textproduct: Seattle/Tacoma

SYNOPSIS

A weak upper ridge will allow for a brief break in the rainfall before a series of systems return cool and unsettled conditions to western Washington for the first half of this week. A pattern shift toward dry and considerably warmer conditions is expected late next week as strong high pressure aloft builds into the region.

SHORT TERM /TODAY THROUGH TUESDAY/

Considerable cloud cover remains in place across most of Western Washington this morning in the wake of yesterdays departing system. The last vestiges of shower activity should be gone over the next couple of hours. The high cloud shield ahead of the next system is just offshore which will offset our chances of seeing much in the way of sun when the lower level clouds scatter out this afternoon. There's a noteworthy change in the forecast trend regarding this next system Monday into Monday night. Models are trending further north with track of the surface low resulting in greater coverage of precipitation...particularly for the southern half of the CWA. This ends up being a decent stratiform rain event in contrast to the convective stuff we saw Friday and Saturday. Put another way, the Seattle area could see a half inch of rain from this system...or roughly just over a third of what we normally get in the whole of the month of the June. Not bad. The remainder of the forecast hasn't changed terribly much with a significant warming and drying trend late in the week which we'll dig into in the afternoon discussion. The previous discussion follows with updates to the aviation portion.

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Some isolated patches of showers on current radar, the most notable over portions of central Snohomish and Skagit counties at the time of this writing and fizzling out as they move southeastward. Otherwise, quiet conditions present.

As stated in the synopsis, a shortwave ridge will bring generally dry conditions to the area today. Not completely dry though as enough moisture exists where forced lifting triggered by topography could give rise to showers throughout the day...such as over the Olympics and Cascades as well as the northeast corner of the Olympic Peninsula. Daytime highs will benefit a little bit from this upper level feature, bumping up a couple of degrees as most interior lowland locations should see temps in the lower 60s.

This ridge manages to hold off the next incoming frontal system at least into Monday morning but rains return by Monday afternoon for most locations...maybe holding off til the late afternoon or early evening for the northern extent of the CWA /Whatcom County/. Between the slow eastward progress of this front and the follow-up parent upper low, no discernible break in the precip is expected between Monday and Tuesday. Latest NBM suggests thunder may be a possibility Tuesday and some CAPE at the surface may be available, LIs stay well on the stable side of things and temperatures remain far from impressive when considering triggering convection. ProbThunder values remain below 20 pct and while it might be slightly overdone, have opted to leave it alone for now and will re-evaluate come future model runs and adjust if needed.

Daytime highs Monday and Tuesday don't really see too much variation from one another with upper 50s to lower 60s expected both days. That said, Monday does show some isolated spots where mid 60s could emerge, whereas Tuesday high temp spread is more uniform.

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LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Tuesday night and Wednesday see PoPs gradually diminishing before generally dry conditions take root by Wednesday evening as residual moisture from the eastbound upper low lingers. Forecast remains on track for an intensifying upper level ridge over the eastern Pacific to begin to flex its muscles into W WA starting on Thursday and continuing throughout the remainder of the forecast period. Data remains very consistent when it comes to rapid warming with daytime highs Thursday in the mid 60s to around 70, then jumping up into the lower to mid 70s for most the interior lowlands...although the SW interior will get to around 80 and Saturday pops further upward into the lower to mid 80s. Taking a peak outside of the forecast window into days 8 to 14, chances of above average temperatures are becoming more and more likely with hints of 90s potentially starting as early as next Sunday. Ordinarily, it would be advised that at this far out, a grain of salt or other preferred table seasoning would be recommended. As data remains persistent, however, prepping in advance for some significant heat and heat risk this upcoming weekend might be warranted.

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AVIATION

Northwest flow aloft over Western Washington will back to southwesterly again tonight as the next in a series of upper troughs and associated frontal systems approaches the area. Remnant low level moisture producing MVFR and pockets of IFR ceilings will scatter out this afternoon, but high and mid level moisture ahead of the next system will spread onshore this afternoon and tonight. VFR ceilings are expected to prevail areawide from mid-afternoon into this evening. Ceilings will deteriorate back to MVFR in increasing rain along the coast mid to late Monday morning with said conditions gradually spreading to most interior terminals 21Z Monday onward.

KSEA...MVFR ceilings this morning will lift again by the afternoon hours for a return to VFR conditions. Surface winds S/SW 7 to 10 knots gradually ease this afternoon and veer light W/NW for a period this evening. Confidence in the surface wind forecast on Monday is relatively low and high dependent on the track of an area of surface low pressure moving into the region. Initial expectations are a light E/SE wind early Monday backing northerly 9 to 14 knots late in the afternoon.

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MARINE

High pressure will persist over the coastal waters today, before another trough and its associated frontal system approach the area waters tonight into Monday. Southerly winds will start to increase across the outer coastal waters tonight and will gradually increase across the inner coastal waters on Monday. The system will then slow and dissipate on Monday as a weak surface low moves toward the coast. A brief period of small craft strength southerlies will be possible across the eastern Strait, Admiralty Inlet, and the Northern Inland Waters as the front moves inland on Monday, with latest HREF probabilities indicating a 70-80% chance of wind gusts exceeding 21 kt.

Onshore flow will then increase in the system's wake as high pressure builds back into the coastal waters. Tuesday's push of westerly winds along the Strait still looks like the strongest of the week, with latest probabilities indicating a 50-60% chance of gales. Onshore flow will continue into Wednesday, but will weaken. A thermal trough will expand northward along the Oregon coast on Thursday and looks likely to expand northward along the Washington coast by next weekend. Flow will then transition to offshore as a result.

Seas will hover between 4-6 ft today, before building back to 6-8 ft by Monday and persisting between this range through much of the week ahead.

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FIRE WEATHER

As upper level ridging builds into the area starting Thursday, conditions, including fuels, will need to be monitored as temperatures are expected to climb to above normal values entering into the week 2 time period. Given the steep climb in temperatures toward the end of the forecast period, extra caution would be advised in any planning during this time period.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 5 AM PDT early this morning for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 5 AM to 1 PM PDT Monday for Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.

Small Craft Advisory from 11 PM this evening to 1 PM PDT Monday 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.