Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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217 FXUS63 KBIS 232009 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 309 PM CDT Sun Jun 23 2024 .KEY MESSAGES... - Isolated to scattered severe thunderstorms are possible late this evening through Monday morning along and north of Interstate 94. The highest chances will be from around Highway 2 to the International Border. - Monday morning thunderstorms may re-intensify by late morning or early afternoon across the Devil`s Lake Basin or James River Valley. These storms could pose a brief severe threat before moving off to the east. - Monday will be very warm with highs mainly in the lower 80s to lower 90s. It will also be quite humid across the south central and east with dewpoints approaching 70 in the afternoon. - We mostly dry out Tuesday and Wednesday with chances for showers and thunderstorms returning Wednesday night through the rest of the week and into the weekend. && .DISCUSSION... Issued at 309 PM CDT Sun Jun 23 2024 An upper level ridge axis is currently located over western North Dakota and will continue to move east through the day. The location of the ridge axis is fairly apparent on satellite imagery given the cloud free sky across the western third of the state and fair weather cumulus over portions of the central and east. This pattern is leading to much warmer temperatures than in previous days and we will see highs rise into mid 70s northeast to the upper 80s southwest. By late this evening, the ridge will flatten a bit as a compact shortwave starts to move across Saskatchewan and eventually into Manitoba by early Monday morning, interacting with a low level thermal ridge. While most of the forcing will remain well north of the International Border, several CAMs continue to suggest that we will see some potential supercell development across the northern third of the forecast area (some even bringing storms as far south as Bismarck). That being said, the HRRR/RAP has trended towards keeping these supercells well into Canada until they dip down into eastern North Dakota in a weakening phase early Monday morning. Thus, the HRRR/RAP are a bit of an outlier at the moment but it is also important to note that these models also have access to the latest data and observational trends. More showers and storms should develop late tonight behind this initial wave but it remains unclear if this activity will pose much of a severe risk. Much of where these initial storms are going to track will depend on where the MUCAPE gradient sets up as storms will likely ride along and just north of that boundary. If storms can sustain themselves across northern North Dakota tonight, they will have a favorable environment for severe weather given plenty of MUCAPE and shear. With DCAPE also forecast to be around 1000 J/kg here and strong 0-3 km shear, will continue to advertise the potential for damaging winds up to 70 mph. Will also continue to advertise hail to the size of quarters but if any supercells can sustain themselves and remain isolated, there is a scenario where larger hail is possible. A low level jet will also be on the increase through the night which will likely lead to additional thunderstorm development late tonight through early Monday morning. Instability will be a bit lower with this warm air advection convection but shear will remain strong. Thus a strong to severe storm cannot be ruled out but the magnitude of the threat remains a bit unclear. Convection will be ongoing through the morning hours on Monday across portions of the north central and into portions of the Devil`s Lake Basin and James River Valley. We will see rapid warming on Monday so some re-intensification of this activity is likely by late morning and into the early afternoon along a surface trough/effective cold front. By 18z, some forecast soundings suggest these areas may see around 2000 to 3000 J/kg MLCAPE and deep layer shear up to 50 knots. Thus, if we do get severe thunderstorms Monday afternoon, they will likely come from strengthening morning convection right before they move east and out of our area. Still, if a storm can get established before moving out, the environment will be primed for severe weather. Hail up to the size of golf balls and damaging winds to 70 mph would be the most likely hazards. Monday will be very warm with most seeing highs in the lower 80s to lower 90s. It will also be very humid to the east of the boundary with dewpoints potentially approaching 70. Dewpoints will dip back into the 40s and 50s behind the advancing boundary. Overnight lows will then range from the lower 50s to lower 60s. Tuesday and Wednesday will see mainly dry conditions with slightly cooler temperatures. Highs will range from the mid 70s to mid 80s both days. Precipitation chances then return to the forecast Wednesday night through the rest of the week and into the weekend. While it remains a long way out, CSU Machine Learning guidance continues to increase the severe weather threat in the Thursday/Friday time frame. The general pattern also continues to look favorable in the various ensembles. So, while it`s a bit too far out for specifics, it will be the next main system to watch. Some precipitation may linger into the weekend with some guidance suggesting a brief cooldown. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1223 PM CDT Sun Jun 23 2024 VFR conditions are generally expected at all sites through the period. The one exception could be tonight and into Monday morning when a few isolated thunderstorms may track across the northern half of the state. Considerable uncertainty remains about how many thunderstorms will be able to form south of the International Border, but low to medium chances (20 to 40 percent) seem reasonable north of Interstate 94 (best chances across the northern third of the state). Will advertise some VCTS at KISN and KMOT but all other sites are too far south to include with confidence at this time. If any stronger storms move overhead, brief IFR to MVFR conditions will be possible along with gusty and erratic winds. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...ZH AVIATION...ZH