textproduct: Eureka

SYNOPSIS

A cutoff low will continue to affect the region through Wednesday with rain showers and light mountain snow. There is also a chance for thunderstorms, mainly this afternoon. A stretch of drier weather is then expected to begin late in the week.

DISCUSSION

A frontal boundary associated with the approaching upper level low continues to push rain through the region early this morning. Snow levels are mostly around 5000 ft aside from northeastern Trinity with locally lower snow levels around 4500 feet. The bulk of the stratiform rain will move off to the east with the back end of the precipitation ongoing in Lake and NE Trinity into early/mid this morning. Generally showers are expected to continue for most of the region today as the center of the upper level low slowly approaches the area and moves overhead.

This afternoon as the upper low moves overhead, the potential for thunderstorms increases. The HREF is showing 200 to 400 j/kg of surface CAPE and lapse rates aloft of around 7C/KM. This should be be enough to develop some thunderstorms. A few of them could be strong with around 30 to 35 kt of deep shear. They will be the most likely in Mendocino and Lake counties in the afternoon. This is also expected to lower snow levels to around 4000 feet Tuesday morning. Snow levels are expected to rise in the afternoon. A Winter Weather Advisory continues for the far northeastern portion of Trinity County into late this morning. Showers are expected to linger into Wednesday as a shortwave moves down the back side of the low.

Thursday and Friday, high pressure is expected to build into the area bringing dry weather to the area. For the weekend, mainly dry weather is anticipated, but there is an upper level low to the northeast of the area. The ensemble clusters are showing different positions of this low. If the solution with the low closer to the area verifies, this may allow a few convective showers over the mountains each afternoon. MKK

AVIATION

Cold low aloft spinning offshore will continue to edge east-southeast toward the northern California coast tonight through Tuesday. Occasional rain with MVFR ceilings and visibilities are expected through Tuesday. Very brief IFR conditions will also remain possible (a 20% chance) as well in periods of moderate rain. Instability will increase on Tue. Isolated strong cells and tstms are possible - mainly over the interior in the afternoon. Long and thin CAPE profiles with low equilibrium levels seem favorable for brief heavy rain, small hail and gusty winds.

MARINE

Seas were still running around 10 ft at 12 to 13 seconds south of Cape Mendo Monday evening. This is a couple feet above wave model guidance, namely NWPS and GFS-Waves. Trend is most likely correct and seas should trend down through the night. Otherwise, south to southeast winds will continue into Tue as a weak surface low meanders about just outside the northern outer waters. A few gusts around 20 kt are possible (20-30% chance) nearshore in the afternoon on Tue. Otherwise, wind speeds are forecast to remain below advisory level Tue. Surface pressure gradients remain flat and insufficient to warrant headlines through Wed as the weak low lifts out to the NE. Greater instability associated with colder air aloft may result in strong cells or isolated tstms capable of gusty winds on Tue. Finally high pressure builds offshore on Thu as the convoluted low complex exists to the southeast. Northerly winds and steep waves are forecast to build Thursday through Friday and advisories will likely be necessary for small vessels.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Winter Weather Advisory until 11 AM PDT this morning for CAZ117.

NORTHWEST CALIFORNIA COASTAL WATERS... None.