Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
946 FXUS66 KEKA 041257 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 557 AM PDT Tue Jun 4 2024 .SYNOPSIS...Hot, dry weather will rapidly build by mid week with high heat risk for many interior valleys, especially Lake County, Wednesday and Thursday. Breezy north to northwesterly winds will return Wednesday and Thursday, with the strongest gusts over the coastal headlands and exposed ridges. Isolated thunderstorms are forecast for the northern Trinity mountain on Thursday during the late afternoon and evening. && .DISCUSSION...A broad upper level ridging and above normal 500mb heights will continue to build over NW California today. IR satellite imagery shows this ridging "flatten" as a shortwave move into WA. This is bringing a few high-level clouds streaming across the northern portion of the forecast area. Otherwise, mostly clear skies with patchy fog due to the radiational cooling this morning. Interior temperatures are forecast to increase into the mid 80s to mid 90s in the interior valleys, except in southern Lake county where highs in the upper 90s are expected. Mainly minor heat risk is expected for much of area today, with a moderate heat risk for Lake County. The warming trend will continue through Thursday. Interior heat will build on Wednesday and then peak on Thursday. Model guidance has been very consistent supporting 850 mb temperatures of 24 to 28C or so over much of the interior. High temperatures in the hottest valleys are expected to range from 100-105F degrees. The heat risk is forecast to be minor to moderate over the area, but a major heat risk is expected to occur over portions of Lake County Wednesday and Thursday. The hottest day for Lake County continues to look like Wednesday. The heat will have impacts on anyone without effective cooling and/or adequate hydration. As a result, a Heat Advisory remains in effect for Lake County from Wednesday morning through Thursday night. A heat advisory may also be necessary for Trinity, interior portion of Mendocino and NE Humboldt where temperatures are forecast to peak to 100F or hotter. Temperatures along the coast are expected to warm up as well, but marine air and stratus will most likely return by tonight into Wednesday morning as northerlies increase offshore. This will put a damper on the warming potential for the North Coast. Highs in the mid to upper 70s in the lee of Cape Mendocino, across coastal SW Humboldt or around Shelter Cove is likely, however. Additionally, a thermal trough is expected to develop near the coast Wednesday. This will promote breezy north-northwesterly winds each afternoon Wednesday and Thursday over the exposed ridges and coastal headlands, with gusts from 20 to 30 mph at times...locally higher gusts possible over the King Range. The interior heat coupled with higher upper level humidity may yield an isolated thunderstorm with gusty outflow winds Thursday afternoon/evening, primarily over the mountains of northeast Trinity county. GFS and NAM model sounding guidances are suggesting elevated instability and steep lapse rates over northern Trinity County. SREF model guidances is also suggesting the thunderstorm potential. Friday and into the weekend, the ridge starts to shift eastward and the flow aloft becomes more westerly. A deeper marine layer should bring cooler-damp air to the coastal counties, mostly north Cape Mendocino. Trinity, eastern Mendocino and Lake counties are not expected to see much change on Friday. Interior temperatures will moderate over the weekend, but most likely remain above normal. Ensemble members and deterministic model guidances are showing an upper- level trough moving over the area on Sunday. Dry weather most likely persist with about 85% of the ensemble cluster analysis with not precipitation over the region. However, this trough may create sufficient instability for thunderstorms over the interior mountains, primarily Trinity County. There is still a great deal uncertainty at this point and for now will hold off on adding storms to the forecast. /ZVS && .AVIATION...Residual moisture closest to the boundary layer has kept mist and fog effects in play this morning despite the greater trend being subsidence and drier air as clearing is expected with VFR at most of the terminals through the day. KCEC and KACV could see a return of IFR conditions overnight into Wednesday morning according to MOS guidance but not all models are in agreement as high pressure will likely keep things clear with anticyclonic motion. A return of gusty northerlies at KUKI is likely this afternoon with soundings showing winds mixing down with drier air all the way to the flight deck. /EYS && .MARINE...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! /EYS && .BEACH HAZARDS...A large long period NW swell will build early Wednesday with significant swell heights up to 11 feet at 16-17 seconds during the morning. This high energy swell has the potential to bring a moderate risk of sneaker waves. Shorter period NW swell of 7-9 feet at 7-9 seconds may mitigate the risk for the Mendocino coast. However, the risk remain with the increasing of beachgoers as temperatures across the interior will be hot. A beach hazard statement has been hoisted for the entire coast. /ZVS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Beach Hazards Statement from late tonight through Thursday morning for CAZ101-103-104-109. Heat Advisory from 8 AM Wednesday to 8 PM PDT Thursday for CAZ114-115. NORTHWEST CALIFORNIA COASTAL WATERS... Hazardous Seas Warning from 6 AM Wednesday to 3 PM PDT Thursday for PZZ450-470. Gale Warning from 8 AM Wednesday 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