textproduct: Seattle/Tacoma

SYNOPSIS

An upper-ridge looks to remain in place to start the week before a well-organized system arrives on Wednesday and lead into Thursday with the potential for widespread rainfall gusty winds. This disturbance will remain in the vicinity through the weekend keeping conditions cool and unsettled.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

Latest satellite imagery shows mid to high clouds across Western Washington this evening. Otherwise, conditions are dry and to remain that way as we start the new week. An upper- level ridge is building over the region and remain in place into Monday. For tonight, areas of fog and low clouds are slated to develop. Overnight lows are forecast to bottom out in the mid 40s to mid 50s.

As mentioned, dry day on Monday with upper-ridge axis directly overhead in response to an upper-trough digging offshore. Monday may likely be the warmest day of the week as temperatures top out near average. Highs for the interior are to range between the lower 70s to lower 80s. Coastal areas firmly in the 60s. The pattern will begin to turn active on Tuesday as the upper-low associated with the aforementioned upper-trough tacks inland, increasing shower activity across the area. The activity will maintain overnight. Low temperatures are to bottom out in the lower to mid 50s from max temps of 60s and 70s earlier in the day.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Widespread precipitation and gusty winds are favored on Wednesday and Thursday as a well-organized disturbance remains on track to enter the region. NBM 24-hour probabilities of rainfall ending Thursday morning over an 1.00" ranges between 15-30% across the interior while the coast and Olympics have 75-95%. More QPF expected to fall throughout the remainder of the day on Thursday. Although there is uncertainty, the upper- trough may maintain over the region through Sunday. Cool and unsettled conditions trending into the weekend as temperatures measure well-below normal.

AVIATION

West to northwest winds continue aloft with brief upper level ridging over the area. High clouds will continue to remain overhead overnight. The biggest forecast question will be if patchy fog/low stratus will be able to develop early Monday morning. High clouds should limit its extent, put areas of fog cannot be ruled out at the most prone places including HQM, PWT, OLM, and PAE. Probabilities remain low at LIFR conditions (10-20%). VFR conditions then continue into tomorrow with high clouds.

KSEA...VFR conditions this afternoon will continue through the TAF period. High clouds will continue to stream overhead tonight. Fog development is uncertain (around 10% chc), but is more likely to remain outside of the terminal. N wind 5-10 kt. 33/62

MARINE

Winds fairly light today as the coastal waters of Washington remain in-between systems. High pressure will briefly nose in on Monday for increasing northwesterly winds. Winds will start to increase once again late Tuesday as a frontal system approaches from the north. The system, which has been delayed slightly in more recent runs, will move through through the middle and latter half of the day with the strongest winds then. The coastal waters (60-80% chc) and the eastern Strait of Juan de Fuca (50-60% chc) will be the most likely places to see gale force gusts, with Small Craft Advisory winds likely elsewhere. Winds will slowly ease Wednesday night into Thursday as the system moves to the south and weakens.

Seas remain around 3-6 ft until Wednesday, rising up to around 8-11 ft then as the system moves through. 62

FIRE WEATHER

A brief warming and drying trend will occur Monday into Tuesday ahead of the next weather system. Relative humidity minimums in the central and southern Washington Cascades will decrease to around 30 percent tomorrow afternoon. Finer, flashier fuels will be more apt to respond to the dip in RH. More clouds arrive ahead of the stronger system for only partly sunny skies on Tuesday. By late Tuesday night into Wednesday, the stronger system arrives for widespread rain, windy conditions, and slight chances for thunderstorms.

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SEW WATCHES/WARNINGS/ADVISORIES

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