Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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704 FXUS63 KFSD 260749 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 249 AM CDT Thu Sep 26 2024 .KEY MESSAGES... - Dry conditions are expected through the period. Above average high temperatures in the 80s is expected through the weekend. - Breezy southerly winds and lowering relative humidity levels will result in elevated fire danger for locations west of the James River Today. - Increasing winds along with periods of near to above average temperatures could bring additional chances for fire danger throughout the duration of next week. && .DISCUSSION... Issued at 248 AM CDT Thu Sep 26 2024 Clear and quiet conditions begin the day today. Like what we have seen the past few days, patchy shallow fog has a low possibility (<=20% chance)of developing this morning, mainly around bodies of water. Should any fog develop, it will quickly burn off as mixing increases as the sun rises. This afternoon will feel closer to Summer rather then Fall as above average high temperatures persist. Temperatures warmed closer to the NBM 95th percentile yesterday. As such, have pushed today`s highs closer to the NBM 95th percentile. Widespread highs in the 80s is expected but locations along and west of the James River should see high temperatures reach up to around 90 degrees F this afternoon. With such warm temperatures in place, dew points are expected to lower a bit more as drier air is mixed to the surface, resulting in lower relative humidity (RH) values across the area. The lowest RH values will come along and west of the James River where RH values will fall to about 20-25% The surface pressure gradient (SPG) will tighten across the area as a surface ridges slides southeast of the forecast area. The tightened SPG along with stronger winds aloft will bring a return of breezy winds to the area, strongest along and west of the James River where gusts up to around 30 mph is expected. The good news about the winds is that the strongest winds reside around 850 mb. Mixing above 850 mb will not result in any stronger winds being transported to the surface. The very warm temperatures, low humidity, and breezy winds will lead to elevated fire danger this afternoon along and west of the James River. While Red Flag conditions look to be met, fuels are still green enough to only have moderate to a small area of high fire danger this afternoon. And chance for fire danger will come to an end this evening as mixing ceases. Low temperatures will fall to the 50s overnight. The SPG relaxes on Friday as another surface ridge slides into the Northern Plains. 850 mb temperatures will cool a bit, down to the upper teens to about 20 degrees C. Mixing this to the surface will result in high temperatures into the 80s across the area. With a relaxed SPG in place, light winds are expected. With light winds and above average temperatures in place, Friday will be another gorgeous day across the area! Low temperatures will again fall to the 50s overnight. Upper level ridging remains squeezed across the Northern Plains for the weekend between the Jet Stream across southern Canada and a vertically stacked low pressure system across parts of the Midwest. This will allow for above average temperatures to persist with highs in the 80s along with light winds and thus beautiful conditions for the weekend! Medium Range guidance remains in decent agreement in a stronger shortwave trough amplifying as it passes through the Northern Plains early next week on Monday. This wave will drag a dry cold front through the region as well which will bring fall like conditions back to the forecast area after it passes through. High temperatures look to lower to the 70s up to the low 80s. The Fall like conditions look to be short lived though as surface high pressure quickly races through the region on Tuesday, delivering a true Fall like day with highs in the 60s, before another shortwave trough takes aim at the Northern Plains on Wednesday. Medium rang guidance is in decent agreement in this wave this far out but the timing of the waves differs. However warm air advection (WAA) ahead of the wave looks to bring a return of above average temperatures to the forecast area. The GFS, Euro, and Canadian ensembles show a 30-60% chance for high temperatures to exceed 80 degrees F. The warm conditions look to be accompanied by breezy winds which may bring elevated fire danger back to the forecast area. The Hot-Dry- Windy-Index (HWDI) supports this as it shows about 50% of its members pointing to elevated fire danger conditions. Something to continue to monitor heading into next week. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1005 PM CDT Wed Sep 25 2024 VFR conditions are expected to continue this TAF period. Taking a look at satellite imagery, clear conditions continue as a weak surface high continues to work its way eastwards. Expect these conditions to continue overnight hours with light and variable winds potentially promoting some patchy valley fog. Breezy southerly winds will return by Thursday afternoon as the SPG tightens leading to wind gusts up to 30 mph mostly west of I-29 to end the TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Meyers AVIATION...Gumbs