Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 031512

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
912 AM MDT Wed Jun 3 2020

Issued at 912 AM MDT Wed Jun 3 2020

Current surface analysis shows low pressure over southern SK, with
warm front extending southeast into the Northern Plains and a cold
front sliding across central MT into northwest WY. Upper level
analysis shows zonal flow across the region, with weak embedded
energy bringing showers and thunderstorms to portion of northwest
into central SD this morning. A couple of the storms have been on
the stronger side with some hail. This activity should move east
out of most of the CWA by midday. Mid morning temps are in the
60s and lower 70s, with relatively light south to southeast winds
in most areas.

Isolated to widely scattered thunderstorms are expected this
afternoon, mostly across western into central SD in area of
stronger instability behind the warm front and ahead of the cold
front to the northwest. Shear is generally most favorable for
supercells from the Black Hills area, south and eastward to
central SD and NE. Severe storm threat should diminish rather
quickly early this evening.

Have updated forecast mainly to adjust pcpn chances over eastern
areas for the rest of the morning and tweak chances a bit for the
afternoon. Highs still look to be in the mid 70s to mid 80s for
most areas, but may need to adjust them down a bit over eastern
areas with storms around this morning.


.DISCUSSION...(Today Through Tuesday)
Issued at 217 AM MDT Wed Jun 3 2020

Weak shortwave energy moving through zonal upper flow
and weak instability continue to create some showers/storms across
parts of the CWA this morning. With a surface high over western SD,
winds are light and variable. Temperatures at 2 AM are in the 50s to
lower 60s.

CAMs show showers/storms moving through western SD this morning,
gradually diminishing as they approach central SD. By mid-
afternoon, 1000-1500 J/kg MLCAPE develops across the western SD
plains, while weak shortwave energy continues to pass over SD.
More thunderstorms will develop, and with 0-6 km shear around 40
kts, a few severe storms will be possible. Most of the activity
will shift into central SD by 00Z with the shortwave. Shortly
afterwards, the next piece of energy will produce another round of
showers/storms across the northwest; however, minimal CAPE will
limit strength. Highs today will be generally in the 80s, with
lows tonight in the 50s.

Continued weak shortwave energy could cause a few isolated
showers/storms Thursday and Thursday night, especially over the
Black Hills. Decent instability and strong shear could result in a
few stronger storms, but overall lack of significant upper support
will limit activity.

Upper ridging builds on Friday, resulting in a mostly dry day, but a
few isolated showers/storms can`t be ruled out. Chances increase
Friday night into Saturday, as a strong wave quickly approaches
through southwest flow. GFS remains the most aggressive in strength
and speed of the wave. Strong moisture transport will support a wet
Saturday afternoon and evening for the northern plains. GFS and EC
are showing PWs more than 200% of normal, and NAEFs is showing PWs 2
to 3 standard deviations above normal. Will continue to watch this
system and its potential for severe weather Saturday.

Looking into next week, models hint at a strong upper low developing
over the Pacific NW, but then they diverge in the track of the low.
Depending on how things progress, next week could be cool and wet.


.AVIATION...(For the 12Z TAFS Through 12Z Thursday Morning)
Issued At 525 AM MDT Wed Jun 3 2020

Band of thunderstorms will linger across portions of western South
Dakota through this morning...mainly north-northeast of the Black
Hills. Local IFR conditions with the strongest cells. Additional
thunderstorms will develop across the area this afternoon. Local
IFR conditions along with hail/strong winds expected with the
storms this afternoon/evening.




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