Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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860 FXUS63 KBIS 222004 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 304 PM CDT Sat Jun 22 2024 .KEY MESSAGES... - Isolated to scattered showers and storms (20 to 50 percent chance) are expected this afternoon and into the early evening. A few storms could become strong to severe. Quarter size hail and 60 mph wins will be the primary hazard. - The next round of isolated strong to severe thunderstorms may come Sunday night into Monday morning across the northwest and north central, followed by a more conditional severe weather threat in the afternoon across the east. - Temperatures continue to warm through the weekend with the warmest day on Monday. Highs will range from the lower 80s to lower 90s. We will then cool slightly through the rest of the week (mainly upper 70s to upper 80s). - Thunderstorm chances return mid to late week. && .DISCUSSION... Issued at 304 PM CDT Sat Jun 22 2024 An upper level shortwave continues to move off into Minnesota as the parent trough moves overhead. A surface trough is currently the focus for scattered shower development as noted on radar, roughly along a line from Rolette county, down through Rugby, eastern Sheridan and Burleigh counties and arcing back to the east over McIntosh county to the South Dakota border. SPC mesoanalysis does suggest the presence of 500 to 1000 J/kg MLCAPE in place across all of western and central North Dakota so these showers should continue to increase in coverage and intensity as daytime heating increases. That being said, shear is currently weak where activity is developing and it should remain weak for the next few hours. Later this afternoon, we could have some more isolated development across the west which will have a similar instability environment, but much better shear. SPC mesoanalysis trends suggests effective shear could ramp up into the 35 to 45 knot range by the 22z to 01z time frame. Thus, there may be a window for a few isolated strong to severe storms later this afternoon and into the early evening hours. Any storms that do become organized will likely weaken quickly with the loss of daytime heating. We will continue to advertise hail to the size of quarters and winds to 60 mph as the primary threats, but larger hail may be possible if we can get any sustained rotating updrafts. After showers and storms fizzle, most of western and central North Dakota will see a mostly clear to partly cloudy sky overnight with lows in the 50s. Sunday will be dry for most of the day as an upper level ridge axis moves overhead. This will mean warmer temperatures for all of western and central North Dakota, with highs ranging from the mid to upper 70s over Rolette county, to the upper 80s and maybe even some lower 90s across the southwest. The ridge will then start to flatten as the axis moves off to the east and a subtle shortwave starts to skirt northwest part of the state by late evening. While most of the forcing will remain north of the International Border, there should be enough of a glancing blow to lead to some showers and storms across the northwest and eventually north central late Sunday evening and into the early Monday morning hours. While the magnitude of strong to severe thunderstorms is currently unclear, there will be favorable parameters in place with MLCAPE ranging from 500 to 1500+ J/kg and 40 to 50 knots of deep layer shear. If convection can tap into the favorable shear, some organization can be expected, probably in some sort of cluster or linear mode. For now, will continue to advertise hail to the size of quarters and wind gusts to 60 mph as the primary threats. Monday looks like it may end up being the warmest day of the forecast period for most with highs forecast to range from the lower 80s northwest to the lower 90s across the southeast. Monday could also see a conditional severe weather threat in the afternoon. The parameter space may end up being impressive across portions of the central and into the James River Valley. Some models suggest an environment characterized by 2500 to 3500 J/kg MLCAPE and deep layer shear ranging from 40 to 50 knots. That being said, confidence of seeing any storms is fairly low. Capping should keep the warm sector free of convection through the early to mid afternoon and most guidance suggests that a surface cold front will already be out of the area to our east before storms initiate. If these trends continue, it would not be surprising to see Monday completely dry for western and central North Dakota. Any western trend will need to be watched. Tuesday is then a bit cooler behind the cold front with highs in the mid 70s to mid 80s. Highs will be similar through the rest of the week until maybe Friday when some cooler temperatures potentially return. Various chances for showers and thunderstorms return Wednesday night through the rest of the week and into the weekend. CSU Machine Learning guidance suggests at least low chances for some severe storms on Thursday and Friday but we have a long ways to go before we get into specifics that far out. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1214 PM CDT Sat Jun 22 2024 Rain will hang on at KJMS for the next hour or so before moving out. Ceilings will also continue to improve from west to east this afternoon, eventually giving way to VFR conditions at all sites. That being said, expect at least a couple more hours of IFR to MVFR ceilings at most sites before lifting. We are expecting some isolated thunderstorms this afternoon and evening across western and central North Dakota but too much uncertainty exits at the moment to pinpoint the exact locations these storms will track. Thus, will not include mention at any specific TAF site at this time. If a stronger storm moves overhead, it will have potential for some hail to the size of quarters and winds up to 60 mph. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...ZH AVIATION...ZH