textproduct: Eureka

KEY MESSAGES

- Temperatures will warm quickly with moderate to major HeatRisk expected Thursday through the weekend.

- Elevated fire weather conditions in Lake County with low afternoon relative humidity and gusty winds Wednesday through Thursday.

- Breezy winds are expected along the coast Wednesday and Thursday afternoons.

SYNOPSIS

Temperatures are expected to warm to the upper 90s to around 100 in interior valley locations by Thursday through the weekend. Breezy winds are expected along the coast each afternoon and evening through at least Thursday. High temperatures in the upper 60s to around 70 degrees can be expected along the coast, warmest possibly this weekend.

DISCUSSION

The main story this week will be a building ridge of high pressure that will bring widespread heat to the interior portions of Northwestern California. As the heat builds, the pressure gradient will tighten over the coastal waters resulting in gale force winds just off the coast and gusty conditions in coastal locations during the afternoon and evening hours through at least Thursday and possibly Friday. This will keep temperatures a bit cooler at the coast but still 60s and potentially 70 degree temps are expected through the weekend. Interior areas will warm into the upper 90s to over 100 degrees for many valley locations, starting in the south in Mendocino and Lake counties on Thursday and Friday, spreading north into Humboldt, Del Norte, and Trinity counties Friday through the weekend. Overnight low temperatures may not cool very effectively in Lake and southern Mendocino counties Thursday and Friday, resulting in increased HeatRisk for those areas. Thus, a Heat Advisory has been issued for those specific areas on those two days. Elsewhere the HeatRisk is currently on the edge of the need for heat products into Trinity and possible interior Humboldt counties over the weekend. The heat will persist into early next week but there may be some moderation around mid next week as a trough begins to deepen over the eastern Pacific pushing the ridge axis farther east. /RPA

AVIATION

VFR is expected to prevail over much of the area over the next 24 hours. A few clouds have been stuck on the near coastal ridges of Humboldt County and it is possible moisture may pool in the Eel River Valley north of the King Range overnight resulting in the development of stratus. If conditions are just right this stratus could then spread north toward Arcata. The TAF includes a few low clouds to account for this possibility. Otherwise the main concern will be afternoon gusty winds along the coast and in north- south oriented valley locations in Mendocino County and northwest- southeast oriented valleys in Humboldt, Del Norte, and Trinity counties during the afternoon hours. /RPA

MARINE

North winds will continue to ramp up over the next 24-36 hours as the pressure gradient tightens over the coastal waters. Gales are expected to develop in the southern zones on Wednesday and then expand north into the northern outer waters zone Wednesday night. Very steep seas will build in response to the winds. Closer to the coast along Humboldt and Del Norte counties the fetch will be smaller and winds slightly less, so only a small craft advisory has been raised for this area. Winds will remain strong through Thursday. The thermal trough will push toward the coast on Friday allowing the orientation of the winds to shift farther north and eventually nearly completely west of the waters late in the weekend. Winds may become light out of the south near the coast as a return surge moves up the coast over the weekend. /RPA

FIRE WEATHER

High pressure is building into the area and bringing warmer and drier conditions. Nearly 10 degrees of warming is expected on Wednesday over Tuesday with nearly a similar jump again on Thursday. Along with the warming temperatures, very dry air is expected to move in and this will lower RH each day. The ridges are expected to see poor RH recoveries by Thursday morning. This will combine with some northerly winds over many of the higher ridges. The strongest winds are expected to be in the Yolla Bolla's and down into the higher terrain of eastern and southern Lake County. This will increase the fire danger so have issued a red flag warning for Thursday morning. Fuels are likely still marginal, but winds of 15 to 30 mph and RH expected to increase only to 20 to 40 percent is concerning enough to highlight the threat with a red flag product. Thursday afternoon RH is expected to drop into the low teens in much of the interior valleys, but the winds are expected to diminish by the afternoon so have ended the red flag warning in the morning. Modeled wind trends will be monitored to determine if an extension into Thursday afternoon is needed.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Heat Advisory from noon Thursday to 10 PM PDT Friday for CAZ113-114-118>120.

Red Flag Warning from 11 PM this evening to 9 AM PDT Thursday for CAZ419-420.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 2 PM this afternoon to noon PDT Thursday for PZZ450.

Small Craft Advisory until 2 PM PDT this afternoon for PZZ455.

Gale Warning from 2 PM this afternoon to 3 AM PDT Thursday for PZZ455.

Small Craft Advisory from 7 AM this morning to 9 PM PDT this evening for PZZ470.

Gale Warning from 9 PM this evening to noon PDT Thursday for PZZ470.

Small Craft Advisory until 10 AM PDT this morning for PZZ475.

Gale Warning from 10 AM this morning to noon PDT Thursday for PZZ475.