562 FXUS66 KEKA 171232 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 432 AM PST Sun Nov 17 2019 .SYNOPSIS...Coastal low clouds will likely persist in parts of the Humboldt coast today, but remain clear most of the day in Mendocino. Inland temperatures will continue to warm today, with chilly overnight lows in the valleys. Some light rain will be possible in Humboldt and Del Norte counties late Monday and early Tuesday, and will be followed by gusty north and northeast winds Tuesday through early Thursday. A period of elevated to critical fire weather conditions will be possible early Wednesday through early Thursday. && .DISCUSSION...While marine stratus and fog slowly expanded along the Humboldt coast overnight, roughly as far north as the mouth of the Klamath River, only patchy stratus and fog have developed south of Cape Mendocino. While some further expansion is possible early this morning, the Mendocino coast will likely remain cloud free for much of the day. Farther north, uncertainty is a bit higher as there is a much more expansive shield of status just offshore, and moving slowly toward the coast. As a result of this steadily advancing offshore stratus, it would seem unlikely that the Humboldt Coast will see much sun this afternoon. Overnight tonight, stratus is expected to quickly fill into the remainder of the coast, resulting in cloudy and foggy conditions along the coast through at least Monday morning, and likely most of the day. Meanwhile, warm and mostly sunny conditions can be expected throughout the interior both today and most of Monday. By late Monday afternoon, a weak cold front will begin to impact the Del Norte and Humboldt coast, and will quickly push through the area during the evening and overnight hours. This will bring light rain to primarily Humboldt and Del Norte counties late Monday through Tuesday morning, with totals generally expected to fall between .25 and .50 inches in Del Norte, and lower across Humboldt. Little to no rain is expected elsewhere, and rain will quickly diminish before Tuesday afternoon. Once the cold front pushes south of the region, substantial northerly winds will begin to develop across the region. This initial surge in north winds will mostly impact coastal areas and along exposed high elevations (in addition to the ocean waters) beginning Tuesday evening and continue through the night. By early Wednesday, these winds will begin to turn from the due north toward the northeast, and this will continue through Wednesday night when they are expected to become more purely offshore. The potential for strong wind gusts will continue along ridges during this time frame, but will diminish along the coast. Winds will quickly dissipate by Thursday morning. While there remains some uncertainty regarding the expected wind speeds in land areas, there is the potential for some gusts in the 35 to 40 mph range. These winds, combined with steadily lowering humidity, will also have fire weather implications. Please see the fire weather discussion below for more details regarding this threat. Otherwise, dry conditions can be expected Tuesday through the end of the week, with diminishing marine stratus along the coast. Temperatures are expected to cool quite a bit on Tuesday through the end of the week, but afternoon values are still expected to remain near normal values, if not slightly above normal by late week. Overnight lows will be much cooler in valleys due to the drier airmass, with widespread freezing temperatures expected in many interior valleys. && .AVIATION...An area of stratus continues to move toward the coast this morning, with localized stratus having already developed at and in the vicinity of both coastal terminals. This large swath of stratus will impact the coast early this morning and bring continuous IFR to LIFR conditions at both coastal terminals through at least mid-morning. IFR to MVFR conditions will be possible this afternoon along the coast. Elsewhere, VFR conditions are expected to prevail. && .MARINE...The prominent northwest swell continues to wane, with buoy data showing the swell around 8 to 9 feet. This swell will continue to subside through the middle of the upcoming week. Localized elevated winds downwind of Cape Mendocino will continue through tomorrow, with a Small Craft Advisory in place for this localized effect in the southern outer waters. Winds will ramp up to Gale Force in strength across most of the waters on Tuesday, though areas along the immediate coast will not see these increased winds (except around Cape Mendocino). Large/steep, short-period seas will develop across most of the coastal waters in response to the Gales. Winds and seas will peak Wednesday morning and weaken through Thursday morning. Otherwise, another long-period northwest swell will move through the waters late in the week. && .FIRE WEATHER...Humidity is expected to be much lower today than in recent days, with generally poor recoveries expected across high elevations tonight. However, while offshore winds will continue, speeds are expected to be generally light and preclude the development of critical fire weather conditions. By late Monday, another weather system from the northwest will reach the area, bringing some light rain to mostly Humboldt and Del Norte counties. While some areas may see a light wetting rain, totals are expected to be light, and very little of this is likely to reach Mendocino and most of Trinity counties. As a cold front pushes south on Tuesday, potentially strong north winds will develop, particularly along the immediate coast and exposed ridges. At some point during the day Wednesday, these north winds will begin to turn offshore, but will also begin a slow but steady decreasing trend. While confidence is increasing regarding these winds, there still remains some uncertainty regarding just how strong these winds will be, especially when they begin to take on a more easterly direction on Wednesday. Meanwhile, another source of uncertainty will be the degree of drying that will take place as these winds increase. Humidity is likely to be somewhat high initially, particularly when winds are more out of the due north. However, humidity is expected to steadily drop over time, especially as winds become more offshore on Wednesday. This all leads to the most important question regarding this event: How quickly will the airmass dry, and how long will this dry air overlap with strong winds? This will determine how significant this event will be regarding fire weather, and at this point, a somewhat wide range of possibilities still exists. Still, there is the potential for some areas to see an extended period of critical fire weather conditions between sometime Wednesday and early Thursday morning, and this is most likely in Mendocino and eastern/southern Trinity counties. Winds are expected to diminish quickly early Thursday, but low humidity will continue through the end of the week. MKK/BRC && .EKA WATCHES/WARNINGS/ADVISORIES... CA...None. NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 9 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