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Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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365 FXUS63 KABR 042000 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 300 PM CDT Thu Jul 4 2024 .KEY MESSAGES... - Showers and thunderstorms continue to decrease in areal coverage, however isolated thunderstorms will persist into the evening hours. While the severe threat is low, lightning remains a hazard for holiday outdoor activities. Soils are also saturated. There have been isolated reports of water over secondary roads in northern Clark County. Additional rainfall will only exacerbate flood issues. - There is a 20% chance of afternoon daytime heating showers and thunderstorms on Friday. - The active weather pattern of showers and thunderstorms will persist into the weekend, mainly focused over eastern SD into west central MN with around a 50% chance of showers and thunderstorms Saturday afternoon and Sunday afternoon. && .SHORT TERM /THIS EVENING THROUGH FRIDAY NIGHT/... Issued at 249 PM CDT Thu Jul 4 2024 The large closed low system continues to rotate over the region. Reports and radar rainfall estimates have generally been an inch or less through early afternoon, however MRMS QPE does suggest a small area in the southeast Brown/southwest Day/northwest Clark/northeast Spink county region which may be pushing over 2+ inches in some spots. We also received one report of water over secondary roads in northern Clark County. Crest unit streamflow captures this area well and an areal flood warning has been issued. Any additional thunderstorm activity will only exacerbate the overland flooding threat. Showers and thunderstorms have gradually decreased in areal coverage as the whole system continues its slow and steady track eastward. However, isolated showers and thunderstorms remain possible through the evening. Especially over areas that have scattered cloud cover and have/will receive some sunshine/daytime heating. The severe threat remains low, however meso-analysis progs do show steep low level lapse rates and up to 1000 J/KG of SBCAPE. Enough to get pulse storms going, maybe even enough for a strong storm to produce some brief, small hail. Conditions should dry out overnight. The region will remain in the northwest flow aloft pattern through Friday. No strong forcing Friday afternoon, but a few daytime heating showers or thunderstorms are possible (20-40%). Mostly sunny skies and seasonal temps are also anticipated. A brief reprieve is expected before another shortwave moves in late Friday into Saturday. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 249 PM CDT Thu Jul 4 2024 A +PNA pattern continues through the weekend consisting of a highly amplified ridge and mid level high over the western CONUS and broad longwave trough over the central CONUS. Within this pattern, several shortwaves will be swinging in from the northwest, riding the base of the trough, and then exiting northeast as it follows the flow on the downwind side of the trough through Sunday. Highs for the weekend will range in the 70s to around 80, which is 4 to 10 degrees below normal! With the northernmost shortwave, ensembles are coming together better on the placement of the surface low, forecasted to be over ~central/southern Manitoba at 12Z Saturday. A cold front will extend from this and westward through MT. A shortwave to our south will feature its surface trough/leeside low forming during the same time. Ahead of the cold front and to the east of the leeside low, moisture will be filtering northward with PWAT around 1 inch and IVT around 200kgm-1/s-1, which is average for this time of year. Surface dewpoints will be in the 50s to lower 60s across our CWA. Ensemble mean indicates broad precipitation (30-50% NBM) during the day. As the cold front tracks more east/southeast and becomes more defined, (along with daytime heating/instability) pops increase to 30-65%, highest east of the Mo River for the afternoon and evening timeframe. Prob of CAPE>1000j/kg is consistent between the GEFS/EC for early afternoon, ranging from 10-50%, highest over our eastern and southeastern CWA. However for 00Z, EC drops to less than 10% and GEFS increases to 30-80%, highest again in same area. Prob of 2000 J/kG per GEFS is 10-20%. Steeper lapse rates of 6-7C are also noted. So with moisture, instability and lift, thunderstorms are possible. Prob of 1000 j/kg and shear>30kts remain low though, between 10-20%, over central to east central SD. With this, SPC does highlight a day 3 marginal risk of severe storms on the northern fringe of this higher instability. By Sunday, the front is forecasted to extend from the eastern Dakotas through central NE as the northern shortwave digs a bit further southeast across the northern Conus. This will continue to bring chances of precip ahead of the front as well as post front, with pops increasing to 30-50% Sunday afternoon, per daytime heating, with chances diminishing towards sunset as the front and low continues to track southeast. Weather looks to be mostly quiet next week as of now with just a slight chance of storms (15-20%) Monday afternoon over our eastern CWA post low. CPC 6-10 day outlook from July 9-13th has a 35-45% chance of above average temps. Probabilities increase for July 11-17 with the incoming ridge (50- 60%). && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1233 PM CDT Thu Jul 4 2024 Terminals KABR,KATY,KPIR,KMBG Showers and thunderstorms continue to rotate around a low pressure system. Widespread rain showers in the KABR/KATY region will gradually become more isolated. However, VCTS continues to be carried at all TAF sites through the evening hours. IFR CIGS and VSBYS will be possible with the stronger storms. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...Serr LONG TERM...MMM AVIATION...Serr