Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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674 FXUS63 KFSD 311907 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 207 PM CDT Fri May 31 2024 .KEY MESSAGES... - Showers and thunderstorms will be capable of lightning and locally heavy rainfall late this afternoon and evening. Isolated funnel clouds will also be possible. The better chances will be southeast of a Yankton to Windom line. - Ingredients are coming together for a potential severe weather outbreak on Sunday afternoon and night. Stay tuned for updates. - Tuesday will be the next better chance for severe weather, but still some question marks, the main one being a potential MCS late Monday night into Tuesday morning which could push the deeper instability south and really limit Tuesday afternoon potential. && .DISCUSSION... Issued at 207 PM CDT Fri May 31 2024 Showers and thunderstorms with locally heavy rain will continue through sunset, then gradually diminish and shift east through the night. Model soundings indicate about 500 to 1000 J/kg CAPE so instability is marginal and shear is very weak so heavy rain and maybe some pea hail are the main concerns. One other thing to watch for will be funnels and possibly a brief landspout. Low LFC`s, 0-3km CAPE of 125-175 J/KG and weak winds in and above the boundary y layer are all supportive. Looking like a decent chance for a small area of 1-3 inches of rain, especially in northwest IA and far southeast SD. With saturated ground and light winds tonight some patchy fog will be possible. Lows should be mainly in the 50s with a few 40s possible in central SD. Saturday should be a fairly quiet day with dry mid levels. Instability begins to build back to the north into southwest and south central SD. This is mainly elevated instability as the surface based instability looks capped. Even the elevated instability will be fighting a cap so the chances will remain on the lower side for now with just a small chance for severe weather. Temperatures will be mild with highs mostly in the mid 70s. Saturday night into Sunday morning will see some elevated instability build a little farther north into central SD towards the James Valley. Elevated instability might approach 1500 J/kg wit h moderate amounts of shear so at least some isolated hailers would be possible during this time. A relatively strong wave and associated cold front will move into central SD on Sunday afternoon with unstable air in place ahead of this boundary. The EC ensemble and GEFS both showing a very good chance for CAPE values to exceed 2000 J/kg which is backed up by the latest GFS and Nam sounding output. Assuming 2000-2500 J/kg CAPE and 30-40 knots of shear would expect a few supercells in central SD towards the James Valley with a likely transition to something more linear between 6-8 pm. Monday should be a quick quieter warm day as another trough develops and moves in for Tuesday. Still a lot of question marks for Tuesday with timing of the wave which will obviously play a role in any severe potential. If timing does allow for afternoon and evening thunderstorms and a morning MCS does not suppress instability south there should be enough support for severe weather. But again, a lot of question marks. Wednesday into Friday looks like northwest flow aloft will develop which should help bring a drier pattern with seasonally warm temperatures. Lows generally in the 50s with highs in the 70s to lower 80s. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1211 PM CDT Fri May 31 2024 Scattered showers and thunderstorms will expand in coverage through the afternoon into the evening, especially across far southeast SD, northeast NE and northwest IA. The main concerns from this activity will be lightning and heavy downpours. This activity will gradually diminish in coverage and shift east of the area from about 3z through 9z. MVFR ceilings will be possible at times through the period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...08 AVIATION...08