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Forecast Discussion for Aberdeen, SD
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000 FXUS63 KABR 240530 AAC AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1230 AM CDT Sat Jul 24 2021 .UPDATE... Issued at 1226 AM CDT Sat Jul 24 2021 Updated aviation discussion below. UPDATE Issued at 914 PM CDT Fri Jul 23 2021 Scattered thunderstorms have occurred across both the northern and southern parts of the CWA this evening, and a Severe Thunderstorm Watch remains in effect until 2 AM for a good portion of the CWA. No changes made to winds or temperatures at this time. && .SHORT TERM...(This Evening through Saturday Night) Issued at 351 PM CDT Fri Jul 23 2021 The main challenges through the period involve severe thunderstorm potential this afternoon/evening and elevated fire weather danger on Saturday. As an upper trough continues to advance east into the Northern Plains, stronger flow aloft continues to encroach on the forecast area. As such, deep layer shear has increased, with effective bulk shear values of 30 to 45 knots. Within the flow are a couple subtle shortwaves, which increase the likelihood for thunderstorm initiation/maintenance. At the sfc, there are two main areas of focus for potential initiation: a sfc trough which extends from south central to north central/northeastern SD, and a frontal boundary that extends from central ND towards eastern WY. Convection may initiate on either late this afternoon and evening, but coverage remains in question as these forcing mechanisms are fairly weak. Any storms that do develop have a very moist environment to work with, especially to the east of the sfc trough (dewpoints in the 70s). Steepening mid-level lapse rates, inverted-v soundings and large DCAPE all favor a wind threat, and a cluster/supercell storm mode makes hail a potential threat as well. There may be pockets of storms during different times and at different locations given the set-up, through the evening hours. By Saturday, the passing front will usher in much drier air on northwest winds, by about 20 degrees plus dewpoint-wise. Minimum afternoon RH values will be in the teens to mid 20s percent. Deep mixing due to the dry airmass in unidirectional flow raises questions about how strong the wind will get. This will determine how elevated the grassland fire danger will be. Guidance points towards the strongest 700-500mb winds being across the north and northeastern CWA, with gusts perhaps up to 25 mph or better at times. Temperatures remain above average as well, with highs in the 90s. .LONG TERM...(Sunday through Friday) Issued at 351 PM CDT Fri Jul 23 2021 Pattern through the period features northwest zonal flow with riding upstream initially. Sunday will feature a subtle feature at 500mb, more or less a speed maximum in the flow with a mid level warm advection push. Tenuous moisture may be enough to generate mid level convection but with a dry layer below 10kft and just a few hundred j/kg elevated/skinny CAPE I really don`t see how any of that works out to much more than a few sprinkles/hundredths of moisture. The ridge upstream slowly amplifies through the start of the work week, becoming the main headline as it features 500mb heights nearing 2 standard deviations above climo and 700mb temperatures around +16C. Monday/Tuesday/Wednesday looks to be the hottest period, with the passage of a backdoor front to undercut the warmer air aloft late Wednesday through the degree/timing of relief it provides is too far out to qualify as something we can forecast well at this point. Back to the Monday - Wednesday time period, model dewpoints increase into the 60s, and lows will stall at around 70, so heat impacts will be a concern to keep an eye on. The ridge retreats back to the west for the latter half of the work week and we`re back into a northwest flow regime with stronger flow aloft. As for moisture chances under that regime, well the blended guidance does suggest some options but at these timescales I really don`t feel confident advertising quite as much moisture as there isn`t much for continuity between these fast moving, subtle systems. && .AVIATION...(For the 06Z TAFS through 06Z Saturday Night) Issued at 1226 AM CDT Sat Jul 24 2021 Terminals KABR,KATY,KPIR,KMBG Scattered thunderstorms will track across the eastern half of the area through the early overnight hours, likely exiting the region by 09Z. Periods of IFR/MVFR vsbys will be possible with the storms. After the storms exit the area, VFR conditions will prevail for the rest of the overnight period and through the day Saturday. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...SD SHORT TERM...Lueck LONG TERM...Connelly AVIATION...SD
Previous Forecast Discussions may be found at
NWS Aberdeen, SD (ABR) Office Forecast Discussions.
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