textproduct: Eureka

SYNOPSIS

Dry conditions will continue across the area today and into early work week with some particularly cold mornings with lows near freezing and freezing. Conditions will slightly warm and moisten next week with increasing chances of wetting rain by mid week.

DISCUSSION

Persistent high pressure over the Northeastern Pacific has begun to shift eastward, promoting very dry and stable conditions across the region. Latest satellite imagery depicts high-level moisture around the northern periphery of the ridge, with some cirrus clouds spreading southeastward across NW California. Cold, dry air advection, alongside offshore winds and clear to partly cloudy skies, is promoting efficient radiational cooling across the area, resulting in cold overnight temperatures. Surface observations reported near freezing to freezing temperatures across the interior valleys, with lows in the mid-20s to mid 30s. Cold Weather Advisory is in effect until 9 AM for apparent temperatures below 30F degrees for southern interior Mendocino and southern Lake counties, and for apparent temperature below 20F degrees for Trinity County.

High pressure is expected to slowly weaken and flatten today into Monday as a weak shortwave trough moves north of the area, bringing and increasing cloudiness. The 500 mb ridge appears to slowly build back early next week, with conditions slightly warming up. The pattern shift as the ridging finally breaks down and an upper level trough dig southward across the Pacific and approaches the area by mid week. At this moment, there is a 50 to 80 percent chances of wetting rain (0.01 inch or more) Tuesday afternoon through Wednesday afternoon, with the highest probabilities along coastal range in Del Norte, Humboldt and Mendocino. There are no major impacts expected with this weather system; if precipitation does occur, it would be more beneficial than impactful, especially after the recent dry spell.

Ensembles and WPC Cluster Analysis suggest another shortwave trough may (38% chance) bring another chance of light showers for the northern portion of the area by late in the work week. /ZVS

AVIATION

VFR conditions and clear skies prevail over all the terminals. Low dewpoints and continued offshore flow will likely keep skies clear across the area, aside from a few areas of patchy valley fog. Any fog will likely lift and scatter shortly after sunrise. Southeast winds increase tomorrow and could be breezy over the coastal headlands, especially CEC. JB

MARINE

Seas continue to subside are likely to fall below 5 ft by today as winds remain light. A series of small, mid to long period west swells fill in through Wednesday, each peaking at around 5 ft. Winds turn southerly and start to increase early Monday. NBM currently shows about a 70% chance for gale force gusts in the outer waters by Tuesday, with slightly higher confidence north of Cape Mendocino. A large westerly swell looks to then build in Wednesday night and Thursday. JJW/JB

EKA WATCHES/WARNINGS/ADVISORIES

CA... Cold Weather Advisory until 9 AM PST Sunday for CAZ108-113- 115.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 10 AM Monday to 2 AM PST Tuesday for PZZ470-475.

Gale Watch from late Monday night through Tuesday evening for PZZ470-475.