Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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998 FXUS63 KFSD 011131 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 631 AM CDT Sat Jun 1 2024 .KEY MESSAGES... - Monitoring potential severe weather outbreak later Sunday into Sunday night. However, confidence in details on location and timing are currently low and may heavily depend on how morning convection evolves. Stay tuned for updates. - Tuesday may be the next chance for severe weather, but still some question marks, the main one being a potential MCS late Monday night into Tuesday morning which could push the deeper instability south and limit Tuesday afternoon potential. - Quiet weather and seasonable temperatures are expected to prevail mid to late week. && .DISCUSSION... Issued at 400 AM CDT Sat Jun 1 2024 TODAY: Ridging surface and aloft should provide a quiet day with seasonable temperatures topping out in the mid-upper 70s. Starting off the day with widespread stratus, but expect this to slowly thin and diminish through midday/early afternoon. May have to watch south central SD for isolated-scattered convective development in the warm advection behind the surface ridge, but consensus in the CAMs keeps this activity largely southwest of our area through the daylight hours. A rare day with light winds will also prevail thanks to the surface high, but this will also lead to some patchy fog early this morning. TONIGHT-SUNDAY NIGHT: Main focus will be on potential for increasing storm coverage and possible severe weather through the latter half of the weekend. Unfortunately, diverging solutions among the various CAMs are leading to low confidence in exactly how things will evolve late tonight through Sunday night. Current thinking is that we will see a complex of storms develop west of I-29 tonight in response to warm advection and an increasing low level jet ahead of a mid level wave lifting northeast in the area. While exact location varies, broader consensus carries this activity eastward through Sunday morning, likely leaving somewhat more stable air and various outflow boundaries in its wake. This could limit redevelopment during the afternoon Sunday, at least initially until stronger forcing arrives with an approaching cold front toward evening, and have trimmed back pops to more of a chance range (30-50%) during the afternoon. Not all CAMs agree with this scenario however, with some indicating more rapid redevelopment by mid-late afternoon west of I-29, so will certainly have to monitor trends to see if they converge on a better consensus. Will still maintain pops ramping up in the evening/overnight Sunday as the cold front and associated mid-upper level trough slide east across the region. Most likely scenario would point to discrete supercells developing along the front in central South Dakota and Nebraska by late afternoon/early evening, transitioning to linear segments as they track east through the evening. Uncertainty lies in what areas will be impacted by the stronger portions of these lines and what lingering role any convection early in the day may have on this evolution. For now, recommended action will be to keep a close eye on later forecasts and have a plan of action should trends point to stronger impacts through our forecast area. Along with the potential for severe weather will come the added threat of areas of heavy rainfall with any storms late tonight through Sunday night. Increasing low-mid level moisture transport will lead to precipitable water values above 1.25-1.50 inches, which reside at or above the 90th percentile of climatology. While location of precipitation bullseye varies greatly among the CAMs/HREF members, several point to a potential for 2-3+ inches of rainfall. While locations near/west of U.S. Highway 81 could likely handle this amount of rainfall, several areas farther east have seen their fair share in recent days and flash flood guidance is much lower as a result. This is reflected in the latest Excessive Rainfall Outlook from WPC, which was bumped to a Slight (Level 2 of 4) Risk for Sunday-Sunday night. MONDAY-TUESDAY: Somewhat similar scenario repeats itself early next week, with weak ridging on Monday giving way to increasing chances for showers/storms Monday night into Tuesday as the next stronger mid-upper level trough swings through the region. Main difference at this point seems to be quicker timing of the upper trough and associated cold front on Tuesday, which leaves limited time for recovery from any morning convection and may limit severe potential for later Tuesday. WEDNESDAY-FRIDAY: We transition to a less active pattern behind the Tuesday trough, which slows and becomes nearly stationary over Ontario or the western Great Lakes through the latter half of the week. This places our forecast area in broad northwest flow with limited moisture and seasonable temperatures. Decent daytime mixing will likely lead to breezy-windy conditions, especially during the late morning-early evening. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 610 AM CDT Sat Jun 1 2024 Widespread MVFR-IFR stratus with patchy LIFR conditions as we start this TAF period. While winds will be rather light today, expect gradual low level drying will help slowly erode the stratus/fog through the morning, with VFR conditions becoming increasingly dominant from midday onward. Attention then turns to potential for scattered showers and thunderstorms developing from southwest South Dakota into Nebraska later tonight. Still some uncertainty exactly where this activity will develop, but there is at least a low chance it could track toward KFSD/KSUX late in this TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JH AVIATION...JH