Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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300 FXUS63 KFSD 172340 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 640 PM CDT Tue Sep 17 2024 .KEY MESSAGES... - Breezy southerly winds continue, the strongest west of the James River. Gusts 30 to 45 mph late this afternoon through the overnight period. - Greater chances for rain (40-60+%) tonight through Wednesday, mainly focused late tonight west of I-29. Moderate (~ 50%) probability of rainfall exceeding 0.25", but low (< 30%) probability of exceeding 0.50". - Moderate chances (40-60%) for showers/storms late week into the weekend, with highest chances currently focused Friday night through early Sunday. Exact timing and location remain uncertain. && .DISCUSSION... Issued at 255 PM CDT Tue Sep 17 2024 CURRENT THROUGH TONIGHT: Showers and thunderstorms that impacted the region this morning have largely diminished, with latest observations showing breezy south/southeasterly winds and temperatures in the 70s to lower 80s. Should see gusts between 25 to 40 mph continue this afternoon, with the strongest generally along and west of the James River. Upper level low lifts northeastward across Montana/North Dakota this evening, causing precipitation chances to return overnight ahead of an advancing cold front. Still a bit of variability amongst the latest CAMS, though most show showers/storms impacting those along and west of the James between 06-09z. While severe weather in not expected at this time, can`t rule out the possibility of seeing gusts up to 50 MPH, small hail, and lightning. QPF amounts have trended lower with the latest forecast cycle, suggesting most locations will see less than a quarter of an inch. WEDNESDAY AND THURSDAY: Upper level low deepens Wednesday, with the aforementioned cold front progged to push eastward across the region. Will likely see showers/storms reach the I-29 corridor prior to/near daybreak, with activity over southwest Minnesota and northwest Iowa expected through the afternoon. That being said, latest guidance does show showers/storms breaking up a bit as they moves across the CWA so coverage may become a bit more isolated through the afternoon. Some CAMs also suggest redevelopment would be possible during the late afternoon/evening, which may pose a marginal severe threat. Still not entirely confident if we will destabilize enough to achieve this, but if storms were to go, believe gusts up to 60 MPH would be the primary hazards with CAPE between 1000-1500 J/kg. Lapse rates still remain meager (< 7 degC/km), suggesting hail should remain around or less than quarter size. In any event, we encourage you to have a way to receive warnings in the event that storms become strong to severe. Though some isolated to scattered activity may still be possible Thursday, think we should trend toward drier conditions through the afternoon and evening. Otherwise, look for highs in the 80s and lows in the 50s to 60s to prevail during this time. FRIDAY ONWARD: Weak ridging builds aloft Friday, allowing dry conditions to prevail briefly before the next shortwave takes aim at the region Friday night into Saturday. Still quite a bit of variability in place concerning the track and evolution of this wave, making it hard to put too much confidence behind any one solution just yet. Nonetheless, most have the better precipitation chances (40-60%) occurring south of I-90 through the weekend. For now, will continue to monitor trends and make further refinements as confidence grows. Otherwise, look for notably cooler temperatures to return, with highs mainly in the mid to upper 60s. Overnight lows will also feel a bit crisp, with temperatures falling into the 40s to lower 50s. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 640 PM CDT Tue Sep 17 2024 Breezy/windy south-southeast winds with gusts of 30-40 mph will continue into the early overnight hours before tapering down, with showers and thunderstorms expected to move in shortly before midnight for areas west of the James River Valley. The showers/storms will be moving north-northeast, with coverage expanding eastwards into the morning hours as the showers/storms become more isolated. Will likely see a couple hour break from the rain from mid/late morning hours into the mid afternoon, when additional showers/storms may be possible, especially east of I-29. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...SST AVIATION...APT