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:

During the middle part of this week (Wednesday-Thursday), a subtle shortwave trough will help to pull monsoonal moisture into the Southwest and the Rockies, leading to an uptick in thunderstorm activity with hit-or-miss rainfall in most instances.

Heading into the weekend (Friday to Sunday), an unusually strong low-pressure system for this time of year will deepen over the Pacific Northwest and Northern Rockies, bringing significant moisture to these regions along with well-below-average temperatures. 

Check out these projected temperature anomalies for Saturday PM to Sunday PM. An impressive cool signal west of the Continental Divide for the end of June! 

5-Day Regional Forecast Breakdown below as follows...

• Colorado
• Utah
• Southwest
• California/Sierra
• Pacific Northwest
• Northern Rockies
• BC Interior & Canadian Rockies

COLORADO

Wed – West of the Divide, a shortwave will arrive from the west and monsoonal moisture will also push into Southwest Colorado, resulting in an uptick in thunderstorm chances with activity favoring the San Juans. The first storms could potentially develop over the northern/western San Juans prior to noon. Storms will generally move from west to east, and heavy rain is also possible in the San Juans. 

East of the Divide, low-level easterly winds will remain with the deepest moisture focusing over the Northern Front Range (RMNP to Ft. Collins).

With shortwave energy and increased westerly flow tracking overhead, there will be a threat of severe weather once again, with large hail (1+ diameter) presenting the main hazard. The greatest threat of large hail will be over the Northern Front Range around Ft. Collins, Loveland, and Greeley, while the threat will also extend well into the foothills and east side of Rocky Mountain National Park, and southward into Denver Metro.

Despite the uptick in moisture, westerly winds aloft will continue to transport smoke from Utah wildfires into Colorado. The smoke will come in waves, bringing periods of hazy skies and reduced air quality. This pattern largely looks to continue over the next 5 days.

Thu – This is shaping up to be a more active day statewide with monsoon moisture more established west of the Divide, while low-level easterly winds will also reinforce moisture east of the Divide. 

Thunderstorms are possible across nearly the entire state and in all mountainous regions. The highest threat of lightning is expected further north from the Elks to the Gores to the Park Range and across Northwest Colorado, while a secondary threat "peak" is also anticipated along the Southern Front Range, including Pikes Peak.

Another severe weather threat (large hail, damaging winds) is expected east of the Divide. Heavy rain is also possible with stronger storms, both west and east of the Divide.

Fri – Moisture levels will start to decrease, but there will still be enough to fuel scattered afternoon thunderstorm chances across most of the state. The Southern San Juans, Pikes Peak, and Palmer Divide look the most favored for now, but stay tuned as these details could always change. 

Three-day rain totals are projected to range from 0.25 to 0.75 inches across most of the high country, with isolated higher amounts possible due to localized heavy thunderstorm rain.

One exception is Summit County and the Mosquito/TenMile Range where thunderstorm coverage and rainfall is expected to be lighter compared to other areas (again, with the caveat that isolated higher amounts than this are still possible). 

Sat-Sun – A powerful low-pressure trough moving into the Northern Rockies will place Colorado under a strong westerly flow, which will scour out all of this moisture. The result will be a significant warming and drying trend both west and east of the Divide, along with strong winds.

UTAH

Wed – Wildfire smoke will continue to plague much of the state as numerous large and active fires are burning in both Southern Utah and Northern Utah.

Generally speaking, smoke will fill the valleys at night and in the morning before dispersing with daytime heating, but fires will also burn more intensely with increased smoke transport downwind during the afternoons and evenings. This will make it tricky to nail down clean-air "windows". 

While hot temperatures and gusty winds have led to extreme fire behavior recently, some monsoonal moisture will sneak into the area on Wednesday, which could be a good or a bad thing for ongoing fires.

Moisture levels will be high enough that stronger thunderstorms could produce locally heavy rain. But if ongoing fires only catch outflow winds from nearby thunderstorms rather than direct hits with heavy rain, that could exacerbate fire behavior and make things worse.

Our StormNet Model is favoring Northern Utah (SLC, Wasatch, Uintas) and Southeast Utah for afternoon thunderstorms in response to two separate shortwaves. Southwest Utah, including the Beaver/Eagle Point area, could still see thunderstorms even if the overall threat is lower compared to other areas.

While wildfires are the greatest concern, if you do head outdoors, be aware of the increased lightning risk. Also, Southern Utah canyons will be at risk of flash flooding with any nearby thunderstorms that occur.

Thu – This is shaping up to be an active thunderstorm day, with storms favoring Northern and Eastern Utah as the monsoon moisture plume gradually shifts eastward.

Storms will still be capable of producing locally heavy rain across most of the state, including flash flooding in the southern canyons, though Southwest Utah may see fewer/lighter thunderstorms as drier air starts to push in.

Fri-Sun – More good news/bad news from a fire perspective. A deep low pressure trough will push into the Interior West, resulting in a significant cool-down throughout Utah with well below average temperatures expected this weekend.

While the cooler air and higher humidity will be good for fires, strong winds are also expected to accompany this cooler airmass which is a downside for ongoing fires. 

Appreciable rain chances with this pattern will primarily be confined to northern portions of the state, from approximately SLC and Park City north to the Idaho border. Rain totals are projected to be on the lighter side overall, but we'll see how this looks as we get closer.

SOUTHWEST

Wed-Thu – Westerly winds aloft will keep most of the Utah fire smoke north of AZ and NM, though some northern areas could see a little bit sneak in from time to time, so it's still worth keeping an eye on our smoke maps. In addition, new fire starts are going to be possible this week as well.

Also, monsoon moisture has briefly become established across the area, which will result in scattered afternoon thunderstorms on both days. Storms will generally favor the higher elevations, but stronger storms could produce locally heavy rain.

Fri – Drier air begins to push into Arizona with minimal lightning potential expected, except along the eastern border. New Mexico will see lingering moisture and a more active thunderstorm day, especially across central and northern areas.

Sat-Sun – Dry and breezy conditions will prevail throughout the Southwest this weekend as a powerful trough pushes into the Northern and Central Rockies, which will scour out the monsoonal moisture.

A cooler airmass will sneak into Arizona over the weekend, bringing heat relief to some areas, while a much warmer airmass will hold over New Mexico, especially east of the Continental Divide.

CALIFORNIA/SIERRA

Wed-Thu – Warm/hot and dry conditions will prevail, with increasing winds on Thursday afternoon in advance of an approaching cold front.

Fri-Sun – Unseasonably cool air will descend into Northern California and into the Sierra as a strong cold front moves through. Temperatures around Tahoe and the Sierra will be well below average through the weekend, and gusty winds will also make it feel noticeably cool.

Scattered light showers are possible from time to time across NorCal, extending as far south as Tahoe (especially near the north shore), but overall rain amounts look to be on the light side. Lightning potential will be minimal.

PACIFIC NORTHWEST

Wed – A very warm airmass will remain in place, but a little bit of moisture will sneak in with an approaching shortwave to help destabilize the atmosphere. The result will be terrain-driven isolated to scattered thunderstorms across the Washington Cascades and BC Coast Range (up toward Whistler). 

StormNet is projecting storms to develop as early as noon-1pm, with the highest threat of lightning expected mid to late afternoon. Storms will generally produce only light/spotty rain with gusty outflow winds.

Thu – Dry conditions will prevail for most of the day, but cloud cover will be on the increase with overcast skies for most areas. As a powerful low pressure system approaches, rain showers will reach Vancouver Island by Thursday afternoon and possibly the Olympic Coast in WA by late in the day. Also, a few isolated thunderstorms couldn't be ruled out over Northeast WA.

Thu Night to Sun – A low pressure system will bring an extended stretch of cool and wet weather to the PNW, with temperatures dipping to well below average levels for the end of June.

Widespread rain is expected throughout WA, OR, and Coastal BC with the Cascades, coastal ranges, and interior mountain ranges projected to receive 1-2 inches of rain. The western lowland will also pick up 0.25 to 0.75 inches.

Friday and Saturday look like the two wettest days, with Sunday likely featuring more intermittent and terrain-driven showers with a drying trend for the lower elevations. 

Snow levels are also projected to dip as low as 5,500-6,500 feet in the Cascades on Friday night and Saturday as the cooler airmass settles in.

NORTHERN ROCKIES

Wed – A shortwave trough will move into the Interior West along with a gradual increase in moisture, resulting in isolated to scattered thunderstorms across Wyoming, Eastern Idaho, and the Bitterroots along the ID/MT border. Storms west of the Divide will produce light/spotty rain and gusty winds, while storms east of the Divide could produce locally heavy downpours along with a chance of larger hail. 

Thu – A more active day is expected throughout the region as monsoonal moisture increases across Wyoming, Eastern Idaho, and Southern Montana, while Pacific moisture reaches Western and Northern Montana.

The result will be more numerous thunderstorms across these regions, with stronger storms capable of producing locally heavy downpours.

Fri-Sun – A cool and wet pattern will take hold as a slow-moving low pressure system moves through the Northern Rockies. Widespread significant rainfall is likely for most of the region, with a good chance of thunderstorms on Friday-Saturday ahead of a major cool-down from later Saturday into Sunday. 

Our PEAKS Model is projecting rain totals of 1-2 inches across Northern/Central Idaho into Western Montana and Northwest Wyoming, while even the Snake River Plain and lower basins see some much-needed moisture.

As colder air arrives, snow levels are projected to drop to 8,000-9,000 feet on Saturday night/Sunday, meaning that many of the higher peaks and passes will see accumulating snow this weekend. Just a reminder that it can snow in this region at any time of year!

BC INTERIOR & CANADIAN ROCKIES

Wed – A quiet start to the day will give way to isolated afternoon thunderstorms, with generally light and spotty rain expected. 

Thu – Another warm day overall, but moisture will increase a bit from the west, resulting in higher coverage of afternoon thunderstorms. Also, there is some threat of storms developing over the higher terrain prior to noon, so heads up if you have hiking/climbing plans.

Fri – A cold front will arrive, leading to a cool-down throughout the region with scattered showers also developing. The threat of lightning will be much lower in this cooler airmass. Showers are possible in all areas, but activity looks to favor the West Kootenay Boundary region (Nelson, Rossland) to the Okanagan region (Kelowna).

Sat-Sun – Off-and-on showers can be expected both days with temperatures remaining on the chilly side. Despite the cool-down, the core of the "cold" airmass will be further south, so snow levels will stay high, generally above 2700 meters (9,000 ft.)

There is a chance of heavier rain developing over the Canadian Rockies on Sunday afternoon/Sunday night as a backdoor cold front sneaks in from the northeast with increasing upslope flow.

Our PEAKS Model is picking up on this signal, with heavier 5-day precipitation totals projected in Alberta compared to most of BC, though the higher ranges of Southern Interior BC also look to do quite well in this pattern in terms of moisture. 

Monday (June 29) to Friday (July 3):

Next week, a trough-dominant pattern is expected to persist west of the Continental Divide, resulting in below-average temperatures as we transition from June into July. Areas east of the Divide are expected to se near to above average temperatures.

Pacific disturbances tracking across the Northwest will bring shower chances to the Cascades and thunderstorm chances to the Northern Rockies (WA, MT, BC, AB favored) with drier conditions expected further south.

This cooler airmass and progressive trough pattern will also keep the monsoon suppressed further south, though southerly flow over New Mexico should bring enough moisture back in later next week for a chance of thunderstorms. There are also some signs of this moisture reaching Colorado around the 4th, but confidence is low for now.

Thanks so much for reading! Next update on Friday.

Alan Smith