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 broad ridge of high pressure over the West Central U.S. will favor above-average temperatures for most areas, and well above-average temperatures east of the Divide. However, a consistent monsoonal flow will also favor the Four Corners states and, to a lesser extent, Wyoming.

A trough off the West Coast will favor cooler temperatures from Northern California into the PNW, and a series of disturbances will also bring rain to NW Washington and Western BC.

COLORADO

The overall trend over the next 5 days will feature an initial slight decrease in thunderstorm activity compared to recent days, initially on Friday, followed by a steady progression of increasing thunderstorm coverage and rainfall amounts across the state as a whole each day from Saturday to Tuesday.

Fri – Isolated to scattered afternoon thunderstorms can be expected, with storms initially developing over the San Juans, Sangres, Elks, Grand Mesa, and Flattops by midday to early afternoon. Storm coverage will spread further east toward the Front Range Mountains by mid to late afternoon, and eventually across the I-25 corridor (more isolated coverage) by late afternoon to early evening.

Moisture levels will not be as high compared to recent days, but storm motions will also be slow and erratic, so any stronger storms that develop will be capable of producing heavy rain.

Sat – Thunderstorm coverage will increase a bit statewide compared to Friday, with StormNet indicating the highest lightning probabilities across the San Juans, Sangres, Saswatch, Mosquito/Ten Mile, and Front Range Mountains.

Storms will be slow-moving from SW to NE in most areas, with stronger storms producing heavy rain.

Sun – Scattered afternoon thunderstorms can be expected statewide once again, with the highest lightning probabilities over the San Juans and Southern Sangres. Storm motions will be slow and erratic statewide, which will increase the potential for heavy rain and localized flash flooding.

Mon-Tue – An uptick in thunderstorm coverage is expected statewide as the high pressure area over the West/Central U.S weakens a bit, allowing some shortwave energy to move in along with increasing monsoonal moisture. Areas east of the Divide, including the I-25 corridor, will also see a better chance of heavy rain-producing storms compared to prior days.

Our PEAKS Model total rainfall forecast through Tuesday has projections of 1-2 inches across much of the Colorado high country, with the heaviest amounts projected over the Southern Front Range Mountains along and south of I-70. Isolated higher totals are also possible where stronger thunderstorms develop. 

UTAH

Fri – Thunderstorm coverage will favor the Southwest Utah mountains and the Wasatch, with more isolated coverage across Eastern Utah (except the La Sals/Moab could see higher coverage).

Storms will be slow-moving from SW to NE, and stronger storms will be capable of producing locally heavy rain, with some flash flooding risk expected, even if less extensive compared to earlier this week.

Sat – Afternoon thunderstorms are possible statewide, but the highest coverage is expected across Northern Utah in response to a shortwave passing north of the area. Storm motions will be a bit faster across Northern Utah from SW to NE.

Across Southern Utah, rainfall may be more isolated compared to most of this past week, but some flash flooding risk still couldn't be ruled out in slot canyons, dry washes, small streams, and burn scars.

Sun-Tue – Isolated to scattered thunderstorms can be expected each day in both Southern and Northern Utah. Stronger storms will be capable of producing heavy rain, especially in Southern Utah where storm motions will be slower.

Overall, rain totals over the next 5 days are not expected to be as heavy compared to what we've seen lately, but isolated higher amounts (than what we show on this map) are still possible in areas where strong thunderstorms develop.

 

SOUTHWEST

Fri – Moisture levels will be modestly above average with afternoon thunderstorm coverage favoring New Mexico, while Arizona will see more isolated to scattered coverage, favoring the Mogollon Rim more than other areas. Strong storms will be capable of producing heavy rain in both New Mexico and Arizona.

Sat – An active day is expected across both Arizona and New Mexico, with scattered to numerous terrain-driven thunderstorms expected. All mountainous areas have a good chance of storms, but StormNet favors the greatest coverage over the Black Mountains in Western New Mexico.

Sun – A similarly active day is expected, and the potential for heavy rain will increase as deeper moisture pushes into the region and temperatures cool off some.

Mon-Tue – More of the same with daily rounds of afternoon thunderstorms developing, some of which will produce heavy rain. The potential for heavy rainfall looks to increase across Arizona in particular, where deeper moisture levels are expected. 

Total rainfall through Tuesday will favor the San Francisco Mountains (AZ), Mogollon Rim (AZ), Southeast AZ Mountains, Black Mountains (NM), and Sangres (NM), but isolated higher amounts are possible anywhere where strong thunderstorms develop. 

CALIFORNIA/SIERRA

Fri – Monsoonal moisture will sneak back into the area, resulting in a chance of isolated to scattered thunderstorms across the Southern and Eastern Sierra, including Mt. Whitney and Sequoia/Kings Canyon.

Localized heavy wildfire smoke is also possible at times to the north & east of the Rock Fire burning near Independence, while a more general light haziness is expected at times across the remainder of the Sierra.

Sat – Isolated afternoon thunderstorms are possible over the Sierra again, with the main threat shifting north a bit to around Mammoth Lakes and Yosemite, but likely staying just south of Tahoe. 

Sun-Tue – Conditions will dry out over the Sierra with slightly cooler air also moving in, at least around Tahoe, while the SoCal mountains and deserts will see some isolated thunderstorm potential as a little bit of monsoonal moisture works its way in. 

PACIFIC NORTHWEST

Fri – Dry conditions are expected with mostly sunny but slightly hazy skies west of the Cascade Crest, while areas east of the Cascades will be dealing with heavy smoke and poor air quality from wildfires once again.

Sat-Sun – The first of two Pacific troughs will arrive, and a cold front will sweep across the PNW on Saturday, bringing much cooler air.

Significant rainfall is also expected across the Olympics, Northern Washington Cascades (north of I-90), and especially the BC Coast Range, with only isolated light/spotty rain for the Puget Sounds Lowlands and Cascades south of I-90.

Wildfire smoke will remain an issue across the Inland Northwest, though the heaviest smoke may be pushed a bit further east away from the Cascades compared to Friday. Strong winds and preceding hot temperatures across the Inland NW on Saturday will lead to fire weather concerns, while Sunday may be less of a concern with cooler air in place, though winds will still be gusty.

Mon-Tue – Another Pacific trough and cold front will move through, bringing a reinforcing shot of cool air. More rain showers are possible across the Olympics, North Cascades, and BC Coast Range, though confidence in terms of coverage and amounts is relatively low.

Total rainfall through Tuesday will range from 0.5 to 1.5 inches across the west side and higher elevations of the Olympic Peninsula, 0.25 to 1.0 inches across the Northern and Central Washington Cascades, and 1-2+ inches across the BC Coast Range and Vancouver Island Mountains/West Coast.

NORTHERN ROCKIES

Fri – Scattered afternoon thunderstorms will favor Western Wyoming, Eastern/Central Idaho, and Southwest Montana as monsoonal moisture begins to push back into the area. Most storms will produce light/spotty rain but isolated heavier downpours could occur with stronger storms.

Heavy wildfire smoke is also expected across Northern Idaho and Northern Montana in response to active wildfires burning across the Pacific Northwest.

Sat – An uptick in thunderstorm coverage is expected across Wyoming, Southern/Central Montana, and Southern/Eastern Idaho. Stronger storms will produce locally heavy rain, though the flash flood risk looks much lower compared to earlier this week when more anomalous moisture was in place.

Sun-Mon – Daily rounds of afternoon thunderstorms will continue across Wyoming, Eastern Idaho, and Southern Montana as these regions will be on the northern edge of the monsoonal flow. 

The best chance of meaningful rainfall with thunderstorms from Friday through Tuesday will be across Wyoming, Eastern Idaho, and Southern Montana, with isolated higher amounts possible than what this map shows in areas where stronger thunderstorms develop.

BC INTERIOR & CANADIAN ROCKIES

Fri – Warm, dry, and smoky conditions will prevail across most of the region, with heavy wildfire smoke originating from fires burning on the eastern side of the Coast Range and across the Northwest U.S.

Isolated thunderstorms are possible on Friday afternoon, but the smoke will be heavy enough that this may actually limit the surface heating needed for extensive thunderstorm development.

Sat – Gusty winds with isolated showers and thunderstorms can be expected ahead of an approaching cold front. This pattern will lead to an increased risk of new wildfires, while smoke transport from ongoing fires will continue to impact the region.

Sun – Cooler air will settle into the area in the wake of a cold front. Meaningful rain showers will also develop across the Northern Cariboos toward Mt. Robson, with fewer/lighter showers across the remainder of the BC Interior and Canadian Rockies.

Some smoke improvement is possible across the Canadian Rockies and Southeast BC as winds across the Eastern Coast Range (where many of the fires are located) shift from SW/WSW to more of a SSW direction.

Mon-Tue – A similar weather pattern is expected with isolated afternoon showers and thunderstorms, mainly on the BC side, while smoke looks heaviest across the Okanagan Valley and north of Highway 1, with potentially less smoke across Southeast BC and Southwest Alberta, barring any new major fire starts.

Wednesday (July 29) to Sunday (Aug 2):

The strength and coverage of the monsoon looks to relax a bit, but a consistent monsoonal flow will still continue across the Four Corners states, with longer-range models favoring Colorado and Northern New Mexico for the highest rainfall totals.

Temperatures will remain above average across most of the West, with the highest anomalies across the Northern Rockies.

However, a trough-dominant pattern over the PNW will favor cooler temperatures in this region, though rain chances appear to be limited, which perhaps isn't surprising as late July/early August is the climatologically driest time of year across this area. 

Thanks so much for reading! Next update on Monday (July 27).

Alan Smith