FXUS63 KBIS 092358 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 658 PM CDT Sun Jun 9 2024 .KEY MESSAGES... - High temperatures the next few days near normal for early June (normal is mid 70s). Above normal temperatures are expected with increasing confidence for Wednesday (80-85 degrees). - Widespread showers and thunderstorms (80 percent chance) expected Monday through Monday night. Isolated severe thunderstorms are possible across portions of western and south central North Dakota (level 1 out of 5 risk), with a small area with a Sight (level 2 out of 5) risk of scattered severe thunderstorms over Bowman and Adams counties. - Chance for showers and thunderstorms (30 percent) return late Tuesday night through Wednesday, before higher chances for precipitation at the end of the week. && .UPDATE... Issued at 647 PM CDT Sun Jun 9 2024 The forecast for tonight remains on track. Mostly clear at the moment across western and central ND with a mid level ridge building across the western Dakotas. Still expect increasing chances for showers and perhaps a few thunderstorms later tonight into Monday as a S/WV trough approaches and crosses the Northern Rockies. && .DISCUSSION... Issued at 235 PM CDT Sun Jun 9 2024 Today, clear and calm conditions are found over most of western and central North Dakota as broad area of high pressure at the surface lingers over the Northern Plains. Slight chances (10 to 20%) for showers can be found across the far southwest today ahead of a weak shortwave advects a vort max across northwestern South Dakota. However, with ample dry air over the low to mid levels much of any precipitation that does fall out of these high based clouds will likely become virga. Highs today remain slightly below seasonable normals, ranging from the upper 60s north to the mid 70s south. Winds will remain generally light out of the east southeast, though it will become little more breezy across the southwest late this afternoon and evening as a weak boundary pushes across the area. The remnants of an upper level low over the southern Canadian Prairies will be absorbed by an incoming pacific shortwave overnight tonight into early Monday, pushing a deepening attendant low center at the surface out of Wyoming and east across the Dakotas. Increased WWA ahead of this system will prime the environment across western and central North Dakota for showers and thunderstorms that will start Monday morning and last through early Tuesday. With high PoPs (70 to 90%) and moderate PWATs, much of the forecast area is progged to have a 40 to 70% chance of exceeding 0.50" of rainfall by Tuesday morning. With two rounds of precipitation expected, with showers developing in the north ahead of the system, then another round ahead of a following cold front in the afternoon, portions of the northwest have modest chances (15 to 25%) of exceeding 1.00" in total. Convection wise, much of southwestern and south central North Dakota has been placed under a Marginal (level 1 of 5) risk for isolated severe thunderstorms, with a small portions of Bowman and Adams counties under a Slight (level 2 of 5) risk. Current model MUCAPE values are advertised in the 1500-2000 J/KG range across the southwest and south central, along with strong 0-6 KM Shear of 35 to 45 knots and decent mid- level lapse rates. The SPC and CSU machine learning have also dialed onto a low tornado risk with the high SRH associated with the low center's triple point, though an interrogation the most recent model soundings have placed our expectations of the tornado threat as being on the lower end of low. As such, we have begun messaging the primary hazards for the thunderstorms Monday afternoon and evening, from around 3 PM to 11 PM CDT, as large hail up to ping pong balls (1.50") in size and winds up to 60 MPH. A few question remain, however, with how far north the axis of instability will penetrate, with regards to how worked over the environment will be by the initial wave of showers and thunderstorm Monday morning, which may help limit the risk of the greatest hazards to far southwest and south central. Additionally, there are some hints that the isolated severe storms may quickly outpace the axis of instability once they develop, which may also limit the hail potential as well, though it is still a little early to say as such with much confidence. Otherwise, highs on Monday are forecast from the upper 60s north to the upper 70s south. Showers and slight chances for thunderstorms (<20% chance) will continue to progress eastward across North Dakota overnight before clearing east of the forecast area early Tuesday morning. At this point, the inciting pacific shortwave will have been replaced by longwave ridging across the Northern Plains, promoting dry conditions and warming temperatures through Wednesday. While highs on Tuesday are similarly forecast the upper 60s and upper 70s as on Monday, a penetrating axis of warm air will see Wednesday as the hottest day of the week, with highs forecast from the upper 70s north to the mid 80s south. A modest shortwave will travel down the zonal flow aloft, allowing a return of showers (20 to 40% chance) across western and central North Dakota early Wednesday through Thursday morning. The ensemble has resolved on a more progressive shortwave, meaning the potential for severe weather over the northern Plains Wednesday afternoon has been pushed mainly out of our area, though we could see some development in the mid afternoon over the southern James River Valley. The passage of the shortwave on Wednesday will erode the overall ridging pattern over the northern Plains, leaving an increasingly southwesterly flow pattern over the forecast area through the later half of the workweek. Temperatures will remain roughly or slight above seasonably normals through the later half of the week, forecast from the lower 70s north to the lower 80s south through Sunday. Conditions will remain dry through early Friday, when a more active, northwesterly pattern returns. Chances (30 to 50%) for showers and thunderstorms will linger through the weekend and into early next week. While the ensemble is fairly discordant at this point of the forecast, some individual members have begun to hint at strong moisture advection from the Gulf across central and eastern North Dakota this weekend and into early next week, which may prime the stage for a comparably spicy pattern than we have experienced over the last week. Confidence is low at this time, however, so we will continuing monitoring model trends over the next few days. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 647 PM CDT Sun Jun 9 2024 VFR conditions are expected to begin the 00Z TAF period. Increasing clouds and lowering ceilings are expected late tonight into the day Monday from west to east as a storm system moves into the region. Chances for showers will push into the west, first impacting the terminals of KXWA and KDIK after 06Z, then spreading to KMOT and KBIS by 18Z Monday. Scattered thunderstorms will also be possible during the day Monday, some strong to severe across portions of western and south central North Dakota. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...NH DISCUSSION...Adam AVIATION...NH