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:

An active monsoonal flow will continue across the Southwest and the Rockies over the next 5 days with above-average moisture levels. Temperatures will also trend to below-average levels across most of this region thanks to the uptick in moisture.

Following a mid-week round of showers and thunderstorms, the Pacific Northwest will head into a hot and dry pattern as a ridge of high pressure builds along the west coast of British Columbia. 

COLORADO

Fri – Thunderstorm coverage will favor southern and western portions of the state, with the first storms developing as early as 11am to noon. StormNet has the highest peak lightning probabilities across the Sangres. Storms will be slow-moving and erratic, generally moving from E to W or NE to SW, and stronger storms will produce heavy rain.

Smoke will continue to impact portions of the San Juans, Sangres, and Wet Mountains in response to active wildfires, while Steamboat and Rabbit Ears Pass have seen a decrease in smoke.

Over time, as the monsoon pattern becomes more consistent, the hope is that wildfire activity will decrease across Southern Colorado due to higher humidity, cooler temperatures, and rain.

Sat – Thunderstorm coverage will continue to favor areas along and west of the Continental Divide as well as the Sangres, with the highest lightning probabilities over the San Juans and Grand Mesa. Storm motions will be slow-moving and erratic, but generally will track from east to west, with stronger storms producing heavy rain.

Sun – Thunderstorm coverage will increase a bit across Northern Colorado, with the highest lightning probabilities stretching from the San Juans to the Elks to the Gores and into the Park Range around Steamboat. Storm motions will be slow and erratic, and heavy rain will remain a threat with any stronger storms.

There is also a better chance of storms developing over the Northern Front Range Mountains, foothills, and I-25 corridor, especially north of Denver. Low-level moisture will be somewhat limited on the plains, so any storms that develop in the urban corridor may only produce spotty rainfall. 

Relatively drier air pushing into Southeast Colorado will result in reduced thunderstorm chances and coverage across the Sangres compared to prior days.

Mon – A similar setup is expected compared to Sunday, with storms favoring Southwest, Central, and Northern Colorado. Storm coverage and chances should further increase across the Front Range as well.

Tue – A significant uptick in moisture is projected east of the Continental Divide, and this should result in an active thunderstorm day throughout the state with stronger storms capable of producing heavy rain. Denver and the I-25 corridor will also have a better shot at seeing more widespread shower/thunderstorm coverage, with heavy rain possible.

Our PEAKS Model total precipitation forecast map through Tuesday continues to favor the San Juans for the heaviest rainfall (1-3 inches across the higher elevations), but you'll notice an uptick in projected rainfall across the rest of the state as well compared to earlier posts this week.

UTAH

Fri – Deep monsoonal moisture will remain in place, with scattered showers and thunderstorms developing across most of the state during the afternoon hours. Storm motions will be slow and erratic, and this will also increase the threat of heavy rain and localized flash flooding, especially in the canyon regions and near fire burn scars.

Sat-Mon – A rinse-and-repeat pattern is expected, with daily rounds of afternoon thunderstorms expected. Coverage will be highest across Southern Utah, and this is where the heavy rain/flash flooding threat will also be greatest. However, Northern Utah will also see storms each day along with locally heavy rain.

Storm motions will be slow and erratic on Saturday and Sunday, but may pick up a little bit of speed and track from SE to NW on Monday.

Flash flooding will remain a significant concern each day in slot canyons, dry washes, etc., across Southern Utah.

Tue – An even stronger surge of monsoonal moisture is projected to arrive from the south, which could potentially lead to more widespread coverage of showers and thunderstorms across both Southern Utah and Northern Utah.

Our PEAKS Model total precipitation forecast map through Tuesday favors significant high-elevation rainfall (1-3+ inches in some areas) across much of Utah, while many lower-elevation areas should pick up meaningful rain as well.

SOUTHWEST

Fri – An active day is expected across Arizona thanks to deep monsoonal moisture along with multiple small-scale disturbances. This will result in widespread showers and thunderstorms across much of the state on Friday, including both the high elevations and low elevations. Storm motions will be slow-moving and erratic, and flash flooding will be a concern as a result.

Lightning probabilities are actually higher across New Mexico, where moisture levels won't be quite as significant, but where more sunshine and better heating/instability can be expected. Locally heavy rain is possible in NM as well.

Sat-Tue – An active monsoonal flow will remain in place, resulting in daily rounds of afternoon thunderstorms with stronger storms producing heavy rain. Flash flood risk will remain elevated as a result.

Total rainfall (projections from our PEAKS Model) will be heavier and more widespread across Arizona from Friday through Tuesday, but New Mexico will see locally heavy rain in this pattern as well, especially across its higher elevations and western portions of the state.

CALIFORNIA/SIERRA

Fri-Sat – A mostly dry pattern is expected with temperatures close to seasonal averages, though a low threat for isolated thunderstorms will exist over the Eastern Sierra on Saturday afternoon.

Sun-Tue – The western edge of monsoonal moisture will push back into the Sierra, resulting in daily chances for isolated afternoon thunderstorms, mainly over the High Sierra and Eastern Sierra. Weaker storms will produce brief/light rain, but stronger storms could produce locally heavy rain across the higher elevations.

PACIFIC NORTHWEST

Fri-Tue – Conditions will begin to warm up and dry out in the wake of the mid-week system, aside from possibly some lingering light showers over the Olympic Peninsula and Southwest BC on Friday morning.

Temperatures will be progressively hotter each day as a ridge of high pressure strengthens across the region.

The biggest thing to keep an eye out for is possible wildfire smoke. There are currently large and active wildfires burning in the Southern Oregon Cascades and Eastern BC Coast Range.

It also appears that there were a number of fire starts due to lightning across Eastern Oregon and Eastern Washington recently, and it remains to be seen what happens with these fires and whether or not we see any large-scale smoke impacts emerge.

NORTHERN ROCKIES

Fri – This is shaping up to be an active day with scattered to widespread showers and thunderstorms, with some subtle shortwave energy moving through while deep monsoonal moisture is also in place. Stronger storms will produce heavy rain, and localized flash flooding also cannot be ruled out.

Sat – Another active day is expected, though the highest lightning probabilities are projected from Central Idaho (White Clouds) toward the Bitterroots and into Southwest Montana, including the Madison, Gallatin, Bridger, and Beartooth Ranges. A decrease in thunderstorm coverage is also expected across NW Montana, including Glacier.

Sun – A decrease in thunderstorm coverage is expected as monsoonal moisture begins to retreat southward. However, we will still hang onto a good chance of scattered thunderstorms along the Montana/Wyoming border and across the Snowy Range in Southern Wyoming.

Mon – The Northern Rockies will be "in between" monsoon moisture surges, with storm chances on Monday primarily confined to the southernmost portions of Idaho and Wyoming, while Montana will see a break.

Tue – Shower and thunderstorm chances will gradually increase from south to north, with activity possibly returning to the Winds, Tetons, Yellowstone, and Sawtooths depending on the timing of this next moisture surge.

Our PEAKS Model total rainfall forecast through Tuesday favors Wyoming and Southern Montana for the heaviest amounts, but isolated higher totals (than what the model shows) are possible anywhere due to the hit-or-miss nature of thunderstorms.

BC INTERIOR & CANADIAN ROCKIES

Fri – A Pacific low pressure system will move into BC and travel from south to north, with moisture and instability reaching the Interior. This will result in an active thunderstorm day with numerous thunderstorms expected across the interior and into the Canadian Rockies. Significant lightning activity is possible.

This setup will feature a mix of wet and dry thunderstorms, meaning that some storms will produce locally heavy rain while others will produce only light rain and gusty outflow winds. Unfortunately, the dry thunderstorms are the most concerning, as these could potentially trigger wildfires.

Sat – Conditions will dry out across most of the region, except around Jasper and Mt. Robson, where wetting rain showers can be expected in response to the low pressure system moving north and east.

Sun – A weak disturbance tracking across the area will result in isolated light showers and thunderstorms with only light and spotty rainfall for most. East of the Canadian Rockies toward Calgary, stronger thunderstorms and heavier downpours are possible.

Mon-Tue – Isolated afternoon showers and thunderstorms are possible both days, with light and spotty rain, mainly over the Canadian Rockies and adjacent foothills/plains, with lower chances across the BC Interior.

Wednesday (July 22) to Sunday (July 26):

A strong monsoonal flow will remain in place, but the focus of the deepest moisture looks to be from Northern Arizona into the Central and Eastern Rockies as well as the adjacent plains. The Sierra could also see some action on the western fringe of the monsoon. Central and Southern New Mexico may see more limited moisture and thunderstorm activity compared to normal. 

Further north, a ridge of high pressure centered over Western Canada will result in hotter and drier conditions across the Pacific Northwest, especially across the interior areas. 

Thanks so much for reading, and have a great weekend! Next update on Monday (July 20).

Alan Smith