Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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977 FXUS63 KBIS 071918 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 218 PM CDT Sun Jul 7 2024 .KEY MESSAGES... - Another round of scattered showers and thunderstorms is expected this afternoon and early evening. Some storms may once again produce funnel clouds, with a weak landspout tornado possible. - The daily potential for showers and storms will focus more over eastern North Dakota Monday and Tuesday, with coverage becoming more isolated. - A warming trend is expected this week, with widespread highs in the 90s likely on Friday. && .DISCUSSION... Issued at 216 PM CDT Sun Jul 7 2024 A persistent cyclonic flow pattern continues to sit over the Northern Plains this afternoon, with embedded mid to upper level circulations rotating around the base of a longer wave trough. While the longwave trough axis has shifted slightly eastward, now from central Nebraska to western Ontario, western and central North Dakota still lie under the influence of the embedded impulses which have generated yet another round of afternoon showers and thunderstorms. As has been the case for the past several days, atmospheric conditions including an unstable and buoyant boundary layer, very weak deep layer shear, and surface vorticity are once again favorable for the development of funnel clouds, with a brief weak landspout tornado possible. The highest chance for funnel clouds and a landspout are shifted farther east, but they still cannot be ruled out with any storm across the entire state. Showers and storms should gradually dissipate through the evening. Highs this afternoon are forecast around 75 to 80, with northwest winds around 10 to 15 mph. We will finally start to see a more notable pattern shift Monday and Tuesday as the downstream trough slides further east and deamplifies over the Great Lakes while a strong western CONUS ridge begins to expand and tilt eastward. Diurnally driven showers and storms remain in the forecast along and east of Highway 83 on Monday and Tuesday, but with lower coverage expected and possibly (hopefully) a lower risk for funnel clouds. This pattern shift will allow temperatures to begin warming back closer to normal, especially in the west. By Tuesday, highs in the 80s are forecast for all of western and central North Dakota. Ensemble guidance shows the upper ridge continuing to build over the Rockies and High Plains Wednesday and Thursday, with a weak surface flow pattern. This should promote a break from daily showers and thunderstorms and continue the warming trend. By Thursday, the NBM is advertising mid 80s east to mid 90s southwest. For Friday into next weekend, ensembles are pointing toward a possible flattening of the ridge that could result in an active zonal flow over the Northern Plains. The NBM favors Friday to be the hottest day of the week as the ridge flattening process is just beginning, with current projections around 90 to 95 statewide and possibly approaching 100 in the far southwest. But Friday could also mark the return of thunderstorm chances lasting through the weekend. This may include prospects for severe weather given the enhanced flow aloft, warm surface temperatures, and NBM dewpoints in the 60s. CSU machine learning guidance confirms this thinking, with low severe probabilities spread across the state Friday through Sunday. Given timing and spatial uncertainty, the NBM is only carrying low PoPs for now. Temperatures are likely to remain above normal (which is mid 80s for highs) next weekend, but there is larger ensemble spread due to lower confidence in the evolution of a closed upper low moving across central Canada. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1243 PM CDT Sun Jul 7 2024 Scattered showers and thunderstorms are likely to develop once again this afternoon and evening. The highest confidence in coverage of showers and storms is from around KBIS to KJMS, where VCTS has been included. Elsewhere, coverage is likely to be more widely scattered to isolated, and far western North Dakota could remain completely dry. Any heavier shower or storm could produce brief periods of MVFR to IFR visibility. Otherwise, VFR conditions are likely through the forecast period. Some patchy fog could develop late tonight into Monday morning, but confidence on exact location is low. Northwest winds around 10-15 kts this afternoon will become light after sunset. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hollan AVIATION...Hollan