Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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197 FXUS63 KFSD 031911 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 211 PM CDT Wed Jul 3 2024 .KEY MESSAGES... - Scattered thunderstorms are likely along and south of the Missouri River and Highway 20 areas later this afternoon and evening. Isolated strong storms are possible, with the greatest focus south of the Missouri River. - Scattered rain may continue into July 4th, but coverage remains uncertain. A low end severe weather risks develops mid- afternoon for portions of SW Minnesota and northern Iowa. - The holiday weekend remains unsettled with nearly daily risks for showers and thunderstorms. Not anticipating any widespread heavy rainfall that would impact flood levels at this time, but afternoon/evening rain risks may get in the way of weekend festivities. - Cooler than normal temperatures will continue well into next week. && .DISCUSSION... Issued at 207 PM CDT Wed Jul 3 2024 THIS Afternoon: Shortwave energy entering the Plains will continue to aid in convection development along an ill-defined surface boundary stretching across northern Nebraska this afternoon. MLCAPE is only expected to reach up towards 1000-1500 J/KG, with effective shear AOA 25-30 knots. Greatest development potential will be in north central Nebraska where EML is weaker. Several clusters of convection will drift eastward into the evening, potentially merging into one or more linear clusters as they approach northeastern Nebraska. Again however, diminishing instability should preclude any widespread organized severe weather risk, so anticipate the greatest risks coming from marginal hail and localized higher wind gusts along or south of the Missouri River and Highway 20. TONIGHT: Additional convection is likely to develop across the western Dakotas and Panhandle of Nebraska later this evening as low- lvl flow backs and deeper 700:500 mb troughing moves into the Plains. This convection will likely track eastward, but could also tend to drive southward into a richer low-lvl airmass across Nebraska after midnight. The end result could be much more scattered shower development through mid-morning across the Tri-State area. Temperatures fall into the upper 50s to lower 60s. 4th of July: Upper troughing will cross the Dakotas on Independence Day, bringing unsettled weather to much of the Tri-State area. Initially, scattered showers and very isolated thunderstorms may move east of I-29 by mid-morning, leaving lowering PoPs into mid- day. The passage of the 850mb and then surface front into the afternoon hours may spark renewed convection over SW Minnesota and NW Iowa early in the afternoon. This will generally be a low CAPE but increased shear environment ahead of the surface boundary, highly dependent if we could see any breaks in cloud cover ahead of the advancing front. That said, the primary risks would be from marginally severe hail, though some enhanced stretching along the surface boundary could result in funnel development. Further west, more diurnally driven shower and thunderstorm activity may develop, though given broad synoptic driving mechanisms, scattered shower activity could continue into the overnight hours. I certainly wouldn`t cancel those evening/sunset plans, but anyone northeast of a line from Huron to Sioux Falls to Storm Lake will need to be aware of scattered rain risks, seasonally cool temperatures, and high relative humidity values continuing through sunset. FRIDAY: The upper trough passes east by Friday morning, bringing a short lived period of mid-lvl ridging for Friday. However, given the cooler low-lvl temperatures, any surface heating could result in isolated shower development Friday afternoon. Temperatures remain below normal. SATURDAY-SUNDAY: Rain chances increase on Saturday as yet another shortwave moves through the Plains Saturday into Saturday evening. Uncertainty on where the greatest rain risks are focused remains high, but rain amounts will generally not cause an impact to overall flooding in the region. A broad trough building over the Plains keeps mostly afternoon isolated to scattered convection risks in the region for Sunday. Temperatures though remain near to slightly below normal in most locations. MONDAY-TUESDAY: Mid-lvl heights begin to rise over the western third of the CONUS early next week, with a persistent trough sliding eastward. Before slightly warmer and drier conditions move into the central US, there will be a brief transition Monday and Tuesday where some increased risk for diurnal convection could be possible. Temperatures remain near to slightly below normal, with some signal for above normal temperatures by the middle to end of next week. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1232 PM CDT Wed Jul 3 2024 VFR conditions continue into the evening. Scattered convection will develop and track along the Missouri eastward into the evening. This precipitation will continue into northwest Iowa into the early overnight hours. Additional showers and isolated thunderstorms move in from the west after midnight, moving towards I-29 after daybreak and SW Minnesota by mid-morning. Scattered MVFR ceilings may develop as this precipitation moves through. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Dux AVIATION...Dux