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Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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555 FXUS63 KFSD 181116 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 616 AM CDT Thu Jul 18 2024 .KEY MESSAGES... - A few isolated sprinkles to light showers will be possible in our southcentral SD counties this morning with only light accumulations expected. - More rain chances (30%-60%) will likely return over the weekend with the better chances expected from Friday afternoon through Friday night. While the exact timing and location of developing storms remains questionable, an isolated severe risk with pockets of heavy rainfall remain possible during the period. - Near to below normal temperatures will continue through the weekend as cooler air funnels into the region. && .DISCUSSION... Issued at 305 AM CDT Thu Jul 18 2024 TODAY & TONIGHT: Another mostly quiet day will be on tap for the day! Taking a look across the area, mostly clear conditions continue as the surface high sits overhead. Light and variable winds along with lingering low level moisture could lead to the development of some patchy areas of fog this morning mostly across our River Valleys and portions of northwestern IA. While the fog shouldn`t stick around long, expect it to gradually erode as mixing restarts. Looking back to our southcentral SD counties, a few light showers will be possible around daybreak as a subtle shortwave interacts with a couple hundred Joules of instability. While widespread development is not expected, decided to add in some smaller POPs (<20%) in Gregory county to capture the potential. Besides that, conditions will be very similar to yesterday with highs topping out the mid to upper 70s and low 80s with light southeasterly winds for the day. By tonight, expect mostly quiet conditions to continue as warm air advection (WAA) strengthens on the backside of the departing mid-level ridge setting the stage for our next precipitation chances heading into Friday. With this in mind, expect our temperatures to slight rebound overnight as lows only decrease into the upper 50s and low 60s. FRIDAY-SUNDAY: Heading into the weekend, the main concern continues to be the increasing rain chances (30%-60%) as a strengthening northern stream wave dives into our area from eastern Wyoming. Starting with Friday, increasing WAA aloft along with southerly surface winds will help temperatures climb into the upper 70s to mid 80s for the day. From here, our attention will turn to northwest as the chances for scattered shower and thunderstorms increase by Friday afternoon as the wave approaches. While some lingering uncertainty continues with the timing and location of developing activity, modest instability values (1000-1500 J/kg) and 25-35 kts of deep layer shear could support an isolated severe weather risk especially west of the James River Valley with the primary hazards being large hail and damaging winds as multicellular storms grow upscale into linear segments. From here, the threat likely transitions to pockets of heavy rainfall as PWATs increase towards 1.50-1.75 inches heading into the evening and overnight hours. By Saturday, the wave will continue to progress southeastwards stalling somewhere across eastern Nebraska and western Iowa bringing continued chances for showers and thunderstorm across parts of our area through Sunday. With all this in mind, most areas can expect rainfall accumulations of up to half an inch through Sunday with pockets of up to an inch possible along the Missouri River Valley. Lastly, with increased precipitation chances through Sunday, expect our temperatures to top out in the mid to upper 70s and low 80s. MONDAY-WEDNESDAY: Looking into the start of the new week, an active pattern will continue aloft as upper-level ridging continues to build across the western CONUS. As a result, intermittent periods of scattered showers and isolated thunderstorms will be possible through Wednesday. Lastly, with multiple precipitation chances ahead; expect our temperatures to stay near to just below our seasonal normals through the midweek with highs in the upper 70s to low 80s expected. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 606 AM CDT Thu Jul 18 2024 Mostly VFR conditions will continue across the area for the durations of the TAF period. Taking a look at satellite, a few areas of patchy fog have developed mostly in our River Valleys and across portions of northwestern IA this morning. While this fog shouldn`t hang around for long, expect it to gradually erode heading into the mid-morning. Otherwise, light and variable winds will become light southerly to southeasterly winds by this afternoon. Lastly, could see some a few scattered showers develop closer to daybreak on Friday mostly near our southcentral SD counties to end the TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Gumbs AVIATION...Gumbs