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FXUS63 KBIS 021502 AFDBIS

Area Forecast Discussion National Weather Service Bismarck ND 1002 AM CDT Thu May 2 2024

KEY MESSAGES

- Widespread rain showers will continue through the morning and much of the day, mainly east of the Highway 83 corridor.

- Expect more hit and miss showers later this afternoon and evening across the west and central. A few isolated thunderstorms are possible. Chances for showers continue Friday.

- Chances for rain return Sunday night, becoming likely by Monday (60 to 70 percent). Monday may also bring a better chance for some thunderstorms. Low to medium rain chances (20 to 60 percent) continue into mid week.

- Near to slightly below normal temperatures expected through Saturday, becoming near to above normal Sunday and Monday.

UPDATE
Issued at 935 AM CDT Thu May 2 2024

Rain continues to fall across the eastern half of the state an the eastern half of central North Dakota. Some showers over north central South Dakota will move into south central North Dakota today continuing rain across central North Dakota. Later this afternoon wrap around showers and thunderstorms may form over much of the western half of the state. Another burst of energy from the upper low will be the driving force for thunderstorms and energy that is currently over northeastern Montana. The forecast remains on track at this time so no further updates were needed.

UPDATE Issued at 612 AM CDT Thu May 2 2024

No major changes were needed for this update. The precipitation axis continues to trend just a bit further east than most of the CAMs were suggesting. However, we have seen some redevelopment across the south central and this activity may still yet push it's way into the Bismarck/Mandan area later this morning and into the early afternoon.

DISCUSSION
Issued at 411 AM CDT Thu May 2 2024

An upper level low was located in the vicinity of the eastern Montana/southern Saskatchewan border early this morning with a surface low centered over southern Saskatchewan. Several shortwaves will rotate around this low and into western and central North Dakota, providing various chances for precipitation through Friday night.

The initial impulse will continue to spread from south central North Dakota and into the east. The heaviest precipitation should remain mostly east of the Highway 83 corridor with the exception of parts of the far south central. The latest NBM shows continued medium to high chances (50 to 90 percent from west to east) for a half inch or more of additional rainfall over the aforementioned areas. While most of the rain from this initial impulse will mainly move out of the area to the east by the mid to late afternoon hours, the upper low is going to be slow moving out. Another shortwave will rotate into our area this afternoon and interact with a surface trough/frontal boundary across portions of the west and central. The latest CAMs suggest that we will see convective showers and isolated thunderstorms developing in the mid to late afternoon hours across the west, eventually spreading into the central. RAP soundings suggest the potential for around 300 to 600 J/kg MUCAPE so some thunder seems reasonable. There will be some strong shear present, but mainly to the east of the instability axis. Thus, severe weather is not expected.

On Friday, we could see a few more hit and miss wrap around showers but this activity looks mainly focused across the northern half of the forecast area for now. Instability will be even weaker on Friday so thunder chances appear low at the moment.

An upper ridge pops up to our west on Saturday with the axis located over central Montana by the afternoon hours, placing western and central North Dakota under northwest flow aloft.
After highs mainly in the upper 40s to the upper 50s today and Friday, we start to clear out and warm on Saturday with forecast highs in the lower 50s to lower 60s. The ridge then approaches the Montana/North Dakota border late Saturday night and crosses the state on Sunday. This will lead to even warmer temperatures on Sunday, with highs forecast to be mainly in the upper 60s to mid 70s.

By Sunday night, the ridge moves off to our east and we transition into nearly meridional flow aloft as a strong negatively tilted trough approaches. An upper low will close off at the base of the trough and eventually swing up to the North Dakota/South Dakota border by late Monday. Several rounds of widespread precipitation appear to be in the cards Sunday night through mid to late week as ensemble guidance suggests this low will have a tough time getting kicked out of the region. Monday may also bring a better chance for some thunderstorms. Shear will be plenty strong, but instability is likely to still be lacking a bit. That being said, CSU Machine- Learning Probabilities suggest at least marginal chances for some severe weather in the Sunday through Tuesday time frame so it will be an interesting period to watch. Chances for showers will linger mid to late week.

After Monday, temperatures will likely cool back to slightly below normal categories through mid to late week with NBM highs mainly into the lower 50s to lower 60s. It is worth noting that ensembles continue to struggle with the pattern beyond Monday, and this uncertainty is evident in significant high temperature spread among NBM members. Thus, the temperature forecast next week still includes quite a bit of uncertainty. As a final note, periods of breezy conditions appear likely, mainly Friday and then most of next week.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
Issued at 612 AM CDT Thu May 2 2024

A disturbance will continue to move from south central North Dakota into eastern North Dakota through the morning.
Widespread showers will continue across much of the central and east along with MVFR ceilings. Western North Dakota will likely remain in VFR categories through most of the period, including the terminals of KXWA and KDIK. KMOT may also remain in VFR categories through most of the period, although ceilings here may come close to MVFR categories this morning at times.
Another round of MVFR ceilings will impact the north towards the end of the period, first at KXWA and then at KMOT. West winds will become windy this afternoon across southwest North Dakota, with some gusts up to 35 mph at KDIK. Winds will be generally light elsewhere. Finally, a few isolated thunderstorms will be possible this afternoon and evening. Winds may become gusty and erratic under any heavier showers or storms.

BIS WATCHES/WARNINGS/ADVISORIES
None.

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