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Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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901 FXUS63 KABR 022151 AAA AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 451 PM CDT Tue Jul 2 2024 .KEY MESSAGES... - There is a Marginal Risk (level 1 of 5) for severe weather Wednesday afternoon and evening across west and central South Dakota. The main threats with the stronger storms will be large hail and strong wind gusts. - The active weather pattern of showers and thunderstorms persists for the Fourth of July into Friday. && .UPDATE... Issued at 450 PM CDT Tue Jul 2 2024 Added some pops to the forecast until sunset as diurnally driven showers and thunderstorms are spreading across central SD and toward the James Valley. && .SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/... Issued at 258 PM CDT Tue Jul 2 2024 Some light showers/weak thunderstorms have crept into the western CWA but will dissipate rapidly with loss of heating. Westerly winds will also decouple. Focus shifts towards convection potential for tomorrow afternoon. Return flow around weak surface high pressure, with an approaching weak shortwave, will result in a weakly unstable atmosphere with skinny CAPE, high bases and 35 to 50kts of westerly/northwesterly unidirectional shear. Thus, the potential for hail and winds with these relatively fast moving cells. Instability and shear drop off rapidly overnight with a second wave coming in during the morning in the west. The main issue with the second round, while PWATs aren`t anything anomalous, is the low shear and skinny shallow CAPE suggesting the potential for slow moving/weak storms with warm rain cloud processes. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Issued at 258 PM CDT Tue Jul 2 2024 Fourth of July looks to be pretty wet as ensembles agree on the shortwave`s axis over western SD/WY and southward into western NE starting out at 12Z Thursday. Down at the surface, the center of the Colorado low is forecasted to be positioned over NE/KS border with a surface trough back over the central and northern Rockies. Another area of low pressure will be centered over Manitoba as well. Moisture will be ongoing from Wednesday/Wednesday night with pops ranging from 60-90% from 12-18Z and 70-90% through 00Z Friday. This means high confidence on widespread coverage of rain showers as this will be a slow moving system. By Thursday evening, the center of the low will be over MO/IL border with the northern low over northern MN. NAEFS really do not show anything out of the ordinary in terms of PWAT as its running around average for this time of year (1-1.25"). GEFS plumes` mean 24 hr QPF, ending Friday at 12Z, ranges from 0.62" at KABR and around 1" at KATY with lesser amounts across central SD. Latest NBM prob of 0.50" ending 12Z July 5 ranges from 35% (just east of the Mo River) up to 55% (Milbank to Watertown.) WPC is more aggressive with the moisture with values between 0.50" up to 1.50+" with the highest totals over our southeastern CWA for the same time period. Due to this, there is a slight risk (15%) for excessive rainfall in this area for Day 3. EFI does indicate QPF of 0.5-0.7 with a shift of tails of 1 over the CWA. Instability remains low as MUCAPE values are 600j/kg and below along with weak mid level lapse rates. There may be just enough for a few brief general storms at times on Thursday (35-55% Prob of thunder per NBM). Both of these systems come together and occlude ~over MN Friday as moisture continues to linger on the western side of this low, mainly James River Valley and eastward (20-35% pops). MUCape increases to 1000-1500 j/kg east of the Mo Friday afternoon and evening providing a chance for thunderstorms. For Saturday, the occluded low is forecasted to be over MI as a weak shortwave will move over the Northern Plains, from the northwest, within a larger longwave trough as the mid level ridge over the western CONUS becomes quite amplified by early Sunday. Either a trough or weak front will accompany this shortwave Saturday as it pushes southeast over the Northern Plains through early Sunday. Highest pops of 20-45% look to be Saturday afternoon and evening with the best chance of rain over northeastern SD into west central MN. By early next week, a +PNA pattern continues with the Northern Plains in ongoing northwest flow aloft with this ridge starting to push a little east by midweek. Temperatures will be 10-15 degrees below average on Thursday with highs only in the upper 60s to the lower/mid 70s. Friday`s temps will rebound a bit in the mid to upper 70s to around 80. Highs will range in the mid/upper 70s an 80s for the weekend. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1215 PM CDT Tue Jul 2 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions for all terminals. Breezy west to northwest winds will decouple this evening. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Wise SHORT TERM...Connelly LONG TERM...MMM AVIATION...Connelly