textproduct: Bismarck

KEY MESSAGES

- Hot conditions return on Sunday with high temperatures and heat index values around 95 to 100.

- Isolated to scattered severe thunderstorms are possible Sunday afternoon and evening. Expected hazards include hail as large as 2 inches in diameter and damaging winds up to 70 mph, with a tornado possible.

- Windy northwest winds expected Monday. Winds combined with low humidity values could bring critical fire weather conditions across parts of southwest and south central North Dakota.

- Brief cooldown expected Tuesday, followed by a warming trend into next weekend.

DISCUSSION

Issued at 234 PM CDT Sat Jul 18 2026

Elevated warm front and weak shortwave will bring some high based showers through tonight from west to east. With limited instability expected, the threat for thunderstorms is low as is the threat for severe weather for tonight. Warm temperatures behind this front combined with some increased cloud cover will bring warmer lows in the 60s tonight. This cloud cover should also limit the fog potential for tonight, although any areas that clear and high light winds could see at least patchy fog return. Confidence in fog is not high enough to include in the forecast at this time.

Sunday, hot temperatures with isolated to scattered severe thunderstorms remain forecast. Starting with the heat, westerly flow aloft with a surface warm front and southerly flow will warm temperatures back into the 90s to near 100 degrees for Sunday. Southerly flow will maintain dewpoints in the 60s providing for Heat Index values near to over 100 degrees in some areas. Heat Risk is moderate to major for most of the CWA, while some extreme risk is showing up in central portions for Wet Bulb Global Temperatures. Today's forecast came in slightly cooler than previous for Sunday, perhaps limiting how widespread the more dangerous heat will reach. Thus issued a Heat Advisory for the higher confidence areas in southwestern and south central portions. Depending on cloud cover, daytime heating, and overall timing of the mentioned fronts this may need to be expanded into north central and eastern portions and will have to be reevaluated at later forecast times.

SPC has maintain and expanded somewhat the Slight Risk (Level 2 of 5) for severe weather on Sunday. CAMs also remain robust Sunday afternoon through Sunday evening. The setup remains similar with a warm front being replaces by a cold front Sunday afternoon through Sunday evening and night. Modest capping will give way to Forecast CAPE approach 3000 J/kg, with 0-6 km shear around 40 to 50 kts as the mentioned front progresses through. Thus kept hazards the same with very large hail up to 2 inches in diameter and damaging winds up to 70 mph. There also remains a conditional risk for a tornado with a very similar setup to what was observed last Thursday. Forecast CAPE and shear would both be sufficient for tornadogenesis with any supercell that remains anchored to the vorticity-rich and baroclinically-weak surface boundary. The biggest uncertainty remains with storm mode. This will depend on how the fronts orientate themselves to a generally westward shear vector, although initially there does look to be a multi- cluster to discrete supercell mode potential. These storms could then remain multicluster or go linear quickly. With inverted V sounding, high CAPE, and high shear, this could bring an increased wind threat. With the uncertainty of storm mode, all should be weather aware for Sunday afternoon and evening. Storms overall look to push out of the area Sunday night. Winds become westerly and temperatures look to remain in the 60s.

On Monday, the shortwave out of Saskatchewan is expected to swiftly move southeast through Manitoba into the western Great Lakes region. Precipitation chances are forecasted to be very low, with a lack of sufficient ingredients for development. A tight pressure gradient, ample cold air advection, and mixing anticipated to push through on the back end of this front will provoke increased wind intensity across North Dakota. For the duration of daylight on Monday, gusty conditions can be expected, peaking in the afternoon. NBM forecasts estimate the highest surface gusts to be in the 40-45 MPH range in the eastern half of the state; however, the NBM sometimes tends to favor higher end solutions for wind, leading to concerns about overestimation bias. Trends in wind intensity will be monitored as we move into a closer forecast range, especially if it trends upwards towards wind advisory criteria.

Also of note on Monday is the risk for critical fire conditions in the southwest portion of North Dakota. While high temperatures on Monday are forecasted to dip in the northern half of the state (from the upper 70s to the mid 80s), in the southern half of the state, highs are expected to remain in the upper 80s and lower 90s due to the forecasted timing of the cold front. Additionally, in the southwest, minimum RH values are anticipated to be low (20-30%) with dewpoints in the mid to upper 40s. With northwest surface winds sustained up to 25 MPH for a good portion of the afternoon and fuels drying due to persistent lack of precipitation in the area, critical fire weather conditions are possible. It is also important to note that there is uncertainty on whether fire weather conditions will come to fruition given possible changes to the timing of the front's passage. Currently, the ingredients for fire weather on Monday line up to occur at the same time, providing sufficient concern that these conditions could occur. We will continue to keep an eye out for any changes or displacements of these ingredients.

Moving through the work week, Tuesday is expected to remain the coolest day of the forecast period. NBM high temperatures remain in the mid 70s to the mid 80s from north to south, respectively. Additionally, winds will decrease from Monday, providing calmer conditions. Multiple ensembles show a prompt progression of the shortwave moving east across the Great Lakes, with a ridge following in the late week. Thus, the heat relief will likely be brief, with highs expected to trend up following Tuesday. Currently, NBM maximum temperatures look to increase steadily throughout the week up to the high 90s by Saturday in the southwest portion of North Dakota, with both maximum wet-bulb global temperature and Heat Risk showing upwards trends as well. Even so, there is still disagreement among ensembles on how hot these temperatures will end up being. This is likely due to uncertainty surrounding the ridge strength and when and where it may flatten as we move into the weekend. Finally, precipitation chances are looking fairly low through next week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1258 PM CDT Sat Jul 18 2026

Mainly VFR conditions expected through the forecast period. Some high based showers are possible today through tonight, although confidence was not high enough to include at any TAF sites. More mid to high level clouds may also be found Sunday morning, with chances for showers and thunderstorms increasing Sunday afternoon and evening. A steady southerly wind will be found through most of the forecast period, although may become westerly Sunday. Hot temperatures also return for Sunday.

BIS WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 1 PM CDT /noon MDT/ to 9 PM CDT /8 PM MDT/ Sunday for NDZ017>020-031>033-035-040>044-046>048-050-051- 059>062.