textproduct: Eureka

SYNOPSIS

A slight chance for interior thunderstorms Monday late afternoon with probabilities even less before sunset. Chilly morning temperatures are expected Monday morning for the coldest interior valleys. Drier weather returns mid next week.

DISCUSSION

The marine layer gets a bit shallower overnight into Monday morning. With the satellite products showing observable stratus thinning out for the interior, temperatures could dip to frost thresholds with no upper or mid-level clouds to hinder long wave radiative cooling. A frost advisory has been hoisted but is marginal as lows near interior Humboldt and Trinity will likely bottom out around 33-35F overnight into Monday morning near Dinsmore, Blocksburg, Ruth, Mad River and Hayfork.

With an upper level troughing pattern passing south of the CWA, a slight risk of thunderstorms for the interior continues with less of a threat than Sunday with 13 - 15 percent chances for Trinity and Mendocino counties. Less of a chance for Humboldt and Lake counties, around 10 percent. Expect most chances of thunderstorms to ease before sunset Monday.

High pressure looks to be the next trend as barometric pressure at the EKA WFO station is steadily rising overnight. Model soundings show dryer air aloft with an inversion, a prelude to seasonal warming and stability in the vertical profile. 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

AVIATION

A very deep marine layer continues to persist across the area with 3kft MVFR ceilings all along the coast and even over most of the interior. MVFR conditions will persist into Monday morning before gradually scattering off the VFR. The timing of scattering, however, has high uncertainty. Interior areas will most likely lift and scatter before 10 am where coastal locations could remain MVFR well into the afternoon. There is more uncertainty as for conditions Monday night into Tuesday. While ceilings will most likely persist, passing low pressure may be enough to lift them so high that conditions could be VFR despite the marine layer. At the very least, IFR conditions are very unlikely (less than 10% chance). /JHW

MARINE

Gentle north winds have built across all waters. Seas have generally remained moderate up to around 7 feet at 14 seconds thanks to a combination of lingering short period seas and modest mid period swell up to 4 feet.

Gentle winds will continue Monday with the swell rapidly decaying through the day. Northerly winds will begin to return to southern waters Monday night and spread into the northern waters by Tuesday. steep short period seas will build in response at least in the outer waters by Tuesday afternoon. Though strongest in the outer waters, short period wave energy will begin to impact the inner waters mid week with short period seas up to around 8 feet. Winds will continue to increase late weak with a 75% chance of near gale conditions by Thursday in the outer waters. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... Frost Advisory until 9 AM PDT this morning for CAZ106-108.

NORTHWEST CALIFORNIA COASTAL WATERS... None.