Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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791 FXUS63 KFSD 111718 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1218 PM CDT Tue Jun 11 2024 .KEY MESSAGES... -While the severe weather risk remains on Wednesday, uncertainty remains on exactly where storms will develop. -Near to above normal temperatures will continue into the weekend with warmest day expected to be Wednesday. && .DISCUSSION... Issued at 402 AM CDT Tue Jun 11 2024 The Short Term (Today & Tonight): Another warm and marginally breezy day is ahead. Taking a look across the area, lingering light showers continue to push eastwards ahead of a cold front roughly positioned along a Huron to Gregory line. As this frontal boundary continue to sweep southeastwards throughout the morning, conditions should begin to clear from west to east as surface wind become more northwesterly. As the cold front is quickly replaced by a mid-level ridge, the SPG will tighten leading to some marginally breezy conditions from the James River eastwards with gusts up to 25 mph possible by the afternoon hours. Otherwise, increasing warm air advection (WAA) and deep mixing with help temperatures increase slightly from the previous day with highs expected to peak in the low to upper 80s by this afternoon. Lastly, with increasing WAA advection expected overnight and light southerly winds, expect our overnight temperatures to stay a touch above normal with lows expected to be in the low to mid 60s. The Long Term (Wednesday-Sunday): Heading into the extended period, hot and muggy conditions return by Wednesday as the 850mb thermal ridge strengthens overhead. Increasing warm air advection (WAA) along with a southerly to southwesterly surface wind will help pull more warm and moist air into the region which will result in a notable increase in surface temperatures from the previous day. The resulting highs will likely vary between the upper 80s to 90s for the day with the warmest conditions along the Missouri River Valley. Shifting gears to our precipitation chances, isolated to scattered showers and thunderstorms will be possible Wednesday afternoon mostly east of I-29. However, the overall severe weather risk still remains uncertain mostly due to how split deterministic guidance is on how the fast the mid-level will progress through the area with its associated cold front. On one hand, the GFS/NAM have the faster solution where convection develops entirely over south-central and southeastern Minnesota by 21z where the nose of the upper-level jet resides. On the other hand, the Euro/Canadian have the slower solution where the base of wave sits across the center of our CWA with convection firing across southwestern MN and our far eastern most column of counties. While its still a bit too early to determine which solution will prevail, the environment is still primed to promote moderate destabilization with 2000-3000 J/kg of MLCAPE and 40-50 kts of deep layer shear which are consistent among deterministic guidance. This along with DCAPE values of 1000 J/kg and mid- level lapse rates of 7 degree C/km will create an environment favorable for large hail up to golf ball size and damaging winds up to 65 mph with any developing discrete supercells initially. While the probabilities are low, an isolated tornado isn`t completely out of the question either. As things grow more upscale after 00z, the primary threat will shift more towards damaging winds. Lastly, with the mix of severe weather hazards; areas along and east of I-29 are outlines in a Day 2 Slight Risk. Looking into the latter parts of the week, a few scattered morning showers will be possible by Thursday morning as mid-level frontogenesis strengthens along the departing cold front. However, only light accumulations are expected. Otherwise, lingering cold air advection (CAA) aloft along with northerly to northwesterly surface winds will keep our temperatures closer to our seasonal averages as highs take a slight dip into the upper 70s to low 80s on Friday and Saturday as heights rise with the approaching upper- level ridging. Looking ahead, confidence continues to increase in a multiple rounds of showers and storms from Friday night into the day on Saturday as multiple mid-level waves lift out of the Colorado Rockies into our area. While some uncertainty remains on the severe weather risk and exact amounts, most ensemble guidance shows low to medium confidence (30%-60%) in up to half an inch of QPF for this time period. Lastly, increasing mid-level WAA ahead of the cold front on Saturday along with southerly to southeasterly surface winds will help temperatures warm back up into the mid to upper 80s on both Saturday and Sunday. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1207 PM CDT Tue Jun 11 2024 VFR conditions prevail through the period. Showers and thunderstorms develop Wednesday, which could briefly reduce categories to MVFR or IFR. Isolated activity is expected in the morning and afternoon hours. More scattered showers and storms are possible in the afternoon and evening hours. Confidence is very low in location of development and evolution, but better chances later in the day look to be near/east of I-29. A couple of storms could be strong to severe with large hail and damaging winds the main threats. Otherwise, winds this afternoon will gusts around 25 knots out of the northwest. Light and variable winds tonight, shifting to southerly through the overnight hours into early Wednesday. Gusts tomorrow again around 25 knots. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Gumbs AVIATION...SG