000
FXUS63 KUNR 100805
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
205 AM MDT Wed Apr 10 2024

.KEY MESSAGES...
201 AM MDT Wed Apr 10 2024

- Very windy today with gusty northwest winds and scattered rain
  and snow showers (minimal accumulations); even a few weak
  thunderstorms are possible

- Warming trend tomorrow through Friday, with very mild weather
  this coming weekend (highs in the 70s with even a few lower 80s)

- Next noteworthy chances for precipitation are Sunday night
  through Monday and Tuesday

&&

.DISCUSSION...(Today Through Tuesday)
Issued at 201 AM MDT Wed Apr 10 2024

The latest water vapor loop and 500-mb height analysis showed a
weak-short wave trough currently moving over the CWA with very
weak radar echoes; a stronger short-wave trough was over
northwestern-to-central MT with scattered showers and even some
GLM and NLDN CG flashes. At the surface, a cold front was over
northern MT and moving toward the CWA while very mild westerly
breezes were over the CWA at this time.

This short-wave trough and cold front will pass over the CWA today.
Low level cold advection and surface pressure rises of 2-4mb/3hrs
point to very wind conditions developing, with northwest gusts of 45-
55 mph expected on the western South Dakota plains. HREF/NBM wind
gusts along with ensemble 850-mb winds of 30-40 kt support the
previously issued wind advisory for much of the SD plains today.
Have added a small chance of thunder to much of this same area
given steep midlevel lapse rates and SBCAPE of 100-300 J/kg --
consistent with the current observations of lightning upstream
(and overnight at that). The Q-G forcing with the wave will be
marginal, so the showers will be diurnally focused with the
highest PoPs from 18z to 00z. SREF/NBM probabilities support
mostly rain, but snow will be the likely precip type across the
BLKHLS and parts of northeastern WY and northwestern SD. Little or
no snow accumulation is expected. The wave and associated showers
should be east of the forecast area by 03-06z Thursday (i.e.,
this evening), so have added some evening PoPs across the eastern
CWA.

A substantial warming trend will occur for Thursday through Saturday
with 850mb temps climbing sharply to around 20C. Highs in the 70s
are likely Friday through Monday. Some 80s are possible toward south-
central SD, although max temps may be moderated some in areas that
have received substantial rain over the last few days. Very small
chances of diurnally driven showers are possible, but nothing
substantial is expected.

The ensembles agree well on another big upper low moving into the
southwestern CONUS by Monday, possibly bringing rain/snow to the
forecast area through Tuesday/Wednesday. Even though confidence
is high with this upper low occurring, there remains much
uncertainty on its precise track across the central CONUS at this
time. However, it does appear this system will be warmer than the
most recent one.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 1003 PM MDT Tue Apr 9 2024

VFR conditions are expected throughout the TAF period for most
places. The exception is for the northern BLKHLS after 06z as some
showers and local MVFR/IFR conditions could develop. Behind a cold
front, strong northwesterly winds will develop Wednesday morning,
especially across the western SD plains where gusts over 40 knots
are expected.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 10 AM MDT /11 AM CDT/ this morning to 7 PM
     MDT /8 PM CDT/ this evening for SDZ001-002-012>014-025-026-
     030>032-042>044-046-047-049-072-073-077-078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Bunkers
AVIATION...Johnson