Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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721 FXUS63 KFSD 051940 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 240 PM CDT Fri Jul 5 2024 .KEY MESSAGES... - Diurnal showers/weak storms will rotate southward across the area this afternoon, dissipating by sunset. Rainfall will be spotty and light, but isolated lightning may impact outdoor activities. - Unsettled weather continues Saturday-Monday, with periods of scattered showers/storms, mainly focused during the afternoon to early evening. A few strong to severe storms are possible Saturday afternoon, with large hail/damaging winds the primary threats. - Cooler than normal temperatures for early July through the middle of next week, but trending closer to normal by the end of the week. && .DISCUSSION... Issued at 240 PM CDT Fri Jul 5 2024 An upper level low continues to spin over eastern WI this afternoon. Relatively cool air aloft on the backside of the low has resulted in weak instability (MLCAPE analyzed around 500-1000 J/KG) across the region, and this had triggered scattered showers east of Interstate 29. Have yet to see any lightning strikes with the activity, though cannot completely rule this out into mid evening as instability increases a bit more as surface temperatures hit their peak for the day. Bulk shear is nearly non existent over the region, so not expecting any strong to severe storms. Any showers/storms will quickly dissipate by late evening as heating of the day is lost and the atmosphere becomes more stable. Otherwise, a weak surface high slides across the region overnight. With that, winds will drop off to nearly calm. Look for lows in the mid and upper 50s. Our area remains under the influence of an upper level trough on Saturday and Saturday night. Models indicate an upper level shortwave tracking over our area on the northwesterly upper level flow during this time frame. This will bring a better chance of showers and thunderstorms to the region for Saturday afternoon and evening. There is a low end potential for isolated strong to severe storms with MUCAPE of 1000-2000 J/KG, this in conjunction with bulk shear of 30-40 kts (focused mainly across the southern portions of the CWA). Even so, mid level lapse rates are on the weaker side - 5 to 6 C/KM, so expect stronger storms to remain isolated, which is supported well by an SPC Day 2 Marginal (1 out of 5) convective risk for the southern portions of our area. As for rainfall amounts, most places will receive a quarter inch or less - though higher amounts are of course possible in a heavier storm. With the anticipation that there could be more convective activity over southwestern MN, total rainfall amounts (focused on Saturday afternoon through Saturday night) may be higher over that area, with the 12Z HREF indicating a 50% probability of that area receiving 0.50" or greater during that time frame. Highs on Saturday remain just below normal for this time of year - in the mid 70s to lower 80s. Low probability (20-30%) rainfall chances continue on Sunday as a weak cold front swings through the area. Severe weather is not expected in the absence of any significant bulk shear along with weak mid level lapse rates. For next week, models continue to show our area remaining under the influence of the upper level trough through at least midweek. Toward the end of the week, a broad upper level ridge over the western CONUS will try to build eastward into our area. Even so, there is uncertainty on how much eastward progression the ridge will achieve - dependent on the evolution/track of tropical system Beryl which is expected to push into the Southern Plains/Lower Mississippi Valley by early/midweek. Next week does appear to be a drier period, with ensembles suggesting a 15% or less probability of our area receiving 0.25" of precipitation in any one 24 hour period for Monday through Thursday. Temperatures look to remain just below normal through at least the middle of the week, perhaps creeping closer to normal by the end of the week. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1140 AM CDT Fri Jul 5 2024 Isolated diurnally driver showers and thunderstorms are expected to develop this afternoon, with the slightly better chances east of Interstate 29. Coverage is expected to be limited at TAF sites. Any showers or storms will dissipate by sunset this evening. Additional scattered shower and thunderstorm development will then be possible over central SD on Saturday morning. Occasionally gust northwesterly winds through this afternoon, then winds become light and variable tonight into Saturday morning. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JM AVIATION...JM