textproduct: Seattle/Tacoma

SYNOPSIS

A frontal system will move out of Western Washington into this evening. High pressure builds aloft over the Pacific Northwest Thursday and Friday, with just a slight chance of precipitation. The upper ridge further builds over the weekend for drier, warmer conditions.

SHORT TERM /TODAY THROUGH FRIDAY/

Drier conditions across Western Washington this morning as a few lingering light showers continue to taper this morning. With the abundant low-level moisture from yesterday's rainfall and decreasing winds, expect to see the spatial coverage of fog to increase this morning toward daybreak. Low clouds gradually decrease through the day with at least partial sunshine for the afternoon. Not much change in the overall picture through Thursday. With the flow remaining zonal, there's the potential for enough of an impact from the next disturbance clipping the far north as it passes across southern B.C. This brings some rain chances to the northern portions of the interior (mostly Whatcom/Skagit counties), but even for the areas that see rain it should remain quite light. As this disturbance exits the region on Friday, a few light showers may linger in the North Cascades, but dry conditions hold for most of the area.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Ensemble guidance remains in fairly strong agreement for the weekend into early next week. the pattern would likely favor a return of high pressure and some light offshore flow. This could yield a somewhat mild start to October, with temperatures into the lower to mid 70s Sunday. The return of more onshore flow would return early next week as the high pressure nudges slightly eastward, bringing temperatures back down closer to 70 for daytime highs with the greater marine influence. Overall, though, mild and dry conditions expected for the long term period.

AVIATION

Majority of terminals VFR this morning with either clear skies or overcast skies. A few terminals with clear skies and light winds have been reporting fog with visibility as low as 1/4SM, particularly north of PAE. Fog still remains a possibility for terminals along the Southern Interior and Kitsap Peninsula if conditions remain clear with light winds. As for the other terminals, low ceilings possible through the afternoon hours. Guidance highlights the chance for MVFR cigs for Puget Sound after 12Z. Improvement expected in the afternoon to VFR after 18z-20z. Light northerly to calm winds early this morning will increase in the afternoon to 6-8 kt.

KSEA...VFR conditions early this morning. Guidance continues to highlight the chance (50%) for MVFR cigs later this morning after 11Z. There is a slight chance (20%)for IFR cigs between 14-17Z. Ceilings will lift in the afternoon after 19-20Z and VFR conditions will prevail into the evening. Light NE winds early this morning 5 kt or less. Winds will shift NW in the afternoon and increase to 6-8 kt. Winds ease this evening, turning NE at 5 kt or less. 29

MARINE

Seas subsiding over the coastal waters this week. Meanwhile, building high pressure over the waters with a thermal low pressure building north along the coast by the weekend. This will induce northerly to weak offshore flow over the waters, but speeds aren't expected to be particularly strong. This will maintain seas generally 3-6 ft over the coastal waters and conditions short of advisory thresholds.

FIRE WEATHER

Mostly dry conditions through the week ahead with additional wetting rain not expected. A few light showers across the north may develop with a passing disturbance late Thursday into Friday. Otherwise, attention turns to a warmer period with temperatures well into the 70s this weekend under stronger high pressure. This may bring a brief switch to light offshore flow as a thermal trough builds north over the region. This looks to shift eastward for a return to onshore flow and closer to normal conditions early next week.

SEW WATCHES/WARNINGS/ADVISORIES

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