Weather Lookup

Discussion

Key messages:

- hot, dry, and smoky conditions continue with the persistent weather pattern through saturday.

- dry thunderstorm potential: thursday afternoon through friday morning across southwest and west-central montana.

- elevated winds and fire weather: saturday and sunday region- wide.

Dry southwesterly flow on the western periphery of the upper-level ridge will maintain hot, dry, and smoky conditions across the northern rockies through the next several days. Air quality advisories have been updated to remain in effect for lemhi county through at least friday. Expect degraded air quality and visibility to persist.

Despite the relatively opaque appearance of the sky due to regional wildfire smoke, intense late-july sunshine has still been able to overcome most smoke-shading effects. Temperatures have still been able to climb to within a degree or two of their clear-sky potential, keeping daytime temperatures several degrees warmer than normal for this time of year during the afternoon and evening hours.

Isolated dry thunderstorm chances continue in southwest montana each afternoon. Attention to detail in the forecast indicates the progression of several weak shortwave troughs embedded in this southwesterly flow ejecting into the region thursday afternoon through friday morning . Strong mid-level lapse rates and sufficient SHEAR combined with a very dry sub-cloud layer will support dry thunderstorms capable of producing lightning and strong erratic outflow winds even during the overnight and early morning hours.

A broad longwave trough off the pacific coast heads inland this weekend breaking down the stubborn ridge that we have been dealing with for quite some time. Strong pre-frontal warming will drive temperatures near the 100 degree mark on saturday particularly for valleys along and south of i-90.

As the cooler airmass begins to pass through saturday into sunday, expect widespread westerly winds sustaining 10-25 MPH with gusts of 25 to 40 MPH across the region. This wind/heat/ and low rh combination will significantly elevate fire weather concerns and create hazardous, choppy conditions on lakes and waterways. This system will remain mostly dry with no significant or notable precipitation expected, but temperatures will drop 10-20 degrees behind the front for sunday and monday bringing temperatures back to near and just below normal for this time of year.

Aviation

Wildfire smoke remains a persistent impact to the regional airspace. Slant-range and surface visibilities continue to bottom out near 5sm at times, especially pronounced during the late afternoon through sunset as optical depth increases and the day's fresh smoke arrives from fires burning in oregon and southwestern idaho. Anticipate continued mountain obscurations. Ridgetop winds will remain out of the west and southwest at 10-20 knots through the forecast period. Hot temperatures will continue to increase density altitudes through saturday impacting aircraft performance particularly at higher elevation terminals and airfields as temperatures continue to creep into the mid and upper 90S each day. Note: amd not sked for kgpi due to missing metars.