Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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120 FXUS63 KUNR 180434 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1034 PM MDT Mon Jun 17 2024 .KEY MESSAGES... - Re-development of showers and storms, some storms may be strong to severe. - Below normal temperatures continue for much of the week, warming up towards the weekend. && .DISCUSSION...(This Evening Through Monday) Issued at 134 PM MDT Mon Jun 17 2024 With the upper trough, currently located over Idaho and western Montana, approaching from the west, fast southwesterly flow aloft continues over the forecast area this afternoon. With the surface low over srn WY/nrn CO, cool, moist easterly flow has covered most of the forecast area with low stratus today, keeping temperatures down and leading to areas of fog and drizzle along the eastern slopes of the Black Hills. The cool temperatures have greatly limited surface based instability over South Dakota today, however above the boundary layer MUCAPE has risen to 500-1000J/kg. In the relatively cloud free regions of northeastern Wyoming diurnal heating has caused SBCAPE to range from 500-1500J/kg so far this afternoon. Shortwave energy is heading northward on the east side of the upper trough, as indicated by the showers developing off the mountains near Casper, WY and moving northward. We may see a few strong to severe thunderstorms, with large hail and gusty winds, over parts of northeastern Wyoming later this afternoon into the evening as the instability aloft reaches the area. While surface based storms are unlikely over western South Dakota, expect to see expanding coverage of elevated storms this evening as the low level jet increases to 40-50kts over western South Dakota. Again there is a possibility for elevated strong to severe storms. Large hail and locally heavy rain will be the main threats over western South Dakota, although locally strong gusty winds will be possible with the strongest storms. The upper trough will cross the forecast area on Tuesday. With a band of drier air moving in from the southwest, the best chances for precipitation on Tuesday will be along the edges, over northwestern and south central, SD. Fast southwesterly flow aloft will stick around for the remainder of the week, with models showing mild disturbances riding the flow almost daily. This will allow for active weather to continue into next weekend, though some days precipitation may be very isolated. Low level flow becomes predominantly out of the south- southeast mid-week and later, and we can expect a warming trend towards the weekend. && .AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night) Issued At 1030 PM MDT Mon Jun 17 2024 MVFR/IFR conditions in storms and low stratus will continue overnight and dissipate early Tuesday morning. Some of the storms will be severe for the next few hours, with large hail and strong, erratic winds. Northwesterly winds will become gusty behind a cold front, diminishing Tuesday evening. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...10 AVIATION...Pojorlie