Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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811 FXUS63 KFSD 051656 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1156 AM CDT Wed Jun 5 2024 .KEY MESSAGES... - Very breezy west-northwest winds with gusts 40 to 50 mph likely early this afternoon into the late afternoon hours behind a frontal boundary. Strongest winds are expected along and north of the I-90 corridor, with a wind advisory issued for counties where gusts at or above (AOA) 45 mph are expected. - Another breezy day expected for Thursday, with gusts up to 40 mph possible. - Pattern shift to northwesterly flow aloft continues into next week. This pattern favors only modest precipitation chances (Saturday), but higher confidence for below normal temperatures and below normal precipitation across the 6 day period of time. && .DISCUSSION... Issued at 401 AM CDT Wed Jun 5 2024 Currently between a strong surface low pressure to our north and a surface high pressure to our south, surface winds will quickly strengthen during the morning hours as the inversion weakens. Aloft, an associated upper-level vorticity lobe moves across portions of the area north of I-90 during the morning hours from west to east. While this may spark a few showers, dry air below 10 kft will evaporate most of the rain resulting in mostly sprinkles expected down by the surface. However, with winds at 600 mb AOA 60 knots, even weak showers may be capable of producing wind gusts in excess of 45 mph. These stronger winds continue to move down in the atmosphere as the front moves through, and as we mix higher up behind the front we`ll be able to bring down a portion of the 50+ knot winds found at the top of the mixed layer. Thus, am expecting a period of 40 to 50 mph winds during the early to late afternoon hours. This has synoptic support from ensemble situational awareness tables (ESATs), which show wind speeds at 850mb are above the 90th percentile of climatology, giving weight towards leaning on higher wind gusts for today. On the bright side, afternoon highs in the mid 70s to mid 80s are still expected. As the front continues to slide southeastwards throughout the afternoon hours, a few scattered showers and very isolated thunderstorms are possible east of I-29, where up to 200 J/kg of CAPE looks to be available. As the surface inversion strengthens during the evening hours, surface winds will weaken into the overnight hours. However, as the surface pressure gradient remains elevated while a surface high pressure slides southwards west of the area, winds will remain semi-breezy with gusts in the teens and possibly lower 20s. During the morning hours Thursday, the inversion will again weaken and allow for stronger winds aloft to be mixed down to the surface. Currently expecting wind gusts to 40 mph again to be possible, but as the ESATs again show winds at 850mb at the 90th percentile of climatology, would not be surprised to see winds come in higher with additional model runs. Temperatures in the lower 70s to lower 80s expected. Friday will see the surface ridge traverse the region, though model guidance does still have some timing differences, which will swing the winds around to become out of the southeast. As a weak surface low pressure develops quickly on the backside of the ridge, we may see light showers possible along the Missouri River Valley throughout the day. Otherwise, afternoon temperatures remain in the mid 70s to lower 80s. As was the case with the previous discussion, model guidance remains poor on the details in the extended as they struggle to resolve the ridge breakdown in similar fashions. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1154 AM CDT Wed Jun 5 2024 Scattered mid-lvl clouds continue to move through along a progressive frontal boundary moving to the southeast. Scattered light rain has been reported along Highway 14, with sprinkles to Interstate 90. Winds will increase quickly behind the passing front this afternoon, with a brief 1-3 hour window with near advisory level winds. We`ll also watch the front progress near Highway 20 by mid- afternoon, with potential temperatures in the mid 80s leading to quick convection developing. For now, feel this activity may be too isolated to include in any prevailing group at SUX. Winds will diminish overnight with VFR conditions into Thursday. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Wind Advisory until 7 PM CDT this evening for SDZ038>040-050- 052>067. MN...Wind Advisory until 7 PM CDT this evening for MNZ071-072-080- 081-089-090-097-098. IA...Wind Advisory until 7 PM CDT this evening for IAZ001>003- 012>014. NE...None. && $$ DISCUSSION...APT AVIATION...Dux