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Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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280 FXUS63 KBIS 011514 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 1014 AM CDT Mon Jul 1 2024 .KEY MESSAGES... - There is a Slight Risk (level 2 of 5) for severe thunderstorms this afternoon and evening in southern North Dakota, and a Marginal Risk (level 1 of 5) for much of the rest of the area. The main hazards are hail up to ping pong ball size and wind gusts up to 60 mph. - Breezy conditions are expected in the James River Valley today. - The chance for showers and thunderstorms on Independence Day is 70 to 80 percent across all of western and central North Dakota. && .UPDATE... Issued at 1014 AM CDT Mon Jul 1 2024 Morning convection is slowly dissipating or moving east, although a lingering boundary is trying to develop new convection. Overall the atmosphere has limit instability currently, as evident by some developing wave/billow clouds. A cold front is still expected to push through this afternoon and evening and bring another round of showers and thunderstorms. Severe weather is still possible with this front. Of note are some morning CAMS initiating this next round early to mid afternoon, which may be slightly earlier than previous forecast. This could indicate the CAMS are overcoming the CAP earlier or bringing elevated thunderstorms earlier. Overall today could end up being active with isolated to scattered thunderstorms, come of which could be severe. For now did not change much except for some minor changes to PoPs based on the latest guidance. UPDATE Issued at 649 AM CDT Mon Jul 1 2024 The low-level jet has weakened considerably and veered per recent VAD wind profiler data from KBIS, so the intensity of convection has gradually diminished compared to earlier. Recent rapid-refresh guidance captures this trend, so we used that along with observed trends to make minor changes to the morning forecast with this update. The rest of the forecast remains on track, focusing on potential severe storms this afternoon and evening. && .DISCUSSION... Issued at 422 AM CDT Mon Jul 1 2024 Showers and thunderstorms continue to roll across the northern half of our area, while surface low pressure across western South Dakota continues to move east. Two main areas of convection are present, with one cluster of storms in Rolette County, and one cluster heading into McLean County, the latter of which has had quite a bit of lightning associated with it. While not severe, the frequent lightning and potential for half inch hail has warranted this cluster getting some Special Weather Statements as it treks to the northeast. Additional convection across far eastern Montana is also making its way into McKenzie and Golden Valley counties, with some more stratiform rain across the northwestern corner of the state. All of these areas of showers and thunderstorms should move northeast/east throughout the night, sustaining themselves with the presence of a relatively strong low level jet, before exiting into eastern North Dakota through the morning hours. Winds across the area have diminished a bit quicker than anticipated, especially across the James River Valley, though we do expect these winds to rise within the next few hours to become a bit more gusty than they are right now. Monday will see the arrival of another wave of showers and thunderstorms across the area, this time in the afternoon and evening hours. Aloft, a trough across Montana is expected to deepen as it moves east through the day, helping aid the deepening of a surface low pressure system and attendant cold front. Southerly surface flow ahead of the cold front will continue to funnel moisture northward into the Dakotas, helping raise dew points into the 60s. As a result, we see a rather narrow corridor of instability positioned north-south across central North Dakota, with deterministic guidance suggesting MLCAPE values in the 1500 to 2000 J/kg range, alongside 40 to 45 kts of 0-6 km shear. Paired with modest lapse rates in the area, we have seen consistent CAMs runs suggesting showers and thunderstorms developing across our area in the early afternoon, strengthening and moving east and into central North Dakota in the late afternoon and early evening hours. Storm mode continues to remain a concern, with model soundings suggesting the potential for a cluster mode, given the rather straight and long hodographs along with the deep layer shear being oriented roughly 45 degrees from the main frontal boundary. As such, our thinking for the hazards remains the same, with ping pong ball sized hail and 60 mph gusts, with a likely timeframe of 3 PM to 9 PM. The SPC maintains a Slight Risk (level 2 of 5) across the south central, and a Marginal Risk (level 1 of 5) for a majority of the remaining area. Chances for precipitation drop off heading into the overnight hours Monday night, as the surface low pressure system moves northeast into Canada. The trough aloft will also drift off to the northeast during this time, helping bring about a gradual clearing through the overnight hours. This brief dry period won`t last for long, however, as a more transient shortwave trough embedded within the flow will pass to our south during the day Tuesday. Some showers and isolated thunderstorms will make their way through western and central North Dakota through the day, quickly moving out by the late evening hours. Severe weather is unlikely given the lack of significant instability and forcing. High temperatures today and Tuesday will be mostly in the mid 70s to lower 80s, with overnight lows in the 50s. The active pattern will continue heading into the second half of the work week, with chances (30 to 60%) for showers and thunderstorms on Wednesday. A rather potent trough is expected to begin deepening to our west Wednesday, bringing about the development of a surface low pressure system to our southwest and the return of showers and thunderstorms to essentially the entire area, with the highest chances in the southwest and south central. The CSU machine learning guidance suggests a low chance for severe hail, but with marginal forcing and instability, chances for severe weather remain relatively low. As this trough deepens and moves east, this unfortunately will also lead to continued precipitation chances for Independence Day. NBM PoPs continue to advertise the greatest chances for precipitation to be during the day on Independence Day, with essentially the entire area covered in 70 to 80% chances. Temperatures this day will also be the lowest of the forecast period, with most areas seeing highs in the upper 60s and lower 70s. Chances for severe weather are still a bit fuzzy this far out, but tentatively, guidance suggests very low chances for any strong to severe storms. All in all, it seems like Independence Day will be cloudy and rainy, with a chance for some thunder here and there. Following Independence Day, we may see a reprieve from the daily chances for precipitation, as long range guidance is continuing to suggest a very potent ridge across the western CONUS building east into the Plains through the weekend and into next week. While we may see some rain on Friday with an upper level trough passing to our northwest, the weekend seems to be a bit drier and a bit warmer as this ridge slowly builds into the area from the west. Details on Saturday are still a bit up in the air, as some models are picking up on an additional shortwave tracking to our northeast and bringing another brief wave of rain to the area, while others are keeping this feature and its associated rainfall away from us. Regardless, NBM spreads in high temperatures don`t seem too wide after the warmup through the weekend, so we are likely to see temperatures rebound back into the mid 70s to lower 80s after the brief cool period on Independence Day. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 649 AM CDT Mon Jul 1 2024 A few showers and thunderstorms will move through western and central ND prior to 18 UTC (a 20 to 40 percent chance at most terminals), but the activity will become more numerous this afternoon and early evening. Severe thunderstorms are possible from about 20 UTC to 02 UTC, especially in central ND ahead of a cold front. Local MVFR to IFR conditions are possible with storms today and this evening. Otherwise, MVFR to IFR stratus will develop in parts of central ND today, impacting KJMS and KMOT (with low to medium odds of impacts at KBIS). Showers and storms will end from west to east in the mid to late evening with a drier westerly flow behind the front. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Anglin DISCUSSION...Besson AVIATION...CJS