


Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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484 FXUS63 KBIS 150600 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 100 AM CDT Tue Jul 15 2025 .KEY MESSAGES... - Isolated strong to severe thunderstorms are possible through the early morning. Expected hazards include hail as large as ping pong balls and wind gusts up to 70 mph. - Well below normal temperatures Tuesday through Thursday, with near-record cold highs in the 60s Tuesday and Wednesday. - Medium to high chances for showers tonight through Wednesday. && .UPDATE... Issued at 100 AM CDT Tue Jul 15 2025 Scattered showers and thunderstorms are found over south western and south central North Dakota at the time of this. One line of storms are found along a quasi-stationary bound stretching from Mercer County through Foster/Stutsman counties, and another is oriented being a surface boundary draped between Bowman and Grant counties. These storms have been fairly pulsey, with some cells along the quasi-stationary becoming severe. A Severe Thunderstorm is in effect for Stutsman and Foster counties through the mid morning, though storms are already starting to diminish at the time of this update. While mainly dry conditions are found in northwestern and north central North Dakota, showers and thunderstorms are starting to move into northeastern Montana. These are expected to move into northwestern North Dakota, expanding broadly across northern North Dakota through the morning and much of the day today. Regarding updates, have made some tweaks to the short term PoPs to account for slightly faster development in the southwest. UPDATE Issued at 1007 PM CDT Mon Jul 14 2025 Thunderstorms have developed over parts of south central ND near the SD border, or mainly over eastern Sioux, Emmons, and McIntosh counties. These thunderstorms may expand a bit more in coverage, with a few strong storms possible, before likely weakening over the next couple hours. Additional development was visually observed a fair bit north of the office and is starting to produce radar returns. This west to east orientated line of development is mainly along and near Highway 200. Per the latest model guidance, this is the area most favored to produce isolated strong to severe thunderstorms tonight. UPDATE Issued at 659 PM CDT Mon Jul 14 2025 Mostly sunny skies are present over southern and northwestern ND with mostly cloudy skies over the northeast. A few showers tried to develop an hour or so ago in the far southwest, but were unable to sustain themselves. That said, showers and thunderstorms are still expected to develop across much of the state this evening and especially overnight. However, CAMs continue to disagree moderately in regard to timing and placement of thunderstorm development. A few severe storms remain possible. && .DISCUSSION... Issued at 354 PM CDT Mon Jul 14 2025 Early afternoon surface analysis shows a quasi-stationary surface boundary extending northeast from low pressure over eastern Wyoming, with the wind shift/trough axis from around Dickinson to Devils Lake to Grand Forks. Flow aloft has turned zonal, with no waves of appreciable amplitude noted in the mid to upper level height fields. A band of showers is moving east- southeast across southern Canada and into far northeast North Dakota, sandwiched between an upper jet to its north and a low level baroclinic zone to its south. Temperatures across southwest and south central North Dakota have soared into the 90s, while far northern areas remain stuck in the 70s. From tonight through Tuesday, a series of deepening shortwaves across southern Canada will force colder air into the Northern Plains, squeezing the thermal gradient against the surface boundary which would otherwise act as a warm front. The clashing of these two air masses is likely to result in widespread showers and scattered thunderstorms throughout the region over the mentioned time period. Ensembles show a break in rain chances, especially for central North Dakota, Tuesday night as Canadian high pressure wedges drier air in from the north/northeast. But this is now followed by guidance consolidating on a higher-amplitude shortwave bringing another round of rain across the state on Wednesday, with the highest chances in southwest North Dakota. QPF threshold probabilities and ensemble mean QPF have slightly decreased from previous forecast iterations, but there are still high chances for at least 0.25" and medium chances for at least 0.5" across western and south central North Dakota. In contrast, north central parts of the state only have medium odds for over 0.25" and low odds for over 0.5". The main concern for the next 24 to 30 hours is the potential for strong to severe thunderstorms. There are still a variety of outcomes being offered by CAMs, but some common themes are emerging. First of all, it is increasingly unlikely that we will see convective initiation this afternoon, as there does not appear to be enough lift to overcome -50 to -100 J/kg MLCIN. If an attempt at initiation is to be made, it would likely be along the quasi- stationary surface boundary. As of 330 PM CDT, a cumulus field was increasing in coverage and density over southwest North Dakota, but satellite shows vertical growth to be limited. The most likely outcome now appears to be for convection to initiate, perhaps rapidly so, sometime around 9 PM to midnight CDT along the baroclinic zone where strong low level frontogenesis and modest low to mid level moisture transport are forecast. The most likely location for this to occur is between Highway 2 and Interstate 94. There are higher odds for initial convection to blossom over central parts of the state, but areas farther west could quickly fill in. There is also a signal for a separate batch of convection with a plume of mid level theta-e that could move from north central South Dakota into the James River Valley. All convection late this evening through tonight should be elevated. Forecast MUCAPE ranges from as much as 1000-2000 J/kg across southern North Dakota to less than 500 J/kg and decreasing with time across the far north. In contrast, there is much stronger shear farther north than south, the magnitude of which will depend on the effective inflow layer. Using the 2-7 km layer as a proxy, forecast effective bulk shear ranges from around 20-30 kts south to as high as 50 kts along the Canadian border. While any part of western and central North Dakota could see a strong to severe storm through tonight, the most favorable combination of shear and buoyancy could be collocated with the strongest mesoscale forcing. Having said all this, it can sometimes be a struggle for elevated convection to realize all of its available potential energy, and it would be a reasonable outcome for there to only be weaker thunderstorms through tonight. Still think that a scenario with at least a few stronger to severe storms is the most likely outcome when taking into account CAMs` reflectivity/UH output. The colder air mass advecting down from Canada should push instability/buoyancy off to the south on Tuesday. There is a low probability that the unstable air mass may not clear the southern James River Valley before thunderstorms become more widespread early Tuesday afternoon, but there is not much model support for this outcome. The other major story for the forecast is unseasonably cold temperatures, especially daytime maxima. Forecast highs in the 60s Tuesday and Wednesday are around 15 to 25 degrees below normal for what should be the warmest time of the year. Southwest North Dakota looks exceptionally cold, with higher confidence in rainy conditions on Wednesday that could keep daytime highs in the upper 50s. Record cold high temperatures across western and central North Dakota are generally in the lower to mid 60s, so there could be a few of these records broken the next couple days. Dickinson in particular is forecast to set new record cold daily maximum temperatures both Tuesday and Wednesday. Low temperatures are forecast to mainly be in the mid 40s to lower 50s over this time period, which is still below normal but not to the same extent as high temperatures are forecast to be. A slow warming trend is expected to commence on Thursday, lasting through the weekend and into next week when highs could return to near or slightly above average. The latest ensemble guidance has trended toward favoring more of an active quasi- zonal pattern that includes a possible shortwave passage late Thursday into Friday that is showing up in mean vorticity fields across all ensemble clusters. The NBM has increased its PoPs into the 30 to 50 percent range late Thursday night through Friday afternoon. There may be enough CAPE and shear to support a strong to severe storm threat over this time period, and CSU machine learning guidance does paint low probabilities for severe weather over southwest and south central North Dakota on Friday. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 100 AM CDT Tue Jul 15 2025 Mainly VFR ceilings and visibilities are found at all TAF sites at the time of this update. Scattered showers and thunderstorms are found across southern North Dakota this early morning. Another push of showers and storms are anticipated to move into northwester North Dakota later this morning, though these should generally become showers by the mid morning hours. MVFR to IFR ceilings and visibility are anticipated if any storms manage to move any terminal, though the confidence remains low at this time. Thus, have generally added PROB30 groups for -TSRA for KXWa, KBIS, and KJMS at the time of this update. A general lowering to MVFR to IFR ceilings is anticipated through the the early overnight period as showers fill in and become more widespread across the forecast area. These showers will linger through the day today and through the end of the TAF period. Northwest winds are expected to become gusty through the morning and afternoon, with sustained speeds up to 20 knots and gusts up to 30 knots. Winds will then diminish through the evening and the end of the TAF period. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Adam/Telken DISCUSSION...Hollan AVIATION...Adam/Telken