Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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795 FXUS63 KUNR 132040 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 240 PM MDT Thu Jun 13 2024 .KEY MESSAGES... - Chances for showers and thunderstorms increase late tonight and Friday, with a marginal risk for severe storms on Friday. - A more unsettled pattern for the weekend and the first half of next week, with occasional chances for showers and storms. && .DISCUSSION...(This Evening Through Thursday) Issued at 240 PM MDT Thu Jun 13 2024 Current surface analysis shows a cool front from the western Great Lakes to the central Plains, with high pressure sliding into the northern Plains. Upper level analysis shows shortwave trough over the upper Midwest, with weak ridging over the northern Rockies and high pressure centered over NM. Skies are mainly sunny with more seasonable temps this afternoon, mid 70s to mid 80s. Winds are relatively light with high pressure moving over the area. Dry and pleasant weather will continue through the evening hours. Low level southerly jet will develop and intensify over the northern/central high plains overnight, mainly from western NE to eastern MT, as high pressure starts to slide east of the region. Theta-e advection will increase across these areas as well. There will be increasing chances for showers and thunderstorms later tonight and especially on Friday (20 to 50 percent), initially across southern parts of northeast WY and southwest SD, then eventually spreading across a good portion of western SD during the day. Breezy southerly winds will bring increasing moisture and some warmer air into the area. Highs will reach the 80s to around 90 across much of the Plains, with 70s over the higher Black Hills. Assuming we get sufficient sunshine and warming during the day, MLCAPE will increase to 1000 to 2000 j/kg by early afternoon from far northeast WY to much of the western SD plains. Shear looks to be strong enough for at least short-lived supercell potential over the Black Hills area. Better upper level support for more widespread storm potential may hold off until late in the day and the evening. A marginal risk for severe storms is in place across most of the area, especially the Black Hills area and eastward, mostly during the PM hours. Large hail and eventually strong wind gusts would be the primary threats from stronger storms. The weekend looks to be decent overall, but Sunday will be the nicer day of the two. A large scale upper trough will move across the Pacific NW into south central Canada over the weekend, with southwesterly flow developing across the northern Plains. Saturday will be very warm, ahead of an approaching cold front, with highs in the mid 80s to lower 90s in most areas. Chances for showers and thunderstorms will increase again in the afternoon, at least over from far northeast WY to the Black Hills and northwest SD, as some embedded energy passes over the region. Better chances again may hold off until late day and evening as the front arrives over northern/western areas. Later timing of front may limit severe potential, but the better chances for stronger storms would mostly likely be from far northeast WY to the Black Hills and northwest SD. Front pushes through the area Saturday night with gusty northwesterly winds and cooler air for Sunday. Sunday looks to be dry as the upper trough tracks well north of the region and much drier air pushes into northeast WY and much of western SD. Highs will be more seasonable, mostly in the 70s and lower 80s. Another upper level system is progged to cross the northwest US into the northern Plains/south central Canada late in the weekend and early next week, with chances for storms returning by later Sunday night and Monday. The first half of next week could be fairly stormy and cool, depending on the exact track of the system and embedded disturbances within, which is still fairly uncertain at this point. Highs look to only be in the 60s and 70s for the Monday through Wednesday period. A warmer and drier pattern could develop toward the end of the week. && .AVIATION...(For the 18Z TAFS Through 18Z Friday) Issued At 1106 AM MDT Thu Jun 13 2024 Isolated showers, and possibly a thunderstorm, are possible mainly over western South Dakota after 06Z tonight continuing through Friday morning. VFR conditions are expected through the TAF period, except near any thunderstorms, where local MVFR CONDS are possible. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...26 AVIATION...10