Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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326 FXUS63 KFSD 161708 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1208 PM CDT Tue Jul 16 2024 .KEY MESSAGES... - Scattered showers with isolated thunderstorms will be possible through this evening. An isolated severe weather risk will be possible mostly across our southcentral SD counties. - Near to below normal temperatures will continue through the weekend as cooler air funnels into the region. - Confidence continues to grow in more widespread rain chances over the weekend. However, the details remain far from certain. && .DISCUSSION... Issued at 335 AM CDT Tue Jul 16 2024 The Short Term (Today & Tonight): A cooler day is ahead! Taking a look across the area, cooler air continues to funnel into the region behind yesterday`s cold front. As a result, many area`s will wake up to temperatures in the low to mid 60s to start the morning as a surface high gradually sides into the area. Looking a radar, a few scattered showers continue to develop across portions of western ND and southcentral SD in response to bits of isentropic lift associated with the rotating Hudson Bay trough in Canada along with support from the right entrance region of an upper-level jet. While these developing showers could make it into areas west of the James River and north of I-90 this morning, the general expectation is for these showers to gradually dissipate by the early afternoon as they approach the more stable airmass (surface high) sitting over our area. Nonetheless, lingering CAA advection along with light northeasterly flow will likely help our temperatures drop below our seasonal normals for the day as highs only reach the mid to upper 70s to low 80s with the warmest conditions along the Missouri River. Our focus will likely turn to the Missouri River Valley by the early afternoon as a few isolated showers and thunderstorms develop ahead of a subtle shortwave diving into southcentral NE. While the better convective chances will likely occur just south of our area in southcentral NE, there is a narrow but decent chance for an isolated stronger storm or two over our southcentral SD counties closer to 21z. With up to 1500-2000 J/kg of MLCAPE and 35-40 kts of deep layer shear to work with, developing storms could quickly become severe with large hail up to golf ball size and damaging winds up to 60 mph possible. With all this in mind, SPC continues to outline the Missouri River Valley in a Marginal Risk (Level 1 of 5) for severe weather. From here, expect any developing activity to progress southeastwards before dissipating this evening. Lastly, expect a much cooler night as colder air continues to makes it way to the surface. With this in mind, overnight low will decrease to the mid to upper 50s and low 60s across the area. The Long Term (Wednesday-Monday): Heading into the midweek, much quieter conditions will continue through Thursday as mid-level ridging quickly moves in to replace the departing upper-level wave. With lingering cold air advection (CAA) aloft and ample mixing at the surface, expect temperatures to continue their cooling trend through Thursday as highs gradually decrease into the low to upper 70s and low 80s on both days with overnight lows in the 50s to low 60s. By Friday, a warm nose will begin to develop on the backside of the mid-level ridge as 850 temps approach 20 degrees C. While this won`t likely translate to a tangible increase in surface temperatures, the warm mid-levels will likely serve as fuel for the approaching clipper wave as it dives southeastwards into our area from the international border. Intermittent periods of scattered showers and thunderstorms will likely develop from Friday into Saturday as the open wave wraps up into a closed low. With borderline convective temperatures and long- skinny CAPE profiles (500-1000 J/kg); the severe weather threat should be rather limited. However, PWATs up to 1.75 inches and warm cloud layer depths of up to 11kft do suggest the potential for pockets of heavy rainfall. With all this in mind, a wet and dreary weekend is ahead to say the least. As the closed low begins to drift southwards by Sunday expect any lingering activity to gradually dissipate throughout the day with much quieter conditions expected to return by Monday. Lastly, with the increased precipitation chances (30%-60%) over the weekend; temperatures will likely continue to hover just below normal with highs expected to be in the mid to upper 70s and low 80s. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1204 PM CDT Tue Jul 16 2024 Scattered showers will move from west to east today but for now the impacts will be very limited. A stronger storm or two will be possible in south central SD later this afternoon but confidence is very low on development. Some patchy MVFR to IFR fog will be possible late tonight and very early Wednesday morning but confidence on this is also low. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Gumbs AVIATION...08