Summary:
- The North Pacific high-pressure ridge remains stubbornly west of its normal position. This has continued to allow low-pressure areas to dip south along the west coast. The meridional circulation over the west has kept temperatures well below average and brought anomalous precipitation south into California.
- Colder than normal1 temperatures in March for the entire western US, especially in the intermountain region.
- March ended up dry across the northern PNW and scattered areas of the intermountain west while California’s anomalous wet second half of winter continued with large inputs from atmospheric rivers.
- A slight warm-up and dry-down are coming in the short-term forecast into mid-April. However, the month is likely to hold to cool to average and wet in the PNW to average or dry heading south. While no large-scale cold events are on the horizon, the cooler conditions overall and any clearing skies at night will likely be an issue in all the usual places.
- Drought improvement across the west has been remarkable. Snow Water Equivalents range from 90-110% of normal in the PNW and northern Rockies to 150-250% above average in California, the Basin, and the rest of the Rockies.
- The forecast heading into spring and early summer tilts the odds to a cool period through April for the western US with California likely closer to seasonal while the PNW is likely to be cooler. Precipitation amounts are expected to be closer to average in the PNW and slightly below average in California. The tropics have faded to ENSO-neutral with continued expectation for El Niño in late summer or fall. PDO remains in a strong negative phase with quite cold near-shore SSTs along the western coast of North America, enforcing the cool spring likelihood and dare I say it, frost risk.
