FXUS63 KBIS 140926 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 426 AM CDT Fri Jun 14 2024 .KEY MESSAGES... - There is a Marginal Risk (level 1 out of 5) for severe thunderstorms this afternoon through tonight, specifically across the southwestern portions of the state. - There is a Marginal to Slight Risk (level 1 to 2 out of 5) for severe thunderstorms Saturday afternoon through Saturday night, covering most of western and central North Dakota. - There is a Marginal Risk (level 1 out of 5) for severe thunderstorms Sunday across southeastern portions of the state. - High temperatures are forecast to peak in the 80s on Saturday (potentially reaching the 90s in the southwest), with a gradual cooling trend through the first few days of next week. - Chances for showers and thunderstorms (30 to 80%) will remain through early next week. && .DISCUSSION... Issued at 425 AM CDT Fri Jun 14 2024 Surface high pressure will keep mainly clear skies as it pushes eastward this morning. The resultant pressure gradient from this pushing east and a developing low lee of the Rockies will bring a breezy southeasterly flow to much of the CWA today. There does lack upper level support and pressure rises for advisory level winds today, although perhaps some sites get close this afternoon if enough mixing can be had. As this low gets more and more developed this afternoon a warm front will form and slowly lift north. This will allow for some warming temperatures today with most areas expected to be in the 80s. By later this afternoon and especially through this evening showers and thunderstorms look to develop along this front or the surface low. These could also be aided by a quick moving mid level shortwave. SPC has maintained a Marginal Risk in southwestern ND for severe weather today. These areas could see strong storms develop upstream and move into the area through this evening. When they do so there looks to be ample CAPE and shear. Storm mode could be discrete to perhaps multicluster. Of concern for today is capping issues, and modest effective bulk shear up to 40 knots. Any stronger discrete cells could have ping pong ball sized hail and wind gusts up to 60 mph. There is higher shear values closer to the forecasted wave away from the marginal risk, however these areas have weaker instability. An isolated stronger storm is possible in areas with general risk from SPC today, yet the marginal risk does still seem to highlight the more robust severe storm environment. This evening's storms then become more isolated tonight. Low temperatures tonight will generally be in the mid 50s to mid 60s. Saturday then looks to be a warmer day with isolated to scattered severe thunderstorms developing later in the day and continuing through the night. Surface low moves eastward Saturday as does the associated warm front. Much of the day looks to be capped with limited chances for showers and thunderstorms in the morning through the early afternoon. High temperatures though will remain warm and generally in the 80s to perhaps some lower 90s. A breezy southerly wind could also be found during the day across the east. Capping could then erode later in the afternoon and set up isolated to scattered severe potential through much of the night. The CAMs at this point are split on whether the cap can erode before or after the arrival of the cold front. If this cap can erode earlier then discrete supercells with all hazards will be possible. Cape values will be higher than Friday, and perhaps over 3000 J/KG in some areas. Effective Bulk Shear will also be high and over 50 knots for some areas. Thus decided to start hail size mentioning at 2 inches, although some soundings are showing historic values at around 2.75 inches. There could also be a brief tornado threat with any discrete cells that can develop ahead of this cold front as STP values are near or slightly greater than 1, LCLs are around 1000 M, shear is abundant, and there is some increased SRH. This is a conditional tornado threat, yet decided to include an isolated tornado possible in our messaging. The wind threat could be two fold. Discrete cells could have wind around 60 mph. As the cold front moves through at night and storms become more linear, the abundant cape, high amounts of 0 to 3 KM shear, and DCAPE near 1000 J/KG could lead to strong winds. Decided to start at 70 MPH in our messaging today given the timing uncertainty. Of importance will be to have a way to receive severe weather warnings Saturday afternoon and evening, and especially Saturday night if storms delay until the arrival of the cold front. Cold front then fully moves through the CWA Sunday. There could be some lingering thunderstorms in the east during the morning and south in the afternoon and evening. The severe weather threat will be isolated to the southeast where SPC now has a Marginal Risk. Large hail and damaging wind gusts will be the main threat, although at this point the threat looks isolated. Behind the front will be breezy to windy westerly winds. These could reach advisory levels, especially with strong pressure rises and strong winds aloft expected during the day. Temperatures will cool into the 70s for most areas, with perhaps some lower 80s lingering in the southeast. A broad trough then looks to bring a secondary front and widespread chances for showers and thunderstorms to start next week. A cooling trend will be found with this front, with many areas seeing highs in the 60s each day. As this trough lifts into Canada mid to late week North Dakota is left in zonal flow. The result could be a gradual warmup each day. NBM continues low chances for showers and thunderstorms as well given proximity to the trough and for any weak waves embedded in zonal flow. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1245 AM CDT Fri Jun 14 2024 Mainly VFR conditions will continue through the forecast period. Clear skies and light winds will be found tonight. Winds become south southeast, and perhaps a bit breezy, during the day Friday. These winds should diminish somewhat Friday evening. Chances for showers and thunderstorms return Friday afternoon through Friday night. Confidence was only high enough to place VCTS in select TAF sites at this time. Thunderstorms could bring brief MVFR conditions. An isolated severe thunderstorm will be possible in southwestern portions of the state during this time period. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Anglin AVIATION...Anglin