textproduct: Bismarck

KEY MESSAGES

- Near normal temperatures on Saturday, followed by well above normal on Sunday.

- Low to medium chances (20 to 40 percent) for hit or miss rain showers on Saturday.

- Medium to high chances (50 to 90 percent) of rain across most of western and central North Dakota late Sunday through Monday night. Low to medium chances (20 to 40 percent) northwest and north central.

- Low to medium chances for thunderstorms Sunday evening through Monday, mainly across the southern half of the state. Isolated strong to severe storms possible Sunday evening.

- Breezy to windy conditions at times Saturday through Monday.

UPDATE

Issued at 938 PM CDT Fri Apr 25 2025

Only change to the forecast was to lower sky cover this evening. Otherwise no changes were needed.

UPDATE Issued at 559 PM CDT Fri Apr 25 2025

No significant changes to the forecast needed early this evening. Generally light winds and clear to partly cloudy skies. Clouds will be on the increase though late tonight.

DISCUSSION

Issued at 258 PM CDT Fri Apr 25 2025

It's a beautiful afternoon across western and central North Dakota this Friday with generally light winds and plenty of sunshine. Today's temperatures are near to slightly above normal with highs ranging from the upper 50s to mid 60s. Tonight's lows are forecast to be in the mid 30s to lower 40s.

Clouds will be on the increase overnight across the south, spreading north through the day on Saturday as we transition back into southwest flow aloft and moisture return starts to kick in. A weak embedded shortwave will move across the state from southwest to northeast through the day on Saturday, leading to some hit or miss showers (20 to 40 percent). RAP soundings suggest that most of the instability will remain south of the state, but we could see some MUCAPE values around 100 to 200 J/kg along the South Dakota border across the far south central and southeast. Thus, a rumble of thunder or two here cannot be completely ruled out, but the probability is low at the moment.

With the increasing cloud cover and showers, temperatures on Saturday are forecast to be just a touch cooler, with highs in the mid 50s to lower 60s. Additionally, a tightening pressure gradient and steep low-level lapse rates may lead to some breezy/windy conditions (winds out of the south southeast). While widespread cloud cover and warm air advection may limit mixing to some extent, the NAEFS does continue to hint at anomalously strong 850mb meridional flow for this time of year. Thus, we could see some sporadic stronger gusts (up to 45 mph) at times through the day, especially under any of the hit or miss showers that are forecast to move across the state.

We will remain in southwest flow aloft on Sunday but neutral to slightly rising heights are forecast, so most of the day will remain dry as the atmosphere remains capped. Cloudy conditions are likely to hang on across the central and east but we may clear out some in the west. Breezy conditions will also move off to eastern portions of the forecast area, in and around the James River Valley. Temperatures will be well above normal on Sunday with NBM highs ranging from the mid to upper 60s over the Turtle Mountains, to the mid to upper 70s across the southwest. As we approach Sunday evening, a western CONUS longwave trough will start to nudge closer. Subsequently, we will also start to see some mid-level height falls across western North Dakota as a surface low deepens somewhere over eastern Wyoming or western South Dakota/Nebraska. Showers and thunderstorms may be ongoing over southeast Montana and northwest South Dakota and this activity should start to move in after 00z Monday along a cold front. New development is also likely to spread north northeast across the state from the southwest and south central in the evening and into the overnight hours, becoming widespread statewide with medium to high chances (50 to 90 percent). The one area that may not see much activity will be the northwest and portions of the north central.

Regarding the strong to severe thunderstorm potential, confidence has decreased a little bit. The highest probabilities in the CSU Machine Learning guidance continue to dip a little bit further south and the EFI has also backed off a bit on the anomalous CAPE signal. Some scenarios continue to suggest MUCAPE values in the 700 to 1500 J/kg across portions of the south but some scenarios keep the best instability limited to the far southwest and portions of the far south central. Either way, deep layer shear should be sufficient for organized convection and some risk of marginally severe hail or severe wind gusts seems reasonable through around 06z Monday or so. Widespread showers and embedded thunderstorms will continue through Monday night (thunderstorms chances will be diminishing to the southeast through the day on Monday). It is looking more and more likely that we will see some widespread beneficial rainfall totals Sunday evening through Monday night. NBM probabilities (for 48-hour rainfall) now suggest medium to high chances (50 to 90 percent) for a half inch of rain or more along and south of a line from southern Golden Valley county, northeast through far western McLean county, and up to the greater Devils Lake Basin. The highest probabilities will be across the south central and southeast with the lowest probabilities northwest and north central. Increasing the threshold to one inch and we still see much of the same area ranging from 40 to 70 percent. Due to the convective nature, some in the higher probability areas may not see near as much as others and some may see amounts even higher. These details will likely not present themselves until the showers and storms have already developed. Finally, it will be windy and cooler behind the front on Monday as strong cold air advection overlaps strong pressure rises and steep low-level lapse rates. Strong northerly winds to around 30 mph with gusts to 45 mph will be possible, with the strongest winds favored over the southeast. Highs on Monday will range from the lower 50s northwest, to the low to mid 60s southeast.

Rain will move out to the southeast Monday night, giving way to a mostly dry Tuesday and warmer temperatures west as we transition into zonal flow aloft. Highs will be in the lower 50s east, to the lower 60s west. A weak shortwave may then move through Tuesday night, leading to low to medium rain chances (20 to 40 percent) Tuesday night through Wednesday. West coast ridge then pops up and nudges closer on Thursday, leading to a gradual warmup through the rest of the week with highs mainly in the 60s.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 559 PM CDT Fri Apr 25 2025

VFR conditions are expected tonight, with low VFR ceilings spreading south to north on Saturday. Areas of MVFR ceilings are possible over western ND Saturday, but at this time kept the only mention at KDIK, as lower ceilings will be more probable over the southwest. Scattered showers will also spread from south to north Saturday over central ND. Included a PROB30 at KBIS and VCSH at KDIK and KMOT. Strong southeast winds will develop Saturday across western and central North Dakota. By Saturday afternoon most areas will see southeast winds 20 to 35 knots.

BIS WATCHES/WARNINGS/ADVISORIES

None.