648
FXUS63 KUNR 291109
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
509 AM MDT Mon Apr 29 2024

.KEY MESSAGES...

- At or above normal temperatures for the first half of the week.

- Showers possible Monday night into Tuesday.

- Cooler and more unsettled weather the latter half of the week.

&&

.DISCUSSION...(Today Through Sunday)
Issued at 217 AM MDT Mon Apr 29 2024

Most recent Water Vapor and upper air models show the upper low
entering Minnesota this morning, with mild upper ridge building
behind it over the northern plains. Surface analysis shows low
pressure system over SK, with a frontal boundary running south
through MT into WY. Current radar shows precipitation exiting the
eastern edge of the forecast area this morning. Temperatures this
morning sit in the low to mid 30s, with light westerly winds.

Warm front slides across the forecast area today, with highs
reaching into the 60s for most of the region (mid to upper 50s for
the Black Hills). Dry westerly flow will drop Relative Humidities
into the 15-20 percent range over parts of the northeaster WY
plains, while western SD will see 20-40 percent humidities.
Upslope flow could allow for some showers to develop over the
central and northern Black Hills this afternoon. Tonight into
Tuesday, an upper low passes north of the region, increasing
chances for showers to much of the area. Higher elevation Black
Hills may see some light snow showers, while the rest of the area
can expect rain. 3-4mb/3hr pressure rises behind the low will
allow for some gusty northwest winds on Tuesday. Low end wind
headlines may be needed over northwestern SD Tuesday afternoon.
This drier northwest flow will also bring elevated fire
conditions, with much of the forecast area seeing relative
humidities dipping into the teens.

Active weather continues the latter half of the week, as upper
trough expands over the northern Rockies and eventually into the
plains. Models differ a bit on the track of this next wave, with
the GFS progging the system further south than the ECMWF/NAM
models. Colder temps the latter half of the week could allow for
more snow potential Wednesday night depending on how the system
tracks. A second wave is expected to move through the northern
plains in the Fri/Sat timeframe, bring another chance for
rain/snow showers early weekend.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Tuesday Morning)
Issued At 506 AM MDT Mon Apr 29 2024

Local IFR/LIFR conditions due to shallow fog will dissipate by 15z
across northwest SD. Otherwise, VFR conditions are expected
through 06z Tuesday. After 06z Tuesday, MVFR CIGS will move into
northeastern WY/far northwestern SD behind a cold front. Isolated
showers are possible this afternoon over the Black Hills with
scattered showers tonight over much of the area.

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...Helgeson