textproduct: Seattle/Tacoma

SYNOPSIS

Zonal flow aloft continues as high pressure remains parked over the Great Basin. Morning fog and stratus will continue likely until Thursday morning, where it will become less widespread. Sunny afternoons are expected, with seasonably warm temperatures. The next chance for rain appears to be Friday as a weak front arrives.

SHORT TERM /TODAY THROUGH FRIDAY/

Fog has become well established throughout the majority of Puget Sound early this morning and will persist through the rest of the morning hours. There is going to be a light offshore gradient today, which should lend itself to a slightly earlier dissipation time than the previous few days. This offshore gradient will also cause a minor dip in the relative humidity this afternoon in the Cascades and valleys. Today's highs will be in the upper 60s, climbing to the low 70s on Thursday.

The system moving in on Friday will be weak, and the expected QPF is minimal around a few hundredths of an inch across the Cascades and northern portions of Puget Sound. While the precipitation won't last very long, the pattern change will usher in cooler temperatures, with highs on Friday knocked back down to the low 60s. Snow levels drop to around 5000 ft late Friday night, so the higher terrain particularly in the North Cascades may see a dusting of snow. Expect breezy winds along the coast, Strait of Juan de Fuca and waterfront areas of Puget Sound on Friday.

21

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Overnight lows will be decreasing over the weekend as the pattern becomes focused on low pressure over the NW. Saturday morning lows will be in the upper 30s across the Cascade passes, and low 40s in the foothills. The lows decrease a few degrees more come Sunday morning. Stay tuned to the forecast as it relates to frost and freeze potential for agricultural concerns and sensitive vegetation.

Cooler temperatures look to continue into early next week as low pressure churns in the Gulf of Alaska. Some of the models depict another chance at rain on Tuesday into Wednesday, but the ensembles are mixed on exact placement of the low and resultant weather systems.

21

AVIATION

Upper level ridging will remain over the region with westerly flow aloft becoming more northwesterly by tonight. Low clouds/fog have already developed across Puget Sound this morning and have brought IFR to LIFR conditions to the majority of the Puget Sound terminals. Elsewhere, conditions remain VFR. Expect fog to continue to expand in coverage through the early morning hours and for predominantly IFR to LIFR conditions to persist through late morning. Fog will then gradually scatter by late morning, with more widespread VFR conditions likely to return between 18-21Z. Light northerly surface winds this morning will increase to 5-10 kt this afternoon.

KSEA...LIFR conditions at the terminal in fog this morning. Predominantly LIFR ceilings are expected through 18Z before fog gradually lifts and scatters. A return to VFR conditions is expected by this afternoon. Northerly winds becoming light early this morning will see an uptick in speeds to 5-10 kt and a shift to the northwest this afternoon between 19-21Z.

14

MARINE

Fog remains the primary marine impact over the area waters early this morning as areas of dense fog have already developed across the eastern Strait of Juan de Fuca and pushed into Admiralty Inlet, the Northern Inland Waters, and portions of the Puget Sound waters. Latest satellite imagery also shows fog over the waters just off of the North Coast and fog pushing down into the western Strait this morning. Expect areas of fog to reduce visibilities down to 1NM or less through the morning hours. Visibilities will then improve as fog slowly scatters into this afternoon.

High pressure will remain situated over the coastal waters the next few days, while a thermal trough builds northward along the Washington coast today. This will continue to promote northerly winds across the coastal waters into Thursday. Northerly winds may become gusty to 25 kt at times across the inner and outer coastal waters off of Grays Harbor this afternoon and again Thursday afternoon, but expect the stronger, more sustained winds to generally remain south of the area. Onshore flow will return by Thursday evening, with guidance indicating a 30-50% chance of westerly winds exceeding small craft strength along the central and eastern Strait of Juan de Fuca. A frontal system will then move into the area waters Friday into Saturday, bringing the likelihood (>80% chance) of small craft strength winds to the coastal waters and the Strait of Juan de Fuca. Seas will build in the system's wake, with latest GEFS probabilities indicating a 60-80% chance of seas exceeding 10 ft across the coastal waters by Friday night.

Winds will ease and seas will gradually subside through the day on Saturday as the system exits the area. High pressure will then build back into the coastal waters by Sunday, while a thermal trough expands northward along the coast again.

14

SEW WATCHES/WARNINGS/ADVISORIES

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