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Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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169 FXUS63 KABR 140521 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 1221 AM CDT Wed Aug 14 2024 .KEY MESSAGES... - Chances for showers and thunderstorms (30 to 45 percent) across central South Dakota tonight, then chances increase (45 to 80 percent) across the entire area Wednesday and Wednesday night. - There is a Marginal Risk (level 1 of 5) for severe storms across the entire area late Wednesday afternoon and Wednesday evening. Large hail and strong wind gusts are the main threats. - Lingering showers and thunderstorms Thursday (30-50%) will taper off from west to east Thursday night. && .UPDATE... Issued at 847 PM CDT Tue Aug 13 2024 Mid-level deck moving across the CWA currently may be bringing a few sprinkles (based on radar) between the James and Missouri rivers, but still expecting better precip potential to ramp up later tonight and closer to 12Z. Did not make any changes to PoPs for the overnight period. Made a few adjustments to sky cover based on satellite trends, but otherwise, no major changes to the forecast for the overnight hours. && .SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/... Issued at 306 PM CDT Tue Aug 13 2024 Upper level ridging will get pushed east tonight ahead of an approaching trough. A leading shortwave will swing across the CWA on Wednesday, followed by the main trough and additional energy Wednesday night. At the surface, the region will be between high pressure to the east and low pressure approaching from the west. Will see increasing chances (30 to 45 percent) for shower and thunderstorm development across central South Dakota during the overnight hours, then across the entire CWA (45 to 80 percent) Wednesday and Wednesday night. The best instability (1700-2200 J/kg) will be confined to south central South Dakota Wednesday afternoon, but 30 to 45 knots of bulk shear across the entire area will aid in some strong to severe storms late Wednesday afternoon into Wednesday evening. The Storm Prediction Center has highlighted the entire area with a Marginal Risk, with large hail and strong wind gusts being the main threats with the stronger storms. The precipitation will exit the area to the east around or shortly after midnight. Low temperatures tonight will be in the mid 60s. High temperatures on Wednesday will be in the 70s to lower 80s. Lows Wednesday night will be in the lower to mid 60s. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Issued at 306 PM CDT Tue Aug 13 2024 The low pressure that will be impacting the weather in the region will be moving out Thursday/Thursday evening and will be taking most of the precipitation with it. After it moves out, a high pressure will start to build into the area Friday evening/Saturday morning. There looks to be the chance for occasional storms (10-20%) to develop along the edges of the high pressure into next week. 200-300mb levels in the models show the area of lower pressure moving over and then through SD Thursday into Friday morning. 700 and 850 mb levels show a lot of moisture with this low. The question will be where this low tracks as it moves into eastern MN and where the wrap around moisture and lift on the back side of the low will be. Most ensembles show a stronger low moving into eastern MN with precipitation wrapping around into northeastern SD. However, about 25% of the ensemble members show the low as much broader and weaker over lower MN, leading to a larger swath of lower precipitation chances over north central and northeastern SD. There is a 20% probability of seeing a quarter of an inch of rain fall during the day on Thursday, but most locations look to see below a tenth of an inch (70% chance). Temperatures still look to remain 4 or so degrees below normal. After the low moves east, the upper levels show a ridge starting to build into the area Friday evening/Saturday morning, and it stays over the region through the forecast period. 700 mb moisture starts to dry out with this ridge overhead, however, 850 mb still have moisture over the area. 500mb has areas of potential vorticity moving along the edge of this ridge as well as pockets of 850 warm air advection and cold air advection. These forcings, along with the moisture at 850mb, provide areas where precipitation could develop over this time period. With the uncertainty of the timing of these pockets, the confidence is low on the locations/timing these storms could occur. The best chances (15-20%) would be during the afternoon and evenings where diurnal heating could affect the pockets as well. Looks like there will be enough shear (30 to 35 kts)on the edge of the ridge for stronger storms, however, the strongest instability, of 1000 to 1500 J/kg, is southwest of the area of shear in southwest SD and western NE. Temperatures during this time will start to warm to near normal values around the mid-80s. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1220 AM CDT Wed Aug 14 2024 Terminals KABR,KATY,KPIR,KMBG MVFR/IFR CIGs are forecast to overspread the region by morning, with areas of SHRA/TSRA as well. Areal coverage and placement of shower/storm clusters are a bit uncertain, but signs point to better coverage during the afternoon/evening hours. Any heavier downpours may produce MVFR/IFR VSBY at times if they manage to move over a TAF site. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...TMT SHORT TERM...Parkin LONG TERM...Vernon/SRF AVIATION...Connelly