Box Elder, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

806
FXUS63 KUNR 062321
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
521 PM MDT Fri Jun 6 2025

.KEY MESSAGES...

- Showers and thunderstorms mainly focused over the Black Hills
  diminishing this evening

- Showers and thunderstorms Saturday afternoon with some strong
  wind gust potential in northern/central South Dakota

- Windy Sunday

- Warming trend mid-week with increasing thunderstorm chances and
  potential severe storms late next week

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 110 PM MDT Fri Jun 6 2025

Water vapor channel satellite imagery shows an upper level trough
moving eastward across Wyoming early this afternoon. Flow is
noticeably stronger at tropopause/jet level, with a distinct PV
anomaly in the models. Lower tropospheric flow is quite weak.

There are two precipitation regimes ongoing today: 1) weak
convection rooted in the mid levels and resultant light
precipitation amounts that has been ongoing from central/southern
Wyoming eastward into Nebraska and far southern South Dakota, 2)
diurnal convection focused within elevated heating regime in the
Black Hills. The latter may have sufficient depth for some charge
separation and lightning later this afternoon, but weak
instability and insufficient low-mid tropospheric flow/shear will
likely limit organization and intensity and convective hazards
beyond lightning. Convection may struggle to maintain east of the
Black Hills as cloud layer flow is weak.

A deepening midlevel trough to our north will force a weakly
baroclinic front through our area tomorrow afternoon. The post-
frontal air mass per model guidance will be slightly more moist,
contributing to a shallow layer of instability atop a deep well
mixed PBL. This should support isolated to scattered diurnal
convection with some potential for strong wind gusts with the more
intense convective cells given the deep PBL mixing. Strengthening
tropospheric flow will support faster storm motions compared to
today (southeasterly at 40-45 mph). There is a low probability of
damaging wind gusts, mainly across roughly the northeast third of
the forecast area where instability is modest but potentially
sufficient mid-afternoon through early evening. The primary
convective threat will be lightning, however.

On Sunday, pressure gradient will be tight between positive MSLP
anomalies in the lee of the Rockies and and trough/surface low to
our east. Coupled with deep diurnal mixing, windy conditions with
gusts to 40-50 mph are expected especially east of the Black
Hills.

Western ridging and associated positive midlevel height anomalies
will migrate eastward across the west and central part of the
country through the week, bringing a warming trend for our region.
Temperatures by Tuesday and Wednesday will rise to at least 10-15
degrees above normal for this time of year. Convection in the
Black Hills due to elevated heating will re-emerge possibly with
the diurnal cycle Tuesday, and more likely Wednesday, as modest
low level moisture return occurs.

Model ensemble spread grows some by the latter part of next week
(Thursday-Friday), though the broader synoptic signal of
increased troughing in the west and somewhat perturbed
southwesterly flow over our region is consistent among the model
suite. Low end severe thunderstorm probabilities exist in the
ensemble-driven CSU machine learning system during this period.
Most models do show instability/shear parameter space favorable
for organized intense convection, with some forcing from upstream
trough.

Early indications for the Day 8-14 period are for above normal
temperatures and near normal precipitation. There is a range of
possibilities in the ensembles at that time range (as is typical),
but a general trend toward retrograding/amplifying ridging over
the area with a progressive pattern still and associated periodic
opportunities for convection.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening)
Issued At 521 PM MDT Fri Jun 6 2025

SHRA/TSRA and associated localized MVFR/IFR conditions are
expected to gradually diminish through 06z. Thereafter, VFR
conditions should prevail through 18z. After 18z, additional
SHRA/TSRA may develop from north to south, with MVFR/IFR
conditions not out of the question. Breezy northwest winds will
develop from north to south beginning around 15z, with gusts to
around 40 kt possible 18-00z across northwestern SD.

&&

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

$$

DISCUSSION/KEY MESSAGES...Bowers
AVIATION...Sherburn