textproduct: Seattle/Tacoma

SYNOPSIS

Upper level ridge centered offshore through Friday will weaken Friday night and Saturday. Surface high pressure building ahead of the next weather system with increasing low level onshore flow Saturday night into Sunday. System arriving Memorial Day with a trailing upper level trough over the area Tuesday. Weak upper level ridge trying to build Wednesday.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Satellite imagery shows a few small buildups over the Cascades along with some high clouds otherwise clear skies over Western Washington this afternoon. Temperatures at 3 pm/22z were in the mid 60s to mid 70s.

Upper level ridge centered offshore remaining in place through Friday. Light flow in the lower levels. Friday looks to be a repeat of today with just patchy fog near sunrise otherwise mostly clear skies. Onshore flow increasing late in the day will put a cap on the high temperatures with mid 60s to upper 70s in the forecast. Lows tonight in the 40s and lower 50s.

Ridge flattens out Friday night into Saturday. Low level onshore flow remaining intact with the marine layer getting inland Saturday morning. The layer will be shallow and dissipate in the afternoon. A little cooler Saturday, about 5 degrees versus Friday, with highs in the 60s to lower 70s. Lows in the 40s.

Surface ridge out ahead of an approaching system building over the coastal waters increasing the low level onshore flow Saturday night. Possible gale force westerlies down the Strait of Juan de Fuca. Increasing cloud cover will keep lows a little warmer, in the mid 40s to lower 50s. Felton

LONG TERM /SUNDAY THROUGH THURSDAY/

Low level onshore flow Sunday combined with high clouds out ahead of the approaching weather system will give Western Washington a mostly cloudy/partly sunny day. Temperatures a little cooler again Sunday with highs mostly in the 60s.

Operational run solutions now trending towards the ensemble solutions yesterday with rain arriving Memorial Day as a front reaches the coast late in the day. Highs only in the 50s.

Front moving through Monday evening with cool upper level trough trailing the front keeping at least a chance of showers in the forecast Tuesday. Lows in the 40s and highs in the upper 50s to mid 60s.

Weak upper level ridge moving into the area Wednesday for a dry forecast. Ensembles not real confident in the strength of the ridge Thursday. Weak system riding by to the north for now producing slight chance pops across the area. Highs near normal, mostly in the 60s. Lows in the 40s and lower 50s.

AVIATION

High pressure offshore will keep the weather pattern consistent tonight into Friday. VFR conditions will prevail through the TAF period for most. The exception will be the Pacific coast once again, where stratus is expected to redevelop and bring IFR conditions overnight into Friday morning. The stratus looks to make it slightly further inland compared to this morning, but still remain short of the Puget Sound interior. Probabilities hover around 30-50% for terminals including OLM, PWT, and CLM for seeing low ceilings. Ceilings should clear quickly aoa 17-19Z Fri. N/NW winds 5-8 kt becoming light and variable tonight. Winds resume tomorrow again NW 5-10 kt.

KSEA...VFR conditions through the period. Probability of seeing stratus is around 25-30%, but confidence is higher on remaining mostly clear overnight. Winds N/variable 5-8 kt becoming light overnight. NW winds 5-10 kt during the day Friday.

62

MARINE

The pattern continues to remain steady with high pressure offshore and lower pressure inland through the rest of the week and into this weekend. Northwesterly winds persist over the coastal waters, with the outer-most areas up to 60 NM waters way experiencing winds up to 20 to 25 kt, thus allowing for a small craft advisory from this afternoon through Friday morning. Winds will ease Friday morning as the gradient decreases as the high shifts westward. Another round of small craft winds is likely Friday night into Saturday with more robust onshore flow from the high moving back eastward closer to shore. Winds look to ease once again Sunday. A low pressure system will traverse the area on Monday, bringing widespread small craft conditions across much of the area waters.

Diurnally driven westerly pushes down the Strait of Juan de Fuca will occur each afternoon and evening through Monday, which will also bring Small Craft conditions to the central and eastern Strait. Saturday look to be the strongest day, with a 30-50% chance of gale force winds through the Strait.

Seas remain 6-10 ft through the rest of the week and this weekend, with the largest and steepest waves over the offshore waters. Dominant periods will be around 8 seconds through Friday, and then once again on Saturday as waves become driven more by the local wind. Waves increase to 10-13 ft Monday into Tuesday as the low pressure system moves through the area.

62

HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 5 AM PDT Friday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 11 AM PDT Friday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm- Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.