Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
978 FXUS66 KEKA 271109 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 409 AM PDT Mon May 27 2024 .SYNOPSIS...High temperatures will be warm and summer-like today inland due to an upper level ridge that has remained over over the Western US during our holiday weekend. After a trough and subsequent cooler temperatures Tuesday, much warmer temperatures are expected late week and are eventually expected to peak on Friday. && .DISCUSSION....Night skies are clear over Trinity and Lake counties as an upper level high pressure over our areas is keeping upward motion from initiating. Coastal stratus has already started its battle to fill in the low elevation coastal areas tonight. Satellite imagery is already showing dense coverage over most of the northern Humboldt coast while at Mendocino and northern Del Norte counties, winds at about 2500ft are flowing offshore. This offshore flow is currently prohibiting the possibility of marine stratus reforming due to compressional heating. HREF probabilities for cloud heights below 1000 ft are around 55 percent for Humboldt Bay, 25 percent for the Del Norte Coast, and 35 percent for the Mendocino coast. whatever stratus that does form is expected to lift by the late morning and mostly clear skies and pleasantly warm temperatures will then prevail throughout this Memorial Day. Temperatures inland Monday will warm steadily throughout the day as solar heating will have no hindrance due to clouds, with high temperatures in the low to mid 80s in most of the interior valleys. Coastal temperatures will range from the upper 50s and 60s with breezy onshore winds building throughout the day. A trough moving through this afternoon will allow for some moisture and instability to move through. This combined with increased temperatures will enhance instability, bringing the potential for some light rain showers to pop up in the higher terrain of Trinity and Mendocino counties. The chance for thunder is nonzero, but with little mid-level moisture and low lapse rates, chances are low. NBM gives around a 10 percent probability to see thunder, while SREF gives around a 20 percent chance. The an incoming trough arriving Tuesday morning will allow the formation of more coastal stratus and even some drizzle. Widespread high altitude cloud cover on Tuesday morning will lead to cooler temperatures inland on Tuesday afternoon. A ridge will reform over the area on Wednesday, gradually warming up the interior. Mid to high 80s are forecast for Thursday, while high 80s to low 90s are forecast for Friday. Afternoon wind gusts are possible as well, with probabilities for wind gusts above 25 mph near 70 percent along the coast Thursday and gust above 30 mph near 35 percent Friday. An even stronger ridge will lead to warm temperatures peaking on Friday as confidence builds among model ensemble members. Ensemble members are even starting to show some agreement on a weaker ridge persisting at least through Saturday. DS .AVIATION....Some status has spread across Humbodlt county along the coast and up the inland river valleys. So far this has brought MVFR conditions, but these are gradually lowering and will likely drop into IFR for a period of time this morning. This is also expanding and may make it into Crescent City this morning bringing ceilings around 1000 feet. These clouds are expected to erode by midday, but return in the evening. An approaching trough may bring some drizzle and lower visibilities along with IFR ceilings tonight. Short periods of LIFR are possible but the probabilities of it being this are lower. MKK .MARINE...An upper level trough moving into the Pacific Northwest will keep winds lighter today and Tuesday. Winds will be slightly stronger south of Cape Mendocino and have extended the small craft advisories out through Tuesday night. Waves are a combination of wind driven seas and a small northwest swell around 9 seconds. Tuesday a new swell builds in to around 6 feet at 12 seconds by the afternoon. Wednesday high pressure starts to strengthen again and this brings near gale to gale force winds to the waters. Confidence is growing in these gales. The NBM is showing over an 85 percent probability of gale force gusts on Thursday. Once these winds pick up the swell is expected to be obscured by the wind driven waves. Winds are expected to start to decrease Friday and into the weekend. MKK && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Wednesday 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