Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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136 FXUS63 KBIS 031436 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 936 AM CDT Wed Jul 3 2024 .KEY MESSAGES... - Low to medium chances (20 to 40 percent) for showers and thunderstorms beginning this afternoon and lasting into the night, with the highest chances in the southwest. An isolated strong storm is possible this evening in the southwest as well. - Scattered showers and thunderstorms are likely on Independence Day, but the entire day should not be a washout. - Slightly below normal temperatures and chances for showers and thunderstorms will continue through the holiday weekend, with highs mainly in the 70s. && .UPDATE... Issued at 931 AM CDT Wed Jul 3 2024 Fog has dissipated around the Turtle Mountains so we have taken the fog out of the forecast. Showers and thunderstorms look to form in the west and southwest around 3PM CT. UPDATE Issued at 623 AM CDT Wed Jul 3 2024 Minimal changes were made to the forecast for this update. Some mid- level clouds continue to linger around across the west, so we`ve updated the cloud coverage to account for these. Otherwise, some fog has begun to develop near the Turtle Mountains, with some reduced visibilities reported in Bottineau. We`ve added in some patchy fog to that area for the next 4 hours, as it will likely dissipate relatively soon. Otherwise, the forecast remains on track. && .DISCUSSION... Issued at 332 AM CDT Wed Jul 3 2024 Presently, mostly clear skies and light winds are being observed across western and central North Dakota. A small patch of mid-level clouds may move into west-central North Dakota over the next few hours, but isn`t expected to linger for long. Lows this morning are forecast to be largely in the 50s across the area. Aloft, broad cyclonic flow is present across the Northern Plains, positioning North Dakota under generally westerly flow. A large upper level trough sits across northern Ontario, forecast to move east through the day today while a secondary trough across southern Alberta and northern Montana is forecast to move east through the northern High Plains at the same time. Ahead of this secondary trough, surface low pressure is expected to deepen across Colorado and Nebraska. As a result, we will continue to see the usual chances for showers and thunderstorms this afternoon and evening while we remain under the active flow aloft. Currently, we see some chances (mostly 20 to 40%) for showers and thunderstorms across the west and south this afternoon and evening. Given the lack of sufficient instability, and only a small corridor of deep layer shear near 40 kts, we are not expecting severe weather to be a concern today. The most recent model runs have pushed the surface low further to the south, and in turn, have pushed much of the necessary ingredients a bit further south as well. Thus, the SPC has moved the Marginal Risk (level 1 of 5) out of our area, which is in line with what we`ve been thinking as well. The most recent CAMs have also kept nearly all of the robust convection to our south in South Dakota, with mostly popcorn showers and thunderstorms in our area. A stray strong thunderstorm cannot be ruled out however, as we do still have that corridor of ample deep layer shear in our far southwest. If something does strengthen down in that area, it won`t last for a long time, but it could bring about some stronger winds and small hail. All in all, the severe risk remains minimal for the day today. Otherwise, high temperatures will remain just below seasonable, with highs in the mid 70s to lower 80s. As this trough continues to move east overnight into Independence Day, additional moisture is expected to be transported north, while the surface low begins to slide northeast into South Dakota. As a result, chances for precipitation will linger around overnight in the south, before expanding north and increasing during the day. NBM PoPs continue to advertise 60 to 75% chances for showers and thunderstorms across all of western and central North Dakota. Given the slightly cooler temperatures, ample moisture, and complete lack of shear, we are expecting the makeup of this precipitation to largely be non-severe spotty showers and thunderstorms. It is worth noting that while chances for rain are rather high across the entire area for the entire day, it is highly unlikely that any given area will see rain for the entire day. Rather, the more likely outcome will be that many locations will see brief, occasional showers, with breaks in between them. Current CAMs do suggest potentially a small area in the south central and southern James River Valley that could see rain for most of the day, but we still are not confident this would be the case. NBM probabilities for exceeding 0.25" of rain have remained rather steady, with the highest chances (40 to 50%) centered across the south central and southern James River Valley. It is also worth noting that while the daytime hours may be showery for much of the area, the chances for rain decrease rather quickly heading into the evening hours and towards sunset. At the moment, chances for rain at 7 PM CDT are somewhere around 15 to 30%, with these chances decreasing further afterwards. There could be some time near the end of the day to enjoy the holiday, but given the spotty nature of the showers, it is still a bit difficult to tell exactly when we can expect the rain to end. Luckily, winds will not be a concern for Independence Day, with sustained northerly winds around 10 to 15 mph expected for much of the area. The overnight hours heading into Friday are expected to be drier, with skies gradually clearing, winds becoming light, and lows in the 50s. We will remain in this active pattern through at least the weekend, with continued daily chances for showers and thunderstorms from Friday through Sunday. Northwesterly cyclonic flow aloft will persist, with embedded shortwaves passing through North Dakota each day. The highest chances appear to be on Saturday, with the shortwave being a bit more pronounced, however this wave is expected to be fairly transient in nature. Most days see chances in the afternoon and evening, before they decrease heading into the overnight hours. The severe threat for these days appear to be low at the moment, with the continued lack of necessary shear and instability combined with relatively weak forcing at the surface persisting through the period. It appears that the extent of what we`ll be seeing is just some pop-up showers and thunderstorms. Beyond the weekend, we appear to be gaining confidence in a breakdown of the active pattern, and the arrival of a warming and drying trend. Long range guidance has begun to come more into agreement with regards to the synoptic pattern on Monday, which is suggesting that the broad ridge across the western CONUS will build east and into the Northern Plains through the first half of next week. WPC cluster analysis suggests a 70% chance of this ridge beginning to influence North Dakota by Monday night, while the 30% solution has it delayed by about a day. The NBM is also starting to advertise this shift in pattern as well, with blended PoPs decreasing and high temperatures increasing through this period. The NBM spreads in high temperatures, while somewhat large heading into the middle of next week, do continue to point at a gradual warming trend through essentially the entire week. We`ll continue to monitor how this pattern breakdown evolves, but at the moment, we are thinking that next week we`ll see drier and warmer weather. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 623 AM CDT Wed Jul 3 2024 VFR conditions are present across western and central North Dakota, and will prevail through the TAF period across all terminals. Generally light winds are expected through the TAF period, with chances for showers and thunderstorms arriving through the afternoon and evening hours today. Showers and thunderstorms are initially expected in KXWA and KDIK starting around 20z to 22z, before expanding east to KBIS by around 06z to 07z. Chances will then continue into the overnight hours. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Smith DISCUSSION...Besson AVIATION...Besson