textproduct: Bismarck

KEY MESSAGES

- A band of snow is forecast to move across much of western and central North Dakota this evening through Friday afternoon. The highest chances for at least 2 inches of snow (around 60 to 80 percent) are focused over central North Dakota, where there is also a low to medium chance (30 to 60 percent) of at least 4 inches of snow.

- There is the potential for narrow bands of heavier snow. If they would develop, higher snow amounts up to around 7 inches would be possible.

- Temperatures will remain below normal through early next week.

- A transition to above normal temperatures is still expected next week, but it could be delayed until the second half of the week.

UPDATE

Issued at 715 PM CDT Thu Apr 3 2025

Heavy snow was falling in the northwest and the radar is starting to fill in towards Minot as well. Everywhere but the far northwest, surface temperatures are above freezing so don't expect snow to accumulate just yet. In the southwest, thunderstorms moved in from Montana with the potential of 50 mph winds and pea size hail. Temperatures around the southwest and central will not drop below freezing until after Midnight, this is when most of the snow could accumulate.

Updated pops with a HRRR/NBM blend to get a better hold on the timing of this line. Fgen still looks pretty strong across the state through this system.

DISCUSSION

Issued at 236 PM CDT Thu Apr 3 2025

Latest surface analysis shows low pressure over south central Montana, with high pressure in the lee of the Northern Montana Rockies. A warm front extends east from the Montana low, with a cold front dropping slowly south through North Dakota. Latest radar shows convection near the warm front in southeast Montana and light stratiform rain showers over northeast Montana. In the upper levels of the atmosphere, a split flow pattern was observed with a broad trough over the Western U.S. and another trough digging over the central Canadian Prairie Provinces.

For late this afternoon and tonight, we will see shortwave energy rotating around the base of the northern trough and through the forecast area. This will help push the southeast MT surface low into southwest ND and bring warm advection into western ND. In addition, moderate to strong FGEN forcing will swing through the forecast area, ahead of the approaching upper trough. These forcing mechanisms are expected to produce an area of precipitation that spreads from west central and southwest ND into central ND this evening through Friday morning, then across the remainder of south central ND and the James River Valley Friday morning and into the early afternoon hours.

Although the synoptic scale forcing is not strong, it is present over western ND this afternoon into this evening, and spreading into central ND late this evening into mid-morning Friday. What is impressive is the moderate to strong FGEN forcing from 925 mb through 700 mb. In addition, at times the strong Forcing is congruent with negative EPV and especially steep lapse rates. Although this is a transient wave, or series of impulses, the FG forcing is such that there could be periods of moderate to heavy snow at times as the entire system propagates west to east across the forecast area. The latest WPC snowband tracker shows the potential for snow bands setting up over southwest and south central ND. With the synoptic scale forcing not being as strong, we could see a better potential for unorganized, or transient bands setting up, rather than a single strong band. This is noted in some of the higher resolution qpf signals. Unfortunately exactly where these bands set up, is still a bit up in the air. However, with central ND being a popular area for bands to propagate across, we included a portion of the southwest and south central in a winter weather advisory. This areas has the highest potential for at least 2 inches of snow, and with the strong signal for FG forcing and steep lapse rates, we thought it would be best to at least start with an area to include within an advisory.

It is certainly possible, probably expected that there may need to be changes to the advisory. The most uncertain areas at this time appear to be the southwest. With our given guidance, and the expected warmer temperatures here today (currently mid to upper 40s) snow amounts here are lighter due to more of a rain/snow mix this evening. However, with the higher elevation in the southwest and far west-central, could definitely see a quicker transition to all snow, especially with the strong FG forcing. If this would happen, it's possible the advisory would need to be expanded into portions of the southwest. Also, there are some of the CAMS that show bands of higher snow amounts poking north of the advisory. Moreso over the north central rather than the northwest. With the orientation of the upper trough and the FG forcing, a southwest to northeast orientation of bands seems reasonable and a few of the CAMS do push some heavier amounts into the north central. Overall though, we felt the uncertainty up there was too high for an advisory at this time. Another area of concern is the James River Valley. there is a southern stream wave that may play a part in resulting precipitation over the JRV Friday. However, again, uncertainty is too high here for an advisory at this time, and it would be late enough that the advisory could be extended to include this area on the evening or overnight shift. Finally, the Morton and Burleigh counties are in the advisory, but unfortunately due to the size of the counties, and the orientation of the heavier snow, they are right on the edge, with higher snow amounts north and lower snow amounts over southern portions of these counties. Due to the steep lapse rates and strong FG forcing, we felt these counties were close enough the the higher qpf amounts to include them in the advisory. The total QPF with this system ranges from around a quarter to nearly a half inch from the west central into the Garrison area of southern Mclean and into western Sheridan county, with another band (0.20in to 0.40in) that extends from eastern Lake Sakakawea into far southwest ND. This is that band that includes northern Burleigh and Northwest Morton counties.

Once the precipitation moves out of the area Friday, we see a mainly dry period from Friday night through Monday night. Friday night into Saturday morning looks to be quite cold for this time of year, behind the exiting system. Forecast lows are mainly in the teens. Highs on Saturday only climb into the 30s over portions of central ND, with 40s west. We do finally warm up next week but the warm-up may be delayed to mid to late week. With a northwest upper flow a diurnally driven shower can not be ruled out next week, but at this time the chances of any significant precipitation look to be low. We may need to monitor fire weather, first on Saturday, but it does look to be cool, then next week, mainly mid to late in the work week.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 715 PM CDT Thu Apr 3 2025

VFR east to IFR west currently. A line of snow and rain is moving through the west currently, and will continue across the state overnight. LIFR CIGs are likely with the heavy snow overnight. As of 00z, thunderstorms are in the southwest, might have to add TSRA to the KDIK TAF if it continues. This system will clear out by 18z.

BIS WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 1 PM CDT /noon MDT/ Friday for NDZ018>022-032>035.