textproduct: Seattle/Tacoma

SYNOPSIS

Upper level ridge offshore weakening Wednesday night. Weak system moving through ridge Thursday going by mostly off the coast. Ridge temporally rebuilds Friday before another system tries to reach the area over the weekend into the first part of next week.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

Satellite imagery shows clear skies over most of the area this afternoon. Fog hanging tough over Thurston county and down the I-5 corridor in Lewis County. Temperatures in the sunshine in the mid 40s to lower 50s with mid 50s along the north coast. Temperatures in the fog still in the upper 30s.

Little change in the forecast the next two days. High amplitude upper level ridge remaining offshore. Light flow in the lower levels over most of the lowlands. Models have been trying to reduce the cross cascade gradients for the last couple of days but it has remained in the -7 to -8 mb range. This will keep fog out of the Cascades foothills. Persistence forecast Tuesday and Wednesday with a little more fog coverage each morning. Thurston county staying foggy for most of the next 48 hours. Lows in the mid 20s to mid 30s with highs mostly in the 40s for the interior and lower to mid 50s coast.

Upper level retrogrades and weakens a little Wednesday night into Thursday. This will allow a weak system to ride over the top of the ridge. System moving by to the west late Thursday with just chance pops along the coast. Another round of late night and morning fog for the interior. Cross cascade gradient weakening keeping the fog/low clouds intact longer over the interior. Highs will remain in the 40s with lows in the upper 20s to mid 30s. Felton

LONG TERM /FRIDAY THROUGH MONDAY/

Extended model drying trend continuing Friday. Operational runs continue the drying trend through the weekend with the offshore upper level ridge rebuilding. Ensemble solutions much wetter in terms of number of solutions with precipitation. Number of wet solutions slowly increasing through the weekend. Sunday night into Monday ensemble solutions are pretty evenly split between wet and dry solutions. With the lack of any run to run consistency will keep slight chance pops in the forecast Saturday and chance pops for the most part Sunday and Monday. Given the model trends will not be surprised if Saturday turns out to be a dry day too. Highs in the 40s through the weekend then a couple of degrees warmer for Monday. Lows in the 30s Friday and Saturday, mid 30s to lower 40s Sunday and Monday. Felton

AVIATION

High pressure/upper ridge will remain in place through the TAF period with weak flow aloft & gradients. VFR at most terminals this afternoon (although a pocket of fog remains in the south interior from KOLM to KCLS, and may not burnoff completely before sunset). Winds remain out of the NE (variable in a few spots) at 3-7 kt becoming light tonight/Tuesday morning (less than 5 kt). Probability for LIFR/IFR fog/mist remains elevated at 50-70% tonight/Tuesday morning, with visibilities down to 1/4 NM (some freezing fog is possible in a few rural terminals). Development is expected shortly after sunset, with the interior terminals having the highest chance. Clearing to VFR is expected from 17-20Z. Winds Tuesday will remain light/variable or NE 3-6 kt.

KSEA...VFR through tonight, with NE winds 3-6 kt (variable at times) becoming calm tonight. Fog likely to redevelop over the terminal (probabilities are highest from 10Z-18Z Tuesday). Clearing to VFR to take place late morning/afternoon. Winds remain light out of the NE less than 5 kt Tuesday.

HPR

MARINE

A ridge with high pressure will remain over the Pacific through much of the week. Winds will be light through the week (offshore at times with the thermal trough along the coast). A possible system may skirt the outer waters towards the end of the week, but another ridge will build behind it. There are no wind concerns in the forecast over the waters. Fog will be possible next couple mornings with the weak gradients (especially in the interior waters), with visibilities under 1 SM possible. Seas through the week will hold around 3-6 ft.

HPR

HYDROLOGY

No river flooding the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...None.