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 monsoonal flow will develop across the West this week as the high pressure ridge responsible for recent record heat will slowly migrate eastward, with south to southwest flow around the western periphery of the ridge opening the door for subtropical moisture to arrive, favoring areas west of the Continental Divide.

A Pacific trough will also impact the Pacific Northwest late this week as it swings from south to north along the West Coast and Cascades, bringing some moisture to this region. 

COLORADO

The main surge of monsoonal moisture will be located west of Colorado this week, with a gradual uptick in moisture expected across the state from west to east as the week progresses, with potential for more significant moisture across a larger portion of the state next week.

Mon – Scattered early afternoon thunderstorms will develop, mainly along and west of the Divide, and also around Pikes Peak and the Sangres. 

Storm motions will be from east to west (opposite of usual) in the San Juans and Southern Colorado around a secondary high pressure area over NW Colorado, and from north to south along the Front Range Mountains.

Chances for heavy rain will mainly be confined to the southern side of the San Juans, where better low-level moisture exists. Elsewhere, storms will produce light rain and gusty outflow winds.

Wildfire smoke will largely be confined to areas near the Gold Mountain Fire (Ouray), Aspen Acres Fire (Wet Mountains), and Fishhook Fire (Rabbit Ears/Steamboat).

Tue – Similar conditions are expected with thunderstorms favoring the San Juans and West Elks, with more isolated to scattered activity for remaining areas near/west of the Divide and along/south of I-70. Thunderstorm potential will be reduced north of I-70.

Storm motions will be from E to W or NE to SW, which once again is the opposite of the usual flow pattern.

Heavy rain potential will once again be confined to the San Juans, across the higher elevations and southern side of the range.

Wed – A very similar setup to Tuesday with storm coverage, intensity, and heavy rain potential favoring the San Juans and Southern Sangres, while storm motions will be from NE to SW. More isolated to scattered activity and lighter rainfall are expected elsewhere across Colorado, mainly along and west of the Divide and also in the Northern Sangres.

Thu-Fri – Moisture will gradually increase across all areas west of the Divide, and the potential for heavy rain producing thunderstorms will also increase, especially west of the Divide and south of I-70 (San Juans, Elks, Sawatch, Sangres).

The heaviest rain amounts over the next 5 days are expected across the San Juans, while little to no rain is expected along the eastern foothills and 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

Mon – Another very hot day is in store, but it won't be quite as hot as on Sunday, when Salt Lake City hit a scorching 109º, breaking its all-time high temperature record.

Monsoonal moisture is increasing across Southwest Utah, and this will be the focus of scattered thunderstorm activity in the afternoon. Storms will be capable of producing locally heavy rain, so slot canyons and dry washes in Southwest Utah, including Zion, will have some risk of flash flooding. Storm motions will generally be from south to north. 

Scattered dry thunderstorms across Eastern Utah, and as far north as the Uintas and Southern Wasatch. Storms in these areas will produce light rain and strong winds.

Southerly winds aloft will also transport smoke from the Stookey Fire (south/southwest of Toole) into portions of the Wasatch Front on Monday afternoon and evening, with downtown SLC right on the eastern fringe. Heavier smoke transport is also possible into Ogden and Logan, while smoke will also settle into the lower elevations east of the fire overnight, including Provo.

Tue – An uptick in thunderstorm coverage is expected statewide, though moisture will remain greatest across Southwest Utah (Zion, Bryce included), where storms will have a better chance of producing heavy rain. Some risk of flash flooding can also be expected in this area. Storm motions will be from south to north.

Wed-Fri – A significant uptick in monsoonal moisture is expected statewide, which will lead to more widespread thunderstorm coverage. An increase in flash flooding potential is also expected throughout the canyon regions of Southern Utah.

While storm coverage will be greatest across Southern Utah, there will still be daily rounds of afternoon storms in Northern Utah as well, with stronger storms capable of producing heavy rain.

The heaviest rain amounts over the next 5 days are expected across the higher terrain of Southern Utah and in the Uintas in Northeast Utah, but keep in mind that pockets of heavier rain amounts (than what our model shows) are possible anywhere due to the hit-or-miss nature of thunderstorms.

SOUTHWEST

Mon – Thunderstorm coverage will be greatest along the Mogollon Rim and around Flagstaff, while pockets of higher coverage can also be expected across the higher terrain of Northern and Southeast Arizona. Storm coverage will be more spotty across New Mexico. 

Moisture levels have increased significantly in recent days, so storms will have the potential to produce heavy rain, especially in Arizona. Storm motions will be from east to west, due to clockwise (anticyclonic) flow to the south of a high pressure center.

Tue – Storm coverage on Tuesday looks a bit more favorable across Northern Arizona and Northern New Mexico, though any higher-elevation terrain (north and south) could see storms. There is also a chance of storms across the higher terrain around Vegas.

Storms will once again be capable of producing locally heavy rain with deeper moisture in place. Storm motions will be NE to SW across New Mexico, E to W across most of Arizona, and S to N across Western Arizona and Southern Nevada.

Wed-Fri – An uptick in thunderstorm coverage is expected throughout the Southwest, and the potential for heavy rainfall and localized flash flooding will also increase.

The heaviest rain amounts over the next 5 days are expected across the higher terrain of Arizona, but keep in mind that pockets of heavier rain amounts (than what our model shows) are possible anywhere due to the hit-or-miss nature of thunderstorms.

SIERRA/CALIFORNIA

Mon – Monsoonal moisture remains in place, which will favor increased cloud cover and scattered showers and thunderstorms across the Sierra. While Tahoe will likely see some showers, the highest threat of lightning will be along the Sierra Crest south of Tahoe and across the Eastern Sierra.

Stronger storms will be capable of producing heavy rain in this region. Storm motions will also be from south to north.

Across the SoCal Mountains, more isolated shower/thunderstorm coverage is expected compared to yesterday, with the highest threat of lightning expected in the mountains east of San Diego. 

Tue – Another active day is expected across the Sierra, with thunderstorm coverage likely favoring both the High Sierra and the area near and north of Tahoe. Moisture levels will remain high, so stronger storms will be capable of producing locally heavy rain. Storm motions will be from SSW to NNE.

A threat of evening and overnight showers and thunderstorms will also emerge over NorCal around Shasta and Lassen. Moisture levels will not be as high in this region, so most storms will only produce light rain, though some localized downpours still cannot be ruled out. 

Wed-Fri – Drier air will arrive from the west, resulting in increased sunshine and a reduction in thunderstorm chances. Isolated afternoon thunderstorm chances will primarily be confined to the Eastern Sierra and the desert ranges of SoCal.

PACIFIC NORTHWEST

Mon – Warm to hot and dry conditions will prevail across most of the region, along with sunny skies, aside from some high-level cloud cover over Eastern Oregon.

Tue – The outer fringe of a monsoon moisture surge will reach Southern and Eastern Oregon. Scattered showers can be expected across Eastern Oregon during the morning hours, while isolated afternoon to evening thunderstorms will develop over Southern Oregon, including a slight chance around Bend.

These will mainly be dry thunderstorms, producing light and spotty rain along with gusty outflow winds.

Conditions will stay dry and sunny across Washington and Southwest BC. 

Wed to Wed Night – A slow-moving low pressure trough will approach from the west, with a southerly flow ahead of the low transporting a moist and unstable airmass into the area. 

This pattern will favor afternoon thunderstorm development across Oregon initially, with thunderstorm chances spreading into Washington on Wednesday night. This will include a threat of thunderstorms across the Cascades, Puget Sound Lowlands, and West Coast.

Thu – This is shaping up to be an active day across the Washington Cascades, West Coast, Olympic Peninsula, and Southwest BC, with more widespread showers and thunderstorms, including the potential for locally heavy rain. A drying trend is expected across most of Oregon, though showers will remain possible across northwest portions of the state.

Across Eastern Washington, the threat of thunderstorms will increase, but moisture levels will be lower, so this may be more of a dry thunderstorm setup with storms producing light rain and gusty winds.

Fri – A drying trend is expected for most of the region, but lingering moisture will result in additional shower chances across the Northern WA Cascades and Southwest BC.

NORTHERN ROCKIES

Mon – Hot and dry conditions will prevail across most of the region, with record highs possible once again (on Sunday, a number of all-time records were broken). Isolated late afternoon and evening thunderstorms are possible across the Bitterroots, Absarokas, Beartooths, and Bozeman area, with any storms producing light rain and gusty winds.

Tue – A shortwave will move through Western/Central Idaho and Western Montana during the morning, with monsoonal moisture also arriving. This will result in scattered terrain-driven showers mainly during the morning hours and afternoon hours with limited lightning potential.

Further east, isolated thunderstorms are possible around the Tetons and Yellowstone, while the eastern side of the Divide in Southern Montana will see a better chance of storms as some low-level moisture arrives from the east.

Wed-Fri – Monsoonal moisture will increase across the region, leading to increased coverage in thunderstorms. Heavy rain will also be possible with storms across Eastern Idaho, Western Wyoming, and Southwest Montana.

Northwest Montana, including Glacier, will be on the northern fringe of the moisture with just some isolated shower/thunderstorm activity expected, along with light and spotty rain.

BC INTERIOR & CANADIAN ROCKIES

Mon-Tue – Warm and dry conditions will prevail, with any afternoon thunderstorm chances confined to areas east of the Rockies in Alberta.

Wed-Fri – A more active pattern is expected as a slow-moving low pressure system approaches with increasing moisture and instability.

Thunderstorm chances will ramp up significantly on Wednesday afternoon and evening throughout the region.

Thunderstorm coverage also looks significant on Thursday and Friday, and this includes a threat of overnight lightning on Thursday night/Friday morning as the low pressure center tracks across the area.

Rainfall will be hit or miss in this pattern depending on the track and intensity of individual thunderstorms, but locally heavy rain will be possible with stronger storms.

Saturday (July 18) to Wednesday (July 22):

A strong monsoonal flow is likely to continue this weekend and next week, with a significant uptick in moisture expected across Colorado, including areas east of the Divide. Areas near the green arrows will have the potential for heavy rain-producing thunderstorms. 

A ridge of high pressure will build over the Pacific Northwest, with increasing potential for a heatwave with well above average temperatures expected. Some models are hinting at a possible disturbance with significant moisture along the eastern side of the ridge across Eastern BC and Western Alberta, but confidence is low.

Thanks so much for reading! Next update on Wednesday (July 15).

Alan Smith