


Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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751 FXUS63 KFSD 041907 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 207 PM CDT Fri Jul 4 2025 .KEY MESSAGES... - Slightly less hot but still humid for this 4th of July with peak heat index values in the 90s. Temperatures more typical of early-mid July (highs mostly in the 80s) settle in for the rest of the holiday weekend through much of next week. - Marginal (Level 1 of 5) risk for severe storms today/tonight. Main concern is isolated damaging wind gusts in the late afternoon and evening west of the I-29 corridor. Lower but non-zero risk that a stronger storm could develop during the overnight hours. - Pockets of heavy rain could accompany storms this afternoon into Saturday morning. The risk for widespread flash flooding is low, but localized urban flooding is possible. - Additional chances for showers/storms focused on Saturday and next Monday night-Tuesday. Some stronger storms are possible early next week, but details are uncertain. && .DISCUSSION... Issued at 205 PM CDT Fri Jul 4 2025 This Evening and Overnight: Mid afternoon WV imagery shows short wave lifting northeastward with a trough axis draped through the central Dakotas down into western Nebraska. These two features have already been the focus of thunderstorm development today and should continue to be so with eastward extent through the evening hours, perhaps aided further late this evening by the arrival of the primary front. Deep layer shear is weak, denoted by both 0-6km shear and EBWD of <20 kts and thus any organization to thunderstorms will be minimal and likely more of a multicell variety. While a lack of shear and rather warm mid levels should limit the hail risk, enough instability exists for a storm to briefly pulse to marginally severe hail levels during initial development. Thereafter, damaging wind gusts to around 60 mph will be the primary risk through the evening with DCAPE values hovering around 1000 J/kg. This is all obviously in addition to lightning which should be of an equal concern for those with outdoor celebrations/activities. A secondary threat to consider that was well discussed in the previous forecast discussion is for locally heavy rain. PWAT sit AOA the 90th percentile of climatology via recent observed RAOBs at OAX and ABR. Additionally, a deep warm cloud layer in excess of 4000m should allow for efficient rain rates in any more persistent storm clusters. While any heavier rain amounts should be highly localized, PMM/LPMM from the HREF show potential for an isolated amount exceeding 2 inches. In terms of timing of thunderstorms, storms will continue through central South Dakota through the afternoon, into the James River Valley by early to mid evening (6 to 9pm) and then into the 1-29 corridor by late evening (9pm to midnight). A secondary wave pivots through the base of the shortwave trough late tonight and very well could keep shower and storm activity lingering across SW MN and NW IA into Saturday morning. Saturday: This previously mentioned strung out vorticity ribbon through the base of the trough lingers east of I-29 through much of Saturday and could keep precipitation chances around, especially by midday through the afternoon/early evening as daytime heating again pushes MLCAPE values as high as 1000-1500 J/kg. Deep layer shear again not supportive of organized severe weather although a storm or two may pulse near the strong category. Temperatures largely in the 80s with apparent temperatures approaching 90 across the Hwy 20 corridor of NW IA where a better overlap of warmer temperatures and moist dewpoints remains. Sunday: A wave pushing into eastern MT/WY Saturday is expected to result in an eastward moving MCS that may approach our western coverage area by the daybreak hours Sunday morning. While an unfavorable diurnal period will likely result in its demise by the time it reaches the James River Valley we`ll wait to see what, if any, convective contamination it leaves behind for the remainder of the day. Monday through Thursday: Fairly zonal flow to start the next work week, eventually transitioning to ridging through the Central US by midweek. A quick moving wave late Monday could bring additional thunderstorm chances with overall pattern recognition and ML probabilities highlighting at least some severe weather risk. Another chance of storms may arrive late Thursday as aforementioned ridging begins to break down. Temperatures in the 80s to lower 90s are currently expected for this period. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1152 AM CDT Fri Jul 4 2025 Main aviation concern will be the timing and impact of TSRA this evening into the overnight hours at the TAF sites as a cold front moves through. Already seeing thunderstorm development across western SD midday which should arrive into the James River Valley by around 00z and then toward I-29 late evening/early overnight. Have timed in most likely period of concern for each TAF site but this will continue to be adjusted through the afternoon hours. Prior to thunderstorms, winds will be out of the south with some gusts in the 20-30 kt range. Winds will take on a more westerly and then northwesterly direction behind the front overnight into Saturday morning. MVFR conditions (perhaps locally lower) are expected in precipitation activity with a broader MVFR ceiling establishing after precip passage into Saturday morning. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Kalin AVIATION...Kalin