textproduct: Eureka

SYNOPSIS

A slight chance of isolated showers and possible thunderstorms persist for the interior this afternoon and evening. High pressure will build into the region for the remainder of the week, bringing warmer and drier conditions with potential for coastal stratus each night/morning.

DISCUSSION

As a low pressure system continues away from Northwest California, there are still very slight chances for isolated showers and thunderstorms for the interior (5 to 10 percent). The top sector of the low will be pulling moisture with an easterly flow at the mid to lower levels. This perturbation will be slightly enhanced by bulk shear which could give a bit of slant, enabling some thunderstorm development. CAPE values are modest and most of the areas of risk are Trinity county as well as NE Mendocino and northern Lake counties near the mountainous eastern flanks and borders.

A shallow marine layer along the coast is anticipated each night/early morning through the end of the week; however, light offshore flow overnight could help stave off extensive stratus development. Also, each afternoon at the coast could see slightly elevated northerly gusts. Otherwise, a mostly dry set up is forecast for the weekend, although there are decent signals for CAPE (~500j/kg), Saturday and Sunday. High pressure will continue to fill in for the next few days bringing warmer temperatures and likely driving up the CAPE values due to the buoyancy of the air parcels. A lack of moisture and CIN will keep a lid on things. Model soundings do show inverted V's but without supercooled droplets or higher dewpoints there will not be enough moisture to pose any sustained or high confidence threats. /EYS

AVIATION

Besides afternoon cumulus over the higher terrain, the only other cloud cover in NW California is from around ACV to the lower Eel River Valley at this time. This cloud cover is bringing MVFR ceilings to this small region, otherwise VFR is prevailing across NW California. The majority of these coastal clouds should dissipate through the remainder of the afternoon but we should see a redevelopment in about the same place overnight with ceilings returning at ACV. Whether overnight cloud cover makes it to CEC is a greater uncertainty as it will depend on how strong the pressure gradient is over the coastal waters and how the north wind strengthens. It is always possible some decently strong southerly return flow happens right along the coast bringing the clouds back to CEC for a few hours later tonight into early Wednesday morning. Farther inland the afternoon cumulus will dissipate through the evening leaving excellent radiational cooling through the overnight hours. This should allow interior valley fog to form once again within the Klamath/Trinity/Eel river valleys. The clouds will stay away from UKI. /RPA

MARINE

Northerly winds will continue to ramp-up over the coastal waters through Friday with near gale to gale force conditions expected beginning as early as Thursday. Small craft advisories are now in effect for the strengthening winds and steep seas. The two inner water zones have been included through tonight as steep seas propagate into the outer portions of those zones. A brief period of lower seas is possible Wednesday morning and early afternoon so the advisories end early Wednesday morning. However, winds and seas will build further by Wednesday afternoon and advisories will need to once again be issued for those areas starting as early as mid afternoon on Wednesday. Persistent winds over the outer waters will keep seas elevated and winds in small craft criteria to near gale Wednesday into Wednesday night. As the pressure gradient further strengthens, gale force gusts will become likely Thursday afternoon through Friday night in the outer zones. Because of this, a gale watch has been raised for both of the outer water zones beginning as early as Thursday morning south of the Cape and Thursday afternoon north of the Cape, running through very early Saturday morning. /RPA

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 5 AM PDT Wednesday for PZZ450.

Small Craft Advisory until 6 AM PDT Wednesday for PZZ455.

Small Craft Advisory until 3 PM PDT Thursday for PZZ470.

Gale Watch from Thursday afternoon through late Friday night for PZZ470.

Small Craft Advisory until 11 PM PDT Wednesday for PZZ475.

Gale Watch from Wednesday evening through late Friday night for PZZ475.