textproduct: Bismarck

KEY MESSAGES

- Windy today, with near-critical to critical fire weather conditions across much of southwest and south central North Dakota.

- A few strong thunderstorms could develop in central North Dakota late this afternoon and evening, but widespread severe weather is not expected.

- Cooler on Tuesday, then a warming trend commences through the rest of the week.

- Very hot conditions could return this weekend, with high temperatures and heat index values potentially above 100 degrees.

UPDATE

Issued at 619 AM CDT Mon Jul 20 2026

The forecast for today remains on track. Current conditions and trends have been blended in for this update.

DISCUSSION

Issued at 425 AM CDT Mon Jul 20 2026

Early this morning, the Northern Plains lie between an upper level high pressure centered over Utah/Colorado and a shortwave trough digging into southern Manitoba. A weak surface cold front extends from northwest Minnesota to north central South Dakota. The Manitoba shortwave will continue diving southeast toward the western Great Lakes today, driving a secondary but stronger cold front through the state from north to south this morning and afternoon. Latest guidance has sped up the timing of the front, which could limit high temperatures to a few degrees cooler than what is currently forecast. Still expecting mostly upper 70s/lower 80s north to around 90 south, with dewpoints mixing down into the 40s from southwest to far south central North Dakota. Windy conditions are expected in the post frontal environment with a strong isobaric gradient and mean mixing layer winds around 25-35 kts. This should reflect in northwest surface winds around 20-30 mph with gusts to 35-45 mph. The strongest winds throughout the day are expected north and east of the Missouri River, diminishing toward the southwest corner of the state. Relative humidity is forecast to fall to at least 25 percent along and south of I-94 from Highway 83 to the Montana border, and closer to 20 percent along the Highway 12 corridor. The strongest winds and lowest RH are not forecast to overlap greatly, but there is a portion of south central North Dakota from around Lake Oahe to Lake Tschida where high resolution guidance indicates 20-25 percent RH (with slightly cooler surface temperatures than the NBM) under a local maximum of 25-30 kt mean BL winds. We have therefore elected to issue a Red Flag Warning for Morton, Grant, Sioux, and Emmons Counties from noon to 9 PM CDT. All other areas south and west of the Missouri River, as well as from around Bismarck to Napoleon to Ashley, are likely to see near-critical fire weather conditions this afternoon and early evening. Elsewhere, higher humidity and fuel moisture content preclude fire weather concerns for today.

A separate shortwave over the Canadian Rockies early this morning will eject toward the region by late afternoon. This may provide enough forcing in combination with diurnal heating and deep cyclonic flow to generate scattered showers and isolated thunderstorms across northern North Dakota late this afternoon and evening. Severe weather is unlikely given MLCAPE no greater than 1000 J/kg and EL heights under 30 kft, but effective bulk shear could be quite strong at around 40-50 kts. The 00Z NSSL- WRF and ARW actually do simulate some long UH tracks through central North Dakota during the early to mid evening. The complicating factor is that the strongest shear (south) and highest CAPE (north) are not forecast to greatly overlap. So will not message a severe potential at this time, but will mention that a few stronger storms could develop in central North Dakota late this afternoon and evening.

Surface high pressure is forecast to extend from Alberta to North Dakota on Tuesday, providing a much cooler and quiet weather day. A few showers cannot be ruled out given the northwest flow aloft, but forecast CAPE is very low. Still anticipating highs in the mid 70s to mid 80s on Tuesday, but we begin warming back up as soon as Wednesday as deep troughing over the Great Lakes shifts eastward while upstream ridging becomes amplified over the Rockies. The heat dome is favored to shift back over the central CONUS by the end of the week, with the Northern Plains lying near the top of the ridge. NBM high temperature projections warm by a few to several degrees each day, culminating with a widespread 100 to 105 degree forecast on Saturday. Ensemble mean 850 mb temperatures around 30 C would support this heat, but 500 mb heights are forecast to be just slightly lower than the extreme heat episode from earlier this month. NAEFS/ECMWF climatological percentiles of lower/mid level heights and temperatures exceeding the 90th percentile but not approaching maxima support this next round of heat not being quite as extreme as the previous one, but it could still be impactful. Chances for thunderstorms remain very low from mid week through the weekend, but that could eventually change given our forecast proximity to the top of the ridge and the preceding northwest flow that could feature a shortwave passage or two.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 619 AM CDT Mon Jul 20 2026

VFR conditions are likely to prevail through the forecast period. It will become windy today, with northwest winds around 20-25 kts and gusts around 30-35 kts. Smoke from distant wildfires could become thicker aloft today, but visibility restrictions at the surface are unlikely. Scattered showers and thunderstorms are possible across northern North Dakota late this afternoon and evening. If a heavier shower or storm moves over a terminal, it may cause brief visibility restrictions. A PROB30 mention has been introduced to the KMOT TAF. There is a low chance for MVFR ceilings developing from north to south later tonight, but confidence in this occurring is not high enough to carry prevailing flight category restrictions at this time.

BIS WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from noon CDT /11 AM MDT/ today to 9 PM CDT /8 PM MDT/ this evening for NDZ034-042-045-046.