A well-established upper-level high pressure system will remain centered over the Interior West through Thursday, maintaining dry and mild weather with afternoon temperatures reaching 10 degrees above normal before a significant pattern change arrives early next week.
Current Pattern: Ridge Dominance Continues
The sinking air aloft will keep dry and mild conditions in place across the region, with Wednesday and Thursday seeing temperatures climb to 10 degrees above normal. Surface winds will remain light during this period, and the resulting stagnant air mass will gradually reveal itself through increased fog and haze during the week.
The most notable fog and haze development will occur across the lower Snake Plain and basins and valleys of southeast Oregon. Through Thursday, fog formation in the Snake Plain will be limited to areas along the Snake River and more broadly to points west of the Canyon and Ada County line into the Weiser Basin.
Forecast adjustments have been made to increase fog coverage across lower valleys each morning as the stagnant pattern persists.
Valley Inversion Impacts: Expanding Fog Coverage
The persistent high pressure will continue creating temperature inversions that trap cold air and moisture in valley locations. The stagnant air mass will gradually worsen air quality conditions, particularly in areas prone to fog development.
Morning fog will become more widespread as the week progresses, with the Snake River corridor and western valleys experiencing the most significant impacts. Drivers should prepare for reduced visibility during morning commutes, particularly in areas west of the Canyon-Ada County line.
Weekend: Ridge Begins to Weaken
The upper-level ridge that dominates the short-term period will begin to break down and move east to end the week. While Friday and Saturday will remain dry, weather model clusters show good agreement on a pattern change early next week as a trough moves in off the coast.
Friday and Saturday will continue the mild, dry pattern with sunny skies and temperatures in the mid-50s, representing the final days of the current stable weather regime.
Pattern Change: Cold Front Approaches
Although exact timing cannot be pinned down yet, weather models all show a cold front crossing the area late Sunday into early Monday. This front will mix out the persistent inversion with increased winds and cooling aloft, finally breaking the stagnant pattern that has dominated recent weeks.
The front will also cool surface temperatures to more seasonable levels by Monday, ending the extended period of above-normal temperatures.
Mountain Snow Conditions for Ski Areas
The current ridge pattern will continue limiting new snowfall opportunities through the weekend. However, the approaching pattern change early next week will bring the first significant precipitation chances in an extended period.
Mountain areas will see the highest precipitation chances Monday morning, with 55 to 75% probability in the west-central mountains. This could bring much-needed fresh snowfall to ski areas, though snow levels will depend on the exact temperature profile as the system moves through.
Precipitation Returns: Monday Focus
Precipitation chances will increase through the day Sunday, before reaching maximum probability Monday morning. Current forecasts show 55 to 75% chances in the west-central mountains and 35 to 55% chances elsewhere.
These precipitation chances will likely increase in coming days as the exact timing becomes better resolved. Beyond Monday, precipitation chances will remain elevated as weather model clusters show good agreement on continued troughing over the area.
Extended Outlook: Active Pattern Potential
The pattern change represents a significant shift from the persistent ridge that has dominated much of the winter. The transition to troughing over the area suggests a more active weather pattern may develop, bringing regular precipitation chances and more variable temperatures.
This change will provide relief from the stagnant air quality conditions and persistent inversions that have characterized recent weeks.
Daily Forecast:
Tonight: Partly cloudy, with a low around 32. Calm wind.
Wednesday: Mostly sunny & continued unseasonably mild, with a high near 55. Calm wind.
Wednesday Night: Mostly clear, with a low around 34. Calm wind.
Thursday: Sunny & very mild, with a high near 56. Light and variable wind.
Thursday Night: Mostly clear, with a low around 33. Calm wind.
Friday: Sunny & continued mild, with a high near 55.
Friday Night: Partly cloudy, with a low around 34.
Saturday: Mostly sunny & very mild, with a high near 56.
Saturday Night: Mostly cloudy, with a low around 37.
Sunday: A 20% chance of rain after 11 a.m. Partly sunny & continued unseasonably mild, with a high near 58.
Sunday Night: A 40% chance of rain. Mostly cloudy, with a low around 39.
Monday: A 40% chance of rain. Mostly cloudy, with a high near 50.
Monday Night: A slight chance of rain and snow. Mostly cloudy, with a low around 32. Chance of precipitation is 20%.
Tuesday: A slight chance of rain and snow. Partly sunny, with a high near 46. Chance of precipitation is 20%.
Stay connected right here for updates on our weather pattern change.
