Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
299 FXUS66 KEKA 031153 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 453 AM PDT Mon Jun 3 2024 .SYNOPSIS...Post-frontal showers tapper off this morning. Hot, dry weather will rapidly build back in mid week with high heat risk for many interior valleys, especially Lake County, Wednesday and Thursday. Breezy north- northwesterly winds return Wednesday and Thursday, with gusty winds over the coastal headland and exposed ridges. There is a potential for late afternoon and evening thunderstorms on Thursday in northern Trinity. && .DISCUSSION...A cold front is moving onshore across northwest California early Monday morning. As of 2AM PDT, a period of heavy rainfall was occurring along the coastal ranges in Del Norte County and northern Humboldt with rainfall peaking into 0.25" to around 0.35"/hour range. As the front continue moving east, rain has spread across Humboldt County and is spreading into portions of Trinity and northern Mendocino. The cold front will continue to eject eastward away from the west coast, with post- frontal showers gradually tapper off during the morning hours. Temperatures will be cooler across the interior with highs in the 70`s. High pressure over eastern Pacific will build quickly over the West Coast in the wake of the this front. The mid level heights will rise slightly, and a warmer airmass will gradually develop across the WRN CONUS during the remainder of the week. Interior highs temperatures are forecast to peak on Wednesday and Thursday, with values across the hottest valleys ranging from 95-105 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. Thus, this will affect anyone without effective cooling and/or adequate hydration. As a result, a Heat Advisory is in effect for Lake County from Wednesday morning through Thursday night. An advisory product is not ruled out for Trinity and the interior portion of Mendocino. Elsewhere, slightly cooler temperatures in the 90s are expected within interior Del Norte and interior Humboldt. Temperatures along the coast are expected to warm up as well, but nothing significant with highs just few degrees above normal. 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 25 to 35 mph at times...locally higher gusts possible over the King Range. NBM probabilities shows a 60% to 80% fro gusts of 40 MPH or more in the KIng Range, and 45% chances for Crescent City. Some moist inflow from the south will bring the potential for late afternoon and evening thunderstorms on Thursday, or even overnight thunderstorms. GFS and NAM model sounding guidances are suggesting elevated instability and steep lapse rates over Trinity County. At this point, include a slight chance of thunderstorm over the Trinity Horn Thursday evening, where thunderstorms development looks possible. Friday and into the weekend, the ridge starts to shift eastward and the flow becomes more zonal. This is expected to start to deepen the marine layer and bring some cooler air to the coastal counties, mostly north Cape Mendocino. Trinity, eastern Mendocino and Lake counties are not expected to see much change on Friday. Temperatures will continue to slightly cool down during the weekend. && .AVIATION...With the passing of an atmospheric river, rain rates have increased in the northern sectors of the CWA. This includes KCEC which experienced heavy rain overnight reducing visibility to 4 miles or less. Gusty southerly winds have begun to ease at KCEC as of 11z and rain rates are expected to decrease by day break. LIFR conditions currently at KCEC will improve to MVFR by the afternoon as ceilings lift and visibility improves. Winds have been out of the southwest at KACV with LIFR conditions expected to improve to MVFR by the afternoon as well. Light rain and low visibility at KACV will improve to MVFR by the afternoon as well. KUKI will begin to get light precipitation by the late morning as the moisture plume shifts south. Gusty north winds return to KUKI by the early afternoon with MVFR to VFR conditions prevailing. /EYS && .MARINE...Summary: A series of small mid period swells through Tuesday will be followed by a seasonably large and long period WNW swell on Wednesday. Northerly winds increase Tuesday in the southern zones, and will strengthen and expand north Wednesday. The short period N seas and long period WNW swell will create a chaotic seas state Wednesday. Today, a slightly larger, mid period NW swell will move in, building to 6-8 ft at 11 seconds early Tuesday morning. Light, split wind flow will transition to strengthening northerlies in the southern zones Monday night. Tuesday, the NW swell will hold in size, then a slightly larger reinforcing mid period swell then pulses in Tuesday afternoon with seas 6 to 8 ft. Northerly winds in the southern waters will further increase, reaching 22 kts south of the cape in the afternoon. A strong gale on the southern periphery of a late season Aleutian low pressure area, driving eastward, will deliver a long period swell on Wednesday. A resulting seasonably large, long period WNW swell (300 degrees) will build in early Wednesday morning, currently forecast 10 to 12 ft at 15 seconds. Northerly winds will be on the increase throughout the day, with gale conditions probable in portions of the waters by late Wednesday. There looks to be some shelter from the strongest winds in the northern inner zones. The combination of steep, short period northerly seas and the long period swell will generate a confused sea state up to 15 ft On Thursday, the long period swell will begin slowly easing in size. The northerlies will offer more potential Gale gusts in portions of the waters in the wind favorable locations south of the capes, with some shelter in the inner zones. /JJW /EYS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Heat Advisory from 8 AM Wednesday to 8 PM PDT Thursday for CAZ114-115. 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