FXUS63 KFSD 090802 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 302 AM CDT Thu Jul 9 2026 .KEY MESSAGES... - Fog, including locally dense fog, continues through the Thursday morning commute. Be prepared for rapidly changing visibility into mid morning, which may drop below two miles at times. - High temperatures remain on track to rise to the 90s to 100 degree mark towards this weekend and into early next week. Be prepared to alter outdoor plans to reduce risk of heat illness. - Mostly dry conditions are expected into early next week. && .UPDATE... Issued at 301 AM CDT Thu Jul 9 2026 Fog and stratus are expanding over the forecast area this morning, continuing into the mid morning hours. Through 2:30 AM CDT, visibility remains at or above 4 miles, but guidance continues to show some low (35% chance or less) probability of visibility falling below 2 miles. May see some brief visibility below one mile if some hi-res guidance is to be believed. CAMs remain consistent on some additional shower development later this morning for northwestern IA. Confidence is low but can't rule out a sprinkle with the stratus. Conditions today are expected to remain dry with highs in the upper 70s to upper 80s and a mix of clouds and sun. A trough is expected to move into the western Dakotas/NE later this afternoon through tonight. Much of the guidance splits the better forcing around our forecast area, with the CAMs following suit (taking convection either north or south), or showing convection weaken on approach. With that, can't entirely rule out an isolated shower/storm through south central SD into the MO River Valley late this evening into tonight if something can move into our area from the west. If this occurs, severe weather is not expected with the lack of shear. Showers may linger into Friday morning as the subtle wave moves south of the area, but confidence in coverage is low (less than 20%). Focus for the forecast remains on the heat building in for the weekend and early next week. Ensemble probabilities of highs exceeding 95 degrees Sunday into early next week remain moderate to high (over 55%) for areas along and west of I-29. If you have outdoor plans, be prepared to alter them to reduce the risk of heat illness. && .DISCUSSION... Issued at 208 PM CDT Wed Jul 8 2026 A few light rain showers persist across mainly northwest Iowa this afternoon. A surface trough and associated cold front continue to track through the forecast area early this afternoon. The mid level clouds associated with these light rain showers continue to sit over mainly northwest Iowa and surrounding locations. This has prevented locations in this area from heating out. The cooler temperatures look to also delay new convective development as the cold front pushes into this area. Still, these clouds look to clear/break up enough to allow adequate instability to develop with a magnitude up to about 2,000 J/kg over the course of the afternoon timeframe. Vertical shear values will be on the weaker side of things with a magnitude of roughly 20-30 knots. Latest hi-res guidance shows that a small, bi-modal severe weather event is on the table for this afternoon and evening. Storms look to develop on both the pre- frontal trough and trailing cold front. Storm development looks to take place across mainly northwest Iowa and adjacent areas this afternoon with a timeframe from from about 4 pm to 10 pm. With the cold frontal forcing, storms look to grow into a line as they push out of the area this evening. While vertical shear magnitudes will be on the lower side, hodographs show a weak but classic veer-back profile. With weak cold advection aloft, lapse rates will steepen just a bit more and allow for a large hail threat.Soundings do show slightly more saturated profiles in the hail growth zone (HGZ) which will tone down the hail threat a bit, with some of the largest stones growing up to half dollar size. DCAPE values will be sufficient with values up to 800 to 1,000 J/kg, keeping a damaging wind threat in place with the strongest gusts up to 65 mph. The large hail threat will come with the initial storm development before transitioning to a damaging wind threat as storms grow upscale. Pockets of moderate to heavy rainfall could result in localized ponding in low lying/urban areas as storms roll through. The storm threat will end this evening, leaving mostly quiet conditions for the overnight hours. Low temperatures will fall to the 60s. Seasonable and mostly dry conditions will return for the end of the week with high temperatures remaining in the 80s to just touching 90F. Winds will be light, making for a pleasant Thursday and Friday. Heights begin to rise aloft on Saturday, beginning to warm temperatures with highs rising to the 80s and 90s. Sunday will kick off the first day of near to above normal temperatures as medium range and ensemble guidance show a 600 dam ridge building into the Northern Plains. This ridge looks to persist through the first half of next week, brining hot and humid conditions with it. The ensembles show a 60-100% chance for highs to exceed 90F Sunday through Tuesday near and west of I-29. Chances for exceeding 100F drop to 40-70% for the same period of time with Tuesday having the highest probabilities. The ensembles also show a broad 40-100% chance for dew points to exceed 60F as well. All these probabilities to say that hot and humid conditions are expected late this weekend and into early next week. A few ensemble members show the ridge beginning to flatten next Wednesday which could begin to trend temperatures down. There remains uncertainty regarding how long the ridge remains strong so something to keep an eye on heading forward. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1227 AM CDT Thu Jul 9 2026 Scattered weak thunderstorms are ongoing along and south of Highway 20 in northwest Iowa at time of issuance. While these storms are not expected to become severe, they may produce wind gusts to 45 mph. Storms will continue to move southeast and clear out of the area in the next couple of hours. A mix of VFR and MVFR is expected for the first half of the period. Low to mid-level clouds are expected to linger into Thursday morning. Winds are light and variable. Patchy dense fog is expected to form, especially east of the James River Valley. Brief periods of IFR visibility and ceilings are possible. Winds remain light and variable though most of Thursday. As a result fog may linger into the mid-morning hours before daytime heating burns it off. VFR conditions are then expected to prevail for the remainder of the period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ UPDATE...SG DISCUSSION...Meyers AVIATION...AJP