textproduct: Eureka

SYNOPSIS

A chance for interior showers and thunderstorms anticipated late this afternoon, with probabilities decreasing into late evening. Drier weather returns Tuesday/Wednesday with a shallow marine layer expected along the coast each night the rest of this week.

DISCUSSION

The influence of an upper level troughing pattern south of Northwest California continues to weaken as the pattern moves off to the east. However, there is still a slight risk of thunderstorms (about a 10 to 20 percent chance) for the interior this afternoon/evening. The highest chance (15 to 20 percent) is for Trinity and extreme NE Mendocino; with less of a chance for interior Humboldt, most of interior Mendocino, and northern Lake counties (around 10 percent). Isolated showers and thunderstorms are expected to taper off before sunset today.

Models indicate a prevailing ridging pattern to develop for the rest of this week. Model soundings show dryer air aloft with an inversion, a prelude to seasonal warming and stability in the vertical profile. A shallow marine layer along the coast is expected, to some degree, each night/early morning this week. Deterministic ensembles are not in agreement over the next precipitation event for the first week of May. Stay tuned as time draws near for developments. /EYS&JLW

AVIATION

Coastal clouds have mostly dissipated except for a small area right around Arcata Bay. VFR conditions should continue along the coast through the evening hours. Model guidance indicates moisture will once again increase through the evening allowing potentially MVFR ceilings to redevelop, particularly north of Cape Mendocino along the Humboldt and Del Norte coasts. Surface condensation pressure deficits are not very low, likely indicating a stratus deck rather than surface fog.

Farther inland showers have formed over the higher terrain and patchy areas of MVFR or lower conditions are likely occurring. However, in general VFR is prevailing, such as at UKI. Showers will come to an end during the evening hours as instability decreases. Some valley clouds are likely to develop where moisture pools overnight. /RPA

MARINE

The coastal environment will be dominated by lowering pressure across the interior west and high pressure building over the eastern Pacific. This will allow the pressure gradient to tighten over the next several days and north winds to ramp-up to near gale or gale on Friday into Saturday. Steep seas will build in response to the winds with seas exceeding 10 feet at around 8 to 9 seconds in the outer water zones. Local model guidance has been trying to push for larger waves approaching 15 feet in the outer waters on Friday. Either way, the seas will be steep and either hazardous seas warnings or gale warnings will likely be needed late in the week into the first part of the weekend for at least the outer water zones. /RPA

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 1 PM Tuesday to 11 PM PDT Wednesday for PZZ470.

Small Craft Advisory from 8 PM this evening to 11 PM PDT Wednesday for PZZ475.