Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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612 FXUS63 KABR 181511 AAB AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1011 AM CDT Thu Jul 18 2024 .KEY MESSAGES... - 30 to 80% chance of precipitation Friday afternoon, with the highest chances across central South Dakota. Ongoing chances of precipitation are possible during the afternoon hours of Saturday and Sunday with chances ranging from 20 to 40%. - High temperatures will range between average to a few degrees below average today through the weekend. - Confidence is increasing on slightly warmer temperatures back to around average by midweek. && .UPDATE... Issued at 1009 AM CDT Thu Jul 18 2024 Current forecast is on track, therefore no changes made at this time. && .SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/... Issued at 321 AM CDT Thu Jul 18 2024 At 3 AM CDT, under a clear sky, temperatures were in the 50s to low 60s. Winds were light and variable or southeast at 10mph or less, as surface high pressure has shifted some to the south and east and is analyzed over Minnesota, Wisconsin and Iowa. There is return flow low level moisture advection happening across the central and northern high plains this morning. By late afternoon, a surface trof (forcing) and the subtle mid-level shortwave (lift) noted in satellite imagery over Saskatchewan are forecast to be entering the region. A few CAMs generate isolated coverage (less than 25 percent) of showers/thunderstorms over the western Dakotas from this forcing/lift combo. Collaborated a small PoP for this afternoon/evening as such. There are additional pockets of cyclonic energy noted in the water vapor imagery rounding the top of the western CONUS upper level ridge that will add additional precipitation chances to the forecast later tonight through Friday. SPC has placed much of the west river zones in a marginal risk (1 of 5) for severe weather. Modest instability/shear appears to be in play late this afternoon through Friday afternoon. Multi-cell to super-cell-type storm mode is anticipated, so perhaps quarter-sized hail and 60-70mph wind gusts might be possible, particularly Friday afternoon in and near the Marginal Risk area. Low level thermal progs today and Friday in this developing return flow south-easterly mixing layer environment show an uptick by a couple of degrees Celsius. High temperatures should range from near 80F degrees along the Minnesota/South Dakota border to near 90F degrees west river today and Friday. && .LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/... Issued at 321 AM CDT Thu Jul 18 2024 Clusters agree on the highly amplified ridge (extending well into northern Canada!) over the western Conus and trough over the eastern CONUS, with a mid level low over the northern Pacific and a low over eastern Canada. This blocking pattern continues through the weekend with not much movement of the Pacific low. Early next week this low starts to move over western Canada, pushing the northern axis of the ridge eastward, (becoming positive tilted) by the middle to end of next week that look to influence our high temps. Friday evening, per northwest flow, the positive tilted shortwave will be moving downstream of the ridge and positioned over the Northern Plains with another wave, to our northeast, over the upper Midwest. Both of these waves will continue to track southeast through Saturday morning and winds turning more northerly. At the surface, a leeside low will be over CO as a trough extends northeastward through central SD. Through 12Z Saturday, this low will shift southeast with the surface trough pushing sightly east/southeast through eastern/southeastern SD. With a northward plume of moisture from the Gulf, dewpoints will be in the lower/mid 60s Friday evening. With surface moisture, lift from the trough, and shortwave help, ongoing chances of showers and thunderstorms are possible, mainly over south central SD, with NBM pops of 20-35% between 00-06Z Saturday. 15-20% pops continue over our southeastern CWA, between 06-12Z, as everything continues to shift southeast. GFS mid level lapse rates over south central CWA will be in between 6-7C with a plume of instability, up through north central SD, with CAPE up to 1500j/kg. Bulk shear between 25-30kts are also noted from north central to south central SD, highest over south central CWA. So strong to severe storms could be ongoing or possible by the evening time with hail and wind being the main threat with the severe threat diminishing with sunset. Ongoing surface trough extending northward from the low into the Northern Plains Saturday and Sunday could bring additional slight chances of showers and thunderstorms. NBM pops range from 20-40% with the best chances being with diurnal heating each afternoon. Marginal moisture will be ongoing as dewpoints remain in the lower- mid 60s and 700mb RH in the 60 percentile range. For early next week it looks overall dry with low chances (15%) of afternoon storms over the eastern CWA. CSU indicates severe potential under 5% for the rest of the long term. Highs for the weekend will range from the upper 70s to the mid 80, with maybe a few upper 80 readings around and west river. The NBM 25-75th spread is only be a few degrees during this time so high confidence exists. As the top of the ridge starts to move over the Northern Plains, highs across the CWA will be in the 80s on Tuesday and the potential of lower 90s readings exists around and west of the Mo River for Wednesday. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 616 AM CDT Thu Jul 18 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions expected for all terminals. Light winds will become more predominantly southerly through the course of the TAF period. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...Dorn LONG TERM...MMM AVIATION...Dorn