Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
715 FXUS66 KEKA 262146 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 246 PM PDT Wed Jun 26 2024 .SYNOPSIS...An upper level disturbance and associated surface front will produce widespread marine stratus and relatively cooler temperatures through Thursday. Slight warming to end the week, with hotter temperatures next week. && .DISCUSSION...Widespread marine stratus once again inundating the NorCal coast with <1000 foot ceilings, reduced viz and drizzle amidst light southerly flow. HREF indicating these conditions will persist through the morning as moist onshore flow advects low fog and mist further inland and into coastal river valleys. Accumulations of a few hundredths of an inch of precip on the Redwood Coast are possible by late morning. An upper level trough will steadily converge onto the north coast, providing just enough lift to mix the BL and break up the stratus deck with afternoon diurnal heating. It is unlikely that cloud cover will completely dissipate before a resurgence of moisture along the surface frontal boundary late Wednesday evening. Hi-res models including HREF have been showing potential for light precip on Humboldt and Del Norte coasts by early Thursday morning as this front traverses the region. With this upper trough also comes cooler temperatures across the CWA. Highs only expected reach the mid 70`s to low 80`s across the interior while coastal highs continue to be dampened by marine stratus. NBM anticipating some valleys in southern Mendocino, Lake and eastern Trinity counties to rise into the upper 80`s, although probabilities significantly fall off at 90 degrees. Enhanced NW winds are also expected this evening and overnight, especially in Lake and Trinity counties. Wind gusts 15-25 mph are possible alongside 20-35% RHs before recovering to 50-60% overnight. A similar pattern is expected Thursday as stratus struggles to clear beneath a marine inversion. Similarly cool temperatures and diurnally driven NW flow expected with the lowest RHs remaining in eastern counties bordering the Sac Valley. Coastal winds may increase in the afternoon as the thermal trough redevelops beneath building high pressure. Broad, weak ridging is expected to continue late this week with slightly warmer temperatures. Additional upper shortwaves will provide similar disturbances this weekend before potentially for a more substantial return to warm and dry conditions early next week. && .AVIATION...A very deep marine layer blanketed much of the Humboldt and Del Norte coastlines...and penetrated well inland today. Impacts at the air terminals were quite variable as CIGS ranged from LIFR/IFR to MVFR. Morning profiler data and pilot reports (pireps) indicated tops from 3000-3400 feet. In Mendocino, tops were barely 2000 feet; clouds could not spill over the coastal range into the UKI Valley...so UKI remain SKC. As of mid- afternoon, expectations are still for at least some partial clearing as a low pressure disturbance approaches the North Coast and disrupts the marine layer. Yet, still expecting lots of diverse cloudiness. Light breezes forecasted at the coastal TAF sites today. However, winds will pick up at UKI in the afternoon with low gusts speeds 18-20 mph. /TA && .MARINE...Light, split wind flow has developed in the northern waters today as a trough passes by. Winds along and south of Cape Mendocino are quickly picking up this afternoon, and there will be near gale gusts near the coast in the northern inners waters (zone 455). Northerlies will increase and spread from south to north across the coastal waters Thursday into Friday, with the strongest winds across the outer waters. Wind driven seas are expected to become steep and hazardous for small craft as result. Small Craft Advisories have been launched for Thursday in the southern zones, and expansion into the northerly zones into Thursday night should be expected. Near gale to locally gale force gusts are possible across the outer waters on Friday, generating steep seas, with short period seas picking up to around 8 to 10 feet at 8 to 9 seconds Friday afternoon. Winds diminish throughout the weekend as another upper level trough moves over the area. && .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