110 FXUS66 KEKA 250757 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 1257 AM PDT Thu Sep 25 2025 .SYNOPSIS...Warm and dry weather will persist this week. Dry northerly flow will clear out most of the coastal stratus this week, allowing for better duration of coastal sunshine. Rain chances arrive late Sunday, with increasing probability for widespread rainfall through early next week. The opportunity for additional rainfall may continue through mid next week. && .DISCUSSION...A cutoff upper low is parked over coastal Central California Wednesday night. Some light showers made it over Lake and Southern Mendocino counties. Due to the dry levels, little to no precipitation was recorded at the surface. A weak front will push the upper low back south on Thursday. High pressure ridging will then attempt to nose back in from the west Friday, when inland valley high temperatures will rise to the low to mid 90s Friday. Offshore winds will increase overnight Friday and into Saturday as the pressure gradient squeezes between the approaching trough and the cutoff low in Southern CA. This will likely bring some warmer temperatures, particularly at the coast. The ridge will quickly begin to breakdown going into the weekend as a NE Pacific trough takes shape and aims towards California. Temperatures will trend much lower Sunday with the arrival of cloudcover and chances for light rainfall as the trough nears. The trough and associated cold front will then move in on Monday. The system will contain a band of high precipital water values and likely a somewhat strong southerly jet. That said, the IVT (integrated water vapor transport) values are forecast to be 250 to up to 500 kg m-1 s-1. This would be sufficient for a weak atmospheric river type system which may bring some periods of heavier rainfall rates. The US Drought Monitor now has a good portion of Humboldt and Trinity County in the 'Abnormally Dry' category, with Del Norte entering 'Moderate Drought', so this rainfall will be welcomed and beneficial. A second trough may take shape and aim towards our region Tuesday or Wednesday, but details are less defined at this moment for how that evolves. NBM holds up to a 64% chance for 24 hour rainfall totals over 0.5 inch Monday and again Tuesday. There is also a moderate chance (40-40%) for over 1 inch of rainfall to fall Monday and again Tuesday. Higher precipitation totals would be likely over the higher more southerly oriented terrain. The ensembles still hold a large range in 24 hour totals, with a lower but growing chance for 1-1.6 inch values. Breezy southerly winds will also be likely with these systems. These series of fronts are currently forecast to turn temperatures much cooler mid to late next week, with some inland frost possible in the coldest valleys. JJW && .AVIATION...The coastal areas are seeing stratus this morning, with CIGS in the LIFR range, although so far they have remained above airport minimums. They may drop slightly towards morning, but are generally expected to remain steady. Thursday morning some northeast winds develop, especially near KCEC and this should help to push the stratus off the coast by midday. Gusty northerly winds are expected to pick up in the afternoon and this should help clear skies out as well. KACV is expected to take longer to clear, but afternoon clearing is still expected. Thursday night coastal stratus is expected to return. Farther south in southern Mendocino and southern Lake counties there are expected to be a few light showers around this morning, but these should end shortly after sunrise and only light rain is expected. There is a small chance of a thunderstorm, but these are generally expected to stay south of the area. MKK && .MARINE...Northerly winds are spreading across the waters this morning and seas have already started to increase. So have started the small craft advisories earlier. These are expected to increase to gale force earlier than expected as well so have adjusted those as well. The hires models have come into better agreement and are showing gales in the outer waters fairly confidently. These are expected to continue on Friday. These gales are expected to bring steep wind driven waves peaking around 12 to 14 feet Friday afternoon. In addition to the wind driven waves on Friday a northwest swell around 15 seconds is expected to build to 6 to 8 feet in the evening. Saturday the winds are expected to diminish and the gales are expected to end. Sunday or Monday these are expected to become southerly and may get near gale force as an early season strong cold front moves through the area. There are still some differences in the deterministic models so have gone with the NBM. Waves are expected to increase rapidly as well. MKK && .FIRE WEATHER...Little to no rainfall was recorded from the light showers that passed over Lake and Southern Mendocino County. Northerlies ramp up over the coastal ranges Thu- Fri, after a cut- off low moves back toward south across southern California. High pressure briefly builds back in Friday when minimum RH drops back to the low teens. There will be a slight improvement in RH Saturday, but values will remain low. Offshore winds may be gusty Friday night into Saturday morning in interior Del Norte and northeastern Humboldt. Northerly winds will surge south through the Sacramento Valley and over the higher terrain of eastern Lake County Friday. This direction is favorable to be terrain enhanced, and will create some locally critical fire weather conditions given the dry minimum RH values. The critical conditions will be localized and mainly over the higher terrain. Gusty south winds followed by widespread wetting rain pis forecast Sunday night into early to mid next week from multiple stronger frontal systems. JJW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 11 AM this morning to 3 PM PDT Friday for PZZ450. Small Craft Advisory from 1 PM this afternoon to 11 PM PDT Friday for PZZ455. Small Craft Advisory until 11 AM PDT this morning for PZZ470. Gale Warning from 11 AM this morning to 3 AM PDT Saturday for PZZ470. Small Craft Advisory from 6 AM this morning to 3 PM PDT this afternoon for PZZ475. Gale Warning from 3 PM this afternoon to 3 AM PDT Saturday for PZZ475. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. Additional updates will be issued as needed. 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