textproduct: Eureka

KEY MESSAGES

* Light rain showers are expected to become more widespread tonight and Thursday morning before tapering off Thursday afternoon.

* Dry, cooler and breezy conditions are expected Friday with frost or freezing temperatures possible Friday night.

* There is the potential for a pattern change to cooler and wetter weather. This may start as early as Sunday or more likely hold off until early or mid next week.

SYNOPSIS

A few showers continue this afternoon with more widespread showers expected later tonight and Thursday morning. Thursday afternoon these showers will taper off from west to east. This will set up a cool and dry Friday with frost likely Friday night. Warm and dry conditions are expected Saturday with the next chance for rain possibly as early as Sunday.

DISCUSSION

A band of light rain showers has set up from Humboldt Bay down through northern Lake county this afternoon. Some of these showers are stronger and have produced a few lightning strikes in northern Lake county. These are expected to diminish later this afternoon and early in the evening. Late in the evening and overnight more widespread showers are expected. The NBM is showing a probability over a wetting rain (over 0.10 inches) of 40 to 70 percent south and east of a line from Big Bar to Redway. It looks like some rain will make it farther west and out to coastal Humboldt, but probabilities are lower and amounts are likely to be less. Thursday by mid to late morning the back edge of the rain is expected to start to push east. New models run show this taking most of the evening to get out of Trinity county. Behind the front areas that do manage to clear are expected to valley fog. The chilly airmass could allow some areas to drop into the mid 30s and see frost, but more likely they will just fog up. Closer to the coast and above a couple thousand feet the ridges are expected to clear out and see breezy easterly winds. Friday is expected to be see quite of drying, but temperatures are expected to remain only in the 60s. This drier air will set up the area for a chilly night Friday into Saturday morning. Easterly winds will likely keep the coast clear and the ridges dry.

Sunday and into early next week the forecast remains highly uncertain. The models have backed off from the wettest solutions. However some of the model clusters continue to show a tenth to a quarter of an inch of rain on Sunday. The models are still showing a fairly even split between a large ridge and trough over the area. This could mean a difference in high temperatures of 55 in the trough or over 75 under the ridge. By Tuesday or Wednesday an increasing number of the cluster members showing a trough moving into the area bringing the potential for some rain. This will definitely be a time period to watch and may be the early signs of a more significant pattern change. MKK

AVIATION...18Z

While general overcast skies are anticipated for Northwest California through the TAF period, VFR conditions are anticipated this afternoon. An approaching low pressure system to the south of the region has aided in scattering and lifting the low clouds from this morning. Light rain showers and lower ceilings are expected for the overnight hours with IFR/LIFR conditions anticipated for coastal terminals by late this evening or very early tomorrow morning. MVFR and more frequent showers can be expected for southern Mendocino and Lake counties overnight. /JLW

MARINE

A mid period westerly swell will continue to gradually subside over the next day. An upper low will continue moving into central California through the end of the week. Northerly winds and seas will remain below small craft conditions as this low moves on shore over the next 24 hours. By tomorrow, northerly winds will begin to increase, especially by tomorrow afternoon, as a dry cold front passes. High pressure will begin to rebuild into the region behind this front. Elevated winds and steep seas are anticipated Thursday through Saturday with a 60 to 80 percent chance for widespread gale force gusts by very late Thursday/early Friday to Friday afternoon. /JLW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 6 PM Thursday to 9 PM PDT Friday for PZZ450-455.

Small Craft Advisory from 9 AM to 6 PM PDT Thursday for PZZ470.

Gale Warning from 6 PM Thursday to 9 PM PDT Friday for PZZ470.

Small Craft Advisory from 9 AM to 9 PM PDT Thursday for PZZ475.

Gale Warning from 9 PM Thursday to 9 PM PDT Friday for PZZ475.