textproduct: Eureka

SYNOPSIS

A strong cold front crossing the region tonight continues to bring unseasonably cool air and high humidity. Light rain along the coast will end by late morning, giving way to clearing skies inland. A rapid warming and drying trend begins Sunday as high pressure builds over the west, though strong northerly winds will persist over ridges and coastal waters.

DISCUSSION

The core of an unseasonably strong upper-level trough is pushing across the Pacific Northwest tonight. The accompanying surface front is currently shifting winds out of the north-northwest and driving a cold advection pattern across northwestern California. High temperatures today will feel highly anomalous for late June, topping out only in the mid-50s to lower 60s along the coast and 60s and 70s in the interior valleys. Far interior peaks may struggle to exit the 50s.

Light rain and drizzle will continue to dampen coastal sections of Humboldt and Del Norte counties through the morning hours before trailing off as dry air builds into the region. Cold air destabilization aloft will generate a marginal 10% chance for thunderstorm development this afternoon over far northern Trinity and interior Del Norte counties.

Tonight into Sunday morning will feature the coldest temperatures of the period. Clear skies and decoupling winds in sheltered valleys will support lows tumbling into the mid-30s in interior Humboldt and Trinity counties. Current NBM joint probabilities indicate a 10 to 20 percent chance of frost in these interior areas when factoring in wind speed, sky cover, and temperature probabilities. High pressure quickly builds inland on Sunday, initiating a gradual warming trend. Sunday interior highs will be in the 70s to lower 80s, peaking in the mid-to-upper 80s by midweek before a weak secondary trough brings slight cooling late next week.

AVIATION

Post-frontal low-level moisture is maintaining widespread IFR to MVFR ceilings and localized visibility restrictions in mist/drizzle along the coast at KACV and KCEC early this morning. Aviation could be tricky through the dawn hours, and conditions could really bounce around during the early morning hours before following a consistent improving trend. Ceilings are forecast to slowly lift to MVFR by late morning (18Z) before drier air breaks through inland. Northwest winds will pick up by this afternoon, gusting up to 23 knots at KACV. Inland at KUKI, VFR conditions will prevail through the entire TAF period, supported by robust north- northwest winds gusting to 21 knots through Saturday afternoon.

MARINE

The cold front has cleared the waters, shifting winds entirely to the northwest. High pressure building offshore will compress the local pressure gradient significantly over the next 48 hours. Small Craft Advisory conditions are expected later today for the southern waters as northerly winds build to 2025 knots with gusts to 35 knots, lasting through Sunday morning.

A Gale Watch will be issued for the outer waters and southern inner waters from Sunday afternoon through Wednesday evening. While the combination of sustained northerly winds of 25 to 30 knots and short dominant periods would meet Hazardous Seas Warning criteria across the outer waters and southern inner waters Monday night through Wednesday night (seas 11 to 13 feet at 9 to 10 seconds), our message will highlight the persistent wind over the waters coming, as the potential Gale Warning would take precedent over a hazardous seas product.

FIRE WEATHER

A dramatic pattern shift is realized today behind the strong cold front. Near-term fire weather concerns are muted across northern zones due to high relative humidity values, with minimums remaining mainly above 4050% today, alongside recent wetting rains across Del Norte and northern Humboldt counties. However, dry interior zones across Southern Trinity and Lake counties will miss out on precipitation entirely. Humidity recoveries for eastern Lake County for Friday night will be more modest, in the 50 to 60 percent range, while remaining excellent elsewhere at 80 to 100 percent. Strong westerly winds of 10 to 20 mph with gusts up to 35 to 40 mph will lash exposed ridges in Lake, eastern Mendocino, and Southern Trinity counties through this afternoon. High pressure returns Sunday, bringing a swift return to warmer and drier conditions through midweek.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from noon today to noon PDT Sunday for PZZ455-475.

Gale Watch from Sunday afternoon through Wednesday evening for PZZ455-470-475.