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000
FXUS63 KUNR 152214
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
414 PM MDT Mon Apr 15 2024

.KEY MESSAGES...

- Through this evening, strong to severe storms across much of the area.

- Tuesday, strong winds and showers. Strongest winds east of Rapid City
  to the Badlands. Windy conditions across portions of northeast
  Wyoming, southwestern South Dakota, and south central South
  Dakota.

- Rest of the week into the weekend looks to be unsettled, windy,
  and colder.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 313 PM MDT Mon Apr 15 2024

Water vapor imagery and upper level analysis shows a large upper low
over Utah and a strong upper level jet rounding the low from the
southern Rockies edging into the central Rockies and western High
Plains. At the surface, there is an area of low pressure in
northeastern Colorado/Nebraska panhandle, with a stationary
boundary/warm front extending northward through into eastern
Wyoming/western South Dakota. Strong southeasterly winds, as a
result of a tight pressure gradient over the South Dakota plains,
are helping to advect moisture into the area. Clouds are clearing
from south to north across the forecast area, with some CU already
forming near the Badlands. Temperatures are currently in the upper
60s and 70s.

For this evening, the cap is quickly eroding, which is going to
cause rapid thunderstorm development. Strong southeasterly/easterly
flow has resulted in dew points in the mid 40s. Expect more moisture
to arrive this evening with MUCAPE of 1000 J/Kg. Most CAMs suggest
storm development later this afternoon and early evening, but
satellite is suggesting convective initiation earlier. Shear is
strong with strongly veered wind profile, which would suggest large
hail and severe wind gusts are possible. Showers and thunderstorms
will develop and increase in coverage. Precipitable water values
will be above average, near or above one inch across much of western
and south central SD, so at least locally heavier rainfall can be
expected, with many areas having high potential (above 50 percent)
of a half inch or more of beneficial rainfall later today into
Tuesday. Severe storm threat should diminish by late evening in most
areas, but could linger into the overnight over south central SD as
the low tracks east across NE.

The main concern for Tuesday will be strong north northwest winds
on the back side of the system as the surface low tracks across
Nebraska and into Iowa by Tuesday evening. Winds will increase
initially across northeast WY late tonight and then across western
SD Tuesday morning. Most of the forecast area will see wind gusts
ranging from 40 to 50 mph on Tuesday, with areas along the
eastern foothills and west central plains having potential for
wind gusts to 60 mph during the midday and afternoon hours. For
now, I have decided to continue the high wind watch for these
areas rather than upgrade. Winds should drop off fairly quickly by
early evening. Showers can be expected across most of the area on
Tuesday, with isolated thunderstorms expected, mainly east of the
Black Hills. Upslope enhanced rainfall will develop for a period
across the northern Black Hills. Highs will mostly be in the 50s
and lower 60s, with 40s over the higher Black Hills. Threat for
severe storms should remain east of the forecast area. Precipitation
will dissipate from west to east during the afternoon and evening
hours.

The rest of the week looks to be unsettled, cool, and windy at
times. A Canadian upper low passes well north of the region midweek,
with northwest flow aloft developing across the region by late week.
A disturbance rotating well southwest of the Canadian low will bring
chances for rain and snow Wednesday and Wednesday night, mainly from
northeast WY to the Black Hills and southern SD. Some minor snow
accumulations are possible, especially across the higher Black Hills
and over Campbell County. Blustery winds can be expected Wednesday
and Thursday, with below average temperatures Wednesday through at
least Saturday. A couple of disturbances could bring low chances for
rain/snow Friday and over the weekend.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening)
Issued At 409 PM MDT Mon Apr 15 2024

Gusty southeasterly winds will continue over much of western
South Dakota into the evening. Scattered showers thunderstorms
will become more numerous this evening and overnight. Areas of
MVFR conditions will develop over the BLKHLS this evening and
deteriorate to widespread IFR conditions after 09Z tonight, but
with VFR conditions over Campbell County, WY. Conditions will
improve from west-to-east Tuesday afternoon as the precipitation
moves east. Strong and gusty northwest winds will develop on
Tuesday, especially on the plains to the east of the Black Hills.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...High Wind Watch from Tuesday morning through Tuesday afternoon
     for SDZ026-030-031-042-072>074.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...MLS
AVIATION...Bunkers