textproduct: Seattle/Tacoma

SYNOPSIS

Onshore marine air keep most of western Washington in the clouds today into Tuesday with pockets of drizzle and a shower or two at times. A ridge will push through Wednesday into Thursday with more sunshine, with increased cloud coverage finishing the week as a dry trough passes through. Stronger high pressure combined with a thermal trough early next week may produce the first 80 degree weather of the year for western Washington.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

Forecast below is on track for the evening update. -HPR

Sunshine has vanished for most in western WA today as stronger marine push continues. Satellite shows a meso low feature just off the tip of Neah Bay rotating clouds across the coast, rotating the clouds inland on the south side of the Olympics, and pushing inland through the interior. There is evidence of a break up of some of the clouds up in Whatcom County early this afternoon, and this will likely spread southwards into the interior this evening to at least give a few glimpses of the sun before dusk. Clouds will fill in again tonight/Tuesday with another overcast day expected. Couple pockets of drizzle/showers cannot be ruled out either with the marine air. Temperatures with the cloud coverage only climb into the upper 50s/low 60s, with lows in the mid/upper 40s. Winds remain out of the southwest around 5-10 mph.

A ridge moves over the region Wednesday, with increased northerly flow aloft expected to disrupt the marine pushes. Sunny skies are expected for much of the west side of the state as the ridge passes overhead. Temperatures on Wednesday will be a few degrees warmer with highs in the mid/upper 60s, and lows Wednesday night in the low 40s/upper 40s. Couple pockets of minor HeatRisk cover the Seattle metro into the south interior.

LONG TERM /THURSDAY THROUGH MONDAY/

The ridge from Wednesday will continue to move eastward Thursday. The day will start out sunny with clouds beginning to return as a trough/cold front pass through the region dry. Cloud coverage will remain into Friday/Saturday with onshore flow behind the cold front. Temperatures dip from the upper 60s/low 70s Thursday into the mid/upper 60s Friday. Most ensembles are showing a large bubble of high pressure forming just offshore the Pacific Coast, with a large ridge extending into far northern B.C. Canada. Depending on how strong a potential thermal trough picks up along the coast underneath the ridge, this could be the first chance western WA has of seeing high temperates at or above 80 this season (looking at Sunday and Monday). The lows during this time appear to cool still in the upper 40s to low 50s, but will have to watch for pockets of moderate HeatRisk with this warm and dry pattern coming up.

HPR

AVIATION

North to northwest flow aloft will continue into Tuesday as an upper trough over the Northern Rockies slowly progress eastward and an upper ridge remains centered offshore. The low level flow is light onshore. Low end VFR ceilings across much of the area this evening are expected to lower back to areas of MVFR overnight into Tuesday morning. A gradually lifting is expected once again Tuesday afternoon.

KSEA...VFR ceilings are expected to lower back to MVFR overnight and continue into Tuesday morning before lifting again in the afternoon. Surface winds S/SW 7 to 10 knots into Tuesday morning will ease Tuesday afternoon and gradually veer around to the W/NW late in the day.

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MARINE

Broad surface ridging offshore and lower pressure over the interior will maintain varying degrees of onshore flow throughout the week ahead. A weak system approaching the region late Thursday or Friday will enhance it enough for possible small craft advisory strength westerlies in the central and east portions of the strait as well as the outer coastal waters.

Steep seas continue over the outer coastal waters around 7-9 ft with a dominant period of 8-9 seconds. These may persist into Tuesday night before guidance suggests a couple of longer period swell trains will arrive.

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HYDROLOGY

No river flooding is expected in the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 9 AM PDT Tuesday 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.