Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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721 FXUS63 KFSD 171857 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 157 PM CDT Wed Jul 17 2024 .KEY MESSAGES... - Patchy fog may develop in river valleys and other low lying areas early Thursday morning. - Below normal temperatures will continue through the weekend as northerly flow filters cooler air into the region. - Low to moderate rain chances (30%-70%) will return this weekend, highest Friday night into Saturday. While exact location and timing remain uncertain, an isolated severe storm risk and pockets of heavy rain are possible during this period. && .DISCUSSION... Issued at 156 PM CDT Wed Jul 17 2024 TONIGHT AND THURSDAY: Satellite images for early this afternoon show a broad diurnal cumulus field. A shallow, weakly unstable layer could bring occasional sprinkles or brief light showers through early this evening. Otherwise cooler than normal temperatures, low humidity, and a light northeast wind make for excellent conditions for outdoor activities tonight and Thursday. The atmospheric pattern over the Northern and Central Plains remains largely stagnant in dry northern flow aloft with strong 1022mb sfc high pressure centered over MN. This pattern favors at least patchy fog development early Thursday morning with 12z HRRR guidance suggesting areas of fog at least in river valleys and/or low lying areas around dawn. On Thursday morning, a weak ridge riding shortwave slides through western SD/central NE. This may bring a few light showers into south central SD, but the main impact is much more likely to be slightly increased cloudiness. Otherwise expect another pleasant day with a light south wind gusting into the teens west of I-29 and highs in the mid 70s to mid 80s. THURSDAY NIGHT AND FRIDAY: Low (<30%) chance for isolated showers and storms develops with warm air advection and another weak ridge riding shortwave late Thursday night into early Friday west of I-29. Aside from this, should still see largely drier conditions than wet through at least the first half of Friday. Warm air advection brings subtly warmer and more humid conditions as well, with highs again in the mid 708s to mid 80s. Chances for scattered showers and storms increase heading into Friday afternoon and night, triggered by a strengthening northern stream shortwave gliding south into the region. Moderate instability and 20-30 kts 0-6km deep layer shear would suggest potential for isolated/marginal strong to severe multicell storms. With a messy wind profile and fairly weak winds aloft, large hail, damaging wind gusts, and locally heavy downpours remain the main threats with the strongest storms Friday afternoon and night. SATURDAY AND BEYOND: Though there will be breaks/dry periods, isolated to scattered showers and storms are expected to linger through Monday with good model agreement in the maturing upper low stalling over IA/NE. This brings fairly humid, though mild (highs in the 70s and 80s) weather for mid-late July. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1229 PM CDT Wed Jul 17 2024 Afternoon cumulus at 4-5 kft may produce isolated sprinkles or light showers this afternoon. Expect VFR conditions to prevail through the period. A light northeast wind becomes light and variable overnight, turning southerly Thursday morning. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...BP AVIATION...BP