Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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833 FXUS63 KABR 120053 AAB AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 753 PM CDT Thu Jul 11 2024 .KEY MESSAGES... - While mainly dry weather will continue, isolated late evening and overnight showers and thunderstorms will be possible through at least the weekend due to weak disturbances moving through the region. Chances of precipitation are less than 40 percent not only through the weekend, but through the middle of next week. - High confidence in hot and muggy conditions Friday through Sunday. High temperatures will be in the 90s (5-10 degrees above average) with dewpoints in the mid to upper 60s. This will result in heat index values in the mid and upper 90s with a few spots to 100 degrees during the afternoon hours. - Temperatures will moderate with lower humidity for the first half of next week. && .UPDATE... Issued at 745 PM CDT Thu Jul 11 2024 Thunderstorms over far northeast South Dakota should continue dropping south-southeast through the over night hours. Based on water vapor imagery, these storms may be connected to a weak short wave. An increasing LLJ over south central SD after 6Z may cause additional convection toward the early morning hours on Friday. Have increased the areal coverage of pops mainly between 9-12Z. Maintained pops at 20 percent, but based on the 23Z HRRR, may need to increase to 30 percent. Will wait for the 0Z model data before making changes. UPDATE Issued at 619 PM CDT Thu Jul 11 2024 Aviation discussion updated below for the 0Z TAFs. && .SHORT TERM /THIS EVENING THROUGH FRIDAY NIGHT/... Issued at 316 PM CDT Thu Jul 11 2024 Generally quiet conditions through the short term, with the main highlight being the building heat beginning on Friday. Currently, temperatures are rising through the 80s, and flirting with 90 degrees over portions of central SD. By Friday afternoon, 850mb temps climb even a few more degrees, with decent southerly mixing winds. Should be able to tack on a few more degrees compared to today`s readings. With that, models are indicating dewpoints climbing a bit higher than today as well. Current apparent T forecast does show heat indices reaching 100 degrees across portions of central SD. Somewhat marginal worthiness for headlines, but may want to hold off until the weekend when even hotter conditons move in. Held off on any headlines on this shift. As for precipitation, there is a surface trough across the western Dakotas and WY/MT border region. This will be a focus for widely scattered thunderstorm potential into the evening hours. Some of this activity may drift into central SD later tonight, potentially aided by an increase of a 35-40kt southwesterly low-level jet across southern SD. Did include slight chance (20%) PoPs for this possibility. This trough remains in place through Friday, and we reset the mechanism again for potential showers and thunderstorms during the late afternoon over western into central SD. With a weak mid-level disturbance also drifting eastward, some activity may persist into central/northern SD into the evening/overnight hours. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 316 PM CDT Thu Jul 11 2024 The high heat and humidity will be the main focus in this period, but along with that will come some chances for convection for some of our forecast area. The Four Corner centered mid level anticyclone will be the main driver of the upper flow pattern across the western CONUS this weekend into early next week. This feature will in part help to drive our increasingly hot conditions this weekend. While this upper high remains to our southwest, our region will see more quasi-zonal flow across the northern tier from the Northern High Plains into the Northern Plains. Mainly weak embedded mid level waves will periodically traverse through this flow across our region. Lee side sfc troughing across the Plains will continue to promote the influx of a warm and moisture rich air mass. Sfc dew point temperatures will climb into the upper 60s to low 70s this weekend. Combining this with temperatures topping out in the 90s to perhaps near 100 degrees will lead to heat indices in the upper 90s to low 100s in spots. Will have to consider heat headlines in future forecast packages if this trend continues. The caveat still at this point on location and timing of this highest heat/humidity will be when and where convection takes place and how that may affect ambient daytime conditions Saturday and Sunday. The aforementioned embedded mid level shortwaves combined with a sfc trough/frontal boundary will lead to development of scattered convection across the region. Guidance progs the first wave in this period will be cresting over the upper ridge late Friday into Saturday across MT/ND and shifting eastward into parts of the eastern Dakotas and Minnesota. Steepening mid level lapse rates and increasing instability on the order of about 3000-5000 J/kg of MUCAPE are progged to be present in the region. The one uncertainty, moreso for our area, is the amount of convective inhibition that could be present at this time, which would curtail any thunderstorm activity. With that modest EML in place, we could be looking at more of a capped environment for our forecast area, with perhaps the exception of our northeast/east zones, which could be on the periphery of the upper ridge. Just will have to continue watching the trends as more hi-res guidance picks up on this wave and hopefully more clarity comes with that. A somewhat continued active pattern will persist into early next week as the pattern remains fairly unchanged. Periodic, low-end chances for more convection will be possible as these mid levels waves move through the region. The passage of a stronger frontal boundary sometime early-mid next week will bring accompanying precip chances along with a cooler and less humid air mass. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 619 PM CDT Thu Jul 11 2024 Terminals KABR,KATY,KPIR,KMBG Prevailing VFR conditions can be expected through the valid taf period. A stray shower or two are possible across central SD late tonight, so will continue the VCSH mention at KPIR. Southerly winds will subside later this evening, with the winds increasing on Friday, mainly along and east of the James River valley. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...SD SHORT TERM...TMT LONG TERM...Vipond AVIATION...SD