textproduct: Seattle/Tacoma

SYNOPSIS

Upper level trough over the area today will dissipate tonight. Weak upper level ridge building in from the southeast over the weekend. Another upper level trough will arrive Monday and remain over Western Washington for most of next week.

SHORT TERM /TODAY THROUGH SUNDAY/

Satellite imagery this morning shows stratus has pushed inland across much of the interior lowlands this morning. Smoky skies are also present over the remainder of the area. Weak upper level trough remaining over the area today with light low level onshore flow. Marine layer will retreat back to the coast in the afternoon. Like the previous two days air mass becoming unstable over the higher terrain in the afternoon creating a chance for convection over the Olympics and Cascades. There is a good chance that these storms will not produce wetting rains. Given the current very dry conditions have upgraded the Fire Weather Watch to a Red Flag Warning this afternoon into the evening hours for the Olympics and Cascades. Any storm that does develop could produce gusty and erratic outflow winds in addition to the lightning output. Highs in the 70s and lower 80s inland and mid to upper 60s coast.

Upper level trough dissipating tonight. Convection threat over the mountains coming to an end quickly this evening. Low level flow remaining light onshore with the marine layer moving inland again late tonight into the early morning hours. The layer will most likely not get to the Puget Sound by 12z. Lows in the 50s.

Weak upper level ridge building in from the southeast Saturday with the flow aloft becoming south southwesterly. This will begin to push the smoke out of the area. In the lower levels light onshore flow continuing with the marine layer getting east of Puget Sound around sunrise. The marine layer will dissipate over the interior by midday leaving stratus just along the coastline. Air mass becoming slightly unstable over the higher terrain in the afternoon. With the south southwesterly flow aloft best chance for a thunderstorm will be near the Cascade crest. Thunderstorm chances will be less than today. Highs in the 70s and lower 80s for the interior and mid to upper 60s coast.

Little change in the pattern Saturday night and Sunday with the weak, 500 mb heights in the lower 580 dms, upper level ridge over the area and south southwesterly flow aloft. Good chance upper level smoke getting out of the area by Sunday. Low level onshore flow will push the marine layer inland from the coast again early Sunday morning. Stratus dissipating back to the coast by midday. Some high clouds embedded in the flow aloft moving through during the day Sunday will have little effect on the temperatures. Highs, you guessed it, in the 70s and lower 80s inland, mid to upper 60s coast. Lows in the 50s.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Upper level ridge flattening out Sunday night with another weak upper level trough digging down from the north arriving Monday. Trough remaining over the area Tuesday. Very little moisture with the trough. The flow aloft will turn northerly bringing upper level smoke back into the area. In the lower levels onshore flow continuing bringing stratus inland each late night and early morning. Highs in the 70s inland and mid 60s coast. Lows in the 50s.

Differences in the models show up Wednesday and Thursday. Some of the solutions produce the same scenario as this weekend with a weak upper level ridge building back into the area from the southeast. The other grouping of solutions keeps the upper level trough over the area. In either solution the low level flow remains onshore. Will go with a climatology forecast for the middle of next week, morning clouds afternoon sun for the interior with highs staying in the 70s. Clouds hanging tough most of the day on the coast with highs only in the mid 60s. Lows both days in the 50s. Felton

AVIATION

The stratus is low to the ground once again, with LIFR ceilings and impacts to visibility due to fog. With slightly stronger onshore flow forecast for today, low stratus and fog will likely be a bit slower to retreat late this morning, and likely not clear out along the coast. This will also promote a slightly earlier return of the stratus late tonight into Saturday morning.

West to southwesterly winds will continue through the morning, though will begin to switch to northwesterly through the central Puget Sound terminals from around 23Z through 03Z Sat and ease late tonight.

KSEA...Stratus continues to slowly lift and erode this morning, with conditions expected to trend to IFR by 1830z, then scatter out by 20z, with VFR through the remainder of the day. Winds predominantly from the southwest this morning, becoming west/northwest (but 5 kt or less) this evening around 02z. A return to light southwest winds then follows overnight, and low stratus likely returns around 12z tonight with IFR/LIFR conditions into the morning tomorrow.

MARINE

High pressure will remain well to the south and west, off the coast of California, allowing winds over the coastal waters to remain light through Saturday. High pressure looks to rebuild offshore of Canada and move southward on Sunday and into next week, bringing back northwesterly winds over the coastal waters.

Diurnally driven westerly pushes down the Strait of Juan de Fuca remains the only area of concern this weekend into next week, with winds likely reaching Small Craft Advisory thresholds each evening.

Seas remain 3 to 6 ft through the next seven days. 62

FIRE WEATHER

A Red Flag Warning remains in effect for the Olympics and Cascades this afternoon and evening for the potential of another round of convection. Similarly to Thursday, most of the storms are not expected to produce wetting rains. Given the dry conditions, any storms that do develop could have gusty and erratic outflow winds, which combined with the lightning and the dry conditions present, could produce new fire starts. There is a small chance the storms could remain stationary over a burn scar. If that is the case, flash flooding can not totally be ruled out.

Chances of thunderstorms will be possible along the Cascade crest on Saturday afternoon and evening, but overall chances for convection will decrease through the weekend with an upper level ridge building into the area. Yet another upper level trough arriving on Monday will increase fire weather concerns again next week. Felton/14

SEW WATCHES/WARNINGS/ADVISORIES

WA...Red Flag Warning until 9 PM PDT this evening for East Portion of the Olympic Mountains-West Portion of the Olympic Mountains-West Slopes of the Central Cascades Generally above 1500 Feet-West Slopes of the North Cascades Generally above 1500 Feet.

PZ...Small Craft Advisory from 2 PM this afternoon to 5 AM PDT Saturday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca.