Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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081 FXUS63 KABR 130532 AAC AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1232 AM CDT Sat Jul 13 2024 .KEY MESSAGES... - On and off chances for showers and thunderstorms (20-40% chances) are possible over the next several days as weak disturbances move through the region. Strong to severe storms are possible, but likely spotty in coverage. - Over the weekend, high temperatures will be in the 90s, potentially reaching the century mark for some areas on Saturday. Heat indices will approach or exceed 100 degrees for many areas. - Temperatures will moderate with lower humidity for the first half of next week before readings warm back up toward the end of the week. && .UPDATE... Issued at 1228 AM CDT Sat Jul 13 2024 Updated forecast for the 06Z TAFs below. UPDATE Issued at 810 PM CDT Fri Jul 12 2024 The current forecast looks good overall. The only change was to increase pops some over north central SD as storms in ND are slowly tracking south-southeast toward the ND/SD border. UPDATE Issued at 618 PM CDT Fri Jul 12 2024 Aviation discussion updated below for the 0Z TAFs. && .SHORT TERM /THIS EVENING THROUGH SATURDAY NIGHT/... Issued at 323 PM CDT Fri Jul 12 2024 Mostly sunny and hot this afternoon across the CWA, especially along and west of the James River, where we had earlier issued an SPS (Special Weather Statement) for heat index values in the mid/upper 90s to around 100 degrees. Latest look at obs does show several locations in the upper 90s heat indices, especially across central SD. Even hotter air moves into the region on Saturday as 850mb temps climb into the mid to upper 20s C by 00Z Sunday for many locations. Actual air temperatures will be well into the 90s for most areas, but add to that the dewpoints in the upper 60s to low 70s, and we`ll see heat indices between 100 and 105 degrees for many areas. Have therefore issued a Heat Advisory for those areas forecast to meet or exceed 100 degrees heat index, valid from 18Z Sat to 01Z Sun. Turning to precipitation chances, it appears there will be some degree of convective development later this afternoon across the western Dakotas in vicinity of the surface trough. Some of this activity may spill into the western CWA counties by early evening. Rather high cloud bases will promote primarily a strong wind threat. In fact, DCAPE values are over 1500 J/KG across the western CWA currently. Rather large dewpoint gradient across western SD, with 40s/50s dewpoints over the far western Dakotas, to near 70 once you reach the Missouri River. So, overall instability increases drastically from west to east across western into central SD, but as this is happening, the cap is strengthening as well. CAMs continue to show widely scattered in nature activity as things head towards the western CWA. Will maintain generally 20-30% chances into the evening hours across the western CWA. On Saturday, thunderstorm chances are a bit murky as we`ll be dealing with capping issues, along with potential outflow boundaries from any morning activity that moves southeast across ND and MN. Plenty of instability will be in place, as well as a surface trough moving into the CWA during the afternoon. Impulse aloft is rather subtle, but could be enough to break the cap into the early evening hours. Areas of strongest surface heating near the surface boundary probably will see best potential for convection. Once again will maintain mainly low chances (20-40%) during the afternoon and nighttime hours. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 323 PM CDT Fri Jul 12 2024 This period begins with persistent high heat and humid conditions on Sunday into Monday as the mid level high remains essentially planted across the Four Corners region of the southwest CONUS. Quasi-zonal flow aloft across the Northern Plains with embedded mid level waves will continue to periodically traverse across our region lending to continued advertisement of 15-30% chances for scattered convection late in the weekend into early next week. After a more clearly defined system moves through early next week, sfc high pressure looks to build in Tuesday and persist through the middle of next week. This should return cooler and drier conditions to the forecast area. Temps modify again by late in the period as the high drifts east and southerly flow draws in warmer and more humid conditions once again. The main focus for precipitation chances in this period will be associated with a deeper upper trough that guidance progs to move out of south central Canada into the western Great Lakes early next week. This system will aid in sending south and east a sfc low pressure system and attendant cold front through our area sometime on Monday. Anticipate this will be our best window for showers and thunderstorms in this period. There will be some associated risk for severe weather with this system, especially east and north(eastern NODAK/northwestern MN) where more favorable ingredients such as instability/shear will be present. After that system departs by Tuesday, a drier air mass will take hold. The aforementioned mid level high is progged to bump up farther north across the Northern Rockies/Northern High Plains by the latter half of this period. This will promote northwesterly flow aloft across our region. Ridge riding weak s/w energy may crest the ridge and shift across our region toward the end of the period, but with no deep moisture available, limited chance for precip seem more likely at this time. Temperature trends through this period will again start off hot and rather humid. Daytime highs in the 90s will persist on Sunday with dew point temperatures in the upper 60s to low 70s. This again could lead to heat indices around 100 degrees during the afternoon. One caveat of uncertainty in this being realized is if there will be any leftover convective debris(cloud cover) that could have a play on daytime temperature readings. With so much uncertainty still in play in terms of convection and it`s placement/timing, it`s hard to put a finger on how hot conditions could get for Sunday and potential need for additional heat advisory headlines. For now, we`ll stick with the going trend of high heat and humidity with the thoughts of re- evaluating the situation as that time draws closer. Temperatures return closer to normal, if not slightly below normal for the middle of the week before we warm back up by late week. Ensemble data suggests increasing probabilities for temperatures reaching or exceeding 90 degrees once again for central SD by Thu/Fri of next week. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1228 AM CDT Sat Jul 13 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions through the end of the TAF period. Rain showers (and a few thunderstorms) continue to push east/southeast over central SD this morning. Chance of thunderstorms tonight that could impact KMBG/KPIR. Low confidence on precipitation forecast so left any mention out of the TAFs at this time. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Heat Advisory from 1 PM CDT /noon MDT/ this afternoon to 8 PM CDT /7 PM MDT/ this evening for SDZ006>008-010-011-017>023- 033>037-045-048-051. MN...Heat Advisory from 1 PM this afternoon to 8 PM CDT this evening for MNZ039-046. && $$ UPDATE...MMM SHORT TERM...TMT LONG TERM...Vipond AVIATION...MMM