textproduct: Eureka

SYNOPSIS

Heavy rain is expected to continue Sunday for much of the area. A short break in the heavier rain is expected Monday, although occasional light showers may continue. Minor flooding and river flooding impacts are possible this afternoon and again by the middle of the week. Strong winds and lower snow levels possible mid to late this week.

DISCUSSION

An area of low pressure is approaching the area from the southwest and deepening to around 1003 mb. This is expected to move onto the Humbodlt or Del Norte county coast this morning. This is also expected to bring heavy rain with it and this is now farther north than previously expected. The ensemble plumes for IVT have come into better agreement. In the north the ensembles are showing a sharp peak close to 750 kg/m/s while farther south they are showing nearly 12 hours of the plume close to 700 kg/m/s. The flood watches remain on track. Northern Trinity and Del Norte county will need to be monitored and possibly expand the flood watch into those areas. Most areas are expected to 3 to 5 inches in the next 18 hours. For more details see the hydrology section. The low is expected to bring gusty wind to the area this morning. Gusts to 45 to 55 mph are possible on the higher ridges of Humboldt, Mendocino and Lake counties. Confidence is low on the exact location and speeds of this low. A brief break in the weather is expected on Monday. There will likely still be clouds and some showers around through the day, but overall it will be quieter weather.

The next weather system is expected to move into the area at some point between Tuesday evening and Wednesday afternoon. Most models are showing a strong low approaching the coast, but they vary in timing by 18 hours. There is certainly the potential for some strong winds to move onshore, but confidence is very low on the strength and the timing. A high end look (90th percentile) from the NBM shows 24 hour peak gusts of 45 to 80 mph. The highest values are on the ridges, but even the valley may see gusty winds. This forecast will continue to evolve as it gets closer.

Not surprisingly there is also high uncertainty in the rain and snow forecast. The GFS solution with the low well off the coast lowers snow levels to around 4,000 feet. This is a reasonable first guess, but the a small shift in the low could bring colder or warmer temperatures. The NBM shows the potential for 4 to 8 inches on the hwy passes of 299, but this is a fairly low probability solution. The most likely impacts are expected to on Hwy 3 at Scott mountain summit. Overall the rainfall looks lighter with this system. IVT values are generally under 500 kg/m/s and focused on the southern portion of the area. But again confidence remains very low on this forecast. The GFS solution has the low slowly moving north off the coast and stalling out. Then it gradually fills but keeps the weather unsettled. Friday and Saturday the models are starting to the show the rain diminishing. MKK

AVIATION...(06z TAFs)

Rain continues after the heaviest of periods and passage of moisture plumes to the area. Sunday will continue with less intensity but steady. Wind and subsequently low level wind shear will complicate flight conditions for KACV and KUKI. With the quick onset of high winds from the south, KUKI will see shear around 05-07z, lasting into the early evening with winds out of the south around 40-45kts at 2000ft. Flight categories will toggle back and forth from MVFR to IFR as periods of rain and lower visibility keep conditions variable. Most of the rain and gusty winds will be south of the 41 latitude as the AR aims from the southwest. /EYS

MARINE

A fast moving and deepening low moving along the more zonal flow aloft is bringing strong winds to the southern waters. Gales have been hoisted for the southern waters to highlight the hazardous situation. Small craft advisories will follow the Gales after the expected easing of the winds, Sunday at 21z. Showers are expected through Sunday with a swell diminishing from the northwest around 7- 8FT at 11 seconds.

Monday, another storm system is expected to move north of the area. This will bring moderate to strong southerly winds north of Cape Mendocino, while generally light to moderate breezes across the southern waters. Monday night into Tuesday, winds are expected to weaken. A larger mid-period westerly swell around 9-11 feet at 12-13 seconds arrives Monday night into Tuesday.

The next storm system likely to bring gales on Wednesday through Thursday. There is a 75-85% chance for wind gusts exceeding 34 kts south of Cape Mendocino on Wednesday and Thursday, while chances increase to 70% across the northern outer waters on Thursday. A larger mid-period south-southwest swell build across the waters on Thursday. /ZVS /EYS

HYDROLOGY

Additional rain continuing through Sunday has the potential to bring minor flooding impacts. The heaviest rain have shifted northward. Heavy rain is now expected across Humboldt county in addition to areas farther south and east. This will again pose a threat for quick rises in streams and creeks along with rock and mudslides. Risk for rock and mudslides will again increase and could impact travel on area highways. At this time, only the Russian River at Hopland is forecast to exceed flood stage, and is expected to peak Sunday afternoon. The Eel is forecast to hit monitor stage Sunday night, but remain well below flood stage. While no other rivers are forecast to reach flood stage, heavy rain focused on the Eel, Navarro, and Mad, river basins could support some or all of these basins to run higher than forecast.

The next weather system on Tuesday and Wednesday will have a higher potential for main stem rivers to reach flood stage. The Russian River at Hopland has a 55 percent chance of exceeding flood stage Tuesday night. The Navarro River has a 40 percent chance. The Eel River has a 30 percent chance of reaching flood stage on Wednesday. These mid-week systems have a particularly high level of uncertainty in the location and amounts of rainfall so these river levels will need to be watched.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Flood Watch from 1 AM PST Sunday through Sunday evening for CAZ103>106.

Wind Advisory until 10 AM PST Sunday for CAZ104-106-109>111- 113.

Flood Watch through late Sunday night for CAZ108.

Flood Watch through Monday morning for CAZ109>115.

Wind Advisory until noon PST Sunday for CAZ114-115.

NORTHWEST CALIFORNIA COASTAL WATERS... Gale Warning until 1 PM PST Sunday for PZZ455-475.

Small Craft Advisory from 1 PM to 9 PM PST Sunday for PZZ455-475.