Western US Daily Summit

Cool and wet Northwest, dry and windy Southwest

Summary

The weather pattern will continue to exhibit a La Nina look over the next week with a persistent cool and wet pattern with below-average temperatures across the Northwest with heavy rain and mountain snow. On the other hand, the Southwest (especially New Mexico and Arizona) will continue to deal with warm, dry, and windy conditions which will result in critical fire danger.

Short Term Forecast

Weather Highlights this Week:

  • Prolonged cool and wet pattern for the Pacific Northwest with heavy rain and mountain snow.
  • Rain and snow showers for the Great Basin and Northern Rockies Wednesday-Saturday.
  • Strong winds, blowing dust, and high fire danger for the Southwest Wednesday-Thursday.
  • Heat builds over the Southwest and California this weekend.
  • Gradual cooling trend next week with showery periods for the Northwest and Rockies.

Current Snowpack Update:

Snowpack is now well above average across the Pacific Northwest and Western Canada (the latter of which isn't shown here) thanks to a cool and wet/snowy spring with consistently below-average temperatures. La Nina has actually strengthened this spring compared to the winter, and during April and May, we have seen a weather pattern more consistent with strong La Ninas with cool and wet conditions over the Northwest.

Warmer and drier conditions over the Southern Rockies have accelerated snowmelt and snowpack is well below average across much of Utah, Colorado, and New Mexico. Snowpack is near average across Wyoming and a bit above average across Idaho and Montana where cooler and more active conditions have prevailed this spring.

California has seen more storms this spring compared to mid-winter but snowpack remains below average.

Current Weather and Forecast for Wednesday (5/11):

We have two main features that will impact the weather across the West over the next few days. An area of low pressure located over California will swing across the Great Basin and Northern Rockies over the next 24-36 hours, while a trough of low pressure in the Gulf of Alaska is approaching the Pacific Northwest.

Valley rain showers and mountain snow showers along with a few thunderstorms will develop across the Great Basin, Wasatch, and Central Wyoming mountains during the day on Wednesday with isolated strong thunderstorms possible across Eastern Wyoming and Montana.

On Wednesday night, rain and snow will become heavier and more widespread along and east of the Continental Divide in Northern Wyoming and Southern Montana, including the Big Horn and Beartooth Ranges.

The Cascades will actually see a relative lull in the pattern on Wednesday with shower chances increasing late Wednesday night as a storm system approaches.

Temperatures will continue to be well below average across the West Coast and Great Basin and there are even frost and freeze warnings in effect for some lowland areas of Oregon and California.

Further south, dry and windy conditions will prevail as a moisture-starved cold front associated with the Great Basin-Northern Rockies system moves across Utah and the Four Corners region. Strong winds will develop throughout the Four Corners states on Wednesday afternoon and this will likely result in widespread blowing dust. Check out our Wind Gust Forecast Map for Wednesday afternoon.

Unfortunately, the strong winds combined with dry fuels and relative humidity values of 5-15% will result in critical fire danger across much of the Southwest, as well as the I-25 corridor as far north as the Denver metro area.

The dry and windy conditions are the last thing we want to see in New Mexico right now. The Calf Canyon-Hermits Peak Fire has burned over 230,000 acres and has grown significantly in recent days. The Cerro Pelado Fire southwest of Los Alamos has also burned 42,000 acres.

What about smoke? Given the location of this fire, we're actually seeing more smoke being transported aloft in the central and eastern parts of the U.S. Check out our Smoke Forecast Map for the upper atmosphere for Wednesday afternoon/evening.

Forecast for Thursday (5/12):

A low pressure system will continue to impact the Northern Rockies on Thursday with moisture wrapping around the low and producing heavy rain/snow across the Beartooths, Big Horns, and eastern plains of Montana and Northeast Wyoming. Mountain ranges further west across Southwest Montana and Central Idaho will see rain/snow showers as well.

Meanwhile, the next storm system will reach the Pacific Coast with heavy rain and mountain snow developing across the Cascades of Oregon and Washington as well as the Coast Range of British Columbia.

Snow levels will continue to be lower than usual for this late in the year across the Northwest with moderate to heavy snow totals likely across the Cascades and especially the British Columbia Coast Range. Keep in mind that a handful of ski resorts are still open across this region...

Also, heavy snow totals are likely across portions of the Northern Rockies, including the Beartooth, Big Horn, Gallatin, and Madison Ranges and this includes Yellowstone National Park. 

Here is a two-day snowfall projection from Wednesday morning through Friday morning:

Further south, winds will decrease on Thursday west of the Continental Divide, but further east, strong downslope winds will continue to result in critical fire danger east of the Continental Divide in Colorado and New Mexico.

Forecast for Friday (5/13):

The storm train will continue across the Northwest as we close out the week. First, rain and snow showers will spread into the Northern Rockies during the day on Friday while the next storm will impact the Pacific Northwest with more rain and snow on Friday afternoon and Friday night. 

The Southwest will continue to stay dry and temperatures will be on the increase, but winds will be lighter at least.

Forecast for Saturday (5/14) to Sunday (5/15):

The weekend will start out unsettled across the Northwest and Northern Rockies with additional showers expected during the day on Saturday.

The Northern Rockies will dry out on Sunday and even the Cascades should see a break early in the day, but then rain will return to the Pacific Northwest on Sunday afternoon and Sunday night as the next system approaches.

Snow levels will also be on the rise across the Northwest this weekend as warmer air arrives from the south.

High pressure building in from the south will result in a warm-up throughout the West this weekend, and especially on Sunday. In particular, the Southwest and California will see well above average temperatures by Sunday afternoon and conditions will be very hot if you have outdoor plans in the desert.

Extended Forecast

Forecast for Monday (5/16) to Tuesday (5/17):

Early next week, a storm system will likely result in periods of showers across the Northwest as well as the Northern and Central Rockies. Snow levels should start out high throughout the region but will start to lower on Tuesday as cooler air arrives.

Outlook for May 18-24:

Temperatures should continue to run below average across the Northwest and Northern Rockies during this period, which has been the story throughout the spring.

The Southwest and California will be warmer, but overall we should see a gradual cooling trend compared to the preceding days. However, there are some hints that we could see strong winds across the Great Basin/Southwest early in this period as a trough of low pressure works its way into the Western U.S.

Precipitation chances will continue to be elevated across the Northwest and Northern Rockies while Utah and Colorado will likely see some action as well. Unfortunately, rain chances are looking minimal across New Mexico, which is the area that needs it the most.

Thanks so much for reading! Next update on Wednesday (5/18).

ALAN SMITH