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Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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392 FXUS63 KABR 121122 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 622 AM CDT Mon Aug 12 2024 .KEY MESSAGES... - Below average temperatures (5 to 10 degrees) continue today. - 15 to 25 percent chance of showers and thunderstorms across central South Dakota for Tuesday. - Additional chances for moisture in the form of thunderstorms run from late Tuesday through early Thursday. Severe storm potential looks limited to Wednesday with a marginal risk (1 out of 5). && .SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/... Issued at 247 AM CDT Mon Aug 12 2024 As of 2AM satellite imagery indicates scattered high clouds moving eastward over northeastern SD through ND with lower clouds over central SD. Temps are ranging in the upper 50s to the lower 60s. Short term models indicate the shortwave, and its surface low, continuing to push southeast and will be over the central Midwest around 12Z this morning, leaving northwest flow across the Northern Plains. Behind this low, a high pressure system will position itself over the eastern Dakotas/western MN this morning and over central MN this afternoon, keeping the area dry. Few of the CAMs do show speckles of precip here and there but left that out of the grids for now. Aloft, a ridge will build slightly over the Rockies/western Plains through the day. To the west of the ridge, a shortwave positions itself over the Pacific Northwest as a deeper trough moves in off the Pacific, over the western CONUS. These waves look to come together tonight into early Tuesday and shift east. This will also push the ridge slightly east with the axis over much of the midwest to the Northern Plains by midday Tuesday, as it amplifies a bit. This will turn our winds aloft more zonal/slight northwest flow. Latest HRRR smoke model looks to indicate another plume of smoke aloft returning this evening over central SD, pushing east overnight. By this evening into Tuesday, RAP indicates a lee side surface trough/weak frontal boundary setting up over the western Dakotas as as several shortwaves will track upwind and along the axis of the ridge. Return flow will help 1000-500mb RH increase over central SD and help dewpoints rise back into the lower 60s across the CWA. CAMs indicates a few rounds of very spotty precip, in the form of showers and thunderstorms, over central SD (with disagreement on location and timing between the models) with NBM being very aggressive on pops. So low confidence on exact outcome for now. For grids I went with more of the CAMs/HREF solutions for pops which range from 20- 25% over central SD. As of now the SPC marginal risk stays to our west. Highs will range in the 70s to the lower 80s across the CWA, which is still 5 to 10 degrees below average. Overnight lows will range in the upper 50s to the lower 60s. Warmer for Tuesday with the ridge, with highs in the upper 70s to the upper 80s, warmest around and west river. && .LONG TERM /TUESDAY EVENING THROUGH SUNDAY/... Issued at 247 AM CDT Mon Aug 12 2024 From a 24 hours ago perspective, looks like a slight slowdown in wave timing for late Tuesday and Wednesday. The southwest flow regime doesn`t get into central SD counties until Tuesday night at which point we`ll have about 1000j/kg MUCAPE and weak shear. NAM PWATs are up over 1.5 inches with the NAEFS up closer to 1.75 (2 standard deviations above climo), with the GFS depicting a 30kt low level jet overhead enhancing the moisture feed. NAM BUFKIT profiles are essentially moist adiabatic, which should be expected this time of year when you mix low level jet moisture with a plume of mixed over Desert Southwest monsoon moisture aloft. Unsure about the NBM 60+ probability POP coverage for just about the entire CWA with the lee low still out by Rapid City drifting towards south central SD by mid day Wednesday, providing limited surface convergence even into the afternoon particularly east river, but rainfall rates from any storms that do develop should benefit from this high moisture content and slow storm motion. As we get into the day Thursday, the weak surface trough has moved over the eastern CWA and should be out of the CWA by the time peak heating has destabilized the low levels. Profiles dry a little but remain essentially moist adiabatic with light winds aloft. Thursday night/Friday an upper ridge builds to the west but fails to proceed east very rapidly, placing us in a northwest flow regime. NBM POP trends continue to come down with better deterministic run consistency and placement of features that are generally unconducive to thunderstorm generation this time of year. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1219 AM CDT Mon Aug 12 2024 Terminals KABR,KATY,KPIR,KMBG MVFR CIGS will eventually break at KPIR. Fog at KABR with an MVFR VISBY will also eventually break down over the next few hours once the sun comes up. Otherwise expect VFR conditions for all terminals. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...MMM LONG TERM...Connelly AVIATION...MMM