501 FXUS63 KFSD 230845 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 345 AM CDT Mon Jun 23 2025 .KEY MESSAGES... - Showers and thunderstorms push to the east through the morning, with any additional rainfall most likely confined to northwestern IA and the lower Missouri River Valley through Tuesday. Severe storm chances are low through the period. - An active pattern will continue through mid week. While some uncertainty remains, the better chance for isolated severe storms and heavy rainfall will be Tuesday night into Wednesday night. && .DISCUSSION... Issued at 339 AM CDT Mon Jun 23 2025 A broad area of showers and isolated thunderstorms continues roughly from just east of the Interstate 29 corridor and westward early this morning - this in association with a cold front pushing across the region collocated with a series of shortwaves lifting northward on a southwesterly upper level flow. The frontal boundary is currently draped from southwestern MN into northeastern NE, and have seen a few pockets of heavier rain with training cells due to convergence along the low level jet and a mean flow nearly parallel to the frontal boundary. This entire area of precipitation is expected to work eastward and weaken through early to mid morning as the better upper level forcing drifts to the north and the low level jet veers to the east. The frontal boundary will completely exit our area some time by late morning/early afternoon as it pushes into southern IA and southern NE by the end of the day. While some risk of showers/isolated thunderstorms will remain over northwest IA during the day, models would suggest that most of this activity will remain to the south of our CWA. Any risk of severe storms is low with the better instability being shunted to our south. It will be a much more pleasant day in terms of temperatures with cold air advection behind the aforementioned frontal boundary. Dew points will be falling through the day (to 40s and 50s for all but far northwestern IA), and highs will be nearly 20 degrees lower than yesterday - only in the upper 70s to lower 80s. In addition, winds are expected to be much lighter than recent days. For tonight through the day on Tuesday, rain chances will mainly be confined to areas through the lower Missouri River corridor and northwest IA as the aforementioned front begins to work back to the north. Not expecting heavy rain with maybe a couple tenths of an inch through the period. The better instability remain bottled up to our south, so the risk of severe storms is low. Temperatures tonight will be fairly pleasant - mid 50s to lower 60s, with highs on Tuesday mainly mid to upper 70s under a coolish easterly flow. For Tuesday night through Wednesday night, rain chances increase again as the frontal boundary works northward back into our area as a series of shortwaves traverse the persistent southwesterly upper level flow. Instability begins to increase a bit through this period (primarily Wednesday afternoon), though bulk shear looks to remain on the weaker side. While there may be a low risk of severe storms during this period, the greater risk may be heavy rainfall. This will be focused on Tuesday night and Wednesday night - with increasing moisture flux convergence in the vicinity of the stalled frontal boundary via an increasing LLJ both nights, this collocated with PWAT values in the top 1 percent compared to climatology. Warmer temperatures and humidity look to return on Wednesday with highs back into the 80s and dew points in the mid 60s to lower 70s. Rainfall chances look to finally be on a downward trend by the end of the week (Thursday through Saturday), this as the persistent upper level jet which has been parked to our west shifts out of the region and the upper level pattern transitions to a less amplified flow. Could see a return of shower/thunderstorm chances by the end of next weekend as an upper level trough drops into the Northern Plains, though confidence is low. Temperatures for the end of the week into the weekend will lie on the warmer side of seasonal averages. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1115 PM CDT Sun Jun 22 2025 Showers and storms continue along/west of I-29 at 4z, and expect these to continue to move north/northeast overnight. Although severe risk has diminished, an isolated strong to severe storm is possible. Expect MVFR to IFR conditions with convection. Additionally, guidance continues to show MVFR ceilings during the day Monday for northeastern NE and northwestern IA, so have kept KSUX into MVFR through the afternoon. Shower and storm chances remain in place for northeastern NE into south central MN during the day Monday into Monday evening. Winds behind the surface front have shifted to the northwest, with winds ahead of the front still out of the south but continue to shift overnight as the front meanders east. Outside of thunderstorms, expect gusts around 20 to 25 knots. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JM AVIATION...SG