National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KUNR 140906
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
306 AM MDT Sun Apr 14 2024

.KEY MESSAGES...

- Warm weather continues into Monday with elevated fire weather
  conditions this afternoon, especially across northeast Wyoming.

- Threat for strong to severe storms later Monday afternoon into
  Monday evening across much of the area.

- Unsettled, windy, and gradually colder weather expected for the
  rest of the week.

&&

.DISCUSSION...(Today Through Saturday)
Issued at 306 AM MDT Sun Apr 14 2024

Current surface analysis shows weak cold front just south of the
forecast area, with high pressure to the north- northeast of the
region. Upper level analysis shows flattened ridge over the area,
with upper low along the central CA coast. Skies are mostly clear
with mild temps in the 40s and 50s. Winds are mostly light and
variable.

Unseasonably warm weather continues today and into Monday, but not
quite as warm as yesterday, with highs mostly in the mid 70s and
lower 80s. South to southeast winds develop in most areas later this
morning and afternoon, with south to southwest winds across
northeast WY. Elevated fire weather conditions can be expected again
in many areas. Humidities will be lowest across northeast WY,
dropping to around 15 percent in most areas, with near critical
conditions likely for at least a brief period. A few showers could
develop in far eastern portions of the forecast area later tonight
into Monday morning, with low level southerly jet intensifying
across the central Dakotas. Gusty southeasterly winds can be
expected later Sunday night and Monday across the SD plains,
especially toward south central SD, where winds could at
least approach advisory criteria on Monday.

Ridging shifts east of the region on Monday as west coast system
moves quickly across the western US to the Rockies by late Monday.
Abundant shortwave energy ahead of the low will push north-northeast
across the high Plains late Monday and Monday night, with increasing
chances for showers and thunderstorms. A Pacific cold front will
also slowly move into the area during the afternoon and evening,
with areas of low pressure along it over northeast WY and eastern
CO. MUCAPE is progged to reach 500 to around 1000 j/kg in many areas
late in the day, highest values generally southeast of the Black
Hills, with modest shear developing from the Black Hills to south
central SD. The best threat for strong to severe storms looks to be
from the Black Hills into northwest SD, and also with any stronger
storms that may make it into southern SD from NE, during the late
afternoon and evening. Strong wind gusts and marginally severe hail
look to be the main threats with any stronger storms, with large
hail possibly more of a threat over far southwest/south central SD.
The best chances for some heavier rainfall look to be across these
same areas as well, with near 50 percent or higher chances for a
half inch or more of rainfall, though convective nature of rainfall
will make the higher amounts more hit and miss.

Upper low will track across the central Plains Monday night and
Tuesday, with areas toward south central SD having the highest
potential for beneficial rainfall later Monday night and Tuesday. As
the low tracks south and eventually southeast of the area, winds
will increase later Monday night and especially on Tuesday. At this
time, there is better than a 50 percent probability of wind gusts
reaching or exceeding 45 mph across much of the forecast area on
Tuesday, with a 30 to 70 percent chance of warning criteria gusts
(near or over 60 mph) across a good portion of the western SD
plains, with the highest chances over the west central SD plains. A
high wind watch may be needed in future forecasts if these trends
persist. After the system passes east of the region Tuesday night,
another upper low is progged to track across the northern/Canadian
Rockies and into south central Canada midweek. The system continues
to look like it will track far enough north that pcpn potential will
be relatively low across much of our area. However, colder air will
push into the area mid to late week, with some chances for light
rain and mostly higher elevation light snow at times. Breezy to
windy conditions can also be expected with the colder air mid to
late week. At this point, next weekend looks mainly dry with more
seasonable temperatures, especially by Sunday.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1012 PM MDT Sat Apr 13 2024

VFR conditions are forecast through the TAF period.

&&

.FIRE WEATHER...
Issued At 306 AM MDT Sun Apr 14 2024

Though green-up is progressing across the area, elevated fire
weather conditions are expected again later today across much of
the area as humidities drop to 13 to 25 percent, lowest values
across the northeast Wyoming plains. South to southwest winds will
gust to 20 to 25 mph across much of the northeast Wyoming plains
this afternoon and will likely produce a period of near red flag
conditions in some areas. Minimum relative humidities will be 5 to
15 percent higher on Monday as low level moisture increases
across the area. However, gusty winds to the east of the Black
Hills will help to produce high to very high grassland fire danger
in those areas.

&&

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

$$

DISCUSSION/KEY MESSAGES...26
AVIATION...Helgeson
FIRE WEATHER...26