textproduct: Eureka

SYNOPSIS

Dry conditions will persist through the weekend. A weakening frontal system will bring isolated showers to the region Monday and Tuesday. A better chance for widespread rain is expected Tuesday night into Wednesday followed by lingering showers into Thursday and possibly Friday.

DISCUSSION

An area of low pressure will approach the Pacific Northwest today with a trailing frontal boundary that will move through Northwest California tonight before stalling over the northern half of the state Monday into Tuesday. Cooler air aloft will increase atmospheric instability over the interior resulting in a chance for showers and possibly an isolated thunderstorm each afternoon due to daytime heating. Coastal areas may see some light showers as the front passes, but otherwise the model trend is for less rain Monday and Tuesday than what had been expected only a few days ago.

Tuesday night into Wednesday, a more potent trough and frontal boundary will move toward the Pacific Northwest and Northern California. Model plumes of integrated vapor transport with this front indicate a weak moisture flux with Integrated Vapor Transport values over 250 kg/m/s during the frontal passage. Thus, a period of moderate to heavy rain will be possible, and is even expected for coastal areas north of Cape Mendocino. In general, rainfall from this system are expected to remain beneficial, but the heaviest rainfall rates could result in minor flooding of poor drainage areas. In addition to the rain, this frontal system will lower snow levels as cold air fills in behind the cold front. The newest guidance trending slightly warming, with snow levels now falling to around 5500 feet instead of 5000 on Wednesday. This small difference in elevation would result in a significant difference for the impacts over Scott Mountain Pass while the heaviest precipitation is occurring. Showers will linger into Thursday as snow levels continue to fall to around 3000 feet, but overall precipitation is expected to be light and additional impacts from snow could be minimal. Lastly, this front will force gusty south winds with 30-40 kt winds at the 925 mb level, approx. elevation of ~2000-2500ft Tuesday night into Wednesday morning. This is just below the advisory threshold for the near coastal ridgelines but model trends will need to be closely monitored for any wind headlines. Models seem to be trending for a return of dry and warm weather next weekend. /RPA & DS

AVIATION

Generally VFR conditions are place across the area this morning. Some low clouds or fog may develop along the coast like previous mornings. However with no fog in sight, have shorted the period of fog in KACV and KCEC. It may still return towards morning, but models are keeping it fairly clear. This afternoon some breezy northwest winds are expected, mainly along the coast. These are only expected to peak around 10 to 12 kt, although a few gusts close to 20 kt are possible briefly in the late afternoon. Tonight it is possible stratus will form again along the coast, but confidence is low on this. MKK

MARINE

Northerly winds are diminishing some this morning, especially in the northern waters and closer to the coast. Late this afternoon and evening these northerly winds are expected to increase again to around 15 to 25 kt. So have started a new small craft advisory for the northern outer waters late this afternoon. Closer to the coast there may be a few gusts close to 25 kt, but for now have held off on expanding the SCA closer to the coast. This will need to be monitored as it gets closer. The waves are currently a combination of wind driven waves and an 8 or ten second swell. These are combined into one wave group in the forecast and may be difficult to distinguish at times. There is also a small 14 second northwest swell, but that is only building to around 3 feet.

Monday afternoon and overnight winds are expected to quickly diminish and become southerly ahead of weak front. This is expected to bring very light winds and seas to the area on Tuesday. Tuesday night and Wednesday morning the front is expected bring stronger southerly winds. Some of the models indicating the potential for gale force gusts in the northern waters. The forecast remains lower than this, but it is possible and will need to be monitored.

Wednesday night through late in the week northerly winds are expected to return and increase to near gale or gale by Friday. The waves look to continue to be dominated the short period wind driven waves. MKK

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 6 AM PDT early this morning for PZZ470.

Small Craft Advisory from 2 PM this afternoon to 7 PM PDT Monday for PZZ470.

Small Craft Advisory until noon PDT Monday for PZZ475.