Big Picture Weather Pattern:

A strong ridge of high pressure will remain over the West this week and will gradually move eastward with time, allowing the anomalous warm to expand in coverage.

Dry northwest winds (blowing from the northwest) on the east side of the high pressure center will keep most of the monsoonal moisture suppressed south of the Mexico border. However, a trough of low pressure over the Central U.S. will allow some moisture to sneak into New Mexico from the east/northeast. 

Record-Setting Heat:

This heatwave has already resulted in numerous record high temperatures in recent days. Most notably, Las Vegas set its all-time high temperature record on Sunday with a high of 120ºF – breaking its previous record of 117ºF.

The Far West will remain very hot over the next 5 days, while we will also see record-challenging warmth spread eastward over time. New Mexico will hang onto cooler temperatures relative to average, while Colorado will see the worst of the heat arrive at the end of this period following a cooler start to the week. 

Idaho will be one of the hot spots this week with triple-digit high temperatures expected in Boise throughout the week.

We are forecasting a high of 107ºF in Boise on Friday and 108ºF on Saturday. Even the higher-elevation towns in Idaho will not escape the heat, as Ketchum (elevation 5,853 feet) will see highs in the mid 90s from Wednesday to Sunday.

5-Day Precipitation Forecast:

In addition to the heat, conditions will also be very dry across most of the West this week. The one exception is New Mexico and Far Southeast Arizona, where thunderstorms and locally heavy rain can be expected. To the north in Central Colorado and Wyoming, areas along the Continental Divide will only see a few isolated dry thunderstorms at best. 

Fire and Smoke Update:

The excessive heat combined with dry air and low relative humidity has resulted in rising fire danger across the West. Large fires are now burning in California, Utah, Oregon, and Washington, and smoke is becoming a factor near and downwind of these fires.

High-res smoke forecast for Monday PM:

High-res smoke forecast for Tuesday PM:

Fire activity can change quickly so be sure to utilize our high-resolution wildfire and smoke tracking tools over the upcoming week as this heat wave persists so that you can avoid spending time outdoors during periods of smoke and poor air quality.

• Active Fires Map
• Real-Time Air Quality Map
• Smoke High-Res (Surface) Map
• Air Quality Forecast Map

Forecast for Mon (Jul 8) to Tue (Jul 9):

New Mexico and the southernmost portions of Colorado will be favored for thunderstorms with locally heavy rain possible. A few isolated thunderstorms are possible along the Continental Divide from Central Colorado to Wyoming. Otherwise, most of the West will be dry.

Areas west of the red line will see temperatures of at least 10ºF above average with record highs possible for some locations. 

Taking a closer look at New Mexico, the east side of the Sangre de Christo Range, the Los Alamos area, the Sacramento Mountains (including Ruidoso), and the Black Mountains will be most favored for thunderstorms. Locally heavy downpours will be possible along with a risk of localized flash flooding, especially over burn scars.

Forecast for Wed (Jul 10) to Thu (Jul 11):

By the middle of the week, the heat will expand eastward with nearly all areas outside of Colorado and New Mexico expected to see temperatures of at least 10ºF above average.

Moisture will largely remain confined to New Mexico, as well as southern portions of Colorado and eastern portions of Arizona. Isolated thunderstorms will also be possible near the Continental Divide in Central and Northern Colorado.

Forecast for Fri (Jul 12) to Sat (Jul 13):

By the end of the week, the heatwave will take hold over Colorado with triple-digit high temperatures expected around Denver. Areas between the red lines will see temperatures of at least 10ºF above average. Areas west of the Cascade Crest in Washington and Oregon will see cooler temperatures compared to earlier in the week.

As for moisture, we will start to see some monsoonal moisture push back into Arizona and portions of Southwest Colorado by Saturday. This is because the high pressure center will be located far enough east to result in a wind shift to southerly (blowing from the south), allowing moisture to arrive from Mexico. 

Outlook for Sun (Jul 14) to Thu (Jul 18):

It will remain hot throughout the West, though the high pressure ridge will be located further east with the highest departure from average temperatures expected over the Interior West, and especially the Northern Rockies.

Also, monsoonal moisture will increase across the Southwest and Southern/Central Rockies, resulting in an uptick in thunderstorm activity.

Thanks so much for reading! Next update on Wednesday (July 10).

Alan Smith