Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
279 FXUS66 KEKA 051253 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 553 AM PDT Wed Jun 5 2024 .SYNOPSIS...High pressure and hot interior temperatures will continue to intensify today and will peak on Thursday. This pattern will bring major heat risk to hot interior valleys, especially in Lake County. Otherwise typical summer weather will continue through the weekend. && .DISCUSSION...Surface high pressure will continue to build today, bringing hot interior temperatures. NBM shows a 15 to 30% chance of highs over 100 this afternoon with a 50 to 70% chance of such highs by Thursday afternoon. Heat risk will be greatest in southern Mendocino and especially Lake County where the strong inversion of the Sacramento Valley will help keep overnight lows as warm as 70. Such prolonged heat will be sufficient to pose a major risk to at risk groups. That said, all forecast highs are well below record highs for this time of year which are closer to 110 for most interior valleys. Beyond temperature, strong solar heating will also help increase surface instability. At the very least, this will most likely generate more impressive and visible afternoon cumulus clouds over high terrain. Model sounding suggest an impressive 600 to 1000 J/Kg of CAPE of the Trinity Alps late Thursday afternoon. Despite this fact, total column moisture is marginal at best and any lifting would have to break through a midlevel cap and reach near 20 kft to for thunderstorm formation. These factors make the formation of isolated afternoon thunderstorms possible though unlikely (10 to 15% chance) Thursday evening. Closer to the coast, high pressure will continue to promote a thin but persistent marine layer with temperatures solidly in the 60s and stubborn coastal fog and stratus. Strong heating, however, will most likely promote gusty north winds in the afternoon that will at least temporarily help disrupt cloud cover. High pressure will weaken into the weekend with a narrow trough crossing the area around Sunday. Such a pattern will push marine influence further inland and bring interior temperatures back into the low to mid 80s. With little moisture to speak of, however, essentially no ensemble members show rain with the trough beyond coastal drizzle. Essentially all cluster ensemble members show a ridge of high pressure centering over the Pacific Northwest early next with low pressure stalled off the California Coast. Such a pattern will bring typical to slightly above average summer temperatures. Only about 15% of ensemble members currently show any temperatures hotter than the current heat wave. /JHW && .AVIATION...Stratus overnight has made its way up the Eel valley, and may make it as far as Ft. Seward before sunrise. Stratus has developed more density in the early morning hours, bringing flight categories down to LIFR at KCEC and KACV with 1/4 to 1/2 mile visibility and 200 foot ceilings. Soundings at the coastal terminals show a subsidence inversion lasting into the early afternoon but mixing and drying out soon after with VFR/MVFR until the evening. Models are showing a southerly reversal which may bring stratus back tonight and a return to LIFR conditions at KCEC and KACV by late tonight. KUKI will have prevailing VFR conditions with a return of gusty northerlies by the afternoon. /EYS && .MARINE...Northerlies have already ramped up this morning with gusts at Pt. St. George and Pt. Arena around 20 to 25 kts. The southern waters will be the first to reach Gale in coverage by the afternoon with the northern waters reaching near Gale in most areas but focused expansion fans will be closest to Oregon waters near the 41.6N latitude. Gale gusts to 40 kt are probable again on Thu, but once again the coverage appears to be localized and confined to narrow corridors in the outer waters. Steep short period waves will steadily build today, reaching 9 to 11 feet at 9 seconds. This is borderline for a hazardous seas warming, but sufficient when decaying NW swell is added. A late season NW swell of 10 to 12 feet at 16 seconds will also arrive early today and then gradually decay through Friday. The combination of the NW swell and locally generated northerly waves will yield seas up 13 to 15 feet by late this afternoon and into the evening. This typical strong northerly wind regime with very steep northerly waves will persist into Thu before backing off on Fri. Steep northerly waves and resurgence of northerly winds is expected for the weekend, though exact magnitude of winds and timing remain uncertain. Combined wave groups this morning around 8 to 10 feet at 11 to 12 seconds will occasionally meet small craft criteria but most of the concern will be for late tonight into Wednesday morning. A combination of Gale force gusts and a long period swell from the NW with 10 to 12 ft wave heights and periods around 16 seconds, will produce hazardous seas in the northern waters and Gales in the southern waters. Of particular concern is the threat for beach hazards in the form of rough surf and sneaker waves as weather will be warm and inviting for beachgoers from Wednesday into Thursday. Do not turn your back on the ocean! Also be cautious around inland rivers with cold water and swift currents! /DB /EYS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Beach Hazards Statement through Thursday morning for CAZ101- 103-104-109. Heat Advisory from 8 AM this morning to 8 PM PDT Thursday for CAZ114-115. NORTHWEST CALIFORNIA COASTAL WATERS... Hazardous Seas Warning until 3 PM PDT Thursday for PZZ450- 470. Gale Warning from 8 AM this morning to 9 AM PDT Thursday for PZZ455-475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png