FXUS66 KEKA 101301 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 501 AM PST Sun Nov 10 2024 .SYNOPSIS...A weak front departs this morning ahead of a stronger front which will deliver breezy southerly winds and a band of moderate to heavy rainfall tonight through Monday morning. Unsettled weather will continue through next week, including a strong front due some time around early Wednesday. && .DISCUSSION...The circulation of a weak, surface low is viewed off the coast this morning on satellite. Only trace amounts of precip were observed from it, and it will soon be absorbed by a stronger, negatively tilted trough and strong associated front that is due to arrive early Monday morning. With increasing southerly winds, warm sector shower activity will develop and persist through tonight. The timing of this next front has shifted earlier. Winds will be gusty later this afternoon, and will continue to increase late tonight with gusts of 25 to 35 mph and higher gusts in excess of 50 mph for the highest interior Del Norte ridges and the King Range through Monday morning. There remains a decent chance (60%) for some gusts to reach 45 mph for portions of Crecent City, especially out closer to Point St George. CAMS are resolving a well-defined precipitation line along the cold front some time to arrive at the coast around 1 to 4 AM Monday morning. This line will likely bring widespread moderate rain and brief, embedded heavy rainfall rates along it (0.3 to 0.4 inches per hour). This combination of wind and heavy rainfall will increase the risk of extra debris and ponding on roadways. Rainfall totals look to be 1-2 inches over the SW facing higher elevation, with interior Del Norte getting closer to 2.5 inches. Lower elevations will range around 0.5 to 1 inch. Southern Lake County is forecast to receive 0.3 to 0.5 inch of rain as well. Instability and forcing will increase behind the front as the cold trough moves through. Isolated thunderstorms will be likely Monday through Monday evening, mainly over the coastal waters and through portions of the North Coast. Lingering showers will briefly ease for some of Tuesday before rain chances increase again Tuesday night ahead of a second and stronger trough, but timing is still in question. Ensemble impact guidance continues to highlight wind and perhaps rainfall as impactful. WPC currently has northern portions of the forecast area at a Marginal Risk for excessive rainfall Wednesday. Currently, the axis of most concentrated IVT is forecast over the Southern Oregon border. Still not expecting flooding concerns at this time due to lower river levels and the current rainfall forecast, which is still at the beneficial level. This second trough will have better dynamics, including IVT values that look to reach 500 and up to 700, and strong winds aloft that will coincide with surface instability. This will bring better confidence for the strong 850 to 925 mb winds that look to be 50 to over 60 kts to mix down closer lower elevations. For this reason, winds continue to be a concern, and Wind Advisories may be needed. There is a 65% chance for winds gusts of over 50 mph out at Crescent City, especially closer to Point St George. Ensembles suggest 55 to maybe 60 mph maximum gusts are possible at that location. Wind gusts over 40 mph are probable along the exposed coastal headlands elsewhere, and the interior ridges of Del Norte and the King Range have a high chance for gusts over 55 mph at this time. There is still uncertainty with the timing and the southern extent of that highest moisture transport, which still could drift farther south over our forecast area and increase our rainfall amounts. A much cooler airmass looks to then settle in behind the fronts late next week. JJW && .AVIATION...A weak front has moved through, but very little rain was reported with it and conditions remained VFR. Today the next front starts to approach the area. This will bring increasing south winds in the afternoon and evening. Conditions are expected to remain VFR through the afternoon with some MVFR clouds possible at CEC in the evening. Southerly winds continue to increase this evening, especially at the higher elevations. Ahead of the front some low level instability should allow some gusts over 30 KT to mix down to the surface. Winds of 40 to 45 kt at 2000 feet will create the potential for wind shear, but it should mainly be speed shear. Late tonight the front is expected to move through and winds may actually diminish with the increased low level stability during the heavier rain. MVFR or IFR conditions are expected with the period of heavy rain late tonight. MKK && .MARINE...Relatively light southerly winds persist across the waters this morning with most areas less than 10 kt. Waves are generally around 8 feet at 13 seconds. Southerly winds are expected to increase this afternoon as a stronger front approaches the area. However, with these ongoing light conditions pushed back the start of the small craft advisory to 9am in the northern outer waters and noon in the southern outer waters. Later this afternoon and evening as the winds get stronger have expanded the small craft advisories to the inner waters and upgraded the gale watch to a warning in the northern outer waters. The ongoing northwest swell is expected to diminish to around 4 to 6 feet at 12 seconds by this evening. Winds will diminish Monday behind the front. Late Monday afternoon through Tuesday morning the models are showing a large swell moving into the waters. The models have backed off slightly on the heights by a couple feet to around 16 to 19 feet at 16 seconds. This swell is currently being generated by a 965 mb low in the Gulf of Alaska. Confidence is growing as the waves are being generated now. Tuesday night into Wednesday models are coming into better agreement on another front moving into the area. This one is expected bring stronger winds with the potential for sustained gale force winds in the northern outers and gale force gusts farther south. Lighter winds are expected Wednesday night and Thursday. MKK .Beach Hazards...The swell has trended slightly lower and now waves heights to 16 to 19 feet at 16 seconds are expected. This is expected to bring breakers of 20 to 22 feet which makes it very close to the high surf advisory criteria of 22 feet. For now will hold off on the high surf advisory in case the downward trend continues. Another wave of 13 to 15 feet at 14 seconds is expected Wednesday night and Thursday. MKK && .HYDROLOGY...A succession of frontal systems will bring likely beneficial rainfall amounts, but periods of heavy rainfall rates will accompany the fronts. The forecast is not certain for where the heaviest rainfall will end up on Wednesday for the stronger front however, and the Weather Prediction Center has placed a Marginal Risk for excessive rainfall for that day. JJW && .BEACH HAZARDS...The swell has trended slightly lower and now waves heights to 16 to 19 feet at 16 seconds are expected. This is expected to bring breakers of 20 to 22 feet which makes it very close to the high surf advisory criteria of 22 feet. For now will hold off on the high surf advisory in case the downward trend continues. Another wave of 13 to 15 feet at 14 seconds is expected Wednesday night and Thursday. MKK && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 PM this afternoon to 5 AM PST Monday for PZZ450. Small Craft Advisory from 6 PM this evening to 7 AM PST Monday for PZZ455. Small Craft Advisory from 9 AM this morning to 9 PM PST this evening for PZZ470. Gale Warning from 9 PM this evening to 3 AM PST Monday for PZZ470. Small Craft Advisory from noon today to 7 AM PST Monday for PZZ475. && $$ 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