FXUS63 KUNR 182322
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
522 PM MDT Mon May 18 2026

.KEY MESSAGES...

- Widespread precipitation tapers off this afternoon and evening.

- Cold temperatures continue with a freeze warning in effect
  Tuesday morning.

- Gradual warmup mid-week with precipitation chances returning
  towards the weekend.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 128 PM MDT Mon May 18 2026

Current Water Vapor and upper air models show troughing just east
of the Rockies running through the northern and central plains,
with upper ridges over the New England region and off the west
coast. 19Z surface analysis depicts a surface low to our east over
MN, surface high over central MT. Radar shows widespread
precipitation across the forecast area, with some of the higher
elevations receiving light accumulations of snow today. Winds are
currently breezy out of the northwest to north, with temperatures
in the 30s to low 40s. 

Precipitation will taper off from west to east late afternoon
through the evening, as trough slides eastward today. Cool
temperatures continue tonight as clouds clear up and light
northwest winds continue. Much of the area is expected to reach
near or below freezing overnight. HREF probability for temps to
reach at or below freezing sit at 80-100% for areas from the Black
Hills and west. Further east will be a bit trickier as cloud cover
will linger into tonight as the trough slowly shifts eastward. A 
Freeze warning has been issued for most of our plains areas, with 
a frost advisory in effect for part of south-central SD for 
Tuesday morning. 

Brief and weak ridge sets over the region mid-week, resulting in
drier conditions and a warming trend towards near seasonable.
Another wave rides southeast from western Canada towards the
northern plains later in the week, increasing chances for
precipitation late Thursday into Friday. Shortwave ridging moves
over the weekend, bringing warmer temps back in as well. By
Sunday/Monday the region should see highs climb back into the 80s
to low 90s. 

&&

.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening)
Issued At 519 PM MDT Mon May 18 2026

An area of precipitation (rain on the plains/snow up high) and 
low clouds will lift northeast this evening. Widespread MVFR/IFR
(local LIFR with the snow) conditions will slowly improve from 
west to east overnight with lingering MVFR/IFR conditions from 
KD07-KICR Tuesday morning. VFR conditions are expected all 
locations after 19/18z.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Freeze Warning from midnight tonight to 9 AM MDT Tuesday for 
     SDZ001-002-012>014-025>027-030>032-041>044-072>078.
     Frost Advisory from 1 AM to 10 AM CDT Tuesday for SDZ046-047.
WY...Freeze Warning from midnight tonight to 9 AM MDT Tuesday for 
     WYZ054>056-058>060.
&&

$$

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