


Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
725 FXUS63 KBIS 290859 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 359 AM CDT Sun Jun 29 2025 .KEY MESSAGES... - Breezy today and Monday, with slightly cooler temperatures and lower humidity. - Other than a 20 percent chance of showers and perhaps a thunderstorm across the far south early this morning and the north this evening, dry weather is expected through Tuesday afternoon. - Above normal temperatures favored Wednesday and Thursday, with highs possibly reaching 90 degrees. - Low chances for showers and thunderstorms during the evening and nighttime hours Tuesday and Wednesday, then medium chances late Thursday. Widespread severe storms are not expected at this time. && .DISCUSSION... Issued at 358 AM CDT Sun Jun 29 2025 Southwest flow aloft prevails over the Northern Plains early this morning. As of 330 AM CDT, only light stratiform rain extending north from a South Dakota MCC was potentially falling across far south central North Dakota, but it may just be virga. Otherwise, quiet weather prevails this morning, with the southern half of the state under a mostly cloudy sky from the anvil of the MCC. A mid to upper level shortwave over southeast Saskatchewan early this morning will deepen and dig into the Northern Plains/Upper Midwest through tonight, with the trough axis reaching western Ontario by Monday morning. This may bring some scattered showers and perhaps a few thunderstorms to northern parts of the state this evening into the overnight hours. At the surface, low pressure over Manitoba/Ontario and high pressure along the eastern slopes of the Canadian and Montana Rockies will tighten the surface pressure gradient today, especially over the northern half of the region. Northwest and north central North Dakota are forecast to see west- northwest winds increase to around 25 mph this afternoon, with gusts as high as around 35 mph. Slightly weaker winds are expected to the south, but it could still be a breezy day there. The westerly surface/low-level flow will push the more humid air mass off to the southeast, and lowering heights will result in slightly cooler temperatures for most areas this afternoon, with forecast highs in the mid 70s to lower 80s. The departing shortwave on Monday will leave behind a transition from cyclonic to anticyclonic northwest flow aloft over the region. Deterministic models are in general agreement that a trailing longitudinal streak of vorticity will mark this transition from western North Dakota in the morning to central North Dakota around midday, and reaching eastern North Dakota by late afternoon. Areas that remain downstream of the vorticity streak during the afternoon could see diurnally driven showers and possibly a few thunderstorms, although mid level lapse rates look exceptionally poor for this time of year (between 5 and 6 C/km). By the time anything develops though, the vorticity streak may have already shifted completely east of our forecast area. Therefore, the most likely outcome is a dry Monday for all of western and central North Dakota. High temperatures and dewpoints on Monday will be similar to today. It is expected to be less windy on Monday than today, but the eastern half of the state will likely continue to see breezy northwesterly winds ahead of surface high pressure sliding into eastern Montana and western South Dakota. Dry weather is expected to continue through Tuesday afternoon under anticyclonic flow aloft and broad surface high pressure over the central CONUS. A deamplification of the upstream western CONUS ridge will allow warmer temperatures to return, with forecast highs solidly in the 80s on Tuesday. A weak disturbance embedded in the northwest flow aloft could spark a few showers and thunderstorms as it passes through the region Tuesday evening into the night. Moisture and buoyancy appear lacking, with ensemble mean MUCAPE forecast to be lower than 1000 J/kg. However, deep layer shear could be as high as 35 to 45 kts, which could be sufficient for a stronger storm with just a few hundred J/kg CAPE. CSU machine learning guidance paints a low probability (5 percent) of severe hail over southwest North Dakota for this time period. But the probability of any shower or storm at any given location is only around 10 to 20 percent. For Wednesday and Thursday, the synoptic scale upper ridge axis is forecast to shift from the High Plains to the Mississippi River. In response, the NBM has increased both its deterministic maximum temperature forecast and ensemble distribution thereof each of these days. Lower 90s have now entered the forecast in some parts of the western half of the state. The deterministic NBM output is actually heavily skewed to the cooler side of the distribution, with the 75th percentile showing 90s everywhere on Wednesday and mid 90s to lower 100s on Thursday. However, the advertised southeasterly surface flow and dewpoints rising back into the 60s would favor a slightly "cooler" outcome. There is a small chance that convection forming across central Montana Wednesday afternoon could make it into western North Dakota Wednesday night, with maintenance being supplied by a strengthening low level jet. Should this happen, severe weather appears unlikely on this side of the state border. By Thursday night, ensembles transition flow aloft back to southwesterly as the upper ridge axis approaches the Mississippi River. In turn, NBM PoPs increase to around 30 to 50 percent Thursday evening into Friday morning. Ensemble mean MUCAPE is considerable over this time period, at around 2000-3000 J/kg. But mean deep layer shear is only currently forecast around 25 to 30 kts. Ensemble solutions begin to diverge more noticeably on the Fourth of July through the holiday weekend, with 3 or 4 distinct regional synoptic patterns showing up in cluster analysis with varying probability, including southwest flow, northwest flow, zonal flow, and top of a ridge. Temperatures are favored to remain near to above average over this time period, and the NBM maintains daily low to medium chances for showers and storms. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 358 AM CDT Sun Jun 29 2025 VFR conditions are expected to prevail through the forecast period. A few light showers are possible across far southern parts of the state early this morning. More widely scattered showers and perhaps a thunderstorm or two could move into northern North Dakota this evening. The probability of RA or TS is not high enough to mention in any TAFs at this time. West- northwest winds will increase to around 15-20 kts this afternoon, with gusts as high as 30 kts across the north. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hollan AVIATION...Hollan