FXUS63 KBIS 021433 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 933 AM 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. && .UPDATE... Issued at 909 AM CDT Sun Jun 2 2024 Current surface analysis shows low pressure over northwest south Dakota with a warm front extending east along the ND/SD border. Isolated to scattered storms lifting northward, along and north of this boundary are producing some small hail this morning in the southern James River Valley. This is within an area of around 35 knots of effective shear and MUCape of 500-1000J/kg so an isolated strong to severe is not out of the question this morning. Farther north and west. The ongoing convection in the north central continues to lift northeast into a more unfavorable environment. The convection along the Montana border has also diminished in intensity. Looking ahead today, could still see a few stronger cells in the JRV this morning. The convection in the west could percolate as it tracks eastward this morning. We're thinking the stronger capping over the southwest/south central would help limit convection while it would have a better environment in the northwest/north central to linger through the morning and into the early afternoon. For pops we utilized a blend of short term guidance but leaned toward the HRRR guidance which seemed to reflect our thinking. Convection lingering north and/or developing central to north central late morning/early afternoon and tracking off to the east and developing farther south during the afternoon. Updated pops and sky cover this morning. latest updates will be transmitted shortly. UPDATE Issued at 632 AM CDT Sun Jun 2 2024 Low level jet keep kicking up storms in the north central and east, all have been non-severe. The CAMs actually have had the line of storms in far eastern Montana so maybe they are performing okay. That line will move in within the next hour, so far it is non severe. The environment over there has about 500 J/kg MLCAPE and 35kts of shear so it could go severe. This storm will be the start of it, still looking like the storms will form an organized line east of the river in the afternoon. && .DISCUSSION... Issued at 300 AM CDT Sun Jun 2 2024 Showers and thunderstorms have developed in the south central and James River Valley. They formed in the region of the low level jet (LLJ). A few of the storms have been strong but not severe so far. The RAP and HRRR have the LLJ increasing in strength before sunrise, so maybe a storm could go severe. There is a lot of shear (55kts) and some MUCAPE around 500 J/kg at this time. Aloft the main wave is starting to move through eastern Montana, with the surface low over southeast Montana. The main front is also in Montana, moving east. The low level jet is forecast to stay over western and central North Dakota 11z when the wave moves further east and pushes it east. None of the CAMs have this early morning convection so it is hard to use them for timing later today, but there might be a break between this convection and the main show. They still have storms firing in Montana this morning and moving east, forming into a line around Highway 85. With CAPE around 1000 J/kg this morning and low level lapse rates over 7 C/km and the high shear, storms initially could be supercells with golf ball sized hail. Then when they form a line it should mainly be a wind threat. DCAPE values aren't over 1000 J/kg so we will be sticking to 60mph winds. The low level helicity in the southwest this morning is over 200 m2/s2 then it moves over to the east and values increase around 400! So there is a possibility of quick spin up tornadoes east of the Missouri River along the line, with the highest chance looking south of the Interstate. Timing for this looks to be late afternoon when the cold front develops the line. SPC still has the slight risk in the east almost to the river, and a marginal for this morning's storms in the west. The storms should move out by sunset. The first half of the week will continue to be active. Another upper low develops in the Northwest and moves across bringing more chances for thunderstorms Monday afternoon and Tuesday. The CSU machine learning forecast has a small hail threat in the south central for Monday afternoon and overnight, otherwise the severe risk is low. Monday will be the warmest day of the week with highs in the 80s, then as the upper low leaves cooler air filters back in. Highs will be back below average in the lower 70s for the mid week and in the mid 70s for the end of the week. Average temperatures are in the mid 70s for the week of June. Wednesday night is when the upper low will start to spin away, putting us in cyclonic northwest flow, with a big ridge building in the west over a Four Corners high. So the weather will be quiet except for breezy northwest winds Tuesday through Thursday with low pressures moving through. Wednesday we may need a wind advisory in the southwest, we'll see. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 632 AM CDT Sun Jun 2 2024 VFR through the period, conditions will decrease in thunderstorms today and this evening. Winds will be east/southeast before turning northwest with a cold front gusting around 15kts. Winds will be erratic in thunderstorms of course. After thunderstorms move through, skies should clear. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...TWH DISCUSSION...TWH AVIATION...TWH