Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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453 FXUS63 KBIS 100859 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 359 AM CDT Mon Jun 10 2024 .KEY MESSAGES... - Widespread showers and thunderstorms (80 percent chance) are expected today through tonight. Isolated to scattered severe thunderstorms are possible across western and south central North Dakota (level 1 out of 5 risk; level 2 out of 5 in Bowman and Adams counties). - Near normal temperatures expected today and Tuesday. Highs on Wednesday will be warmer, in the 80s, possibly reaching 90 in the southern James River Valley. - Chance for showers and thunderstorms (30 percent) return Wednesday evening, before higher chances for precipitation at the end of the week and through the weekend. && .DISCUSSION... Issued at 359 AM CDT Mon Jun 10 2024 This morning, a shallow ridge aloft was moving into western North Dakota, while a shortwave trough was in place over the Northern Rockies, moving east. A surface low associated with the trough was beginning to deepen in northwest Montana, with low- level warm air advection spreading across eastern Montana and western North Dakota ahead of the approaching system. Scattered thunderstorms were ongoing in eastern Montana and southwest North Dakota as a low- level jet strengthened, but in an environment of very little bouyancy and weak bulk shear. Additional showers were visible on radar across the rest of Montana and into Wyoming. Southeast surface winds were beginning to strengthen in response to the low deepening. The expectation for today is for showers and thunderstorms to become more widespread as the surface low deepens and approaches from the west. High-res guidance is painting a relatively consistent picture in convection spreading northeast, initially along the warm air advection before additional development along a cold front as it pushes east through the afternoon and evening, following the trough axis. This afternoon into the early evening is the most likely time we would see strong to severe thunderstorms develop, when instability is maximized, as that is the primary limiting factor. The 00Z HREF did back off a bit on forecast MUCAPE, keeping values maxed out around 1000 J/kg in southwest North Dakota. Bulk shear still looks quite sufficient for severe thunderstorms, in the 40 to 50 knot range, while mid- level lapse rates are marginal. The tornado potential is low but non-zero, as forecast soundings continue to show high SRH, although this would be for a narrow window of time this afternoon in western North Dakota. Otherwise, main hazards are large hail up to the size of ping pong balls and damaging wind gusts up to 60 m. Uncertainty also comes from how earlier showers and thunderstorms, as well as widespread cloud cover, will impact the environment later in the day and potentially put a ceiling on storm strength. Some CAMs are advertising isolated storms developing in western North Dakota after the front moves through this evening, so something to keep an eye on. Heavy rain is also a possibility, with forecast PWATs on the upper end of climatology, especially if some locations get multiple rounds of heavy precipitation in a short amount of time. Northwest North Dakota has a high probability of at least 0.50" through tonight, with a 20-40% chance of at least 1" of rain. Precipitation chances taper off late tonight in our eastern counties as upper ridging begins to build into the western Canadian Prairies, starting a modest warming trend for the Dakotas. Tuesday should be a pleasant June day with highs in the mid 70s to lower 80s and mostly sunny skies, with a bit of a breeze east behind the exiting system. We warm up further still on Wednesday as a low-level thermal ridge extends into the region, bringing forecast highs to the 80s, with potentially some upper 80s in the James River Valley. Our next shortwave also comes through on Wednesday, and the timing of the wave and attendant cold front could impact how warm temperatures get if it moves through faster than expected. Right now, the timing of the front/wave keeps shower and thunderstorm development just east of the forecast area, but if this slows up, the James River Valley could have potential for some stronger thunderstorms. Dry and seasonable on Thursday before a more active pattern is projected to set up this weekend, as a closed low deepens over the Four Corners region before moving northeast through the central CONUS. Blended POPs increase across the area Friday afternoon and evening, continuing through the weekend and into Monday. Southerly return flow Friday and Saturday is hinting at increasing instability, so another window to watch for some potentially stronger storms. Temperatures through the weekend look to be near to slightly above normal for mid June. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1255 AM CDT Mon Jun 10 2024 VFR conditions to start the TAF period ahead of increasing clouds, lowering ceilings, and widespread precipitation chances through the period as a storm system moves through the area. Chances for showers and thunderstorms move into western North Dakota by 09Z, first impacting KDIK then KXWA, with precipitation moving into central North Dakota (KMOT/KBIS) around 18Z, and finally the James River Valley (KJMS) by 00Z. Some strong to severe thunderstorms are possible across portions of western and south central North Dakota during the day Monday. MVFR ceilings are likely across northwest and north central North Dakota Monday afternoon and evening. Additionally, MVFR conditions are possible around heavier showers and thunderstorms. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Jones AVIATION...Jones