Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
522 FXUS66 KEKA 042312 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 412 PM PDT Thu Jul 4 2024 .SYNOPSIS...The long-duration extreme, record breaking heat wave will continue. The strong dome of high pressure will begin to center over N CA, with even further increasing temperatures through the weekend. Hot temperatures will remain next week. The heat risk will also be accompanied with fire weather concerns. && .DISCUSSION...Afternoon observations reveal widespread inland temperatures over 100. Weak surface low pressure is attempting to guide stratus up from the south and closer to the Mendocino coast. This is expected to be achieved tonight, with coverage eventually up the Humboldt coast. This may impact coastal temperatures if coverage makes it over land, but models have been overestimating the cloud cover thus far. Weakness in the northerlies with additional southerly return flow will bring additional chances for coastal stratus at times through the weekend. Visible satellite is not currently showing smoke making it into the area from the Shelly fire in Siskiyou County, but some smoke and haze may push back west overnight. The strong dome of high pressure (597 dam) is currently centered just off of the CA coast. The high will continue moving closer to N CA, and will be centered over us on Saturday, which will be the hottest day. The center of the high will only slighlty weaken and nudge SE, where it will remain parked thereafter. The Excessive Heat Warning has been expanded into Southern Humboldt, and most of the heat products have been extended through Monday for this reason. Temperatures will only slowly tick down early next week, but Moderate to Major HeatRisk will continue for the interior valleys, likely much of next week. Fire weather conditions will be a growing concern as the high moves in and the diurnal westerly to north westerly winds become further invigorated alongside weak coastal surface low pressure areas. A stronger coastal trough looks to form early next week and may be able to grab some mid level moisture around it from the south. At this time thunderstorm formation does not seem likely, but the pattern will be watched closely given the current drying underway. && .AVIATION...SKC prevail across all TAF sites and over the region today. Visibilities were mostly VFR except along the coast where periods of MVFR occurred due to haze and possibly pockets of wildfire smoke in the morning. Winds were mostly light today as the pressure gradient was weaken by shifting surface pressure...and a southerly reversal of winds. Some model data is very pessimistic about low Vis and some stratus at the coast on Friday morning. /TAA && .MARINE...Winds and seas will continue to subside considerably this afternoon, rapidly reaching sub-advisory levels across all zones. Hi- res models are anticipating a surge of coastal stratus riding up the coast along a southerly wind reversal late tonight into Friday, potentially producing widespread marine fog. Otherwise, weak NW wind waves and a long period southerly swell will moderate wave heights to 5-6 feet at 8 seconds through Sunday. Northerly winds are expected to redevelop into early next week beginning in the southern waters. && .FIRE WEATHER...The building heatwave will continue to bring enhanced fire danger through the weekend. As highs climb closer to 110, RH has cratered, with many interior valleys reporting RH values between 5 and 10% this afternoon. Overnight conditions will bring little relief with very poor RH recoveries of 25 to 40%. As the strong area of high pressure moves eastward, the local pressure gradient will become more favorable for enhanced diurnal winds as RH values continue to crash to the low teens and single digits. Reg Flag conditions are expected to be met, especially in the afternoons and evenings in NE Trinity County Saturday through Sunday and Southern Lake County Friday through Saturday.. Elsewhere, periods of critical fire weather are expected during the afternoons where terrain winds are enhanced, such as along the Trinity River Valley. Strong thermal belts will help promote critical conditions even at night, especially with moderate, dry northeast winds building each night on high ridges, primarily in the Klamath Mountains. JHW/JJW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Heat Advisory until 8 PM PDT Monday for CAZ102-112. Heat Advisory until 9 AM PDT Friday for CAZ104-106. Excessive Heat Warning until 7 PM PDT Monday for CAZ105-107- 108. Excessive Heat Warning from 10 AM Friday to 8 PM PDT Saturday for CAZ106. Fire Weather Watch from Saturday afternoon through Sunday evening for CAZ283. Excessive Heat Warning until 8 PM PDT Monday for CAZ110-111- 113>115. Red Flag Warning from 3 PM Friday to 11 PM PDT Saturday for CAZ264. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 PM PDT this evening for PZZ470- 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