Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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829 FXUS63 KFSD 191129 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 629 AM CDT Wed Jun 19 2024 .KEY MESSAGES... - Aside from a few stray showers east of Highway 60 this morning, expect a mostly dry, cooler than normal day. - Another round of rain spreads in late tonight through Thursday night. Severe weather threat is low, but have high confidence in widespread rain. Highest rainfall amounts are most likely to remain near/north of the I-90 corridor (Little Sioux River basin). Probabilities of additional >0.50" totals are high at 70-80% north of I-90, with 1" probabilities above 50%. Isolated amounts of 2-3+ inches are possible. - Risks for thunderstorms continue into Friday, with potential for strong to severe storms Friday afternoon and night. - Cooler temperatures and likely dry conditions Saturday night into early next week, though rain chances return Monday night. && .DISCUSSION... Issued at 419 AM CDT Wed Jun 19 2024 TODAY AND TONIGHT: Radar early this morning shows mid level echoes based at 10kft sliding into south central SD, which are likely not resulting in anything aside from increased cloudiness. Further east, a few stray showers trek northeastward near and east of Hwy 60 in northwest IA. As the departing stationary front sags south this morning, model soundings suggest the drying 925-700mb layer will largely cut off rain aside for perhaps a few sprinkles in northwest IA this morning. Strong sfc high pressure sliding by to our north brings light winds and a nice respite from the rain for most of the region this morning and afternoon. Temperatures remain cooler than normal for this time of year as cooler air aloft builds in behind the front departing south. Stratus tracking in from northern SD should mix out by early afternoon, but cirrus and maybe some cumulus will linger during the day limiting diurnal heating. Expect highs to only reach the lower to mid 70s. Little to no weather impacts continue through the evening, though cloud cover and rain chances increase from the west overnight as several weak mid level waves approach in southwest flow aloft. THURSDAY: Initial warm air advection induced scattered showers and isolated thunderstorms look likely to enter the region via south central SD around or after midnight tonight, spreading east through the region Thursday. With anomalous moisture content via precipitable water at the top 3% of ensemble guidance for this time of year, occasional heavy downpours and prolonged moderate rain is likely with showers and storms spreading through southeast SD and southwest MN Thursday morning and early afternoon. Weak instability (<500 J/kg MUCAPE) minimizes severe weather threat, but HREF probability matched mean rainfall paints a broad 0.50-1.00" swath near and north of a Yankton to Sioux Falls to Jackson line. Worst case scenario NAM based guidance suggest a few locations may receive 1-2"+ of rain Thursday morning. While there is still fairly low confidence in the location of the axis of heaviest rain and exact amounts, Thursday morning will still be fairly poor for outdoor activities. More likely to see breaks in the rain Thursday afternoon than morning, especially south of I-90. On Thursday night, rain chances ramp up as convective remnants track in with a wave from the NE Panhandle. Continued high moisture content coupled with the nocturnal LLJ feeding in primes the environment for another period of moderate to heavy rainfall. With the aforementioned stationary front lifted north to near the Hwy 14 corridor, higher confidence in the heaviest rainfall amounts occurring near and north of the I-90 corridor with a high (>50%) chance of at least a half inch of rain in this area. North of I-90, deterministic guidance suggests potential for locally heavy downpours producing 1-2+" overnight. FRIDAY AND SATURDAY: As aforementioned front lifts north and puts us deeper into the warm sector Friday, we`re in for a hot muggy day with dew points in the 70s and highs in the 80s to near 90 degrees. Confidence in details regarding breaks in the rain decreases considerably for Friday and Saturday. However Friday night into early Saturday brings the next potential for severe weather as the jet stream sags a bit further south (increasing deep layer shear) and we destabilize more than previous days ahead of a stronger wave in zonal flow aloft. Encourage those with outdoor plans Friday/Friday night to monitor this period for details regarding severe weather and heavy rainfall threat. SATURDAY NIGHT AND BEYOND: Deterministic models mostly put us on the north/dry side of the sfc front by Saturday afternoon, favoring drier conditions and near seasonal conditions Saturday night through Sunday. An early look into next week favors a warmer and wetter than normal pattern continuing. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 627 AM CDT Wed Jun 19 2024 Pockets of MVFR stratus and isolated showers linger in the region this morning, but confidence is low in these impacting any TAF sites. Otherwise expect light northwest winds to turn more northeast and eventually east during the day with VFR cirrus prevailing in the region. Another round of showers and storms is expected to spread in late tonight with IFR to MVFR conditions, locally heavy downpours, and gusty erratic winds expected at times. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...BP AVIATION...BP