Marine Weather and Tide Forecast for Issaquah, WA

SHORT TERM /TODAY THROUGH WEDNESDAY/
Latest satellite imagery showing center of circulation for the current upper low over the coastal waters of the norther OR coast. As such, both on satellite and radar, seeing a wave of moisture being rotated up into the southern portions of the CWA with echoes moving to the west- northwest.

As this feature pushes inland today, that will keep the chance of showers in the forecast for W WA at least into the late afternoon before drying starts moving slowly over the area from west to east.
The coast should see activity wrap up by late in the afternoon while locations east of the Sound seeing showers linger into tonight.
Given the isolated thunderstorms that happened Sunday afternoon and with models suggesting some instability...will leave model generated ProbThunder alone...especially since it falls in a pretty narrow window of the mid to late afternoon time frame.

Models remain consistent in bringing in an upper level ridge into W WA late tonight resulting in largely dry conditions Tuesday. This is not a strong ridge by any means, being largely ineffective in scouring out any lingering moisture. Thus, though generally dry conditions are expected both Tuesday and Wednesday, there will still be a fair amount of clouds over the area and a persistent chance for showers over the Cascades.

High temp forecasts remain consistent with previous runs with little change throughout the near term period: lower to mid 60s for the interior, mid to upper 50s for the coast and water adjacent locations.

18

LONG TERM /THURSDAY THROUGH SUNDAY/
Deterministic models starting to fall in line with each other, bring the next system into the area Thursday...their timing about 3-6 hours off from one another.
Ensembles provide some fine tuning for the return of chances for precip to the area...generally landing in the late afternoon/early evening. As has been the case with most of these recent systems, neither PoPs nor QPFs look terribly impressive...the former running 30-50 pct mostly and the latter falling short of 0.05 of an inch.
Depending on where you look, there seems to be a more favorable opinion of the Friday system when it comes to generating rainfall.
Deterministic models are not really doing a good job of handling it but ensembles provide a better picture with a strong preference for overnight Friday and into Saturday. QPF values still fall short of meh, with the ensemble mean falling largely right around 0.05 of an inch, but there are a fair number of perturbations that clime to 0.10 of an inch or higher. As the trough responsible for this sinks southward for the remainder of the forecast period, some disagreement as to whether or not a closed low emerges. Regardless of that, ensembles show chances slowly eroding throughout the day Saturday and while not entirely gone Sunday, majority of locations see only a slight chance by then.

This generally troughy pattern will not allow for any significant change to the temperatures over W WA, with the bulk of the long term echoing those of the short term.

18

AVIATION
An upper level low will spin through the Pac NW today for scattered showers. The flow aloft is northerly. The air mass is moist and slightly unstable with a slight chance of afternoon thunderstorms in the interior and Cascades. Pockets of low clouds and MVFR cigs this morning with more widespread MVFR conditions Tuesday morning. 33

KSEA...Pockets of low clouds and possible MVFR cigs this morning.
Light S/SW winds this morning, increasing to 4-8 kt this afternoon.
Showers in the vicinity from 19-02Z. 33

MARINE
A 1000 mb low will weaken and shift east into Oregon today, with onshore flow increasing tonight. Small Craft Advisory winds are likely through the Strait of Juan de Fuca. Seas will also build to around 10 ft over the outer Coastal Waters. High pressure sets up offshore with lower pressure inland on Tuesday. This pattern will remain intact through Thursday with the next frontal system moving inland on Friday. 33

HYDROLOGY
The daily hydrology discussion has ended until the start of the next rainy season; it will only be included as needed.

SEW WATCHES/WARNINGS/ADVISORIES
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Tuesday 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 PM this afternoon to 5 AM PDT Wednesday 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.