textproduct: Eureka

SYNOPSIS

Dry weather and above normal daytime temperatures will continue through the next 7 days. Overnight and morning temperatures will remain chilly with patchy dense fog along the river valleys and around Humboldt Bay.

DISCUSSION

High pressure over the area has weakened due to an elongated shortwave trough upstream and west of the California coast approaches. While mid- to upper-level high pressure remains over the area, a surface low will move toward the California coast today. This slight change in the weather pattern will promote the surface flow becoming more southerly which will support more onshore flow, resulting in a slightly deeper marine layer with some low pushing into the interior river valleys this morning through midday. The surface low will continue to track southward along the California coast Otherwise, dry weather and above normal daytime temperatures will persist.

The ridge is expected to rebuild on Thursday and Friday leading to offshore flow. This dry, offshore flow will most likely reinforce the chilly overnight low temperatures. This will promote clearing sky conditions on Thursday, with mostly sunny skies across much NW California Friday and into the weekend. A weak shortwave trough will bring increasing cloudiness Saturday night and Sunday. Coastal stratus is anticipated to redevelop, with a slightly deeper marine layer along the North Coast. Inland however, generally dry conditions and above normal daytime temperatures are expected to continue through the next 7 days.

After a long stretch of dry weather, long-range models are suggesting an increasing chance of precipitation from mid- to late next week. Stay tuned for updates as confidence of this weather pattern change increases. /ZVS

AVIATION

A strong and persistent marine inversion has settled back in along the coast this evening with IFR fog and ceilings. That said, slightly more unstable air above will most likely prevent any dense fog with only a slight chance (30% chance) early Wednesday morning. Conditions will most likely lift to VFR during the day Wednesday for a couple hours in the afternoon, though there is a chance (about 35%) that IFR fog and clouds hang around all day with no reprieve. Midlevel MVFR to VFR ceilings will persist across the interior through the day Wednesday. /JHW

MARINE

Generally light winds 10 kt or less and seas 6 feet or less are expected to continue into much of Wednesday as weak pressure gradients continue over the waters. Northerly winds will begin to increase in the afternoon and evening Wednesday as a weak low approaches the central and southern California coast while high pressure noses toward the Pac NW coast. Even with this synoptic scale set-up, surface wind fields appear only marginal near gale with gusts just near 34 kts in the outer waters by Thursday. The chance of much higher gusts over 34 kts is very low (20%). The primary hazard may end up being steep northerly wind waves which are forecast to build to 10 feet or more Thu evening and last into at least Friday evening.

The fairly tranquil marine conditions over the last several days will be coming to an end for the outer waters. Deteriorating marine conditions will be hazardous for small craft. At this time, confidence in hazardous conditions for the inner waters is not as high with much greater mesoscale variability in space and time. The likely points for gales and large steep waves will be near Pt George and around or just downwind of Cape Mendocino. Hazardous northerly winds and waves should begin to shift westward on Saturday, though steep waves may through much of the day. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 10 AM to 10 PM PST Thursday for PZZ470-475.

Gale Watch from Thursday evening through late Friday night for PZZ470-475.