Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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986 FXUS63 KABR 140813 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 313 AM CDT Sun Jul 14 2024 .KEY MESSAGES... - Potential for strong to severe storms this evening and continuing through the overnight hours. Main threats include, hail up to 2" in diameter, wind gusts between 60-70 mph (higher gusts possible), and tornadoes. - Hot conditions continuing today, with highs in the upper 80s to upper 90s. Heat indices will range from 90 to perhaps 100 degrees with the hottest conditions expected across central SD. - Temperatures will moderate with lower humidity for the first half of next week before readings warm back up toward the end of the week. && .SHORT TERM /TODAY THROUGH MONDAY AFTERNOON/... Issued at 312 AM CDT Sun Jul 14 2024 As of 3:00AM satellite imagery shows a shortwave over the Northern Plains and vort max over southern ND which is aiding in quite the bowing linear system that continues to push east/southeast over central SD. This line produced 70-80mph+ wind gusts along the way. This system will continue to track towards the southeast and into Southeastern SD within the next few hours. Northwest flow continues aloft over the Northern Rockies through the Northern Plains, north of a large and persistent mid level high over the southwestern CONUS. This is leading to ongoing shortwave pulses and moderate winds aloft as this pattern continues. By this evening into the overnight, a stronger shortwave moves in from the northwest and over the northern Rockies and eastward over the Northern Plains. This shortwave will continue to push east and over the eastern Dakotas/MN through Monday. At the surface, the frontal boundary will be south of the CWA with a high pressure system over ND by 12Z. By this afternoon, this front will lift as a warm front (associated with a low over eastern Montana) with much of northeastern SD to the north of the front. By this evening, the center of the low moves over ND with the warm front pushing more north/northeast and a surface trough setting up over central SD, south of this low. This low will sink southeastward with the center of the low over north central SD by 12Z along with its cold front. We still have a fair amount of instability being in this moist air mass as ML/MUCAPE values this evening will be 2000-3000 j/kg and even still 1500-2000+j/kg into the overnight, per HREF, with RAP values trending a little higher. Low and mid level lapse rates are quite steep across the CWA and bulk shear between 40-50kts out of the northwest, increasing to 50-60+kts late tonight as a LLJ ramps up. With this synoptic and meso setup, instability will easily be able to punch through the cap as HREF 2-5km UH>75 (organized convection) and UH>150 (right mover supercells) paintballs do show these discrete cells starting this late afternoon/evening (around the trough)with large hail, over 2" possible, being main threat along with that threat of tornadoes as SPC has a 2% risk. RAP hodographs do show a nice low level curvature becoming more long and straight. HREF then shows more of a linear system moving in from ND tonight into the overnight as the LLJ/shear ramps up with shear becoming more parallel to the front. This would make it more of a wind threat with gusts of 60-70+ mph, especially if we get more of a bowing effect within the system like we did this morning. CAMs are not really showing the discrete cell setup but NAM Nest/HIRES ARW/NSSL WRF do a good job with the timing and areal coverage of this possible bowing system. Due to this threat, a Slight Risk (2/5) of severe storms cover most of the CWA with a with a Marginal Risk (1/5) over south central SD this afternoon through late tonight. This includes a 15% hatched area for wind, meaning wind gusts could be over 74kts, along with a 15% hatched area for hail. Overall pops range from 30-60%, highest over the eastern CWA with the possible linear system. Temps did not get as warm as what the NBM had on Saturday, this was mostly due to the smoke aloft, creating a thick haze. This looks to be the main story for today as elevated smoke continues over the Northern Plains per HRRR elevated smoke model. This will decrease our highs a good 3 degrees with highs ranging in the upper 80s east of the James River to the lower to mid 90s west of here with possible upper 90 readings across south central SD. Heat indices to the upper 90s and isolated areas around 100 are possible across south central SD. A bit cooler behind the cold front for Monday with highs in the 80s. && .LONG TERM /MONDAY EVENING THROUGH SATURDAY/... Issued at 312 AM CDT Sun Jul 14 2024 Very little in the way of change to the extended part of the forecast right now. See below for the previous shift`s discussion covering the extended forecast. (previous shift`s discussion: .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 311 PM CDT Sat Jul 13 2024) The main theme in this period will be the return of a drier, cooler air mass into the region behind a departing convectively producing disturbance early in this term. Mid level flow across our region will remain quasi-zonal early at the start of this period Monday morning as an expansive mid level anticyclone remains centered over the Four Corners region. Guidance continues to prog embedded mid level shortwave energy tracking through our region early Monday. Combining this with the passage of a cold front will lead to scattered convection across the region and in our forecast area. Monday morning should continue to feature leftover convection that will be departing the eastern fringes of our forecast area. Can`t rule out additional isolated convection later in the day as the frontal boundary sags farther south through the CWA. Some hi-res guidance suggests this scenario as favorable instability and deep layer shear will remain present. However, at this time blended guidance is going with dry conditions by Monday afternoon, so we`ll stick with that trend. The deeper upper trough axis will work through the Upper Midwest and western Great Lakes on Monday. This will help to shove the sfc frontal boundary farther south and east with sfc high pressure building in across the Dakotas by Monday afternoon and Monday night. Cold air advection will take over driving in a much cooler and drier air mass. The center of the high will shift southeastward across the central and eastern Dakotas on Tuesday and looks to remain fairly persistent trough at least midweek, perhaps even a bit longer than that. The aforementioned mid level anticyclone over the Four Corners is progged by longer range guidance and the clusters to amplify northward across the Northern Rockies/Northern High Plains into Western Canada. This will lead to mainly dry and relatively cool northwesterly flow aloft across our region until the end of the week. Parts of our region will likely get into return flow once the sfc high shifts farther east of our area late in the week. Warmer temperatures and perhaps a touch more humidity will return late in the period. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1153 PM CDT Sat Jul 13 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions are expected through Sunday evening. A line of thunderstorms may move through or near KMBG and KPIR through 9z before exiting. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...MMM LONG TERM...Dorn AVIATION...Wise