textproduct: Eureka

KEY MESSAGES

* Interior Heat: An upper-level ridge has moved westward causing temperatures to rise above normal across inland valleys into early next week.

* Slight Threat for Isolated showers/thunderstorms. A 10 to 20% chance for thunderstorms Monday and Tuesday. The highest chances are in Trinity County on Tuesday afternoon.

* Coastal flooding: Minor coastal flooding around Humboldt Bay possible at the evening high tide tonight through Tuesday night.

SYNOPSIS

Hot temperatures return to much of the interior today. Monsoonal moisture will bring cloud cover and moisture Monday and Tuesday. Isolated thunderstorms or showers are possible Monday and Tuesday in the interior.

DISCUSSION

An upper level trough in British Columbia continues to inch eastward while an upper ridge over the Southwest US continues to expand westward. This ridge will bring above normal temperatures to the interior with 90s likely for most valleys and the warmest areas possible exceeding 100. Monsoonal moisture from the south has started to stream over the area in the form of high clouds. So far, none of these have resulted in showers that reached the ground. This may change overnight as additional moisture streams in early Monday morning. CAMs are showing a higher potential for a few rain showers, especially in Mendocino, Lake, and Trinity Counties. Instability is limited, but an isolated thunderstorms is possible with an especially strong shower. Dry surface conditions will likely prevent most precipitation from reaching the ground. This pattern continues Monday afternoon and overnight through Tuesday morning. Instability still remains limited, but a stray thunderstorm cannot be ruled out. Thunder chances increase Tuesday afternoon with added surface heating. The highest chances are in Trinity County with up to 20% chance for thunderstorms, though CAMs within range show convection both farther west and farther east.

High temperatures are forecast to remain in the 90s for most interior valleys with the warmest areas exceeding 100 early next week. Additional cloud cover early next week may nudge these forecasted temperatures down a few degrees. HeatRisk remains minor to locally moderate. Coastal areas remain in the high 50s to mid 60s with stratus forming overnight and partially clearing by the afternoon. Drier air returns midweek as the Pacific Northwest trough moves southwestward. A deeper marine layer will likely bring interior temperatures down by a few degrees, while bringing more widespread, and possibly persistent, coastal stratus. High pressure returns late next week, returning warmer interior temperatures. /JB

AVIATION...(18Z TAFs)

Coastal stratus remains off the Humboldt and Del Norte coasts early this afternoon, but has retreated offshore. Some periodic stratus impacts are possible into the afternoon as the stratus disperses. Breezy northerly winds are likely across the area in the afternoon, especially along the coast. Stratus is likely to return again tonight with a southerly return flow likely to advect stratus northward from Humboldt Bay to CEC. LIFR to IFR ceiling impacts are likely should stratus develop with visibility reductions possible around sunrise. Stratus will likely lift and scatter shortly after sunrise. VFR conditions are likely for the interior areas for the next 24 hours. There is a small chance for thunderstorms (10%) for much of the interior area overnight and into Monday. /JB

MARINE

Northerly winds peak this evening with localized gale force gusts in the lee of Cape Mendocino and sustained winds of 20- 25 kts in the outer waters. Nearshore winds will be much lighter at 10-20 kts, but could still be breezy this afternoon. Northerly winds ease somewhat Monday into Tuesday, but will remain strong in the lee of Cape Mendocino. Strong winds and steep seas return mid to late next week. Seas will be dominated by wind waves and a short period northwest swell. Steep wind waves may propagate to the inner waters even as winds remain milder. /JB

FIRE WEATHER

Monsoonal moisture has arrived to the area and will peak Monday and Tuesday. There is high uncertainty if this will lead to thunderstorms as instability is low, but with warm and dry low levels, any thunder is likely to be dry. Some CAM runs are showing some potential for convection starting early Monday morning and afternoon and again Monday night into Tuesday morning. These pulses will start in the south and move northward. Most models show this feature, but instability is much weaker. Thus there are several slight chance opportunities for a few isolated storms over the area. The highest chance for thunderstorms remains on Tuesday afternoon when the heating of the day increases thunderstorms chances to around 10-20% in Trinity County and into the Yolla Bollys. This may still nudge westward and southward, but is highly dependent on how far east the moisture nudges. Some models do show moisture completely to the east of the area, still, so confidence generally remains low. /JB/RPA

COASTAL FLOODING

High astronomical tides may lead to minor coastal flooding at the evening high tide each evening through Tuesday evening. Minor flooding occurs when the North Spit tide gauge reaches 8.8 ft MLLW. The astronomical tide is forecast to be 8.22 ft tonight, 8.32 ft Monday night, and 8.23 ft Tuesday night. With an anomaly of 0.5-0.6 ft, the tide may exceed 8.8 ft, which would could bring minor flooding impacts to King Salmon and Jackson Ranch Road in the Arcata Bottoms. /JB

EKA WATCHES/WARNINGS/ADVISORIES

CA... Coastal Flood Advisory from 9 PM this evening to midnight PDT tonight for CAZ103.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Advisory from 9 PM this evening to midnight PDT tonight for PZZ415.

Small Craft Advisory until 9 PM PDT this evening for PZZ455.

Small Craft Advisory until 11 PM PDT Monday for PZZ470.

Small Craft Advisory until 3 AM PDT Wednesday for PZZ475.