textproduct: Eureka

KEY MESSAGES

* A developing trough will bring dramatically cooler conditions by Friday and the weekend.

* Strong, gusty north wind close to shore and along ridges this weekend.

* No wetting rain forecast for the next 10 days.

* Minor coastal flooding possible Sunday around Humboldt Bay.

SYNOPSIS

A break in the unseasonably hot weather pattern will begin Friday. Much more seasonable cooler and moister conditions arrive by the weekend alongside strong north winds near shore. Chances for wetting rain remain near zero.

DISCUSSION

After another day of much warmer than normal conditions, the stuck pattern will begin to breakdown Friday from the influence of an area of low pressure and deepening trough to the north. The marine layer will still be shallow through Friday morning, with more areas of dense fog likely. Another Dense Fog Advisory may be needed to cover the hazardous driving conditions which have been developing.

The deepening trough and associated cold front will dramatically cooldown the region Saturday. Interior temperatures will be 15 to over 20 degrees colder Saturday than what will be observed Friday. Coastal temperatures will also be chilly, in the mid to low 50s. Strong northerly winds will make it feel extra cold for those exposed coastal areas.

A deepening upper low digging southward along the Pacific Northwest coast, coupled with strong ridging to the east, will support a very tight pressure gradient and strong northerly winds Saturday. These winds will be focused over the coastal areas, where gusts of 30 to 40 mph can be expected, particularly on the coastal ridges.

Probabilities for wind gusts over 40 mph for most populated coastal areas are low apart some select coastal headlines. Areas from Trinidad and the surrounding higher terrain standout for high chances for gusts over 40 mph. Chances for gusts over 45 mph up to 50 percent include a stretch of highway 101 north of Trinidad. The King Range area has high, 70-80% chances for gusts over 55 mph. A wind Advisory may be required to cover this threat. As the low progresses southward Sunday, winds will turn northeasterly and gusty, particularly across the interior ridges.

Areas that receive the stronger overnight winds, particularly from the warm downsloping easterly winds Sunday through Monday morning will have warmer overnight lows. Wind sheltered areas with clear skies and dry air may allow for freezing conditions Sunday morning and into early next week. Ensembles remain dry throughout the extended forecast period (next 10-14 days), though much weaker high pressure will generally result in more seasonable temperatures.

AVIATION

The possibility of flight categories improving by by 22z has improved for KCEC as pockets of drier/stratus free areas are affecting the density of the offshore marine stratus blanketing the coastline. Low 300ft ceilings are presently what is keeping the flight categories at LIFR but HREF and NBM are quite confident in clearing out, which has already started at KACV as of 1930z with VFR conditions. Model sOundings do show a significant inversion returning once again overnight into Friday morning so expect low visibility from ground fog at KCEC and KACV. With the arrival of the low pressure trough, we will get some mixing and instability for the weekend which will lift the marine layer Saturday evening. Stout northerly winds may introduce low level wind shear LLWS at KCEC and possibly KACV. VFR conditions will continue for KUKI. /EYS

MARINE

What appears to be a steepening pressure gradient from an upper level trough will be sending strong geostrophic winds over the area by the weekend. Sustained winds of 25-35kts with gusts up to 47kts over the weekend are expected. Wind waves mixed with fetch driven seas from greater distances will combine to make 10-13ft wave heights with periods 10-12 seconds out of the NW. The initial response will be steep square waves which have been anticipated with the hoist of a Hazardous Seas Warning in the northern outer waters overnight into Friday morning. The arrival of the Gale force winds will follow and so a Gale Warning has been hoisted as well for late Friday around midnight, expanding into the southern waters as well for Saturday early morning. Southerly long period swell will also cause beach hazards with near sneaker wave activity as some of the SW facing beaches will be exposed to 1-3ft at 15-22 second swell, Friday through Sunday.

FIRE WEATHER

Northerly winds will be on the increase over the coming days. The marine influenced flow will trend RH higher, but there will be a period of lingering dry air and breezy winds Friday afternoon. Minimum RH will be in the low 20s to teens with wind gust 15 to 25 mph through that period. Good recoveries will then develop Friday night. Strong northerly winds will arrive Saturday for mainly the coastal areas. A northeasterly wind surge will then arrive Sunday through Monday morning, when minimum RH drops back into the 20s.

COASTAL FLOODING

EKA WATCHES/WARNINGS/ADVISORIES

CA... Heat Advisory until 11 PM PDT this evening for CAZ110>114- 118>120.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 6 AM Friday to midnight PDT Friday night for PZZ450.

Gale Warning from midnight Friday night to noon PDT Saturday for PZZ450.

Small Craft Advisory from 6 AM to 3 PM PDT Friday for PZZ455.

Gale Warning from 3 PM Friday to 9 PM PDT Saturday for PZZ455.

Small Craft Advisory until midnight PDT tonight for PZZ470.

Hazardous Seas Warning from midnight tonight to 9 PM PDT Friday for PZZ470.

Gale Warning from 9 PM Friday to 9 PM PDT Saturday for PZZ470.

Small Craft Advisory from midnight tonight to 9 AM PDT Friday for PZZ475.

Gale Warning from 9 AM Friday to 9 PM PDT Saturday for PZZ475.