Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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729 FXUS63 KABR 101733 AAC AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1233 PM CDT Wed Jul 10 2024 .KEY MESSAGES... - Low chances (15-25%) of showers and thunderstorms will continue over portions of far eastern SD and western MN today, mainly early this morning and again this afternoon. - The sky will continue to look milky due to smoke sliding in from Canadian wildfires through at least Thursday. - 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 1227 PM CDT Wed Jul 10 2024 Aviation discussion updated below for the 18Z TAFs. UPDATE Issued at 1013 AM CDT Wed Jul 10 2024 Not much needed in the way of updates through 00Z this evening. Satellite reveals the smoke aloft is not all too thick, nor are we seeing any visibility reductions from surface obs. Only impact from this forecast-wise is a small sky cover increase, but rather negligible. Will see temps rising into the 80s for most areas today, with light northeast winds. Any afternoon thundershowers look to be confined to the far eastern/southeastern CWA, which 20 PoPs are already in place for. && .SHORT TERM /TODAY THROUGH THURSDAY AFTERNOON/... Issued at 406 AM CDT Wed Jul 10 2024 The north to northwesterly flow aloft will continue to support smoke from Canadian wildfires moving across the area through at least Thursday. The 06Z run of the HRRR-Smoke indicates the potential for some of the smoke to near the surface, particularly over central SD late this evening into early Thursday morning. We will need to wait and see if that additional smoke is able to reduce visibilities slightly. As noted, the exiting shortwave over eastern SD/western MN continues to help support persistent showers and thunderstorms over our far southeastern counties at 09Z this morning, which will sink southeast over the next few hours and exit the forecast area. It will be difficult to completely rule out showers or a rumble of thunder anywhere over our eastern 2-3 rows of counties through the day today. Daytime heating will again help bring some summertime cumulus clouds and another round of showers and thunderstorms closer to the SD/MN border this afternoon. The main concern will again be lightning, at the 500mb support points more to far southeastern SD/southwestern MN/IA this afternoon. Our light north to northeasterly winds will switch out of the south late this evening and overnight. This will be the beginning of much warmer air pushing into the forecast area, as well as dewpoints rising into the mid 60s. Temperatures over central SD will rise into the low 90s. Given the ridge moving in, and in between systems at the surface, dry weather is expected Thursday. && .LONG TERM /THURSDAY EVENING THROUGH TUESDAY/... Issued at 406 AM CDT Wed Jul 10 2024 Over the course of the extended there will be little change to the overall upper level pattern, with a high amplitude upstream ridge folding over/deamplifying overhead during the short term period...with zonal flow aloft and a building high over the Four Corners region. That high is relatively short lived this weekend, and for the start of the week its become suppressed/flattened and a ridge begins to build back over the Pacific Northwest/Northern Rockies. All during this timeframe, we will see subtle waves traverse the flow across the Dakotas and southern Canada the first few of which we can address with some confidence here... Elevated convection is possible Friday morning in association with mid level warm advection and one of the weak upper waves having crested the upstream ridge. NAM/GFS BUFKIT point to moisture being above 12kft with a deep dry subcloud layer, and as such NBM low POPs and no mention of thunder at this point is acceptable. Saturday morning features higher NBM POPs in association with another weak mid level wave. Harder to point to an impact this wave is having on NAM/GFS BUFKIT profiles, but we can note a subtle increase in moisture at 10kft... but at the same time there is just as equally a significant dry layer below cloud level. Thereafter there is a much better environment for convection with any associated waves as the elevated mixed layer appears to be forced southwards. GEFS plumes for both days only show between one and 4 members generating any moisture for any of the sites in the CWA through this Friday- Saturday timespan. So the main focus during the extended is temperatures. 850/700mb temperatures increase to between 1 and 2 standard deviations above climo, starting during the day Friday. NBM high temperature range (25th to 75th percentile) for sites in the CWA are between 4-6 degrees, with the higher range close to 100 degrees aside from Watertowns mid 90s. NBM dewpoints for the weekend also remain in the mid/upper 60s with the 75th percentile at between 70-71 degrees. That keeps heat index values below or only just briefly to 100 degrees. Again, speculate that with the ample moisture east river has received over the last few weeks that corn enhanced evapotranspiration is being underrepresented by the NBM, and it will be interesting as we get closer to the weekend to see what CAMS have to add. And of course any of this heat could be tempered by elevated smoke as fires continue to burn in the Northern and Canadian Rockies. Thereafter, NBM temperatures, GEFS 850mb temperatures and deterministic guidance show temperatures moderating. Deterministic guidance 700mb representation of the elevated mixed layer show it is suppressed slightly southwards and weaker. This decrease is even more dramatic at 850mb. NBM dewpoints also level out significantly, down into the low to mid 60s according to the 25th/75th percentiles. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1227 PM CDT Wed Jul 10 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions are forecast through the TAF period. Cannot rule out a stray SHRA/TSRA near/east of KATY this afternoon, but with most guidance keeping precip east of there, will leave mention out of the TAFs. Smoke aloft is rather thin, so will only mention FEW250 to account for this. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...TMT SHORT TERM...KF LONG TERM...Connelly AVIATION...TMT