Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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725 FXUS63 KABR 222327 AAA AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 627 PM CDT Wed May 22 2024 .KEY MESSAGES... - A slight risk for severe storms (2 out of 5) exists as a low pressure system nears the region Thursday afternoon. Threats include damaging wind (~60-70 mph), large hail (~up to ping pong sized) as well as a low tornado probability. - Showers and weak storms are expected into early Friday. The unsettled weather pattern then continues with additional chances of moisture Saturday into Monday (30-50%). - A chance of frost (30-40%) exits for north central South Dakota Saturday morning. && .UPDATE... Issued at 623 PM CDT Wed May 22 2024 See updated aviation discussion below. && .SHORT TERM /THIS EVENING THROUGH THURSDAY NIGHT/... Issued at 236 PM CDT Wed May 22 2024 Weak upper level ridging will transition to southwesterly flow ahead of another fast moving closed low system. As such, surface return flow winds and warm air advection will develop tonight and into Thursday. The combination of a low level jet, weak upper level energy and WAA will be enough lift for some accas-y type cloud development/thunderstorms early Thursday morning. As previous forecasts mentioned, the hi-res models pick up on this and continue to develop weak simulated radar returns. Attention then turns to Thursday afternoon as the surface low approaches the region. A fairly well defined warm front, surface trough and trailing cold front appear to set up. Looks like a decent CAP in the warm sector, but dewpoints will be rising into the upper 50s/60s and CAPE values a modest (but sufficient) 500-1500 J/KG. Thunderstorms will likely be tied to the surface trough, giving a somewhat limited window, but they will also be accompanied by an upper level ~70-80 kt jet streak, and as such, 0-6 KM shear in the 50-60 KT range. Current trajectories suggest mean storm motion will not allow storms to move off the surface boundary. Hodographs show decent curvature from 0-3 km, so cannot rule out supercellular development. However, it also looks like any right moving storms will struggle to move off the boundary making it difficult to reside in the more favorable environment. The exception may be areas just north of the warm front or near the intersection of the warm front/surface trough. This includes our northern CWA and northward into North Dakota. Here storms may take on a more discrete mode. Additionally, any supercell development would likely be pretty shallow given the strong shear/low-medium CAPE environment. Nonetheless, severe storms are expected. Current threats include SPC 15% probs for wind (~60-70 mph) and hail (~up to ping pong sized) as well as a 2% tornado probability. Much colder air moves in behind the low pressure system, with additional light rain showers possible into Friday morning. Temperatures will drop into the mid to upper 30s across parts of north central South Dakota, but breezy winds should prevent frost development. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 236 PM CDT Wed May 22 2024 An upper level low continues to pass over the area Friday morning. It will continue to move northeast across the region through Saturday morning, though shortwave energy remains. The next low comes through Monday. The GFS brings the center of the low right over SD, but the Canadian and EC keep the center in ND. Tuesday morning brings a ridge to the area that will continue through the end of the period. Rain chances will decrease through the day Friday as the low moves to the northeast. Low level chances (20-25%) remain through Saturday with the shortwave energy remaining in the region. Sunday afternoon, higher chances (30-50%) return as the Monday low starts to move towards the region. With these rain chances comes a chance of storms. Mid level lapse rates are a little on the low side, sitting at around 6.5 C/km. MLCAPE is also pretty low except in the Canadian model in central SD. Given this, if storms do form, they will most likely not be severe. Monday has some 20 to 30% chances as the low moves through. Tuesday through the end of the period looks dry. Temperatures through the first part of the long term will be below average with highs in the 60s to low 70s. Once the ridge moves in Tuesday, highs will start to warm up towards 80. We still have a chance for freezing temperatures Saturday morning. Areas along the ND/SD border in north central SD have a 10-20% chance of lows below 32 degrees. This has decreased in the last model runs and we will continue to watch the trends. Winds Friday look to be strong with gusts of 30-35 mph likely across most of the forecast area and 35+ mph possible in higher elevation areas. Winds will start to diminish during the evening hours and remain around normal for the rest of the period. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 623 PM CDT Wed May 22 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions will prevail across the area tonight and through the day Thursday. South to southwesterly winds will increase into the 15 to 30 knot range late Thursday morning and Thursday afternoon. There is a chance for thunderstorms to affect KMBG and KATY late Thursday afternoon. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...Serr LONG TERM...KK AVIATION...Parkin