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 strong subtropical ridge of high pressure will build over the Central and Northern Rockies this weekend, resulting in record-challenging heat across parts of this region along with dry conditions.

As the center of high pressure migrates into the Northern Plains by Monday, the ridge strength (measured by 500-millibar heights) will be nearly 3 standard deviations above average, which in July is indicative of a significant heat wave.

As the high pressure ridge strengthens this weekend, a stronger monsoonal flow pattern will also develop as subtropical moisture becomes entrained into the flow aloft around the southern and western periphery of this ridge.

This increase in moisture will be most notable across Arizona, Southwest Utah, Nevada, and California from Sunday through Tuesday, and will lead to an uptick in thunderstorm activity and meaningful rain chances.

COLORADO

Fri – Moisture is on the decrease compared to recent days, but enough will hang around for another round of afternoon thunderstorms.

West of the Divide, development is possible prior to noon over the Eastern/Southern San Juans, but overall activity looks to be more isolated through the afternoon hours, and most storms will only produce light/spotty rain. 

Across the eastern mountains, thunderstorm coverage will be a bit higher compared to West of the Divide, and this includes the Front Range and Sangres. Most storms will produce light rain, but stronger storms could produce heavier downpours. Stronger storms could also produce large hail near and east of Pueblo. 

Wildfire smoke has decreased in most areas in recent days. On Friday, Northern Colorado looks to be in good shape again for the most part, while pockets of heavier smoke can be expected closer to large fires burning in Southern Colorado.

Sat – Isolated afternoon thunderstorm chances will primarily be confined to the I-25 corridor, Southern Front Range (south of I-70), Pikes Peak, Sangres, and Eastern San Juans. Any storms that develop will produce only light rain and gusty outflow winds.

Sun – Limited monsoonal moisture will sneak into Southwest Colorado, resulting in scattered thunderstorms over the San Juans, with more isolated activity extending into the Elks, Sawatch, and Sangres. This will mainly be a dry thunderstorm threat due to a lack of low-level moisture, with storms producing light/spotty rain and strong outflow winds.

Mon-Tue – Western Colorado will be just on the fringe of a deeper monsoonal moisture surge setting up across Arizona, Utah, and Nevada. Still, an uptick in thunderstorm coverage is likely west of the Divide, especially in the San Juans, where locally heavy downpours will be possible with stronger storms. Minimal thunderstorm activity is expected east of the Divide. 

UTAH

Fri-Sat – Hot and dry conditions will prevail across most of the state aside from some isolated thunderstorm chances over the Uintas (more so on Friday).

Sun – Thunderstorm chances will develop across Southern Utah as the leading edge of monsoonal moisture arrives, with activity expected to favor the Southwest (Zion and Bryce region). Low-level moisture will be limited, so this will likely be a dry thunderstorm setup with storms producing light/spotty rain and gusty winds.

Mon-Tue – Thunderstorm chances will increase statewide as deeper monsoonal moisture arrives, with the southwest corner of the state remaining the most favored. On Monday, there will be enough moisture for a localized heavy rain and canyon flash flooding threat in Southern Utah (especially in the southwest).

On Tuesday, moisture levels will be even higher with an increased threat of heavy rain across Southern Utah, while the higher terrain in Northern Utah could also see locally heavy rain with stronger thunderstorms.

SOUTHWEST

Fri – Thunderstorm activity will favor Southern New Mexico and Southeast Arizona, and there is enough moisture in place for stronger storms to produce locally heavy rain. Northern areas will be drier, though some isolated activity is possible along the eastern slopes of the Sangres in NM.

Sat – An active day of thunderstorms is expected across Southern, Central, and Northeast New Mexico, while moisture will also expand across Southern Arizona with more widespread thunderstorm coverage. Storms will be capable of producing locally heavy rain across both of these regions. 

Sun-Tue – The first significant monsoon surge of the season will take hold across Arizona, with a significant uptick in thunderstorm activity and (locally) heavy rainfall potential expected statewide.

New Mexico will see less thunderstorm coverage compared to Arizona, but scattered thunderstorms can still be expected each day, with locally heavy downpours possible.  

CALIFORNIA/SIERRA

Fri-Sat – Hot and dry conditions can be expected with sunny skies on Friday giving way to some high-level cloud cover on Saturday. 

Sun – Isolated thunderstorm activity is possible over the High Sierra and SoCal Mountains as the leading edge of monsoonal moisture arrives. Storms will generally produce light rainfall, though some localized downpours cannot be ruled out over the higher terrain.

Mon-Tue – Deeper moisture will arrive, resulting in higher coverage of afternoon thunderstorms across the Sierra and SoCal Mountains, along with a better chance of heavy downpours occurring with stronger storms.

PACIFIC NORTHWEST

Fri-Sun – A cold front will move through, bringing cooler temperatures, especially west of the Cascade Crest, where temperatures will drop to below average levels.

Off-and-on light rain showers can be expected across the Washington Cascades, Olympics, and Southwest BC, with heavier rain expected over the North Shore Mountains up toward Whistler (0.25-0.50") and even higher amounts expected north of Whistler.

The Inland Northwest will see drier conditions through the weekend, and smoky conditions can also be expected across Northeast Oregon (including the Wallowas) due to a recent uptick in wildfires across the area.

Mon-Tue – Hotter and drier conditions can be expected for most of the region as high pressure nudges in from the south, but some high-level cloud cover could move overhead at times. 

Monsoonal moisture will also reach Southern and Eastern Oregon, where afternoon thunderstorms will be possible both days. 

NORTHERN ROCKIES

Fri-Sun – Hot and dry conditions will prevail as high pressure builds over the area, with some areas expected to challenge all-time record high temperatures. Only some spotty isolated thunderstorm chances are expected east of the Divide, with most areas staying dry. 

Mon – Another hot day is expected, but high-level cloud cover is also expected across Western Idaho and Montana in response to an approaching monsoonal moisture surge.

Tue – The heat wave will begin to abate as monsoonal moisture pushes into the region, which will also result in an increasing potential for thunderstorms. The latest model trends are also hinting at a swath of more widespread rain showers (0.10 to 0.25" projections) tracking across the Central Idaho Mountains into Western Montana. 

BC INTERIOR & CANADIAN ROCKIES

Fri – Mostly dry conditions are expected, other than some isolated light showers over the interior ranges of BC. Smoke from Fraser Valley wildfires will be worst across the Okanagan region, Monashees, and Selkirks (near the Hwy-1 corridor), with the latest models indicating lesser amounts of smoke reaching further east into the Canadian Rockies.

Sat – A better chance of showers and thunderstorms can be expected around Revelstoke, Rogers Pass and northward over the Icefields Parkway and Mt. Robson, including some locally heavy downpours, with lower chances of storms further south around Banff. Areas further south toward the U.S. border will also see drier conditions.

Sun-Tue – Drier conditions are expected overall, though some isolated afternoon shower/thunderstorm activity cannot be ruled out. 

Wednesday (July 15) to Sunday (July 19):

An active monsoon will be in place during the second half of next week, with moisture favoring Arizona, Utah, Nevada, Wyoming, and portions of Idaho and Montana, while the higher terrain in California will get in on the action at times as well. 

In Colorado, areas west of the Divide also will see a notable uptick in moisture and thunderstorm chances in this pattern, while moisture looks more limited east of the Divide in Colorado and southward into New Mexico.

Outside of the monsoon region, some models are indicating a disturbance moving across the Pacific Northwest, with rain showers possible in Washington and BC, but confidence is low. Otherwise, the PNW is likely looking at a significant warming trend with well-above-average temperatures expected.

Thanks so much for reading! Next update on Monday (July 13).

Alan Sith