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Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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284 FXUS63 KABR 150513 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 1213 AM CDT Thu Aug 15 2024 .KEY MESSAGES... - Showers and weak thunderstorms will wrap back into northeast South Dakota and western Minnesota Thursday afternoon (30 to 50 percent chance). - 10 to 25 percent chance for afternoon and evening thunderstorms this weekend into next week. Timing and location are uncertain at this time. && .SHORT TERM /THIS EVENING THROUGH THURSDAY NIGHT/... Issued at 311 PM CDT Wed Aug 14 2024 An upper level trough will track across the area tonight and Thursday, keeping some decent shortwave energy over the area. The trough will exit to the east Thursday night as ridging begins to build in from the west. At the surface, a frontal boundary currently over western South Dakota will become the focus for thunderstorms this evening. Central South Dakota has seen a little bit of clearing this afternoon, which has aided in some higher instability (1500-2000 J/kg of MUCAPE). Already seeing the beginnings of some convective development across north central South Dakota, and per many of the CAMS, this will become a line of storms that will intensify and track eastward across the CWA. Timing is one of the big questions with the line of storms, along with where the strongest part of the line will go. Latest model runs have shown decreasing amounts of shear available this evening across the northern part of the CWA, but still generally in the 25 to 35 knot range. Some of the CAMs are hinting that the line of storms may drift a bit more to the south this evening, while others track the line straight east across the entire CWA. The better instability will definitely remain south, but the shear may be enough to keep the line going across the north too. The main threats with the line of storms will initially begin as large hail and strong wind gusts, then will transition to more of a wind threat vs hail. Heavy rain and lightning will also be threats throughout its life span. The storms will exit the CWA to the east during the early overnight hours, with the remainder of the night being quiet. The low will wrap up over Minnesota on Thursday, and may see some wrap around shower activity across the eastern CWA, especially in the afternoon. High pressure will settle in Thursday night, bringing a return to dry conditions. Low temperatures tonight will be in the lower to mid 60s. High temperatures on Thursday will range from the mid 70s east to the mid 80s along and west of the Missouri River. Lows Thursday night will be in the upper 50s to lower 60s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 311 PM CDT Wed Aug 14 2024 As the low pressure moves out of the area Friday evening into Saturday, a ridge will start building in over the area and will stay around till the end of the forecast period. Occasional development (10-20% chance)of precipitation could occur along the edge of the high pressure through SD. However, timing and location is difficult to nail down with the difference in model guidance. Model clusters all show ridge building and staying in area over the forecast period, however there is some variance in strength and amplitude. By day 5, one cluster with 25% of the Canadian members and 50% of the GEFS members (24% of total members)show the ridge being surpressed from a more northerly wave. The deterministic GFS also shows a similar pattern which allows multiple shortwaves easier travel along the ridge over the area. The deterministic models at 500mb show pockets of potential vorticity moving over the forecast area once the ridge moves in. Those pockets of potential vorticity as well as area of Warm and Cold air advection that move along the edge of the high pressure shows where upper level forcings are located to help with the development of precipitation. While drier air moves in after the low at 700mb, there is some moisture in the 700 and 850 mb levels that occasionally moves in to the area over the forecast period. The locations and timing of this moisture along with the timing and location of the other forcings make it difficulty to nail down when and where precipitation will develop. Deterministic and ensemble models also show this variability with very little consistency on when occasional pockets of precipitation develops through SD along the top of the ridge. Some ensemble clusters show occasional areas of higher CAPE and shear Friday evening, Saturday afternoon and evening, and Sunday afternoon. This shear and instability shows where development of storms could occur, however the clusters also show a fair amount of CIN that could inhibit development of severe weather making it harder to know if it will happen. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1211 AM CDT Thu Aug 15 2024 Terminals KABR,KATY,KPIR,KMBG MVFR/IFR CIGs still possible/likely across KABR/KATY during the TAF period, with lesser chances of seeing this over KPIR/KMBG. By Thursday afternoon, scattered -SHRA/SHRA expected across eastern SD, possibly affecting KABR and KATY and will include a vicinity (VC) mention at this time. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...Parkin LONG TERM...Vernon/SRF AVIATION...Connelly