textproduct: Seattle/Tacoma

SYNOPSIS

Weak system moving by to the north will enhance the low level onshore flow overnight. Low level flow turning northerly Sunday afternoon and remaining northerly into Tuesday leading to less morning clouds and warmer days. Weak upper level trough moving over the area Wednesday afternoon through Thursday. Upper level ridge building over Western Washington beginning Friday.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/

Satellite imagery shows plenty of fair weather cumulus over Western Washington with a weak upper level shortwave just offshore this afternoon. Temperatures a little below normal, mid 60s to lower 70s over the interior and mid 60s along the coast.

Weak upper level shortwave moving by to the north tonight. Increasing low level onshore flow with and behind the shortwave with the marine layer making its way back inland early Sunday morning. Lows tonight in the upper 40s to mid 50s.

Mostly cloudy Sunday morning. Low level flow turning northerly Sunday afternoon. This will get rid of the marine layer over the interior resulting in some afternoon sunshine. Highs in the mid 60s to mid 70s.

Low level northerly flow continuing through Monday night which will keep the marine layer at bay. Temperatures aloft warming slightly with 500 mb heights near 580 dms Monday afternoon. Highs warming into the 70s and lower 80s. Lows Monday morning in the upper 40s to mid 50s. Felton

LONG TERM /TUESDAY THROUGH SATURDAY/

Upper level trough digging offshore Tuesday pushing 500 mb heights into the lower to mid 580 dms over Western Washington. Highs warming into the mid 70s to mid 80s over the interior and near 70 along the coast.

Upper level trough axis reaching the coast Wednesday afternoon with the trough slowly moving over the remainder of the area Wednesday night into Thursday. Slight chance of showers in the mountains as the trough moves overhead. For the lowlands slow cooling trend with high Wednesday in the lower 70s to lower 80s and just 70s for Thursday.

Upper level trough moving east Thursday night. Upper level ridge building Friday and Saturday with 500 mb heights rising into the mid 580 dms. This could be the start of a sustained warm spell over the area. Highs warming into the mid 70s to mid 80s by Saturday inland with highs on the coast remaining near 70. Felton

AVIATION

VFR observed area wide this afternoon as previous marine stratus has scattered with diurnal heating. However, another round of strong low- level onshore flow this evening will reintroduce marine stratus into western Washington tonight into Sunday morning. MVFR ceilings likely to form along the coast (KHQM) between 02-04z - gradually spreading inland towards Puget Sound terminals around 10-12z Sunday. Stratus is forecast to burn off to VFR by 18-21z. Breezy west to southwesterly winds for Puget Sound terminals and coastal terminals this evening with gusts near 20-25 kt. Surface winds should subside on Sunday morning.

KSEA...VFR conditions will prevail this evening through tonight. The NBM has a 20-25% chance of ceilings below 3,000 ft developing over the terminal after 09z but if manifest, VFR should return by 18z. Southwest winds gusts up to 20-25 kt 03z onward but should subside into Sunday morning.

MARINE

A weak surface trough will remain over the offshore waters tonight before high pressure broadly rebuilds into the coastal and offshore waters Sunday and Monday and remaining into midweek. This will promote a fairly typical summer pattern with varying degrees of onshore flow promoting a diurnally driven increase in westerlies through the Strait of Juan de Fuca near daily. Northwest winds over the coastal waters are likely to increase later Monday into Tuesday as thermally induced surface low pressure expanding over the interior of Western Washington tightens the onshore gradient.

FIRE WEATHER

The lack of offshore flow through the middle of next week will keep fire weather concerns at a minimum. Warming temperatures late next week will begin to increase the fire weather risks going into the weekend. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 3 AM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.