains, as warmer air pushes in from the west. Winds
will remain variable in direction and mostly on the light side.

&&

.SHORT TERM...(Today Through Thursday Night)
Issued at 211 AM MDT Wed Mar 29 2017

08z surface analysis had weak high over the CWA and inverted
trough across eastern NE into eastern SD. Water vapour loop showed
upper low entering TX panhandle with precipitation shield mainly
southeast of the CWA, although some weak returns/-RA noted over
south central SD under weak 75kt jet streak aloft.

Today, upper low moves northeast with lingering lift exiting the CWA
this morning and staying southeast of the CWA this afternoon. Patchy
fog expected early this morning given tight T/Td spreads and general
moistness of boundary layer. Sunshine will develop in the afternoon
with highs slightly above normal and near guidance.

Tonight, another upper trough crashes the northwest US coast pushing
shortwave ridging and weak low level return flow over the CWA. Lows
will be near guidance.

Thursday, upper trough splits with main energy diving into the four
corners area. Return flow increases with surface trough moving into
the western portions of the CWA. PoPs warranted with best chances
Thursday night in the far west where 850-700mb frontogenesis
combined with synoptic lift to produce a band of mostly rain.
Temperatures may become cold enough late Thursday night for some
snow over northeast WY into the Black Hills, but accumulations will
be minor.

.LONG TERM...(Friday Through Tuesday)
Issued at 211 AM MDT Wed Mar 29 2017

Friday, aforementioned upper low digs deep into the southwest US
with lingering lift supportive of some rain over mainly southwest
half of the CWA. Could be a bit of snow early. Temperatures will
be near guidance.

Saturday through Monday, a bit of rain possible under weakly
unstable flow aloft.

Tuesday, better looking storm system approaches from the west with
upper low bringing PoPs to the CWA. Disagreement with timing and
placement of low; something one would expect for Day 7, but
something to be watched.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Thursday Morning)
Issued At 515 AM MDT Wed Mar 29 2017

East of KGCC, widespread MVFR/IFR CIGS will continue through
early this morning with local IFR/LIFR VSBYS due to patchy fog,
especially near the Black Hills. Conditions will improve from west
to east later this morning through the afternoon hours.
Widespread VFR conditions expected tonight.


&&

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

$$

Update...26
SHORT TERM...Helgeson
LONG TERM...Helgeson
AVIATION...Helgeson



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