Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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871 FXUS63 KABR 102326 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 626 PM CDT Mon Jun 10 2024 .KEY MESSAGES... - High chances (>60%) for rainfall late this afternoon though the overnight with a passing frontal boundary. Strong to severe storms possible over central SD, with hail to around one-quarter inch and wind gusts around 60 mph. Severe threat diminishes rapidly east of the Missouri River. - There is a 20-40% chance of showers and thunderstorms Wednesday into Wednesday night, mainly along and east of the James River Valley. Some storms may become strong to severe. && .SHORT TERM /THIS EVENING THROUGH TUESDAY NIGHT/... Issued at 237 PM CDT Mon Jun 10 2024 Convection has recently moved into northwest SD and will be watching progression of this into the far western CWA over the next few hours. Ribbon of moderate instability (MLCAPE 1000-2000 J/KG) generally stays over western SD (UNR CWA) during the event, but some of these higher values do nudge their way eastward over Corson and Dewey counties by 00Z this evening. Later this evening, MUCAPE values are only around 500 J/KG or less across central SD, and fails to materialize much further east at all. So, with the lack of instability later this evening, do not think the severe storm threat will progress much further east than the Missouri River valley. That said, with the frontal boundary pushing eastward, models do still indicate general showers and thunderstorms advancing eastward across the CWA, although perhaps diminishing in overall areal coverage as it does so. Aside from the "main show" precip event later this evening, we are seeing an initial area of light rain across central SD within the warm air advection region and mid-level cloud deck. Had to add small PoPs for this as it looks to hold together for at least a couple hours yet as it heads towards the James River valley. Tuesday will bring dry conditions in the wake of tonight`s passing frontal boundary. Rather warm air aloft and decent northwest mixing winds should allow highs to climb into the 80s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 237 PM CDT Mon Jun 10 2024 Clusters agree well on a broad low amplitude ridge over much of the central and northern CONUS starting out Wednesday morning with a broad area of low pressure in Canada. This is leaving the Northern Plains in zonal to slight northwest flow aloft with winds increasing to 40-50kts (and 70-80kts at 250mb) towards the afternoon and evening. 850mb to the surface, a trough will move in over the CWA as it pushes east into MN towards evening. To the northwest of this, an occluding surface low is forecasted to be over Alberta/Saskatchewan border, with a cold front trailing over the western Dakotas/WY early Wednesday morning. It will track east/southeast over the Northern Plains, with much of eastern SD into western MN ahead of the cold front by ~late afternoon into the evening. With this synoptic setup, 850mb winds will be out of the southwest (on the PVA side of this trough) east of the Mo River with GFS IVT indicating ample amounts of moisture surging north and northeastward on the warm side of the low. This will raise dewpoints well into the upper 50s into the lower 60s along with max temps reaching into the mid to upper 80s into the lower 90s (NBM forecasted high of 94 for KABR!). This will make the atmosphere quite juicy with low/mid level lapse rates increasing to 7-8C, per NAM/GFS, over eastern SD into west central MN. EC Ens has finally caught up with the GEFS with prob of CAPE>1000 j/kg ranging from 40-90%, highest over eastern to southeastern SD into western MN at 00Z Thursday. Prob of CAPE>2000 j/kg is highest at 50-60%, with both ensembles pegging eastern/ southeastern SD into southwestern MN. Deterministic GFS has the 2000+ j/kg threat extending further west over the James Valley than the ensembles. It is interesting to note that NAM has areas of 3000- 4000j/kg along parts of SD/MN border. So something to watch. Bulk shear is consistent among the ensembles, increasing to 40-50kts by the evening time. Latest NBM shows 20-40% pops around and east of the James River late Wednesday afternoon through the evening. The SPC has a Day 3 Slight Risk (2/5) from eastern SD into western MN with a 15% hatched area indicating a 15% chance greater probability of significant severe weather within 25 miles of a point in this area, which means larger hail/higher wind gusts and the possibility of tornadoes is not out of the question. This is still a couple days out so things could still shift a bit. The past few model runs have shifted this threat slightly east. Another weak system right behind could bring more moisture for early Thursday as NBM has 20-45% pops. Otherwise, the unsettled weather pattern continues as confidence is increasing on a system that could affect the area heading through the weekend with pops ranging from 30-60% as the mid level pattern switches to more of a -PNA setup. Warmer than average temps continue through the end of the week into the weekend. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 636 PM CDT Mon Jun 10 2024 Terminals KABR,KATY,KPIR,KMBG A line of thunderstorms at 2315Z from around MBG to just west of PIR will continue to slide east around 45 mph. The main concern with these thunderstorms will be lightning, some reduction of visibility with blowing dust ahead of moderate to heavy rain. Estimated rainfall along the line has been around 0.4-1". Expect these storms to continue to weaken as they shift east, into a less favorable atmosphere. Still, have included wind gusts of 30-40kts at both PIR and MBG and will continue to monitor the upstream observations. VFR and mainly dry conditions and lighter winds will return to all locations by 06Z Tuesday. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...TMT LONG TERM...MMM AVIATION...KF