This year's dry, warm winter in the western United States will continue virtually unchallenged for the foreseeable future, with little beneficial precipitation expected over the next week. The conditions will only serve to worsen the exceptional drought, leading the way to a potentially devastating wildfire season.
The map at the top of this post shows temperature anomalies in Celsius, showing the country evenly split between bitter cold and abnormal warmth. The latest run of the GFS model predicts that temperatures on Friday afternoon will clock in at nearly 10°C above normal in parts of the West, mostly focused around Nevada.
The next wave of cold weather in the central United States will likely spill over the Rockies and bring temperatures back to normal levels across the West during the first half of next week, but it's going to be short-lived. The models hint that in the medium-range (later next week and beyond), temperatures could register warmer-than-average during the day and cooler-than-average at night.
The next couple of days will feature more of the same ol' calm weather we've seen for the majority of this winter. While the eastern United States deals with a brutal cold snap of epic proportions, it's pretty calm in the West. If you factor out the slow-motion disaster playing out with regard to the region's water supply and dying vegetation, one could say it's been absolutely gorgeous. The same jet stream that allows trough after trough to dump snow and cold over New England is sustaining a near-constant ridge of high pressure over the western portion of North America. Ridges of high pressure are consistent with mostly calm weather and warmer-than-normal conditions, and that's exactly what we're seeing in the West.
The big question people have asked of the pattern this winter is why the setup of "ridge in the west, trough in the east" has been so constant and unwavering since the season started. It's almost a "chicken or the egg" type of question, but it appears that the ridge is the cause of the country's weather woes. Like droughts, ridges of high pressure can create conditions to sustain themselves. Warm temperatures warm up the surface of both the land and the ocean, which serves to warm the air via conduction, and warmer temperatures are associated with ridges of high pressure. It's the feedback cycle from hell that's creating Hell. The atmosphere strives for balance, so when we have a big ridge towards the west, it fosters the development of troughs that dip over the eastern U.S.
The ridge will begin to break this weekend, allowing temperatures to drop back down around normal for a couple of days, bringing along with it the chance of rain/snow. That precipitation is a literal drop in the bucket, unfortunately; outside of Colorado and northern Idaho, the Weather Prediction Center doesn't give anyone west of the Rockies more than a half an inch of precipitation over the next seven days. Any snow at higher elevations would be negligible compared to what they should see by the end of February.
This is terrible news for the drought, which has gotten better in some spots and much worse in others.
Beneficial rainfall over the past month has allowed parts of the west coast—especially along the coast and in eastern Washington—to drop down one category on the drought monitor; the biggest improvement was across northern California, where several areas dropped from "extreme" to "severe," which is still pretty bad, as the name suggests. The worst category of drought, "exceptional," is gaining ground in eastern California and western Nevada.
This combination of warmth and drought will spell disaster once even warmer and drier air invades the region during the spring and summer months. The uncontrolled spread of devastating wildfires requires four ingredients: warm air, low humidity, dry fuel, and high winds. According to the Climate Prediction Center, the sustained dry and warm conditions will likely continue through the spring for the vast majority of the West (temps | precip), and the existing drought will create near-perfect conditions for dangerous fires to spark and spread throughout the region this year.
Warm and sunny is nice when you're driving with the windows down, but it's truly a slow-motion disaster when it lasts this long. It's not as sexy as seven feet of snow in Boston or a major tornado outbreak in Alabama, but dwindling reservoirs and the impending fire season will affect tens of millions of people, and the threat only grows worse with each week that passes without relief.
[Images: Tropical Tidbits, WPC, author]