Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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423 FXUS63 KABR 301754 AAC AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1254 PM CDT Tue Apr 30 2024 .KEY MESSAGES... - Scattered light showers this morning. - Thunderstorms developing in the afternoon mainly east river. For far northeastern SD/western MN, cant rule out a storm or two with one inch hail or greater and/or winds in excess of 60mph from about noon through about 5pm. - Active pattern continues with at least 3 or 4 notable waves moving through the region providing rainfall chances. Thunderstorm chances (including potential for severe storms) overall, look rather low through the period. - Near to below normal temperatures early in the period potentially warming to near or above normal beginning Sunday into early next week. && .UPDATE... Issued at 1242 PM CDT Tue Apr 30 2024 Aviation discussion updated below for the 18Z TAFs. UPDATE Issued at 1013 AM CDT Tue Apr 30 2024 Made a few minor adjustments to the forecast grids this morning to bring them more in line with the observed trends, otherwise things remain on a decent track. Showers and a few scattered thunderstorms will continue to shift east-northeast across our forecast area through this afternoon. A couple of stronger storms will be possible in our far southeast zones during the afternoon hours. We`ll try and make a run at the low to mid 60s for highs this afternoon, but if cloud cover remains extensive and given the rainfall, we may fall a bit short. UPDATE Issued at 621 AM CDT Tue Apr 30 2024 Aviation discussion updated below for the 12Z TAFs. && .SHORT TERM /TODAY THROUGH WEDNESDAY AFTERNOON/... Issued at 333 AM CDT Tue Apr 30 2024 Mild level warm advection responsible for some very small convective cells which are increasing in coverage from Mobridge to Faulkton at 2am...pushing steadily east-northeast. Mild level cloud deck is more expansive in central/eastern SD, and while it will have an impact on temperature forecast (cooler through the morning hours), it won`t have quite the impact on heating as the last several days. Compact, negatively tilted shortwave will dominate the weather for today, with about 50kts of flow at 500mb out of the southwest, and a 90kt jet streak nosing up into southeast South Dakota. BUFKIT profiles for KATY show rapidly steepening mid level lapse rates before frontal passage followed by a cooling profile with skinny CAPE in a high shear environment thanks to the aforementioned strong mid-level flow. CAM ensembles 25th/75th CAPE values range from a few dozen to upwards of 700j/kg and a 25th/75th range in 0-6km shear of about 50kts to around 60kts. Granted, we are on the very northern extent of this plume of instability, CAMS do initiate surface based convection in the far eastern CWA before it moves into western Minnesota. Overall QPF should be limited by rapid speed of convection along with the short interval in which it is in the CWA. Winds on the backside continue to slide, with the CAM ensembles 25th/75th percentiles running between low 20s to about 30mph. That is a little lower than the NAM/GFS BUFKIT mixed winds which top out around 30-35kts, but fall well short of NBM and its near advisory level winds for our more wind prone areas. The period of dry weather extends overnight before flow aloft becomes southwesterly. Mid level warm advection within this regime will support shower development lifting from Nebraska into central/eastern South Dakota during the day Wednesday. && .LONG TERM /WEDNESDAY EVENING THROUGH MONDAY/... Issued at 333 AM CDT Tue Apr 30 2024 Pattern looks to remain rather active in the extended period, with multiple shortwaves moving across the Northern Plains, bringing periods of rainfall chances. First shortwave kicks off right away as models show energy crossing the region Wednesday night through Thursday. Highest probabilities for >0.25in rainfall (24-hr period ending at 00Z Friday) amongst the GEFS/GEPS/ENS are well southeast of the region, but percentages within the CWA generally fall between 30% and 50% on the Grand Ensemble. ENS is the lowest, ranging from about 15% to 50%, while the GEPS is the highest from 40% to 80%. Highest inherited PoPs from the NBM range from about 50% to 70% across the CWA Wednesday night through Thursday. Friday night into Saturday provides another opportunity for organized precipitation. Probabilities for >0.25in (24-hr period ending at 18Z Saturday are considerably lower than this first wave mentioned above, generally around 40% or below amongst the GEFS/GEPS/ENS. And yet, more shortwave energy potentially for Sunday into Monday. As for thunderstorm chances (including severe storm potential) with these waves, a look at probability for surface CAPE >500 J/KG, surface CIN >-25 J/KG, and 0-500mb bulk shear >30 kts show little to no chances of occurrence through the entire extended period. So, don`t really see anything too convincing for organized strong to severe storm potential at this time with these 3 or so waves moving through during the extended period, or even general thunder in any sort of organized/noteworthy coverage. As for temperatures, generally 50s and 60s for highs during the first half of the extended, with signs of warming towards the end of the period (beginning Sunday) as highs rebound into the 60s and 70s. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1242 PM CDT Tue Apr 30 2024 Terminals KABR,KATY,KPIR,KMBG Rain showers with embedded thunderstorms will continue to push across portions of northeast South Dakota through the afternoon affecting the KABR and KATY terminals. Occasional lighter showers will be possible at KPIR and KMBG through the afternoon. KATY will have the best chance to see a few -TSRA/TSRA with tempo vsby reductions to MVFR. Lower cigs will be possible through the majority of the afternoon hours at KABR and KATY before improving to VFR this evening. Gusty west to northwest winds between 25-35 kts will be possible at KPIR and KMBG through the afternoon into the evening before relaxing by mid to late evening. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Vipond SHORT TERM...Connelly LONG TERM...TMT AVIATION...Vipond