textproduct: Seattle/Tacoma

UPDATE

Light rain showers and drizzle evident over the coast, Olympic Peninsula and isolated areas of the interior. This activity will persist throughout the evening and become more widespread overnight into the early morning on Wednesday as a weak frontal system progresses through the area. Overnight lows are to bottom out into the mid 40s to lower 50s. The previous discussion remains below along with an updated marine and aviation section.

SYNOPSIS

A weak front will pass through today into Wednesday for a few showers across the north interior, Olympics and Cascades. A ridge will build over the region through the end of the week for another round of warm and dry conditions. The pattern flips to unsettled this weekend and early next week as a couple of systems pass through.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

A shortwave trough will pass to the north in B.C. tonight into Wednesday. The associated low pressure system with this trough is located over Graham Island this afternoon, with a warm front extending down the Pacific Ocean just offshore of the coastline. Cloud coverage will remain fairly intact for most of the day as the system passes through. There remains a chance of showers going into Wednesday morning, although coverage is expected to remain confined to the northern parts of the coverage area (north Olympics/Cascades, and interior). Rain amounts will be light, and only the Neah Bay to Quillayute areas will see any bump in wind speeds with gusts up to 20 mph this evening/Wednesday morning. The associated cold front will track more towards the Canadian side of the border.

High pressure will build back in under a ridge, beginning late Wednesday and building into Thursday. Conditions will dry out going into Thursday with skies gradually clearing out (except for the morning period where there will be a chance of some patchy fog in a few low-lying areas should cloud coverage clear out). But otherwise, temperatures will gradually warm on Thursday with highs back into the upper 60s to mid 70s, and lows in the upper 40s to low 50s. The high pressure/ridge pattern will result in a brief period of offshore flow, with winds becoming gusty in the Cascades Thursday morning up to 20 to 30 mph. With fuels largely recovered from recent rains, fire weather conditions are not expected to be a concern with this pattern.

LONG TERM /FRIDAY THROUGH TUESDAY/

The dry pattern from Thursday will continue into Friday, with Friday being the warmest/driest day of the forecast. More areas will also see highs into the mid 70s, and a few Cascade Valley locations may see an isolated instance of an 80. Once again, breezy east winds with gusts up to 20-30 mph will be likely Friday morning. The pattern will shift going into the weekend as the ridge departs. A trough will dig southward from Alaska with a couple of systems passing through this weekend and early next week. The first system Saturday will be quick, with the bulk of the precip falling as rain with snow levels over 8,000 ft. A few north Cascade locations may see up to an inch of of rain (as well as some snow at the highest elevations). The system early next week (late Sunday through Tuesday) will be cooler and wetter overall (but spread out over a 48 hour period compared to the Saturday system). Snow levels will drop to 5,000 ft which should lead to more snow in the mountains. Winds will become breezy at times with both systems, but the risk for hazardous winds at advisory level remain low at this time. HPR

AVIATION

Generally low end VFR to MVFR across the western Washington terminals this evening as a frontal system pushes inland, bringing light rain and widespread clouds. More widespread MVFR conditions are expected to expand inland early Wednesday after roughly 10z, with areas of IFR/LIFR along the Pacific Coast, Strait of Juan de Fuca, and Kitsap Peninsula. Southerly winds increase a bit toward 10 kt after 06z tonight into early Wednesday. Winds through the TAF period will remain mostly SW to SE at 10 kt or less. Conditions will dry out Wednesday afternoon, with most inland terminals returning to VFR as low and mid clouds erode. Areas closer to the coast will likely continue to see MVFR to IFR ceilings through Wednesday evening.

KSEA...VFR this evening under a solid mid-level cloud deck that will continue to thicken and lower through the evening. MVFR ceilings are favored to develop early Wednesday morning, with a 10%-15% chance of IFR ceilings. Light southwest and increase to around 7-9 kt this evening, easing Wednesday morning and remaining out of the south through much of the day Wednesday before shifting northeasterly Wednesday evening.

15

MARINE

A frontal system will continue to move inland tonight into Wednesday. Winds along the northern coastal water coastline may approach small craft, but are expected to remain below 20 kt. High pressure will rebuild inland Wednesday through Friday as a thermal trough builds along the coast, generating offshore flow. The flow will switch back to onshore later this weekend into next week as a couple of frontal systems pass through. Winds will likely surpass 20 kt over most area waters over the weekend and into early next week.

Seas will remain around 4 to 7 ft through the weekend, then increase to 10 to 14 ft with the system early next week, peaking Monday.

HPR/15

SEW WATCHES/WARNINGS/ADVISORIES

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