textproduct: Eureka

KEY MESSAGES

- Cooler conditions ahead of an approaching low pressure system.

- Improved RH recoveries overnight along with a deepening marine layer will quell fire weather concerns for the area.

SYNOPSIS

A cool down will persist through the week and progress into next weekend. Coastal stratus will become more persistent with only partial clearing likely in the afternoons.

DISCUSSION

An upper low off approaches the northern California coast today. This troughing pattern has started to funnel moisture into the area off of the coast of Central California. Instability is limited with this moisture surge, but a few high clouds and virga showers are possible for southern Mendocino and southern Lake Counties. Interior temperatures are forecast to be cooler than average, especially as the week progresses. Increased vertical mixing from this troughing pattern will support breezier southerly winds and deepen the marine layer which will aid in boosting overnight recovery RH values into Tuesday. The frontal boundary will stall a bit and we can see eddy circulation via visible satellite feed. Overnight stratus development will be of concern tonight as the southerly surge continues. Northerly winds return Wednesday morning with variable headings as unsettled conditions continue. With that said, the coastal areas are likely to remain in the low to mid 60s. The troughing pattern supports a deep marine layer which, along with light winds near the coast, may keep stratus persistent at the immediate coast through at least Wednesday. The troughing pattern remains in place for the next week. Today will be the last warm day before temperatures ease for most interior areas. Moisture and instability is limited with this troughing pattern which will limit any thunderstorm potential. Generally mild, seasonable weather is likely for the remainder of the week. /EYS

AVIATION

Near offshore circulation can be seen from satellite observation which will encourage lower ceilings and visibility degradation through the evening. Other than the brief few hours of VFR at KCEC, the coastal terminals have and will be wrought with LIFR/IFR conditions as the marine layer deepens and the cyclonic flow reinforces low cloud/stratus density near the coast. Southerly winds will veer westerly by the afternoon Tuesday with very little reprieve from the flight categories mentioned previously. KUKI may be the only terminal for our CWA with extended periods of VFR. What is concerning is the southerly push and the deepening marine layer which models may not pick up. The marine layer thus far is not deep enough to advect into Ukiah valley. /EYS

MARINE

Winds will continue to ease except for areas in the lee of the Cape, which are opposite of the usually localized ares we see gusting up due to the southerly bearing-exposing the north side to higher winds. Also, seas will gradually subside, but remain steep in the outer waters into the evening. Generally mild conditions are expected late tonight into Tuesday morning, with northerly winds increasing south of Cape Mendocino by Tuesday evening.

FIRE WEATHER

The current weak ridging pattern will give way to a weak troughing regime, bringing cooler temperatures and helping recovery RH values overnight. Minimum daytime RH values will also improve. Trinity Lake county will still have minimum RH values in the upper teens to 20's Tuesday but will continue to improve as the work week progresses and the offshore low pressure system approaches BC and Washington coast, bringing moisture into the area albeit slight. The marine layer deepens and will also moderate temperatures and tamp down fire weather conditions. Winds will generally remain light and terrain driven, aside from southwesterly afternoon breezes.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 6 PM PDT this evening for PZZ470- 475.