032 FXUS63 KBIS 130606 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 106 AM CDT Fri Jun 13 2025 .KEY MESSAGES... - Below average temperatures through Friday, then near average this weekend through next week. - Daily low to medium chances for showers and thunderstorms this weekend through next week. A few strong to severe storms are possible each day. && .UPDATE... Issued at 1258 AM CDT Fri Jun 13 2025 Scattered showers continue over much of the area, with a bit greater coverage over the southern James River Valley. Expect the coverage to gradually diminish as we continue through the night into the early morning hours. Otherwise, the other concern is possible fog development. Have expanded areas of fog through much of the southwest as visibility continues to gradually diminish, and spread patchy fog through most remaining southern areas per latest guidance. UPDATE Issued at 1038 PM CDT Thu Jun 12 2025 We felt another update was warranted to mention that we removed thunder for most of the area outside of the far southern James River Valley. Also, scattered showers continue to redevelop ahead of the S/WV and with easterly upglide flow, so re- increased POPs a bit for the next few hours and went with coverage wording. Overall, a pleasant early Spring night (despite it is mid-June). UPDATE Issued at 936 PM CDT Thu Jun 12 2025 There were no major changes to the forecast at this time. Scaled back on thunder potential with most areas outside of the southern James River valley stable. Will maintain a heavy rainfall wording in the HWO across this same area (our far southeast), with training storms still possible over the next few hours. UPDATE Issued at 638 PM CDT Thu Jun 12 2025 Main forecast updates with this product issuance was mainly to increase the fog potential southwest a bit. Also blended hourly weather elements based on latest sfc obs and trends. Overall, minimal changes were needed. See below for more detailed discussion. && .DISCUSSION... Issued at 347 PM CDT Thu Jun 12 2025 Negatively-tilted mid level troughing is analyzed from southern Alberta to the southern Red River Valley this afternoon. A pair of distinct shortwaves, over southwest Saskatchewan and eastern North Dakota respectively, can be seen on water vapor imagery with mid level drying evident through South Dakota. Shower and thunderstorm activity has unfolded as expected across central North Dakota, but is significantly less than expected in western parts of the state. Recent CAMs hint at some redevelopment later this afternoon and evening, but confidence in this outcome keeps trending lower. Meanwhile, there is marginally sufficient buoyancy on the order of around 500 J/kg MUCAPE from south central to southeast North Dakota to support a few thunderstorms. So far this afternoon, observed lightning has been sparse and mainly limited to Grant and Sioux Counties. Switching gears, near-surface smoke has notably improved across the state but still exists at lower concentrations across the north. It may take until Friday night for the smoke to fully disperse, but conditions are not expected to worsen significantly beyond current observations. This evening through tonight, strong low level frontogenesis is forecast to develop over the southern James River Valley and remain nearly stationary. Moisture transport feeding into the resultant warm frontal boundary underneath strong cyclonic curvature vorticity should provide enough lift for widespread showers and likely at least a few thunderstorms to persist over this part of the region for much of the evening and overnight periods. Several ingredients are in place that could promote high rainfall rates, including precipitable water around 1.25 to 1.5 inches and warm cloud depths around 3000-3500 m. Additionally, forecast storm motion/deep layer wind vectors oriented perpendicular to the moisture transport vectors could yield training convection. The 12Z HREF localized probability-matched mean QPF paints a swath of 2-4 inches from Dickey County eastward, and its ensemble maximum QPF approaches 5 inches. Widespread flooding concerns are not anticipated with this event, but localized minor flooding of urban and poor drainage areas is a reasonable outcome given this setup. Mid level cyclonic flow on top of a diffluent easterly surface flow is forecast to maintain cloud cover across much of western and central North Dakota on Friday, limiting forecast high temperatures to the 60s. Mostly dry weather is expected on Friday, with a few lingering light showers possible in the morning. Friday morning could also feature fog across the southwest, but it is uncertain how dense the fog will be, and this could be a case of ceilings lowering to the surface along areas of higher terrain. Strong to severe convection is forecast to approach the MT/ND border Friday evening, but there is strong model/ensemble consensus that the threat for severe weather will not expand into western North Dakota. Nevertheless, there are still increasing chances for showers and a few sub-severe thunderstorms from western into south central North Dakota Friday night. For this weekend through most of next week, ensembles favor broad, low-amplitude upper ridging over the Northern Plains with intermittent shortwaves temporarily flattening the ridge. This results in a slight warmup back to near normal temperatures, with forecast highs mainly in the 70s to lower 80s. Given the expected more active pattern but with high timing uncertainty on shortwave passages, the NBM maintains nearly continuous low to medium rain chances from this weekend through the middle of next week. Boundary layer moisture is also forecast to increase over this time period, which in turn should yield instability/buoyancy that is more favorable for strong to severe convection. Machine learning guidance shows low probabilities for severe storms nearly every day through the extended period, with no one particular day standing out above the rest. Forecast details on any severe weather will remain very uncertain at longer time ranges, but this is the most ensemble support for stronger convection there has been so far this season. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1258 AM CDT Fri Jun 13 2025 Scattered rain showers will gradually taper off overnight into early Friday morning. Ceilings will continue to lower to MVFR and eventually IFR levels from southwest to northeast through the forecast period. These lower ceilings may only reach as far northeast as KMOT late Friday morning. Southern North Dakota could see LIFR ceilings overnight into Friday morning, along with fog in the southwest. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...JJS DISCUSSION...Hollan AVIATION...JJS