The cold front is moving through a little faster than previously thought. It has already passed through Missoula and Kalispell and is moving towards the Continental Divide. This will help to slow it down a little bit, but it can still be expected in Great Falls before noon, Billings between 3:00-4:00, and Glendive between 6:00-7:00. Even ahead of the cold front, winds will be strong today. Winds will become even stronger as the front passes and winds will shift from the south to the west. Relative humidities are still expected to drop below 25% across the southern half of the state, with humidity values even less in the southeast counties, closer to 10-15% during the afternoon. Red Flag Warnings across southern Montana are effective through midnight tonight, with other wind highlights along the Rocky Mountain Front and the western valleys. On top of all the wind and humidity fire hazards, there is a chance of pop-up thunderstorms which could produce lightning.
Fires will likely grow today, and some new fires may even start from the lightning potential, so smoke will cause air quality problems. Overnight, surface winds shifted in response to the low pressure system and cold front approaching the Northern Rockies today. Smoke from the Ash Creek Complex and other fires in southeast Montana settled to the ground and drained into the Billings area. 1-hour average exposures got as high as UNHEALTHY FOR SENSITIVE GROUPS after midnight, but have since returned to GOOD levels. Air quality in Billings may reach MODERATE or UNHEALTHY FOR SENSITIVE GROUPS again early this afternoon, but as most fires are east of there, once the cold front comes through, the stiff west wind will clear most of the smoke out of the area, and Sidney should also see particulate levels fall back to GOOD. Air quality concerns will fall back to all of the towns in the southeastern counties, which may see UNHEALTHY FOR SENSITIVE GROUPS. If the Pony Complex grows again today, Bozeman should see additional smoke accumulations from MODERATE to UNHEALTHY FOR SENSITIVE GROUPS.
The July 4th holiday looks to bring calmer and more pleasant weather behind the cold front. Temperatures will be at or just above normal with mostly sunny skies. Winds off the Rocky Mountain Front will still be breezy, but elsewhere, mostly calm winds are expected. During the afternoon hours, some stronger gusts may mix down to the surface, though. Relative humidities should stay at or above 20% to the west, but may drop as low as 15% out east. For the rest of the week, temperatures will be a bit warmer as another ridge of high pressure sets up. Some moisture will come from the south each day, so there will be a steady chance for some pop-up thunderstorms in the afternoons, mostly to the south.
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The cold front is currently pushing across the state and winds are blowing strong. Today will be a critical fire weather day with strong frontal winds, wind shift, low relative humidity, and a chance for thunderstorms. As strong west winds push into eastern Montana, smoke will get out of Billings and Sidney, where we have seen air quality impacts. All of the southeastern counties will see smoke impacts with several fires burning out there. By tomorrow, the weather will calm down and the fire danger will not be quite as high. |