textproduct: Eureka

KEY MESSAGES

* Interior Heat: An upper-level ridge has moved westward causing temperatures to rise above normal across inland valleys again today and Tuesday.

* Slight chance thunderstorms. A 10 percent chance for thunderstorms Monday afternoon through early Tuesday. Then a 20 percent chance in Trinity County on Tuesday afternoon and evening.

* Coastal flooding: Minor coastal flooding around Humboldt Bay possible at the evening high tide through Wednesday 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 and moisture. The highest chances are in Trinity County with up to 20% chance for thunderstorms. Some of the CAMs within range show convection mainly in Trinity county.

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. Next Sunday and Monday more monsoonal moisture is expected to stream north over the area. The NBM is showing over 1 inch PWATS and some low end instability. This will need to be watched as it gets closer as the NBM already has some 10 to 20 percent chances for thunder. At this point these look like they may be on the wetter side. MKK/JB

AVIATION

Light southerly winds overnight at the coastal terminals with high pressure and not much cloud cover could produce encourage light ground fog development as radiational cooling commences. Model guidance does not suggest low visibility as much as it does suggest ceilings below 500 feet and likely to be around 300feet Monday early morning. Winds veer westerly by the afternoon Monday and improve flight categories to VFR at KCEC and KACV. Prevailing VFR conditions at KUKI are expected with northerlies gusting up by the late afternoon. /EYS

MARINE

Northerly winds ease overnight in the southern waters but remain elevated south of the Cape Mendocino with localized gusts up to 30+ knots. Nearshore winds will be much lighter at for the northern inner waters, but could still be breezy Monday afternoon for the southern waters. Gale force gusts are likely to arrive Tuesday late afternoon/early evening just south of the Cape once again. Combined seas at 10 feet or less will diminish into mid- week. Wind waves could increase seas by Thursday evening and back off by Saturday morning. /EYS

EKA WATCHES/WARNINGS/ADVISORIES

CA... None.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Wednesday for PZZ455-475.

Small Craft Advisory until 11 PM PDT Monday for PZZ470.