Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
820 FXUS66 KEKA 252136 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 236 PM PDT Tue Jun 25 2024 .SYNOPSIS...Interior warm and dry conditions continue while marine stratus dampens coastal temperatures. Potential for high-based storms will diminish as mid-level moisture pushes out of Northern California. An upper level disturbance mid-week will allow for relatively cooler temperatures through Thursday. A warming trend returns for this weekend into next week. && .DISCUSSION...This afternoon, mid-level tropical moisture funneled to the region by upper level high pressure over the Southwestern United States continues through Northwest California bringing the threat of elevated instability. Into this evening, dry lightning is a potential threat, especially for interior Mendocino and Lake counties with an even lesser threat for interior Humboldt and Trinity counties. Lower levels are consistently dry, limiting development but still posing a threat for gusty winds and potential for dry lightning strikes. More on this will be mentioned in the fire weather section below. Otherwise, Pacific high pressure continues to flatten and weaken as an upper level trough moves into the Pacific Northwest. Models suggest that a weak front, associated with the trough, will pass through Northern California by early tomorrow. As a result, cooler temperatures are expected throughout the region, especially for the interior where tomorrows high temperatures are forecast to be 5 to 10 degrees cooler. This pattern change, expected early Wednesday into Thursday, will also bring slightly elevated westerly winds. This will be a concern for fire weather in the case of any dry lightning starts - NW wind gusts from 15-25 mph are possible alongside RH`s <30% in Lake/S Mendocino counties. At the coast, lack of significant winds and an inversion will keep stratus locked in with minimal afternoon clearing through the middle of the week. Towards the end of the week, broad ridging will build back into the region leading to a general warm up for the interior before the potential for another disturbance early next week. && .AVIATION... ACV/CEC...Coastal fog is being stubborn today as an eddy system has developed along the Del Norte and Humboldt coasts. Winds remain relatively light (>10kts) yet cloud coverage and visibilities have been highly variable. At ACV, visibilities have been fluctuating between 10mi and 1.25mi as the stratus layer flows in and around the air space. CEC remains socked at the moment as southerly flow advects a steady flux of low stratus over the terminal`s peninsula. Later this evening, the marine stratus layer should remain or reform, depending on the state of clearing today. LIFR conditions are forecasted due to decreased visibilities from mist as well as low cloud ceiling heights, as model guidance shows a 60% chance of cloud bases >500ft at ACV. UKI...An upper level trough is approaching our area within the next 16 hours or so. This upper-level disturbance will lead to a change in the prevailing conditions in the terminal space. Firstly, there is a non-zero chance of vicinity thunderstorms around UKI. There have already been reports of showers in Mendocino Co. as spotty convective showers are flowing into the area from the Southwest. Secondly, the cloud layer above the terminals will be broken then scattered at the middle levels, so VFR conditions should still persist through the TAF period. && .MARINE...Sea conditions are forecasted to calm in the next few days due to a decrease in the strength of the thermal trough which drives most of our strong northerly winds. Winds south of Cape Mendocino will be stronger than other areas of the coastal waters, yet no official hazards are currently forecasted for this area. A swell arriving from the northwest (4ft at 9s) will be the main factor influencing the sea state tonight into tomorrow. A persistent stratus layer has formed in the coastal waters as well and could possibly lead to decreased visibilities in the early hours of the morning tomorrow (20% chance of >1mi.) Seas will continue to diminish until late this week when the thermal trough builds again ins strength and strong northerlies return to flow. && .FIRE WEATHER...Low potential for isolated dry lightning continues into this evening within elevated convection. Still, some of these storms could produce gusty outflow winds. Increasing NW flow tomorrow combined with <25% RH values may pose a fire weather risk in the case of any potential starts this afternoon. Greatest threat to fuels are areas below 2000 feet. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None. && $$ 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