textproduct: Bismarck

KEY MESSAGES

- Scattered showers and isolated thunderstorms west and north central, with showers becoming widespread through Friday morning. Locally heavy rainfall is possible. - Scattered showers and isolated thunderstorms continue southwest and central Friday and Friday evening, then mainly dry late Friday and through the weekend.

- Temperatures near to slightly below normal through the weekend with highs generally in the 70s. The exception being some 60s northwest and some lower 80s southeast.

UPDATE

Issued at 1154 PM CDT Thu Aug 13 2026

Current forecast remains on track. No updates planned. Showers continue over eastern Montana and far northwest and north central ND. This was covered well with the previous update.

UPDATE Issued at 1015 PM CDT Thu Aug 13 2026

The forecast remains in good shape at the time of this mid to late evening update. Shower coverage across northwestern North Dakota continues to increase along with the H5 vorticity associated with an approaching shortwave this evening. Shower coverage upstream is similarly increasing as the surface low lofted along by the shortwave has begun to cross over from northern Wyoming into southeastern Montana. Precpitation coverage across our forecast area, especially the west, is expected to increase overnight as this low moves across the ND/MT border. Latest short term CAMs are trending the axis of heaviest precpitation a little further south into central North Dakota than previously forecast, mainly as this low is forced along a more southerly route due to the broad center of high pressure over Manitoba lingering through Friday afternoon. This scenario would allow more of the forecast area to fall under the 0.25"+ storm total rainfall through Friday night, though the greatest amounts by far are still expected over the northwest into the north central.

UPDATE Issued at 620 PM CDT Thu Aug 13 2026

Scattered showers continue to skim across portions of northwestern North Dakota at the time of this early evening update. Little to no thunderstorm activity has been observed with the limited convective environment over the forecast area, though a few isolated rumbles of thunder can be found across the border in eastern Montana. Further downstream in northern Wyoming, the next round of showers that is expected to lift across into western and north central North Dakota have begun to develop. Overall, the forecast remains in good shape at this time, with no major adjustments required.

DISCUSSION

Issued at 245 PM CDT Thu Aug 13 2026

Currently, broad upper level ridging across the central CONUS with much of the Northern Plains in the right entrance region of a strong upper jet streak located north of the Great Lakes region and over the New England area. Overrunning flow across western North Dakota coupled with embedded mid level impulses riding over the aforementioned ridge contributing to scattered showers this afternoon west into north central. Only weak MUCAPE about, roughly a few hundred J/kg, but enough for a few isolated showers now popping up over central ND where cloud cover decreased earlier allowing for some sfc heating. Instability and shear remain weak through the day, so while a few thunderstorms are forecast, the threat for severe weather is very low if not zero.

We remain on track for numerous showers and a few thunderstorms developing tonight into tomorrow over western into north central North Dakota, with the greatest probability for heavier rainfall over the far northwest. This materializes as a surface trough, now developing over southeastern Montana, develops over eastern MT into western ND late tonight/Friday AM, coupled with a well- defined embedded S/WV lifting northeast across eastern MT to across northwest North Dakota 06Z tonight through Friday morning 12-18Z. Any heavier shower/thunderstorm will be capable of heavy rainfall given elevated PW values, though models in pretty good agreement that the best combined forcing will be over northwest North Dakota, so maybe pockets of heavier precip outside of this area. EFI values remain focused northwest as well, now at 90 percent with shift of tails still at a value of 2 (all pointing to an extreme QPF event). We opted to maintain no hydro headlines for this potential event, as a best practice is to treat these as short-fused products once it becomes more evident that elevated messaging is needed. Will continue to highlight in the HWO.

Aforementioned sfc trough advances east across western and central North Dakota during the day Friday along with a continued unsettled southwest flow aloft with multiple embedded impulses pushing through. This will bring decent chances for showers and a few thunderstorms to most areas Friday morning and afternoon, ending gradually Friday night as forcing decreases and high pressure builds in from the west. Locally heavy precip remains possible with PW values remaining elevated until late Friday night.

The remainder of the weekend will be mainly dry and cooler, with surface high pressure over the region along with zonal flow aloft. Embedded waves riding over a broad upper ridge building over the Rockies look to bring some chances for showers/thunderstorms to the local region during the day Sunday into Sunday night.

A quasi-zonal flow aloft is advertised for the first half of next week, and will result in temperatures trending warmer/more seasonal, along with daily chances for showers and thunderstorms.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1154 PM CDT Thu Aug 13 2026

Increasing coverage of showers and isolated thunderstorms across western and north central North Dakota will promote lowering ceilings and visibility through the end of the TAF period, with MVFR to IFR ceilings expected at KXWA, KMOT, and KDIK. Have left mentions of thunderstorm activity out of all sites, as confidence in timing and location is very low. Shower activity across the south central is expected to be more limited, thus low VFR ceilings are expected at KBIS and KJMS throughout the TAF period. East winds are expected to be light tonight, before turning southeastern and strengthening Friday morning and afternoon. Gusty winds sustained around 15 knots and gusts up to 25 knots are expected across portions of south central North Dakota Friday afternoon.

BIS WATCHES/WARNINGS/ADVISORIES

None.