Expires:No;;345475 FXUS63 KABR 251132 AAA AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 632 AM CDT Thu Apr 25 2024 .KEY MESSAGES... - Sustained south-southeast winds around 30 mph today, as well as gusts between 35 to near 45 mph are expected, strongest over north central SD, and throughout and east of the James River valley. - A low probability risk of a strong storm or two may present across north central (generally west river forecast zones) South Dakota by early evening, with primarily a wind threat (small hail possible, too). - Two systems back to back will bring wetting rain to the forecast area. The first system moves in this afternoon through Saturday. The second system arrives Sunday, lasting through Sunday night. - Probability of 48 hour rainfall totals, ending Saturday evening, ranges from 60 to 95%, highest over the James River Valley and eastward. Additional rainfall expected Sunday. && .UPDATE... Issued at 623 AM CDT Thu Apr 25 2024 See below for an aviation forecast discussion for the 12Z TAFs. && .SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/... Issued at 403 AM CDT Thu Apr 25 2024 At 3 AM CDT, skies are generally clear across the western half of forecast zones, while accas and convective debris cirrus cover a good portion of the eastern half of forecast zones. Temperatures on southeast winds of 10 to 20 mph have only fallen into the upper 40s to low 50s. Return flow low level moisture is also evident with dewpoints running anywhere from 5 to 15 degrees higher than this time yesterday. A line of elevated showers and embedded thunder, that developed a few hours ago, continues to work east early this morning, toward the South Dakota/Minnesota border. The synoptic set-up for today/tonight showcases the potential for strong sustained south-southeast winds around 30 mph, with some higher gusts expected throughout the day and into tonight. Within this strong return flow wind pattern, the advection of Gulf of Mexico moisture (seen this morning surging northward through Kansas and the Colorado high plains) up into South Dakota will be possible. UNR's CWA will have the best low level forcing (north-south oriented lee-of-the-Rockies and Black Hills surface trofs) for convection routed in the BL today/this afternoon. Storm motion by late this afternoon/early this evening would take any storms moving with the mean wind northeastward, potentially toward Corson/Dewey counties. Deep layer shear would support generally multi-cellular to perhaps marginally supercellular storm-mode, with generally 500-1000J/kg MLCAPE to work with. 0-1km and 0-3km SRH are not overly impressive, but given that convection would be moving into a strongly mixed BL of southeasterly winds by late this afternoon/early this evening, perhaps some loosely organized wind-threat may be possible, if storms line out or build into efficient cold-pool generating clusters. Saw some of the 00Z hi-res CAM guidance inferring bowing signatures and outflow. Latest HRRR guidance still showing something along this line of reasoning as well. Model trends all still pointing to the initial push of showers and thunderstorms really getting going between 21Z today and 03Z tonight. However, on Friday, guidance appears to be a little slower with the timing of the first parent upper circulation lifting out of Colorado now, in effect, shifting any Friday heat-of-the-day convection (and severe potential) in the warm sector/along the warm front further south of this CWA. Plenty of clouds and cooler conditions in and out of rain on Friday really limiting MLCAPE and MUCAPE over this CWA. Right now, looking like areas of general shower and thunderstorm coverage over this CWA on Friday. && .LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/... Issued at 403 AM CDT Thu Apr 25 2024 For the start of the long term, rain will be ongoing, along with a few possible thunderstorms, as ensembles agree pretty well on the position of the mid level low at 00Z Saturday over SD/NE area, with the axis of the negative tilted trough expanding southeastward. This will be a fairly stacked low at this time to the surface. GEFS/GEPS indicate a slightly deeper sfc low (988mb) than EC (992mb). North of this low, a cold front will also be swinging east/southeastward over the Northern Plains. The low will then track northeastward (occluding along the way) and forecasted to be over ~eastern SD/MN at 12Z Saturday. We see a little bit of a difference aloft, as GEFS keeps the mid level low closed with GEPS/ENS showing an open wave at this time. The CWA will be more on the trowel/wrap around part of the low as increased moisture surges northward and west around the low Friday evening and more of our eastern CWA by Saturday morning, per GFS IVT. NAEFS still shows 90%-97% above climo for PW, at 00Z Saturday, with values 0.75-1", highest values over the James River Valley. NBM shows this moisture well with pops ranging from 73-97%, highest around and east of the James River, from 00Z-12Z Saturday. Through the day on Saturday, the upper wave weakens along with the surface low as it pushes northeast. Pops chances linger early over the eastern CWA and decrease slightly by the afternoon as a surface trough will keep pop chances. Pops range from 25-55% 12Z Sat-00Z Sunday. Ensembles agree pretty well on the position of the second trough that will move in over the Southwestern US along with a developing Colorado low by 00Z Sunday. The ensembles agree on it becoming a closed low, but timing is a bit off with GEFS having it form earlier. By Sunday evening, inconsistencies start to form between the ensembles on where the axis of the trough ends up (somewhere over the Central Plains) along with its intensity. At the surface, this low will push northeast and over the ~Upper Midwest by 12Z Monday as ensembles show this more of a broad and less intense low than previous. Pops will increase to 40-75%, highest over south central SD from 00Z-12Z Sunday and 50-80%, highest east of the Mo River between 12Z Sunday-00Z Monday as the CWA will again be on the northern side of the low then wrap around/trowel. Pops decrease west to east Monday morning. IVT transport indicates this surge northward of moisture but mainly over more southeastern SD and eastward. EC EFI indicates this too with values 0.5-0.6 over eastern and southeastern SD. Chances of light precip (15-25%) return Tuesday as a weak/low sfc trough moves in from the northwest. Confidence is low on this due to several days out. Latest NBM prob of 48hr QPF>0.50" from 00Z Saturday-00Z Monday ranges from 50-85%, highest over James River Valley and eastward, which matches up to where that better moisture is. Overall, probability of CAPE>500 j/kg and shear>30kts remains low, but not zero, as prob ranges from 5-12% over the eastern CWA Friday evening. Shear ranges from 20-30kts out of the south, per GFS, with the better CAPE values over FSD area with our southeastern counties on the northern fringe of this. SPC does have a marginal risk over FSD area Friday. CSU is more aggressive on that severe chance extending further north. So for now, this leaves a chance for general thunderstorms over the James River Valley. Otherwise, the coolest day looks to be Sunday as we will be on the cool side of the system, with forecasted highs only in the 40s/around 50. Temps will gradually warm next week with highs in the 70s Tues/Wed. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 623 AM CDT Thu Apr 25 2024 Terminals KABR,KATY,KPIR,KMBG VFR skies/vsbys are anticipated through early this afternoon. But, by late this afternoon, increasing low level moisture from the south should start to translate into lower (sub-VFR) cigs, first at KPIR prior to 00Z, then at the other terminals generally after 00Z. Expect areal coverage of showers and embedded thunderstorms to begin to increase by early this evening, as well. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Dorn SHORT TERM...Dorn LONG TERM...MMM AVIATION...Dorn