Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 040443

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1043 PM MDT Wed Jun 3 2020

.DISCUSSION...(This Evening Through Wednesday)
Issued at 258 PM MDT Wed Jun 3 2020

Current surface analysis shows low pressure over southeast SK,
with warm front extending southeast into eastern ND and a cold
front sliding across northwest SD into eastern MT. A surface
trough is also in place over western portions of the Dakotas, with
another boundary noted along the SD/NE border in the wake of
morning convection. Upper level analysis shows zonal flow across
the region, with weak embedded energy helping to produce isolated
to widely scattered thunderstorms. Temps are mostly in the mid 70s
to mid 80s.

Widely scattered thunderstorms are expected late this afternoon into
early this evening across western into central SD in area of higher
instability near the trough 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
thunderstorm watch is in effect until 700 PM. Large hail looks to be
a bigger threat with any severe storms, but strong wind gusts are
also possible. Cold front will progress slowly into northern
portions of the forecast area overnight, with chances for showers
and a few storms mostly from northeast WY to northwest SD.

On Thursday, the cold front will slowly move southeast across the
area. Lingering showers and thundershowers are possible early in the
day across mostly northern areas. Highs will range from the upper
70s across northern areas and the Black Hills to the upper 80s over
far southern SD. Chances for showers and thunderstorms will then
increase in the afternoon, especially over the Black Hills and areas
to the east along and ahead of the front. Shear looks to be stronger
tomorrow for supercells, but CAPE somewhat weaker. Isolated strong
to severe storms look possible again in the afternoon and early
evening, but the potential may depend more on strength of upper
forcing, which looks rather weak at this point.

Cold front will settle south of most of the area on Friday, with
highs in the mid 70s to mid 80s, warmest conditions from parts of
northeast WY to far southwest SD. Weak ridging will build over
western areas in the afternoon, likely limiting chances for storms
over most of the area during the day. Will just keep some low
chances over the Black Hills for the afternoon. Southwest flow aloft
will develop Friday night and Saturday as large trough is expected
to develop over the western states. Chances for showers and storms
should increase again over the weekend, especially later on
Saturday. Potential for severe storms looks to be greater on
Saturday, along with locally heavy rainfall.

Upper trough will slowly progress east-northeast Sunday and early
next week, with embedded low likely moving from the northern Rockies
to south central Canada. Warm conditions over the weekend will give
way to cooler air early next week. Chances for showers and storms
into early next week will be dependent on the track of the upper
trough and any disturbances that could move northeast across our
region. Will keep at least low end chances in the forecast for
most areas early to mid week.


.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 1042 PM MDT Wed Jun 3 2020

Another disturbance will bring a chance for showers and a few
storms overnight into Thursday morning, mainly from northeast WY
to northwest SD. A cold front will slowly slide southeast across
the area late tonight and Thursday. Isolated strong to severe
storms are possible in the afternoon, especially from the Black
Hills to central SD.




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