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Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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679 FXUS63 KBIS 041745 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 1245 PM CDT Thu Jul 4 2024 .KEY MESSAGES... - Numerous showers and scattered thunderstorms are expected today, especially during the afternoon. However, the entire day will not be a washout, as much of the activity will be of the "hit or miss" variety. - Slightly below normal temperatures with daily chances for showers and thunderstorms will continue through the holiday weekend. Highs will mainly be in the mid to upper 70s. - A gradual warming and drying trend is expected to begin next week. && .UPDATE... Issued at 1235 PM CDT Thu Jul 4 2024 Storms are increasing in coverage with the warming of the day as expected. As of right now, we have two main areas of relatively dense lightning: one across the west (mainly the northwest where we also have had reports of pea size hail), and another along a line from just east of Harvey, down into southwest Kidder county. Showers and storms will continue to increase in intensity and coverage as they rotate around the upper low currently located over South Dakota. While the severe threat is low with this activity, there will be plenty of lightning so be alert if outdoors for holiday activities. We are also growing at least a little more concerned about some training convection as the upper low will be stubborn to kick out of the region. Over these areas, we will have keep a close eye on the rainfall rates as these storms are very efficient rain makers and not moving very fast. No major changes were needed for the gridded forecast update. Just blended in the latest observations to the forecast. UPDATE Issued at 917 AM CDT Thu Jul 4 2024 No major changes were needed for this update. Just adjusted precipitation chances slightly over the next couple of hours based on the latest radar trends and observations. Recently, the only thunderstorm activity has been over Bottineau and Foster counties. We expect that lightning activity will be on the increase towards the late morning or early afternoon. UPDATE Issued at 626 AM CDT Thu Jul 4 2024 Minimal changes were made with this forecast update. Showers and isolated thunderstorms are ongoing across the south central and southern James River Valley, with coverage expected to increase and expand across the rest of the area through the afternoon and early evening hours. Shower development in the west has been a bit slow to begin, but within the past few radar scans, popup showers have begun to form in northeastern Montana and southern Saskatchewan. For the most part, just blended the current observations into the forecast. && .DISCUSSION... Issued at 331 AM CDT Thu Jul 4 2024 At the moment, surface low pressure is positioned across northern North Dakota, while a trough aloft continues to deepen and pass across the Dakotas. Showers and isolated thunderstorms have already begun to develop across the southern half of the area this morning, with additional showers slowly making their way south from southern Manitoba and southern Saskatchewan. Lightning activity has been limited due to the near complete lack of instability, but a few isolated lightning strikes have been reported to the north of Bismarck. Mid- to high-level clouds have expanded across nearly the entire area, and will remain across the area through the day today. Lows this morning will mostly be in the lower to mid 50s, with light and variable winds. Confidence remains fairly consistent with regards to the forecast for Independence Day. As the aforementioned trough and attendant surface low slowly move east through the day, wraparound moisture will help with the formation with numerous showers and isolated to scattered thunderstorms across all of western and central North Dakota. These chances will be maximized from the early afternoon through the evening, before beginning to decrease towards/after sunset. The important thing to know with the setup for today is that while chances for showers will be pretty high (roughly looking at 60 to 70% chances across essentially the entire area), the spotty nature of these showers will make for a very "hit or miss" day when it comes to storm activity. There`s a good chance that any of these numerous storms will impact any given location, but the storm itself will be rather short lived, allowing for breaks between rounds of rain. Basically, the day today will not be a washout, but there`s a pretty good chance that most locations will see a quick round of rain at some point during the afternoon and evening hours. Luckily, given the persistent cloud coverage, lack of instability and shear, and the weak forcing at the surface, severe weather will not be a concern today. Given the influence of the trough aloft, high temperatures will be relatively cool, with most areas staying in the low to mid 70s. Under the slack pressure gradient, winds will generally be light, with a few areas in the far southwest potentially seeing speeds up to 15 mph. Beyond the holiday today, we can expect near daily chances for showers and thunderstorms through the weekend. Cyclonic northwesterly flow aloft will allow for a few additional shortwaves to pass across the Dakotas, bringing about these chances for showers and thunderstorms. These chances are maximized every afternoon and evening, with the highest chances in the northwest on Friday, the north-central on Saturday, and in the northeast on Sunday. While severe weather remains unlikely with these waves of precipitation, the CSU machine learning guidance has picked up on a narrow corridor of low severe hail chances across the James River Valley on Sunday. At the moment, the shortwave passing through the area on Sunday does appear to be the most robust out of any of the waves through the weekend, but the forcing and instability still appear to be marginal at best. We will continue to monitor this period for any severe potential over the coming days. Generally, with the pattern persisting through the weekend, we can expect highs each day to be mostly in the 70s, with overnight lows mostly in the 50s. Winds will generally be light and out of the northwest, with sustained speeds maxing out around 10 to 15 mph. Heading into next week, confidence has continued to increase in a breakdown of the cyclonic pattern aloft, resulting in a slow warming and drying trend through the week. The large ridge currently in place across the western CONUS is forecast to very slowly build eastward through the coming days, with the 850 mb thermal ridge expected to begin influencing North Dakota on Monday. Chances for rain decrease thereafter, with clearer skies and drier conditions expected under the ridge. NBM spreads in high temperatures have narrowed considerably through Wednesday, with the 25th/75th spread only reaching 5 to 6 degrees during this period. Even though the spread increases heading into the end of next week, the general warming trend actually continues even further. We`ll have to continue monitoring the extended period to see the extent of this warming trend, but as it stands right now, we may start seeing widespread highs in the 80s by Thursday, with temperatures increasing further beyond that point. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1235 PM CDT Thu Jul 4 2024 Hit or miss thunderstorms continue to increase in coverage and intensity as expected early this afternoon. The isolated to scattered nature of the convection makes the precipitation forecast complicated for any individual point. Thus, we are relying heavily on vicinity wording and tempo groups for the 18z TAF period. Severe storms are not expected but the strongest storms may produce locally heavy rainfall and small hail. If a heavier storm moves overhead, brief MVFR to IFR visibilities will be possible. Some embedded MVFR ceilings are not out of the question either but it seems that most will see VFR ceilings through the period. Showers and storms will start to diminish in the evening. Winds may become gusty and erratic in and around any thunderstorms. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...ZH DISCUSSION...Besson AVIATION...ZH