Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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313 FXUS63 KABR 271509 AAB AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1009 AM CDT Mon May 27 2024 .KEY MESSAGES... - Continued unsettled conditions across northeast SD and west central MN today with a 30-60 percent chance for showers and thunderstorms. Storms will generally be weak with no severe weather expected. - Windy conditions develop today with northwest winds between 15- 30 mph. - A 40-60% chance of precipitation exists Wednesday night, and a 45-75% chance exists on Thursday. Beyond that, a general 20 to 40% chance of rain remains in the forecast for Friday through Sunday. && .UPDATE... Issued at 1007 AM CDT Mon May 27 2024 Current forecast is on track, therefore no changes made at this time. && .SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/... Issued at 357 AM CDT Mon May 27 2024 The weather pattern during most of this forecast period will continue to reflect an unsettled theme as a couple of upper level disturbances move across the region in a northwesterly upper flow regime. The good news is it looks to finally dry out once the end of the period arrives on Tuesday. The first upper level low and it`s associated sfc reflection sit across ND this morning. Models prog this system to track southeastward across our CWA during the day today. There`s a few leftover showers exiting our far eastern zones early this morning from the sfc trough that pushed across central and northeast SD the latter half of yesterday. More scattered showers persist underneath the mid level low in ND this morning. That activity will shift east- southeastward with time. Daytime heating and some modest instability in combination with mid level energy and a back-door cold front in our eastern zones will aid in the development of more showers and weak thunderstorms during the day. Hi-res model guidance suggests that most of this activity should be confined to areas east of the Missouri Valley, mainly in the James Valley and east into west central MN. So, we`ll continue to advertise a 30-60 percent chance for showers and storms, mainly around the midday and afternoon hours. The pressure gradient does tighten up with time through the day, so expect increasing northwesterly winds that will gust generally between 25-35 mph but parts of the Missouri Valley and West River zones could see gusts between 35-40 mph. Guidance indicates highest probabilities of winds gusting to 40mph will be across our southwest zones(SW of Pierre) and those chances only sit around 50%. The second mid level disturbance is progged to work southward across the region late tonight into early Tuesday morning. This will help touch off another area of showers and a few thunderstorms. This mid level trough axis will be mainly impacting our eastern CWA once again with a low end 20-40 percent chance of precip. Sfc high pressure will gradually build southward into the forecast area on Tuesday which will help to return dry conditions to the area along with more sunshine. Temperatures will continue to be near normal to slightly below normal through this forecast term. This will largely be driven by cloud cover and precip chances, especially today into tonight. && .LONG TERM /TUESDAY EVENING THROUGH SUNDAY/... Issued at 357 AM CDT Mon May 27 2024 Ensemble clusters analysis seems to suggest that models have gotten closer to yes, regarding how things shape up in the flow pattern aloft from Friday through Sunday; leaning moreso toward a slightly more progressive push east out of the region of a slightly less deep upper level trough by the end of Saturday. The pattern appears to flatten out some right at the end of the period. Models are continuing to ratchet up the PoPs for Wednesday night (up to 40-60% now) over the western/central tiers of counties in the CWA. There is a model tendency to over-inflate precipitation potential in these types of set-ups (upper level ridge overhead with troffing to the west and a surface boundary to the west of the CWA and a stout low level jet expected). All too often, models (including multiple ensemble member solutions of multiple ensemble systems?) bring precipitation too far east. They assign a push of precipitation northward into NoDak, and rightly so, given the mean storm motion in this environment. But, there is a tendency to over- extend or smear qpf too far east. Not saying it won`t rain somewhere in the CWA Wednesday night. And, not carving up the PoPs grids either. Perhaps the greatest (subjective convective conceptual model) probability of measurable precipitation is Wednesday evening (between 00Z and 06Z Thursday), and not all the way to the Interstate 29 corridor. Perhaps it is relegated to just the far (west river) west counties in the CWA. If outflow boundary/cold pool consolidation from convection in the neighboring CWA to the west happens and a decent gust front is pushed east into the Missouri River valley, perhaps convective potential lives to reach U.S. Highway 83 in the CWA. Models are also ratcheting up PoPs on Thursday (up to a 75% chance now) and Thursday night (up to a 65% chance over and east of the Prairie Coteau), which checks all the boxes for convection. Return flow heading into Thursday should be plenty of time to draw a better low level moisture feed up into the region (low level instability/CAPE). There should be some sort of mid/upper level lifting mechanism in the region, along with a surface boundary for forcing. And deep layer shear is currently progged at ~25 to 30knots. Despite the presence of surface high pressure over the region heading into the weekend, the remaining mid-level baroclinic zone over the region could become active at times if any additional transient pieces of shortwave energy pass overhead in developing zonal flow Saturday/Sunday. Still eyeing up the strong mixed layer winds out over Corson/Dewey counties by the end of peak heating/mixing on Wednesday as a possible candidate for a wind advisory. The strong low level jet that establishes across the whole CWA Wednesday night is expected to re-connect with the boundary layer on Thursday across the James and Big Sioux River valleys over into west central Minnesota, potentially re-centering advisory criteria southerly winds on Thursday to those areas of the CWA. Temperatures in the models and ensemble S.A. tables (for 850hpa thermal anomalies) are beginning to highlight the potential for some warmer (perhaps much above normal warmer) weather during the first full week of June. For the purposes of this 7-day forecast, there is a warming trend noted Saturday and Sunday, with some locations over and west of the Missouri River valley expected to warm into the 80s on Sunday (June 2nd). && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 646 AM CDT Mon May 27 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions are expected through tonight. KABR and KATY could experience some temporary sub-VFR conditions if heavier showers or thunderstorms that develop should happen over terminal airspace. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...Vipond LONG TERM...Dorn AVIATION...Dorn