textproduct: Eureka

SYNOPSIS

Conditions will remain hot and dry inland, while a deepened and a relatively persistent marine layer keeps temperatures cooler along some portions of the immediate coast. Cool down expected early next week.

DISCUSSION

Strong ridging will build into the region following a weak upper trough. Already warm temperatures will continue to increase into the mid-90's across interior valleys for Saturday and Sunday. NBM probabilities for highs >90 degrees are >80% as far as Redway and Laytonville as warm temperatures chip away at the marine layer. Areas of Moderate HeatRisk in interior Trinity, Humboldt and Mendocino will be a concern for sensitive individuals. Breezy terrain driven winds expected across the interior each afternoon. Otherwise, daytime highs will be significantly dampened along the coast with a persistent marine layer. Areas of coastal drizzle are possible on Saturday morning, after which the marine inversion will begin to compress and remain slightly closer to the coast, likely no longer reaching Ukiah by Sunday. An approaching upper trough will help to tighten the coastal pressure gradient Sunday into Monday - gusty northerlies south of Cape Mendocino expected, including Lake County (SW flow in higher elevations of eastern Lake County). This will pose a slight fire weather concern as daytime RH's are still 25 to 30%.

High pressure will begin to break down beginning early next week as a positively tilted upper trough over WA/OR begins to extend into NorCal. Temperatures are expected to cool off significantly with highs in the upper 70's to mid 80's (with isolated valleys potentially reaching 90) through midweek. Long range models show anomalously low heights sitting over the eastern Pacific/PNW through at least Wednesday with generally northerly flow and terrain driven afternoon winds expected. NBM beginning to hint at a chance for thunder Tuesday and Wednesday afternoon with cool upper temperatures and mid level moisture availability, but there is still high uncertainty.

AVIATION

(18Z TAFs) Another day of Stratus along the coast today. LIFR/IFR conditions are present at terminal sites with minimal clearing expected. brief periods of VFR are possible as mixing at the surface clears out the clouds, yet stratus and fog is expected to return again this evening leading to LIFR conditions once again. Dense fog with a 30% probability of degraded visibilities under 1SM at KACV and KCEC and cloud ceilings <500ft are likely with 50-60% probability of reforming again overnight.

Inland terminals can expect VFR conditions, light elevated winds, and even potential smokey skies today. Fog returning to river valleys is expected again tonight. KUKI shows about a 20-30% probability of fog returning its way up the Russian river valley, however low RH model outputs and minimal southerly wind keeping it unlikely.

MARINE

High pressure is beginning to build back toward the coast over the eastern Pacific Ocean forcing a return of the northerly winds. The pressure gradient will continue to tighten into the weekend with moderate to strong northerly breezes Saturday and Sunday, with the strongest winds over the outer waters zones and downwind of Cape Mendocino. Seas will build in size as short period, steep wind waves form due to the persistent winds. Small craft advisories have been hoisted from Saturday to Sunday over the outer waters due to these steep seas and breezy winds. Winds and seas will subside early next week due to another upper level trough diving south over the coastal waters, weakening the surface high pressure gradient that causes our strong northerly winds. Light winds and low seas are anticipated for much of the coming work week.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 11 PM Saturday to 5 PM PDT Sunday for PZZ470.

Small Craft Advisory from 3 PM Saturday to 11 PM PDT Sunday for PZZ475.