Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
149 FXUS66 KEKA 240000 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 400 PM PST Sat Nov 23 2024 .SYNOPSIS...Series of fronts will bring periods of rain, mountain snow and gusty southerly winds Sunday through Monday. Drier weather and colder temperatures are anticipated for mid to late next. && .DISCUSSION...Radar reflectivity imagery showed light showers moving across the area this afternoon. A brief break in the rain is expected this evening before precipitation increases again by early Sunday morning. The next round of moderate to locally heavy precipitation rates is expected to arrive Sunday as a surface cyclone approaches the west coast. Periods of light to moderate and brief locally heavy precip is expected to continue Monday as another shortwave trough progresses across the area. These fronts will be progressive and have less moisture flux compared to our long duration AR Tue-Fri. 6-hourly rainfall and snowfall rates and storm total rain and snow amounts are forecast to be much less with limited potential for major impacts. We posted a weather story graphic of 2-3 day rainfall totals on our web page and facebook page. Highest 2-3 day totals are expected over the King Range and Del Norte County (2-4 inches of storm total rain). The precip is forecast to wind down through the day on Tuesday as the northeastern Pacific trough complex shifts eastward across the area and above normal 500mb heights builds toward the west coast. An occluded frontal boundary will approach the North Coast late tonight into Sunday morning. The surface pressure gradient is forecast to tighten by midday Sunday as a low level jet (925mb) around 50 kts develops over the North Coast. A well-mixed boundary layer near or along the surface front will allow for higher momentum air to mix down to the surface. Gusts to 40-55 mph are probable over the coastal headlands and higher terrain of interior Del Norte and Humboldt. NBM and HREF ensemble means indicated gusts of 25-35 mph for the lower elevations, while the ECMWF ensemble indicated mean gusts near 50 mph for Crescent City and near 40 mph for Humboldt Bay and Eel delta. Even below advisory gusts could cause trees to uproot due to saturated soil. Isolated low-topped thunderstorms will also be possible mostly over the coastal waters and near the coast in response to mid level cooling and southerly flow at the surface late Sunday into Monday. The greatest risk for storms appears to be south of Cape Mendo initially on Sunday. Convective activity is expected to shift northward Sunday night into Monday. Some small hail is possible. Freezing levels look to high for any accumulations. The main threat will be lightning strikes and perhaps very brief heavy downpours. Swift storm motions will preclude any major concerns for flash flooding or debris flow. Snow levels start around 3000-4000 feet Sunday, and are forecast to gradually rise to about 4500-5000 ft through the day Sunday into Monday. Up to 1 feet of snowfall is expected above 4500 feet in NE Trinity County from Sunday afternoon into Monday afternoon. A Winter Storm Warning is in effect from late Sunday morning for elevations above 4500 ft in NE Trinity County, which includes Scott Mountain Pass on Highway 3. Lighter snow accumulations around 1 inch are possible for Buckhorn Summit and Trinity Center before levels rise in the afternoon. Precip rates are much lighter over lower elevations and the potential for low snow levels is much lower compared to the heavy snow event we had on Wednesday in NE Trinity. Upper ridging is forecast to builds into the West Coast downstream the mid-upper level trough Tuesday night and Wednesday. This will restore more peaceful and dry weather mid to late next week, though after multiple days of rain, valleys will no doubt fog up during the night and morning hours. Chilly morning are expected Wednesday and Thursday morning with low temperatures ranging from mid 20`s to mid 30s. DB && .AVIATION...Intermittent MVFR has plagued the Redwood Coast today as scattered showers move over the coastal terminals. Shower activity is forecast to decay tonight as a another front approaches the coast. VFR is expected overnight, and south winds are forecast to sharply increase Sunday morning. Winds increase through the day tomorrow, and gusts of 30 to 40 kts are possible along the Redwood Coast tomorrow afternoon. MVFR ceilings should redevelop by around midday as this feature approaches, and intermittent IFR cigs and vis from rain and mist are likely as it moves overhead. /TDJ && .MARINE...Seas weaken through this afternoon as short period SW and NW waves decay. Southerly and southeasterly winds will increase tonight into Sunday as another surface low and cold front approaches the coast. This front looks dynamic and unstable, with 40 to 50 kt winds present just above the surface. Convective showers should intermittently mix down these stronger winds across all zones, especially as the boundary of the front sweeps overhead. Have hoisted a gale warning in response. Greater uncertainty arises early next week as additional frontal systems or troughs pin-wheel around a nearly stationary surface low that will wobble around over the NE Pacific, however winds generally look lighter with these waves. Northerlies, at least for the outer zones, may return mid to late next week as a rex blocking pattern develops offshore...with the associated low centered to our south and offshore of the Central CA Coast. This may bring a prolonged period of relatively light winds and low seas late next week. MH/TDJ && .HYDROLOGY...All main stem rivers continued to recede today. Eel River at Fernbridge is forecast to recede below monitor stage late this afternoon. Additional rainfall is expected to arrive Sunday through Monday, with 6 hourly rain rates of 0.50in in the King Range and windward slopes of Del Norte. Receding trends will flatten out or trend up with minor rises, especially in the Smith basin by the end of the 3 day period. Smaller streams and creeks may be more responsive to short duration to modest rain rates and minor impacts are possible due to saturated grounds. DB && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Wind Advisory from 6 AM to 4 PM PST Sunday for CAZ101-102- 104>106. Winter Weather Advisory until 4 PM PST this afternoon for CAZ107. Winter Storm Warning from 10 AM Sunday to 4 PM PST Monday for CAZ107. NORTHWEST CALIFORNIA COASTAL WATERS... Gale Warning from 5 AM to 5 PM PST Sunday for PZZ450-455. Gale Warning from 2 AM to 5 PM PST Sunday for PZZ470-475. && $$ 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