textproduct: Eureka

SYNOPSIS

Shower activity and the chance for thunderstorms today. Isolated to scattered thunderstorm chances increase across the interior Thursday. Breezy NW winds over the interior ridges and channeled terrain today, shifting to the coast this afternoon. A warming and drying trend expected late week into the weekend.

DISCUSSION

A closed low centered over interior California continues to track southward, funneling cooler temperatures and showers across the area. Before daytime heating begins, expect enhanced northwest winds across the interior for exposed ridges and NW-SE channeled terrain this evening into Wednesday, with gusts from 25 to 40 mph possible. These winds will shift towards the coast through the afternoon, with NNW gusts of 25 to 35 mph over the coastal headlands and exposed ridges.

This cooler and unsettle weather pattern is expected to continue through Thursday as the low settles over California before it weakens and shifts eastward into the Great Basin. The atmosphere is abnormally moist with PWAT values increasing up to 1.0 inches today and Thursday. These PWAT values are about 150-200% of normal across the entire area. While instability diminishes across the area on today; however, some shallow instability with a cold air aloft will be capable of produce moderate showers bands rotating around the low and moving toward the coast. There remain a slight chance (10-15%) of thunderstorms for Trinity County this afternoon and evening, with a non- zero probabilities elsewhere. On Thursday, the back side of the closed low will promote an increased chance of convective showers and thunderstorms. There is a 15-30% chance of thunderstorms across the interior on Thursday, with the highest chance in Trinity County.

Weak ridging builds in briefly on Friday, while the low exits the area shifting to the east to northeast. This will bring drier air to the region. However, some lingering moisture will still yield in isolated mountain showers and thunderstorm is the Trinity Horn on Friday. High temperatures are expected to increase and become more seasonably for this time of the year. A shortwave trough may bring an increasing cloudiness and some isolated mountain showers and thunderstorms again to Trinity County on Saturday.

The slightly stronger 500 mb ridge appears to slowly build Sunday through early next next week. This will result in drier weather with a gradual warming trend. Minor HeatRisk will likely returns on Monday and Tuesday, especially across the interior valleys as temperatures almost reach 90F. /ZVS

AVIATION

VRF to MVFR conditions will remain through the morning. However, certain coastal valleys will experience IFR ceilings. Northwest winds will build, especially for coastal terminals increasing the likelihood of LLT. A band of rainshowers will impact the area beginning in northern areas first before flowing southward through the day. Expect MVFR to IFR ceilings Wednesday night along the North Coast with possible MVFR ceilings developing inland. Interior terminals will experience a slight (10-20%) chance of thunderstorms between 16Z and 00Z. Gusty, turbulent winds are possible near these storms. DS

MARINE

Steep, mid to short period seas up to 14 feet continue to dominate the sea state in all waters. Moderate north winds have built in the outer waters and will push closer to shore into Wednesday. Marginal gale conditions will build first in the southern outer waters early this morning. These gale force gusts will be brief. Stronger gale conditions are to be expected in the northern outer waters this afternoon. Near gale force gusts will push into the inner waters throughout the day. Seas will remain steep and hazardous throughout the day.

Winds will weaken and pull further offshore on Thursday. Just as short period seas begin to fall. That said, an unusually long period northwest swell will build up to around 7 feet. Such a swell is quite unusual this late in May and will bring at least a moderate increased risk of sneaker waves to North Coast beaches. Otherwise, winds will be mostly calmed to around 10kts or so by Thursday afternoon as short period seas begin to fall. Moderate north breezes will begin to return to all waters Friday and into the weekend. /JHW

FIRE WEATHER

Breezy NW winds with gusts from 20-30mph are expected into today over the exposed ridges and channeled terrain across the interior. Daytime relative humidity values are in the upper 30s to mid 40s percent in Trinity and Lake counties, with coastal counties closer to 80 percent. An enhanced fire weather threat exists for zones 418 and 421 due to strong wind gusts up to 40 mph and low daytime RH values around 35 percent with overnight recoveries around 70 percent. Winds are the expected to diminish throughout the day on Wednesday for the interior, yet coastal headlands will remain breezy through the afternoon today. /ZVS

BEACH HAZARDS

Surf is currently elevated thanks to mid period seas up to around 14 feet. These shorter period seas and winds will calm Wednesday evening into Thursday. At the same time, an unusually long period northwest swell for this time of year will build Wednesday evening and through the day on Thursday. The forerunners of this swell will begin to build in at just couple feet around 24 seconds. The swell will peak Thursday around 8 feet at 16 seconds. Though falling short period waves will somewhat mask the swell, there will be a moderate increased risk of sneaker waves on area beaches. The greatest risk will be in areas of mostly calm winds on beaches that are exposed to the northwest. Never turn your back to the ocean and stay on dry sand if on the beaches. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement from Wednesday afternoon through Thursday evening for CAZ101-103-104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Thursday for PZZ450-455.

Small Craft Advisory until 3 PM PDT Wednesday for PZZ470.

Gale Warning from 3 PM to 11 PM PDT Wednesday for PZZ470.

Small Craft Advisory until 3 AM PDT Wednesday for PZZ475.

Gale Warning from 3 AM to noon PDT Wednesday for PZZ475.