Area Forecast Discussion
Issued by NWS Aberdeen, SD

Home |  Current Version |  Previous Version |  Text Only |  Print | Product List |  Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
878 FXUS63 KABR 111931 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 231 PM CDT Tue Jun 11 2024 .KEY MESSAGES...
-- Changed Discussion --
- There are slight chances to chances (15-45%) of showers and thunderstorms tonight through Wednesday night. The precipitation chances Wednesday afternoon look to remain along and east of the James River Valley. Some storms may become strong to severe. - High temperatures on Wednesday are forecast to warm into the upper 80s to mid 90s, which is 10 to 15 degrees above normal. - A storm system Friday night through Saturday night and early Sunday will bring a 30-60% chance of showers and thunderstorms. The storm system may produce locally heavy rainfall over eastern SD and western MN.
-- End Changed Discussion --
&& .SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --
Issued at 228 PM CDT Tue Jun 11 2024 At 2 PM CDT, skies are sunny and temperatures are warming through the 70s and 80s on a 10 to 20 mph west-northwest wind, including gusts up to 35 mph at times. Surface high pressure is over the region, while mid/upper level heights continue to rise. These height rises will stall out overnight as an upper level low pressure system currently moving into B.C. (Canada) and the Pacific NW scoots across the international border overnight and out over the northern plains on Wednesday. The attendant cold front is forecast to progress across the CWA on Wednesday, potentially reaching the James River valley as peak-heating kicks in. More surface high pressure and low level dry/cold air advection is chasing this frontal boundary through the CWA. By 10pm-ish Wednesday evening, the frontal boundary should be clear of the far eastern CWA. Throughout the day on Wednesday, though, toasty warm air that will have been advected into the boundary layer over the CWA will help to support high temperatures well above normal, into the 90s over much of the CWA. There will be a low level jet developing over the region overnight, along with a decent mid-level WAA event on top of it. A glance through model soundings in BUFKIT indicates there is potential for ample low/mid-level moisture return/advection into this region overnight into Wednesday morning, when the higher-octane low-level moist air collecting down over southern Nebraska and on down into Kansas gets transported up into this region. If there is a time when the cross-hairs of mid-level WAA, nose of the low-level jet and leading edge of the best low/mid-level moist air advection all align over this CWA, expect late night/early Wednesday morning isolated (15%) to scattered (40%) coverage elevated showers and thunderstorms. After the low level jet dissipates, convective potential settles into whatever (if anything) can develop along the cold front. By early afternoon, a fairly modest warm layer aloft will be serving as a thermal capping inversion. NAM soundings are probably a tish overdone on moisture/instability (~3500+J/kg CAPE), generating "fat CAPE" large hail soundings; hail CAPE at or above 1000J/kg) and meaningful straight-line hodographs (50knots of deep layer shear). It`s going to boil down to whether or not there is actually enough boundary layer moisture around for storms or if the capping inversion along the boundary will hold, keeping robust updrafts at bay. Leaning toward little to no convection across the eastern zones on Wednesday. But, if sustainable convection were to occur, supercells would be the mode, supporting some rather large hail, potentially, and strong wind. Eventually, convection could start to line out, given forecast 0-3km shear heading into the evening hours. But, thinking is that by then, storms are expected to be departing this CWA, taking any sort of severe threat with them. While surface high pressure is trying to build into the CWA Wednesday night, the gradually southward-shifting mid-level baroclinic zone trailing the surface frontal boundary will move over the CWA, creating elevated night-time shower potential over the CWA.
-- End Changed Discussion --
&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
Issued at 228 PM CDT Tue Jun 11 2024 The main challenges in this period will be precipitation chances returning late in the week and temperatures during the course of the upcoming weekend into early next week. Beginning Thursday morning, sfc high pressure will be building into the Dakotas from the northwest. We may see a lingering shower early in the morning, otherwise anticipate dry conditions will the rule through the day and into Friday morning. Temperatures will remain seasonal for this time of year with overnight lows in the 50s and highs in the upper 70s to mid 80s. The pattern will quickly shift back into active mode by Friday afternoon and Friday night. By then, the next storm system will already be taking shape across the southwest CONUS. An upper trough is progged to dig into the PacNW toward the end of the week. A low amplitude shortwave ridge across the Northern Plains and Great Lakes Thursday will shift east and our region will get into southwest flow aloft. An upper level wave across the Desert SW/Four Corners Region will shift northeast into our region by late Friday into Saturday. More rounds of showers and thunderstorms will be possible by the end of the work week into the weekend. Best opportunities for precip still remain concentrated more across our eastern forecast area from late Friday night through late Saturday night where a 40-60 percent chance exists. There could be some pockets of moderate rainfall with this system across our east. WPC`s excessive rainfall outlook pegs our eastern zones with a marginal risk for seeing heavy rain. At this point, NBM`s probabilities for reaching or exceeding a half inch of rainfall in a 24 hr period ending at 7 AM Sunday is 40-50 percent across northeast SD and west central MN. Temperatures look to remain relatively mild through the weekend into early next week. The only caveat right now in the analysis is it`s a bit difficult to nail down exact values due to the prolonged unstable flow pattern will be in early. Thicker clouds and rainfall versus areas of sunshine will be the driving factors in how warm daytime readings get. Another disturbance is progged by guidance to shift through the region early next week as the upper trough axis remains anchored across the western CONUS. There is some uncertainties in timing and placement of the wave by the deterministic and ensembles, so have continued the trend with a 40-50 percent chance for showers and storms Monday into Tuesday.
-- End Changed Discussion --
&& .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1229 PM CDT Tue Jun 11 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions are forecast through Wednesday afternoon. Tonight into Wednesday morning, there could be a few showers or thunderstorms around. Too tough to nail down timing or coverage right now, so left -shra/-tsra out of the TAFs for the time being. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...Dorn LONG TERM...Vipond AVIATION...Dorn