My Favorite Summer Weather Map Layers:

• StormNet Lightning Risk
• Current Lightning Strikes and 1-Hour Risk
• Current Radar
• Forecast Radar
• Forecast Total Precipitation
• Current Air Quality
• Smoke Surface Forecast (ground level)
• Smoke Sky Forecast (average smoke ground level to upper atmosphere)
• Forecast Air Quality (low-res 3-5 day smoke outlook)

5-Day Big Picture Overview:

A monsoonal flow will continue to become established across the Southwest and the Rockies, favoring areas near and west of the Continental Divide. Temperatures will trend cooler across the Four Corners, while the Northern Rockies will remain above average despite some modest cooling compared to prior days.

A low pressure trough will also reach the West Coast before tracking from south to north along the coasts of Oregon, Washington, and BC, bringing some rain and thunderstorms to western portions of these regions. 

COLORADO

Wed – Thunderstorm activity will generally favor areas west of the Continental Divide and south of I-70, with the greatest coverage in the San Juans, West Elks, and Sawatch. The Sangres will also see a bit of action, especially in the southern half of the range, while the Northern Front Range Mountains could see some storms as well.

The San Juans could see development prior to noon, and this is also where the threat of heavy rain will be the greatest, as moisture levels will be more substantial here.

Storm motions across the state will generally be slow-moving from north to south. 

Wildfire smoke on Wednesday will be heaviest in the Sangres, Northern San Juans, and the Steamboat/Rabbit Ears Pass area. The hope is that wildfire activity will gradually subside later this week as the monsoonal flow pattern takes hold, but this may happen more quickly over the San Juans than in other areas.

Thu – Moisture will continue to gradually increase west of the Divide and south of I-70 (and also across the Sangres), and these areas will be favored for thunderstorm development and heavy rain potential once again. Coverage will be more isolated north of I-70 and into the Front Range.

Storms will be slow-moving from N to S or NE to SW.

Fri-Sun – Thunderstorm coverage will continue to favor areas along and west of the Divide as well as the Sangres, with only some isolated cells drifting eastward onto the Front Range foothills. 

Thunderstorm chances and coverage will slowly increase north of I-70 each day, and by the weekend, we'll be looking at increased potential for heavy rainfall with storms throughout the high country.

The heaviest rain amounts over the next 5 days are expected across the San Juans, while little to no rain is expected across the plains. Keep in mind that pockets of heavier rain amounts (than what our model shows) are possible anywhere in the mountains due to the hit-or-miss nature of thunderstorms.

UTAH

Wed – Thunderstorm coverage will favor Southwest Utah and Northeast Utah (Uintas), with more isolated activity expected across the remainder of the state. Atmospheric moisture levels will be significant, so any stronger storms will be capable of producing heavy rain.

There is also an increased risk of flash flooding throughout the canyon regions of Southern Utah, with the greatest threat expected across Southwest Utah, including the Zion and Escalante regions. Storm motions will be slow and erratic, which also increases the flash flooding risk. 

Despite the uptick in moisture, smoke from the Stookey Fire will continue to impact SLC and the Wasatch Front at times. Increasing relative humidity will help firefighting efforts, but whether or not this fire receives beneficial moisture is highly contingent on the hit-or-miss nature of thunderstorms.

Thu – This is shaping up to be an active day with scattered to widespread thunderstorm coverage throughout the state. Moisture levels will be even higher, meaning that heavy rain is possible in both Northern and Southern Utah, while the canyon regions of Southern Utah will have a substantial risk of flash flooding. Storm motions will be slow and erratic once again. 

Fri-Sun – An active monsoonal flow pattern will remain in place with daily rounds of scattered thunderstorms statewide. Stronger storms will be capable of producing heavy rain, and a daily threat of flash flooding will exist in the canyon regions of Southern Utah. 

Our PEAKS Model is projecting total rainfall amounts through Sunday to range from 1-3 inches across the higher ranges of Southwest Utah as well as the Uintas in Northeast Utah, and 0.5-1.5 inches across the Wasatch. 

Keep in mind that pockets of heavier rain amounts (than what our model shows) are possible in any areas due to the hit-or-miss nature of thunderstorms.

SOUTHWEST

Wed – Thunderstorm coverage will favor the higher elevations throughout Arizona and New Mexico, with more isolated activity expected near Vegas. Storms will be capable of producing heavy rain, with the highest threat of flash flooding expected in Northern Arizona. 

Storm motions will be faster-moving from NE to SW across New Mexico, and slow and erratic across Arizona.

Thu – Another active day is expected with thunderstorm coverage favoring Northern and Eastern Arizona, as well as Northern New Mexico. The Vegas area will also see an uptick in thunderstorm chances.

Storms will be capable of producing heavy rain, and the risk of flash flooding is expected to increase throughout Arizona. Storms will also be slow-moving from ENE to WSW.

Fri-Sun – This looks like an active stretch across both Arizona and New Mexico, with scattered to widespread thunderstorms expected each day. Deep moisture will remain in place, and storms will be capable of producing heavy rain and localized flash flooding.

Higher elevation areas in Arizona and Western New Mexico, as well as the Sangres in Northern New Mexico, are generally looking at a total of 1-3 inches of rain through Sunday based on our PEAKS Model Forecast.

Keep in mind that pockets of heavier rain amounts (than what our model shows) are possible in any areas due to the hit-or-miss nature of thunderstorms. 

CALIFORNIA/SIERRA

Wed – Monsoonal moisture is on the decrease following an active few days. The main push of moisture is heading eastward now, with drier air coming back in from the west. Even so, some isolated thunderstorms are still possible across the Eastern Sierra and adjacent foothills late in the afternoon.

Thu-Sat – Mostly dry conditions are expected, though a stray afternoon thunderstorm couldn't entirely be ruled out on any given day across the High Sierra and Eastern Sierra.

Sun – Monsoonal moisture will attempt to sneak back in, resulting in a chance of thunderstorms over the Sierra, though models are in poor agreement about how strong this next possible moisture surge might be.

PACIFIC NORTHWEST

Wed – Moisture and instability will be on the increase in response to an approaching low pressure trough with a southerly flow developing. Scattered thunderstorms will develop during the afternoon and evening hours along the east slopes of the Cascades in Oregon and Southern Washington, as well as the northeast mountains of Washington.

Locally heavy downpours will be possible with stronger storms, but there is also a risk of dry thunderstorms (light rain and gusty winds), which could potentially trigger or enhance wildfire activity. 

Wildfire smoke is also expected to impact Western Oregon (mainly along/near the Cascades) and Northeast Oregon at times thanks to a recent uptick in wildfire activity.

Wed Night – As the low approaches, an overnight threat of thunderstorms will emerge across Western Washington and Northwest Oregon, including both Seattle and Portland. Most storms will only produce light rain and gusty winds, but locally heavy downpours could occur under stronger cells. 

Thu – The low pressure system will track from south to north along the coast, bringing widespread rain to the Olympic Peninsula, Northwest Oregon, and Southwest BC. Scattered showers and thunderstorms with lighter and more spotty rain amounts can be expected across the Cascades, Puget Sound Lowlands, Eastern Washington, and Northeast Oregon.

Lightning potential will be greatest across Western Washington, Southwest BC, Southeast Washington, and Northeast Oregon during the day, while a more significant overnight threat will emerge across Northeast Washington overnight.

Fri – An overall drying trend is expected aside from some lingering light showers in the morning over Northwest Washington and Southwest BC. Clearing skies are expected by the afternoon.

Rain totals with this system will generally range from a quarter-inch to a half-inch across the Olympic Peninsula, Northern Cascades, and Southwest BC, with lighter amounts elsewhere.

Keep in mind that pockets of heavier rain amounts (than what our model shows) are also possible anywhere due to the hit-or-miss nature of thunderstorms.

Sat-Sun – Hot and dry conditions will return to the region, though the warm-up will be delayed initially across Western Washington compared to other areas. Mostly sunny skies can be expected, while wildfire activity and smoke are wild cards.

NORTHERN ROCKIES

Wed – Significant monsoonal moisture is in place, but a stable layer in the atmosphere will limit thunderstorm coverage west of the Continental Divide. Higher thunderstorm coverage is expected east of the Divide, especially in the Beartooths, Absarokas, and Northern Winds in Wyoming and Montana. Storms will also be capable of producing heavy rain in these areas.

Thu – An active thunderstorm day is expected throughout this region, both west of the Divide and east of the Divide, with storms capable of producing heavy rain. 

Fri-Sat – An active pattern will continue with scattered thunderstorms developing throughout the Northern Rockies both days, with storms capable of producing heavy rain as deep monsoonal moisture remains in place.

Sun – The deepest moisture will retreat south of the area, resulting in a lull in the pattern with only some isolated thunderstorm activity expected.

The heaviest rainfall over the next 5 days is expected across the Beartooths, Absarokas, and eastern plains and foothills of Montana. 

Keep in mind that pockets of heavier rain amounts (than what our model shows) are possible anywhere in this region due to the hit-or-miss nature of thunderstorms.

BC INTERIOR & CANADIAN ROCKIES

Wed – An active day is expected with scattered thunderstorms developing throughout the region. Most storms will produce light rain and gusty winds in the BC Interior, while heavy rain is possible in the Canadian Rockies along and east of the Alberta border. 

Thu – Isolated to scattered thunderstorms will develop again, though coverage looks a bit lower compared to Wednesday. Most storms will only produce light and spotty rain.

Fri – This will be the most active day of the week, with scattered to widespread thunderstorms expected throughout the region in response to a low pressure system moving into BC. Some storms could be on the stronger side as well.

Rainfall will be hit or miss as is typical in thunderstorm setups, but stronger storms will be capable of producing heavy rain.

Sat-Sun –  A warming and drying trend is expected with shower/thunderstorm chances primarily confined to northern areas such as Jasper and Mt. Robson.

Monday (July 20) to Friday (July 24):

An active monsoon pattern will continue across the Southwest and the Central Rockies, with frequent thunderstorms expected along with heavy rain potential. Temperatures are also expected to be cooler than average across this region as the monsoon pattern becomes well established. 

Areas east of the Divide in Colorado also will have better chances of thunderstorms and meaningful rain in this pattern compared to the week prior. Further west, the Sierra looks to be right on the fringe but may see some action at times.

Further north, a high pressure ridge over the PNW will result in well above-average temperatures, but there are also some hints of a Pacific disturbance with some moisture sneaking across Washington, BC, and Alberta around midweek. 

Thanks so much for reading! Next update on Friday (July 17).

Alan Smith

In case you missed it, I just posted a North American Monsoon Season Outlook for July to September.

View → Monsoon Season Outlook