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

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

COLORADO

Mon – Areas east of the Divide will be the focal point of active weather on Monday afternoon, in response to a cold front sliding in from the northeast on Monday morning.

Low-level east/southeast winds will transport moisture from the Gulf toward the Front Range, while wind shear will increase in response to an upper-level disturbance arriving from the southwest.

Isolated thunderstorms will initially develop over the Front Range Mtns, Mosquito/Ten Mile, Sawatch, Gore, and Elks by early afternoon, with more numerous storms expected east of the Divide in the Front Range foothills.

More intense thunderstorms are possible across the I-25 corridor and adjacent plains by mid-afternoon, with storms tracking from SW to NE.

For the city of Denver, our StormNet Model has some lightning risk as early as 1pm, but with the highest threat of lightning between about 2:30 p.m. and 7 p.m.

There is also an elevated threat of large hail (1+ inch diameter) across the Denver Metro area and I-25 corridor. Our StormNet Model indicates the highest threat being from roughly downtown Denver northward to near Ft. Collins, and across the northeast plains.

If you can, park your car under a sheltered area this afternoon if you live in these green or blue shaded areas, just in case. 

Tue – Last Friday, I mentioned a potentially wetter system moving in on Tuesday. However, since that time, models have shifted further north with the system and widespread meaningful rains are no longer expected.

Colorado will still see an influence from a low pressure trough moving across the Interior West, but the main impacts will be strong winds, high fire danger, and isolated to scattered thunderstorms that produce brief rain.

StormNet is actually picking up on an early morning lightning risk over the San Juans on Tuesday morning, so heads up if you have early outdoor plans.

The thunderstorm risk will then extend eastward from mid/late morning through early/mid afternoon and will primarily be confined to areas south of I-70, with the highest threat favoring the Eastern San Juans and Sangres.

On Tuesday evening, a cold front will reach Northwest Colorado with isolated thunderstorms possible around Steamboat and the Park Range after 6pm, and a threat then extending into the Northern Front Range, including RMNP overnight.

Wed-Fri – A significant drying trend is expected in the wake of Tuesday's trough, with little to no chance of thunderstorms or rain from Wednesday to Friday. Winds will remain gusty each day, which will keep fire danger elevated across most of the state.

Temperatures will be above average on Wednesday, but then a strong cold front will arrive on Wednesday night, leading to a much cooler day with below-average temperatures on Thursday. Temperatures will quickly heat back up on Friday.

UTAH

Gusty winds are going to be common throughout the week statewide in response to an active jet stream across the Western U.S., and this will keep fire danger elevated throughout the week. Moisture opportunities are going to be limited as models have backed off significantly on rainfall with Tuesday's system. 

Still, Tuesday will be unsettled across Northern Utah as a cold front moves through with enough moisture for scattered showers to develop during the daytime hours, mainly from SLC and Park City northward.

Most areas around SLC will see less than a tenth of an inch of rain, while Logan and the Bear River Range will see higher amounts of a tenth to a quarter of an inch.

Thunderstorms are also possible across Northern Utah from midday into the afternoon hours, though the risk is fairly modest according to our StormNet Model, ranging from 10-25% in most areas. 

Tuesday's cold front will bring some nice heat relief to Northern Utah that will last from Tuesday to Thursday. Southern Utah will be less impacted and will stay hot for most of the week, except for Thursday, when a stronger cold front will reach the south with one day of more noticeable heat relief.

SOUTHWEST

Hot, dry, and breezy conditions will prevail across Arizona throughout the week, resulting in consistent high fire danger. Per usual, temperatures will be more comfortable in higher-elevation areas like Flagstaff, but fire danger will still be elevated in this pattern.

New Mexico will see varying levels of thunderstorm chances from Monday to Thursday with storms generally producing light and spotty rainfall. As a result, fire danger will be on the increase here as well due to warm/hot temps, gusty winds, and the potential for dry thunderstorms.

Mon – Isolated thunderstorm chances will remain confined south of I-40 for much of the day, before expanding northward into Santa Fe and Taos late in the day.

Tue – This will be a more active day as a trough moves across the region, with scattered thunderstorms possible at all hours of the day, including the morning. Still, coverage will be greatest early to mid-afternoon when there is better daytime heating.

Wed-Thu – Conditions across NM will be hotter and drier overall with low-grade thunderstorm chances confined to the southeast corner of the state.

Fri – A surge of Gulf moisture will arrive, resulting in an uptick in thunderstorm chances across most of New Mexico, with perhaps some isolated activity extending into the higher terrain of Arizona.

Storms in NM will have a better chance of producing heavier downpours and meaningful rain, especially across the southern half of the state. If Arizona sees in thunderstorms, they will likely produce little rain.

CALIFORNIA/SIERRA

Mon – A trough moving across the PNW will bring cooler temps and rain showers to NorCal during the day on Monday, along with gusty winds.

Rain will be heaviest along the northern coast and adjacent hills around Crescent City with totals ranging from 1-2 inches, while Eureka to Ft. Bragg will see 0.25 to 0.75 inches.

Inland, rainfall will be lighter and more spotty with the west side of Tahoe only picking up around a trace to a tenth of an inch. However, it will be a chilly day along the lakeshore and up in the mountains especially when factoring in the gusty winds. 

Tue-Fri – The rest of the week will feature a gradual warming trend with increased sunshine and overall nice conditions for outdoor recreation. Winds will become gusty each afternoon with an active jet stream in place across the Western U.S. 

PACIFIC NORTHWEST

Mon-Wed – A low pressure system will bring widespread rain and chilly temps region-wide from Monday afternoon to Tuesday evening, followed by lighter and more terrain-driven showers on Wednesday.

Areas along the West Coast from the Olympic Peninsula southward to the OR/CA border will see 1-2 inches of rain, with locally higher totals in the Olympic Mountains. 

Areas along the Cascade Crest into the BC Coast Range are also looking at 1-2 inches of rain, while the western foothills of the WA Cascades will see heavier totals of 1.5-4 inches. 

Elsewhere, the Puget Sound lowlands, including Seattle, will pick up 0.75 to 1.5 inches of rain, while the Willamette Valley, including Portland, will see 0.25 to 0.75 inches. Vancouver, BC is looking at about a half-inch to one inch (12-25 mm).

Across the Inland Northwest, the mountains of NE Washington and Northern Idaho will see pockets of 1-1.5 inch totals, while the lower elevations while the lower elevations will generally see a quarter inch to a half-inch.

Snow levels will range from 6,000 to 7,000 feet on Monday, but will come down to 5,000 to 6,000 feet on Tuesday and Wednesday as temperatures drop.

Overall, the first half of the week will be very wet and chilly across the PNW, and this will include snow for the higher elevations of the Cascades and BC Coast Range. 

Thu-Fri – High pressure will begin to build late this week, resulting in dry and sunny conditions along with warmer temperatures.

NORTHERN ROCKIES

Mon – A break in the pattern is expected during the day along with warmer temperatures, so this will be a good weather window before showers begin from west to east on Monday night.

Tue – A low pressure system will move across the area along with a strong cold front (by June standards). More numerous rain showers can be expected along with isolated to scattered afternoon thunderstorms. Lightning chances will mainly be confined to Southern Montana and Northern/Western Wyoming. Snow levels will range from 8,000 to 10,000 feet.

Wed – With a colder airmass in place, a secondary wave of lighter rain and snow showers will move through Northern Idaho, Western Montana, and NW Wyoming.

Snow levels will be lower with this round, ranging from 7,000 to 8,000 feet (quite low for this time of year), but most areas will see only light amounts. The best chance of significant snowfall (more than a few inches) is over the Beartooths, and to a lesser extent, the Bighorns and Winds. 

Overall, both Tuesday and Wednesday are shaping up to be cold and wet days across the Northern Rockies, even if this system isn't as wet as the one from 7-10 days ago.

Pockets of 1+ inch precipitation totals can be expected across Northern Idaho, as well as the northern ranges in Montana (Glacier, Flathead, Mission, etc.) and around Greater Yellowstone.

Thu-Fri – Warmer and drier conditions can be expected for most areas as a ridge of high pressure builds in from the West, but winds will remain gusty each afternoon as the jet stream lingers overhead.

The one exception to the drying trend is Glacier NP and the eastern ranges of Montana, where additional showers and thunderstorms are possible, especially on Friday, as disturbances sneak in.

BC INTERIOR & CANADIAN ROCKIES

Mon – A break in the pattern is expected with dry conditions and warmer temperatures before the next system moves in on Monday night.

Tue-Wed – A low pressure system will move through along with a cold front, resulting in more widespread showers favoring the Monashees and Selkirks in the BC Interior, with lighter showers for the Purcells and Canadian Rockies.

Snow levels will be higher than the last system, generally ranging from 7,000 to 8,000 feet, but could dip to 6,000-7,000 feet at times across the BC Interior.

Thunderstorm activity will be limited in the mountains in this pattern, with a better chance of thunderstorms expected just east of the Rockies on the Alberta prairies. 

Precipitation totals will be highest across the Monashees and Selkirks, ranging from 0.75 to 1.5 inches (17-38 mm), while the Purcells and Rockies will see lighter amounts. 

Thu-Fri – An unsettled pattern will continue with a WNW-to-ESE-oriented jet stream overhead, which will favor additional shortwave disturbances and shower chances, especially in the afternoon hours. Of the two days, Friday looks the most active and will also feature the best chance of thunderstorms.

Outlook for Saturday (June 13) to Wednesday (June 17):

A ridge of high pressure will build along the West Coast, resulting in a significant warming and drying trend over the far western states, including the first heat wave of the season for lower-elevation interior areas (away from the immediate coast).

The warm anomalies (departure from average temperatures) will be most pronounced over CA, OR, WA, and BC. East of the Continental Divide, temperatures are expected to be near to below average during this stretch.

In terms of rain and thunderstorm chances, areas east of the Divide will have the best chance as disturbances sneak in from the northwest. Also, Gulf moisture will continue to pump into New Mexico, which should keep thunderstorm chances going, with some of this activity potentially sneaking into Arizona as well.

There are some indications of the ridge breaking down as early as Wednesday the 17th, with some models hinting at a chance of showers sneaking into BC and WA, but confidence is low this far out.

June 18-22:

Longer range models are in general agreement that the West Coast ridge will break down during this period, with below-average temperature anomalies projected across the PNW and even in the Southwest, and neutral anomalies elsewhere. In other words, no major heat waves are anticipated.

A stronger-than-normal west-to-east oriented jet stream is also expected to return to the West, which could mean a return to gusty winds for many areas. 

Rain chances are a bit uncertain this far out, as long-range models are not hinting at any strong wet or dry anomalies. So overall, I would expect fairly seasonal conditions throughout the West heading into late June, and even a bit on the cooler side (for this time of year) in some areas. 

Thanks so much for reading! Next update on Wednesday.

Alan Smith