textproduct: Eureka

SYNOPSIS

A decaying front will bring a chance of light to moderate rain to mainly Del Norte and northern Humboldt Counties tonight. Light rain chances linger into Wednesday morning and then decrease in the afternoon. Blustery to strong northerly winds are forecast to develop behind the front on Wednesday and continue into Thursday.

DISCUSSION

Light to moderate rainfall will increase across Del Norte and northern Humboldt Counties this evening and overnight. A long southwesterly fetch of subtropical moisture (PWATS >1") associated with a decaying cold frontal boundary will intersect the coastal topography late today into tonight. High resolution mesoscale models continue to show the highest chances for hourly rates over 0.10 inches arriving late today into this evening for coastal Del Norte. HREF 90th percentile 24-hour rainfall exceeds 1 inch near the ORCA border while the 10th percentile ending 5 AM Wed is on the order of half an inch. NBM has a much larger spread with over 90 more ensemble members. Amounts from the national blend are generally around a tenth or two on the low end (10th percentile) but also near 1" in 24 hours on the high end (90th percentile). The front and moisture influx will likely weaken considerably as the boundary sags SE and rainfall amounts will be much less for Humboldt, around a tenth or two. Some places in southern Humboldt may not get any measurable rain at all. Rain chances are forecast to decrease on Wed as northerlies steadily increase offshore. Residual drizzle and low clouds may persist into the afternoon and evening hours as chilly N-NW breezes develop.

Otherwise, dry and stable weather will continue for the remainder of the area through the week and into the weekend. Generally above normal high temperatures with minor heat risk is forecast as a broad flat ridge aloft dominates. There will be slight cooling on Wed in the wake of the cold front, however max temps will still be above normal. The warmest locations will continue to be in Lake, Trinity and interior Mendocino Counties where max temps will likely warm up into the lower to mid 80s toward the end of the week (Thu and Fri). Robust offshore flow, dry air and clearing skies will make for exceptional longwave cooling for wind sheltered valleys. The chance for early morning frost and subfreezing temperatures will increase for mostly the interior valleys Thu morning and again Fri morning. Coastal areas may also have frost too but winds and cloud cover may hamper the cooling. Persistent east to northeast breezes through the night will keep the exposed ridges dry and much warmer through the night and no frost is expected for locations in the thermal belt and along mountain ridge tops.

Longer range models and national blend of models are trending wetter/colder next week, Monday March 30 to Friday, April 3rd. Higher end scenario (90th percentile) suggests multiple inches of rain spread out over multiple days while a lower end scenario (10th percentile) would yield only half an inch or less over multiple days. There is considerable variability and spread 7 day to 9 days out, but this is the first promising sign for significantly cooler and wetter weather I have seen in quite sometime.

AVIATION...18Z TAFs

Southerly winds increased Tuesday afternoon. Southerly winds at CEC through 2000 ft AGL up to 30 kts will bring a low end threat for low level turbulence through 0Z Wednesday. Light rainfall will continue spreading in with the front, mostly over CEC. Light rainfall to light drizzle will also impact KACV into Wednesday morning.

MFVR ceilings have a high probability of occurring at the coastal terminals (60-70%) this afternoon and overnight. There is a lower chance for IFR, but MOS and HREF do show higher chances for periods of IFR CIGS. Have included PROB30 chance for IFR CIGS in 18Z TAFS. Chances for IFR decrease after the front slowly passes by 12Z, but there will be lingering chances for IFR with possible light drizzle going into 15Z Wednesday.

MARINE

A quick round of increased southerly winds over the northern waters will quickly ease into Tuesday evening. The quick duration of these southerly winds will not allow for much short period seas development.

Northerly winds will quickly build in behind the front Wednesday morning as a strong area of high pressure strengthens in from the west over the Pacific Northwest. Winds have trended slightly lower for these northerly winds, but the strengthened pressure gradient will generate some sustained gale strength winds, with gusts currently forecast to reach over 40 kts starting Wednesday afternoon in the southern waters. The northerlies will quickly expand northward through Wednesday evening. Steep seas will reach 12 to 15 late Wednesday through late Thursday. Winds will begin to ease late Thursday. Gale conditions are forecast to reach into the inner zones, but the limited coverage and duration still warranted a Hazardous Seas Warning due to the combination of gales gusts and large, steep seas.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 5 PM PDT this afternoon for PZZ450-470.

Hazardous Seas Watch from Wednesday evening through Thursday morning for PZZ450.

Hazardous Seas Watch from Wednesday afternoon through Thursday morning for PZZ455.

Gale Watch from Wednesday evening through late Thursday night for PZZ470.

Gale Watch from Wednesday afternoon through late Thursday night for PZZ475.