FXUS63 KBIS 021931 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 231 PM CDT Sun Jun 2 2024 .KEY MESSAGES... - Scattered severe thunderstorms today. Threats include hail up to the size of golf balls, damaging winds up to 60 mph, and a tornado or two possible. - Chances for showers and thunderstorms continue through the first half of the week. Temperatures will be near to slightly above average, with highs in the lower 70s to lower 80s this week. - Strong northwest winds are possible Tuesday through Thursday. && .MESOSCALE... Issued at 230 PM CDT Sun Jun 2 2024 The main focus for the development of severe convection through 4 PM CDT is over south central North Dakota. A broad inverted surface trough is analyzed extending north from low pressure in western/ north central South Dakota along and west of the Highway 83 corridor in North Dakota. Preliminary data from the 19Z KBIS RAOB shows effectively no SBCIN. Current satellite trends show a couple areas of agitated cu with some orphan anvils: a more prevalent line from southern Emmons through western Logan Counties and a secondary line from eastern Burleigh into northern Kidder Counties. Despite these current trends pointing toward robust convection with severe potential, mid to upper level forcing is lacking in the area of interest, with better forcing much farther west over western North Dakota unlikely to catch up. In fact, a storm was intensifying over eastern Slope County as of 125 PM MDT. If sustained updrafts are realized, the CAPE/shear parameter space supports severe storms, with large hail being the primary threat initially with discrete storms. && .DISCUSSION... Issued at 116 PM CDT Sun Jun 2 2024 An active upper level flow will remain over the Northern Plains through mid-week. Strong to severe convection today associated with an upper level impulse congruent with a surface boundary developing over central ND early this afternoon and moving to the east. Latest surface analysis shows a possible weak circulation near Bismarck with a warm front extending east into the James River Valley. On and off convection has been occurring in this area of warm advection all morning long, with a few stronger cells from time to time. One severe thunderstorms warning was issued associated with this activity in the past 30 minutes. Additional convection is situated from southwest through north central ND. This convection has not been as strong as of yet, but does look to be intensifying a bit within the past hour. There looks to be a shortwave around northwest ND at this time from the WV imagery, which seems reasonable given the recent uptick in convection. A special 19Z sounding will be released to help determine the extent of the erosion of CIN over the south central. In general, it looks like the potential for convection will continue over central ND as the surface trough becomes more established within an area of increasing instability and diminishing CIN with strong bulk shear already situated over the area. Initially if discrete convection can sustain itself, large hail looks to be the initial threat. Of course a local strong gust also can't be ruled out. We do think as we go through the afternoon, convection may develop into more of a linear form, with winds becoming the bigger threat. Whether or not this occurs by the time convection moves out of the forecast area, remains to be seen. After this wave moves through we get a brief break late tonight into Monday before another, stronger wave moves through the area. This wave will develop a closed upper level circulation over southern Canada with another strong impulse tracking eastward along the International Border through Montana and then lifting northeast into southeast Saskatchewan. At this time, the severe threat looks a bit limited, mainly due to the timing. The brunt of the forcing pushes through the local area late Monday night into early Tuesday, beyond the diurnal maxima for instability. However, think we could have a narrow window of opportunity for some strong to severe convection Monday evening. Currently SPC has the area within a general risk for thunderstorms. The CSU Machine learning probabilities does show a finger of higher probabilities extending from the eastern Dakotas, back into southwest ND. We'll have to continue to monitor as we get closer. On Tuesday, the upper low tracks form southern Saskatchewan into southern Manitoba. We could be dealing with ongoing showers and thunderstorms from overnight Monday into Tuesday morning, but by Tuesday afternoon, the strongest forcing will have moved to our east. Most of the forecast area would be within an unfavorable location for shower/thunderstorm activity. The far north may be close enough to the low for some shower activity. Depending on the eventual timing of this system the James River Valley could also see some potential afternoon shower/thunderstorm activity should the system slow a little. Currently though, the higher probabilities for convection remain east of the forecast area Tuesday afternoon. As we move through mid-week the upper low lingers a bit over southern Canada, keeping the forecast area within a favorable area for strong west to northwest winds Wednesday and possibly again on Thursday over eastern portions of the forecast area. We could eventually need wind highlights, especially Wednesday. The ECMWF SA page has a pretty strong signal (and increasing) for winds and wind gusts Wednesday across most of the forecast area. Then a weaker signal for the far northwest/north central into the JRV on Thursday. The potential for showers and thunderstorms does diminish quite a bit beyond Tuesday with just some lingering showers north and east on Wednesday, then dry conditions Wednesday evening and through the remainder of the forecast period. Temperatures through the period remain in the seasonable range with highs mostly in the 70s but with a few 80s possible Monday, then some 60s possible Tuesday through Friday. Lows generally in the 40s and lower 50s through the period. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1208 PM CDT Sun Jun 2 2024 Scattered showers and thunderstorms will track eastward across central North Dakota this afternoon and early evening. These storms will have the potential to produce MVFR-IFR visibilities in heavy rain, in addition to strong winds and large hail. The activity should exit the James River Valley by early evening. Thereafter unless we see an are of patchy fog, VFR conditions are expected through the rest of the 18Z TAF period. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ MESOSCALE...Hollan DISCUSSION...TWH AVIATION...TWH