textproduct: Seattle/Tacoma

SYNOPSIS

Upper level low off the coast today will remain in the vicinity through Sunday. The low will move east Monday. Weak upper level trough over the area Tuesday and Wednesday.

SHORT TERM /TODAY THROUGH SATURDAY/

Upper level low weatherpersons woe. Satellite imagery shows upper level low offshore about 200 miles northwest of Hoquiam. Showers spinning around the low covering most of the area west of Puget Sound. Temperatures at 3 am/10z were in the 50s.

Upper level low offshore today drifting south moving into Western Oregon Friday morning. Showers rotating around the low moving through the area at times through this evening. Air mass somewhat unstable with increasing instability in the afternoon. Lapse rates at 00z Friday near 7C/km, lifted indexes between 0 and -3 and convective temperatures in the mid 60s. Chance of thunderstorms along the coast this morning with a chance of thunderstorms over the entire area this afternoon. Thunderstorm and shower chances decreasing quickly this evening as the air mass stabilizes and the low moves south. Highs today in the 60s. Lows tonight in the mid 40s to lower 50s.

Upper level low over Oregon Friday wobbles back to the north over Western Washington Saturday. Shower chances increasing again Friday night into Saturday especially for the Cascades and Southwest Washington. Highs Friday in the 60s and Saturday in the 60s and lower 70s. Lows in the mid 40s to lower 50s. Felton

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

What is left of the low hanging out west of the Cascades Saturday night and Sunday keeping a chance of showers in the forecast mainly over the Cascades. Low kicking out to the east Monday with a weak upper level trough developing over the area Tuesday and Wednesday. Little in the way of moisture with the trough. Low level flow light bringing up the possibility of some morning fog both days. Highs in the mid 60s to mid 70s. Lows in the upper 40s and 50s. Felton

AVIATION

South to southwest flow aloft for at least the first half of the day today before shifting more southeasterly to southerly as an an upper low digs southwards along the Washington coast. Although some terminals have seen their winds go light and variable, majority are reporting south to southeasterly with speeds running 5-10 kts. HQM is the exception where speeds linger in the 10-15 kt range.

Widespread VFR conditions this morning although isolated spots of MVFR can be found along the coast and over the islands. With showers over the western half of the CWA and slowly moving eastward, locations under heavier precip could see cigs dip into MVFR briefly, however cells of this nature are scattered. This limits the degree of confidence for TAF inclusion at this time. Lingering moisture from both precip from yesterday and approaching showers may allow for a brief drop in cigs early this morning into high-end MVFR as well. Locations more prone to lower cigs /HQM, OLM, PWT/ could see cigs fall even lower into brief periods of IFR. By late morning/early afternoon, widespread VFR conditions are expected to return thanks to increasing instability. That said, there is a risk for isolated thunderstorms this afternoon and early evening, however latest model guidance might be overestimating potential. Will not rule out development, but would assign only a 10-20 pct chance of occurring...most locations leaning toward the lower end of that range while locations in the SW interior /HQM, OLM/ leaning toward the upper end. Cigs area-wide likely to lift to mid-cloud levels tonight.

KSEA...VFR conditions are expected to continue for much of the TAF period, with the exception mentioned above as high-end MVFR conditions may briefly emerge around 15Z and linger into the late morning. As per current radar, showers are east of the terminal, but likely to start entering the area around 13-14Z. After the first wave passes through, scattered showers will linger in the forecast. Given their scattered nature, confidence is shaky regarding any direct impacts to terminal, and VCSH seems like the best bet for now. Above thunderstorm discussion applies, with SEA falling into the lower end of expectations. South to southeasterly winds 5-10 kts turning more southwesterly this afternoon. Speeds generally will remain consistent.

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MARINE

A Small Craft Advisory continues this morning for the eastern Strait of Juan de Fuca, Admiralty Inlet, and northern inland waters as breezy southerly winds persist in these areas. An additional Small Craft Advisory for the coastal waters will also remain in place throughout the morning hours, this one for a mix of breezy winds and heightened seas. Winds and seas will continue to ease together slowly through the day and into Friday as broad low pressure lingers over the region. Northerly winds develop Saturday and continue into early next week.

Showers remain in the forecast today with a 10 to 15% chance of thunderstorms for all waters Thursday afternoon.

Seas 8 to 10 feet early this morning, steadily falling below SCA criteria by mid to late morning. Seas further ease to 4 to 6 feet by tonight and remain there through the weekend.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 11 AM PDT this morning for Admiralty Inlet-Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm- Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands.