textproduct: Eureka

SYNOPSIS

Mostly diurnal, pervasive coastal stratus will continue the pattern of low clouds, fog, and seasonal temperatures along and near the coast. Inland areas will see warm afternoon temperatures early this week before a building high pressure system ushers in hotter conditions for interior valleys by mid- week.

KEY MESSAGES

- Seasonable temperatures along the coast with persistent overnight and morning coastal stratus and fog into early/mid week. - Warming trend this week expected with a high likelihood of a stronger warming trend mid to late week. - Up to a 5 percent chance of afternoon thunderstorms over northeastern Trinity County Today.

DISCUSSION

An upper-level trough shifting past the Pacific Northwest will maintain a persistent cloud layer across coastal sectors, yielding regular diurnal cycles of low clouds and localized beach fog. Afternoon/evening lifting and scattering of low clouds will be more likely mid to late in the week. Inland, a high pressure system over the Four Corners region will suppress deep mixing, but sustain seasonably hot temperatures with valley highs reaching into the 90s to near 100 degrees in topographically favored hot spots like Big Bar.

As the upper trough continues to approach the Pacific Northwest today, it will draw a narrow corridor of mid-level moisture northward from the tropics. Weak mid-level lapse rates and limited instability will keep thunderstorm potential highly isolated and locked primarily east of our area, though up to a 5% chance of an afternoon lightning strike remains warranted across northeastern Trinity County near Trinity Lake. By Wednesday and Thursday, the upstream trough weakens, allowing the interior heat dome to build westward. This transition will initiate a more robust warming trend, pushing daytime valley temperatures deeper into the high 90s and low 100s for late next week.

AVIATION

Gentle, generally onshore flow is expected for coastal terminals of Northwest California. This will reinforce a rather persistent coastal stratus layer along the coast and up nearshore river valleys. This afternoon/evening, coastal stratus is expected to cling a bit more over coastal areas with only minimal scattering/lifting of low clouds. LIFR/IFR conditions are expected again along the coast throughout tonight with some potential for fog early tomorrow morning. VFR conditions are anticipated for most inland terminals throughout the TAF period. /JLW

MARINE

Northerly winds over the inner coastal waters will stay light at under 10 knots as a thermal trough anchors over the interior and encourages localized nocturnal wind veering. Consequently, Small Craft Advisories remain strictly confined to the outer waters from 10 to 60 nautical miles out. Today, an approaching Pacific Northwest trough will weaken the inland thermal gradient, relaxing the marine wind field and allowing hazardous small craft conditions to drop off across the outer zones early this coming week.

EKA WATCHES/WARNINGS/ADVISORIES

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