Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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250 FXUS63 KFSD 162323 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 623 PM CDT Mon Sep 16 2024 .KEY MESSAGES... - Temperatures remain above normal through mid to late week. Nighttime lows show greater departures above normal (10-15F) than daytime highs (5-10F) due to anomalously high low level moisture/dew points. - Low (generally < 20%) rain chances through Tuesday afternoon. Confidence in timing and placement is low, but expect amounts to remain light, with less than a quarter inch through this period at any location. - Greater chance for rain (40-70+%) Tuesday night through Wednesday, mainly focused Tuesday night west of I-29. Moderate (~ 40%) probability of rainfall exceeding 0.25", but low (< 25%) probability of exceeding 0.50". - Moderate chances (40-60%) for showers/storms late week into the weekend, with highest chances currently focused Thursday night and Friday night through early Sunday. Exact timing and location remain uncertain. && .DISCUSSION... Issued at 246 PM CDT Mon Sep 16 2024 CURRENT: 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. Have seen a few additional showers try to develop along the MO River Valley over the last hour or so, but dry air in the lower levels has quickly put a damper on any further upscale growth. TONIGHT THROUGH TUESDAY: While a lull in precipitation is expected for much of the evening and overnight period, do have renewed chances, albeit low (<20%), along and east of I-29 prior to/near daybreak Tuesday. Latest CAMs have started to come into better agreement though some variances still exist concerning the duration and extent of coverage. May need to up PoPs a bit in the coming shifts if trends suggest a similar story to this morning, where the increasing LLJ aided convection. As alluded to in the previous discussion, expect any showers/storms Tuesday morning to push eastward through the afternoon as the strongest wave and WAA lift across the area. Though severe weather in not expected at this time, can`t rule out the possibility of seeing gusts up to 50 MPH, and small hail. Rainfall amounts look to remain less than a quarter of an inch. Similar to today, expect breezy S/SE winds to continue as the SPG tightens in response to a developing low pressure on the lee side of the Rockies. Currently have gusts between 25 to 35 MPH, with the strongest generally along and west of I-29. May see a few areas west of the James River flirt with Wind Advisory criteria, though the threat of this remains marginal at this time. Otherwise, look for afternoon highs to rise into the mid to upper 80s with the aid of WAA. Lows during this time will also remain quite mild, as temperatures only fall into the mid to upper 60s. WEDNESDAY AND BEYOND: Unsettled weather looks to continue through mid-week as the aforementioned low pressure lifts northeastward. While the center of this low is still progged to move over the Montana/North Dakota border, still expect to see impacts across our area Tuesday night into Wednesday ahead of an advancing cold front. Given the better dynamics in place, could see QPF range between 0.25 - 0.5 inches, with locally heavier amounts still possible. Though some isolated to scattered activity may still be possible Thursday, think we should trend toward drier conditions, at least through Friday afternoon, before the next wave arrives Friday evening. That being said, model variability does increase heading into the weekend, making it hard to put too much confidence behind any one solution just yet. For now, will continue to monitor trends and make further refinements as confidence grows. Otherwise, look for above average temperatures to continue through Friday. Near to potentially below normal temperatures will then return over the weekend, though this will largely depend on the timing and track of the second low pressure system. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 623 PM CDT Mon Sep 16 2024 Isolated showers/storms will remain possible for the next hour or two before trailing off for the rest of the evening hours, with breezy southeasterly winds continuing with gusts into the 20s. Shortly after midnight, additional scattered showers/storms may develop, and while no flight restrictions are currently expected the storms could mix down some stronger gusts into the 30s. LLWS looks to be rather borderline given the mostly unidirectional winds and breezy surface layer, so have left LLWS out of the TAF. Showers/storms will be trending down into the afternoon hours, with breezy winds continuing. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...SST AVIATION...APT