Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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203 FXUS63 KBIS 121821 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 121 PM CDT Fri Jul 12 2024 .KEY MESSAGES... - Isolated severe storms are possible across all of western and central North Dakota late this afternoon and into tonight. Hail to the size of quarters and winds up to 60 mph will be the main hazards. - Isolated to scattered severe storms are possible late Saturday afternoon and into the night. Hail to the size of golf balls and damaging winds up to 70 mph will be the main hazards. A tornado or two is possible northwest. - Isolated to scattered severe storms will be possible once again on Sunday. - Expect very warm temperatures and high humidity through the weekend. && .UPDATE... Issued at 120 PM CDT Fri Jul 12 2024 Diurnal cumulus have formed in the James River Valley in the higher moisture sector and the east side of the surface trough. Dew points in western part of the state are starting to dry slightly as drier air moves in from Montana throughout the day. There are some scattered showers near the northwest in Montana and Canada. UPDATE Issued at 1000 AM CDT Fri Jul 12 2024 Showers were heading towards the northwest in Montana, so PoPs were added an 2 hours ago. Now they have does, so the forecast was returned to 0% chance of rain there. The rest of the forecast is still on track. UPDATE Issued at 621 AM CDT Fri Jul 12 2024 All of the shower activity has pretty much either dissipated or moved out of the area. For this reason, we elected to go ahead and remove precipitation chances through the rest of the morning. Otherwise, no major changes were needed for this update. && .DISCUSSION... Issued at 348 AM CDT Fri Jul 12 2024 Western and central North Dakota sits under the eastern slope of a broad upper ridge draped over the western US. An embedded shortwave continues to bring some localized height falls to portions of the region as it passes through early this morning. While thunderstorm activity diminished recently, there are still a few showers floating around out there, mainly over the central. The ridge will pop back up today in the wake of this morning`s shortwave, leading to plenty of sunshine and very warm temperatures. Highs will range from the upper 80s to the upper 90s. Isolated triple digit readings are not out of the question across the southwest. A stout cap and rising heights will keep a lid on convection through most of the day but we could start to see some height falls around 00z as the next ripple of a shortwave flattens the ridge. Low to medium chances (20 to 40 percent) for showers and storms should develop across the west by late afternoon, spreading into the central overnight. Regarding the severe weather potential late today and tonight, there will be plenty of instability, even well into the overnight hours. The latest RAP runs have consistently been advertising widespread MUCAPE values of 2500 to 3500 J/kg. That being said, deep layer shear will be rather marginal, ranging from 25 to 35 knots or so. A surface trough (almost a pseudo dryline) will be the most likely boundary for initiation with a cold front on it`s heels. The deep layer shear and anvil level winds will be near parallel to the boundary over some locations and more perpendicular over others. Thus, storm mode may be a bit messy with multi-cell structures/line segments and maybe a few transient supercells. The most likely hazards will be hail to the size of quarters and winds up to 60 mph. We will mainly clear out by early Saturday as modest ridging once again builds in through the day, limiting the daytime convection potential. A few lingering showers are not out of the question during the first part of the day. The next subtle wave approaches the northwest by the evening hours, bringing more low to medium chances (20 to 40 percent) of showers and storms. Thunderstorms are likely to be ongoing across northeast Montana Saturday afternoon before making their way into the northwest in the evening or night. They will be moving into an environment characterized by plenty of instability and strong deep layer shear in the 45 to 55 knot range. A couple of supercells and/or bowing structures will be possible as this activity moves from the northwest and into the central through the night. Hail to the size of golf balls and damaging winds up to 70 mph will be possible with this activity. A tornado or two may also be possible across the northwest early in the event if storms can remain discrete. The other concern for Saturday could be some borderline Heat Advisory criteria across our far southeast, mainly over eastern portions of LaMoure and Dickey counties. At the moment, the gridded forecast keeps apparent temperatures here under triple digits Saturday afternoon, but it won`t take much to bring those values up past 100 given dewpoints forecast in the 70s and highs in the low to mid 90s. Sunday may then be a similar story, with more isolated to scattered severe storms possible late in the day given more strong instability and shear. Specifics should start to come into better focus as we get past some of these other waves first. Sunday remains very warm and humid but maybe just a touch less than Saturday. Highs will range from the lower 80s north to the low to mid 90s south. The new work week will then feature diminishing thunderstorm chances and cooler temperatures as the ridge retreats west and amplifies. Forecast highs on Monday range from the lower 70s over the Turtle Mountains to the mid 80s southwest. Tuesday and Wednesday will see highs mainly in the lower 70s to the lower 80s. Most guidance then has us warming again to end the week as the ridge starts to approach once again. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 120 PM CDT Fri Jul 12 2024 VFR through most of the period. There`s a chance of thunderstorms late this afternoon through about 06z. Confidence is a little low so kept it all VCTS for now. Clouds in the James River Valley have formed as MVFR and should lift higher this afternoon. Winds will be light, may be gusting to 15kts this evening. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Smith DISCUSSION...ZH AVIATION...Smith