textproduct: Eureka

SYNOPSIS

Breezy to strong north and northeast winds are expected through tonight. Dry weather and interior high temperatures well above normal are expected Friday through Sunday. Significant cooling and potential for widespread precipitation will arrive next week.

DISCUSSION

Gusty northerlies will continue through this evening and then ease up overnight into Friday morning. E-NE winds develop tonight and persist into Friday morning over the interior with strongest gusts up to 30-40 mph over the higher elevations/ridges and along the southern/eastern periphery of Lake County.

The airmass will remain dry tonight under offshore flow. Adiabatic warming from the large scale subsidence will likely result in a wide range of overnight low temperatures. With a warmer airmass building tonight and winds generally diminishing, wind sheltered valleys and coastal areas will stand the best chance for frost and freezing/subfreezing temperature. Some wind sheltered valleys will dip down into the lower to mid 30's while breezier wind prone areas exposed to adiabatic warming may not even dip below 60F (mostly in the thermal belts and ridges). Frost advisories have been issued for the interior valleys of Mendocino County as well as coastal areas of Del Norte and Humboldt again. Interior portions of Humboldt and Del Norte are 6 days from the start of the growing season (Apr 1) while Trinity County is 21 days away (Apr 15). That is why frost/freeze products have not been issued for these zones.

Otherwise, dry and stable weather is expected for the remainder of this week and into the weekend. Generally above normal high temperatures and areas of minor heat risk are forecast for mostly the interior as a broad flat ridge aloft dominates. The warmest locations will continue to be in Lake, Trinity and interior Mendocino Counties where max temps are projected to peak into the upper 70s to mid 80s Fri-Sun. This is 10-20F above late March averages. Overnight low temps will remain seasonably chilly with perhaps some valley sites cooling into the lower to mid 30's, especially in the valleys of Trinity. Overnight temperatures will remain elevated (50s and 60s) within the thermal belts and over the ridges exposed to breezy E-NE winds through the night. No huge changes are anticipated this weekend except for an increase in coastal stratus and perhaps a ramp up in onshore or NW winds.

National blend of models continue to trend much cooler and wetter next week, Monday March 30 to Thu, April 2nd. Our long stretch of above normal warmth in the interior will finally come to an end next week with highs trending near or just under early April normals (upper 50s to mid 60s) by mid week (Wed). Moreover, precipitation chances will be on the rise throughout the forecast area next week. How much precipitation and the exact timing remains uncertain. Highest WPC/NBM 6-hourly rates appear to arrive on Wed, but this could easily speed up or slow down by 12-24 hours. NBM 3-day totals 5 AM Mon-5AM Thu range from over 2 to 5 inches on the higher end (90th percentile) to not much more than half an inch on the lower end (10th percentile). Most of the precip is concentrated in the usual wet spots of Del Norte, SW Humboldt and NW Mendocino, while southern Lake and southern Mendocino may end up with much less. There is a 60-80% chance for over 6-8 inches snowfall for the high mountains over 3-days too. National blend still has 6-hr and 12-hr thunderstorm chances less than 15%. If the cold core aloft dips far enough south we could definitely see some low top thunderstorms and small hail. March is usually the max on average for small hail. The wet season is not over just yet and the weather could get quite active by mid next week. Stay tuned for updates and more details.

AVIATION

Besides some high clouds streaming over the region, skies have remained clear today. A few valleys will likely see fog develop tonight with lighter winds across the interior. Additionally, some coastal clouds may develop south of Cape Mendocino, but otherwise clear conditions and VFR are expected at all the TAF sites through the forecast period. Northerly gusty winds along the coast today will decrease through the evening, becoming light easterly during the overnight hours. Winds will again increase during the late morning and afternoon on Friday but should be lighter than what has been occurring today. /RPA

MARINE

Northerly winds are peaking this afternoon with surface high pressure situated a little west of the waters. A building thermal trough will attempt to push toward the coast tonight allowing the tightest pressure gradient to shift west and north of the waters. Thus, the near gale to gale force northerly winds will decrease Friday morning leaving steep seas, especially in the outer waters. Small craft conditions will most definitely persist through Friday night with the potential for hazardous seas warnings following the gales in the outer water zones.

Winds will decrease over the weekend as an area of low pressure begins to develop off the California coast. This will significantly reduce the pressure gradient across the waters. A weak front is forecast to move through the waters on Monday allowing the northerly winds to increase slightly in its wake. The next chance for strong winds will be mid next week as a more potent frontal system moves into the region. /RPA

EKA WATCHES/WARNINGS/ADVISORIES

CA... Frost Advisory from 4 AM to 8 AM PDT Friday for CAZ101-103.

Frost Advisory from 3 AM to 9 AM PDT Friday for CAZ110>113.

NORTHWEST CALIFORNIA COASTAL WATERS... Hazardous Seas Warning until 6 AM PDT Friday for PZZ450-455.

Gale Warning until 6 AM PDT Friday for PZZ470-475.