textproduct: Seattle/Tacoma

SYNOPSIS

An upper level trough over the region will weaken today and high pressure aloft will rebuild across the area Monday into Tuesday for a warming trend. Another weak trough offshore will temporarily cool temperatures somewhat midweek before a longer term warming trend begins toward next weekend with a strong ridge of high pressure.

SHORT TERM /TODAY THROUGH TUESDAY/

No significant changes made to the forecast this morning. The previous discussion can be found below with updates to the aviation and marine sections:

Persistent troughing just offshore will keep some clouds around today and hold back temperatures to near climo today before lifting back into British Columbia as a strong upper ridge centered east of the Rockies exerts a little more influence on the area. This will lead to an upward trend in temperatures with warmer interior areas getting back into the 80s Monday and Tuesday and a chance for moderate HeatRisk for Seattle metro southward.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Heights stay relatively high into Wednesday as an upper low cuts off offshore. As with most cut-off lows, models are having a tough time resolving how this system will evolve as it lifts back onshore around Thursday. This should temporarily delay an impending extended warm spell that is still expected to begin next weekend. While it's still early days, we'll need to monitor how this system tracks onshore because it could trigger some convection...something we don't need in fire season. Models remain in relatively good agreement with strong upper ridging regaining control by the weekend for what looks like the beginning of an extended period of above normal temperatures.

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AVIATION

Strong low-level onshore flow has brought in widespread MVFR stratus for most terminals this morning but clouds have began to scatter. Surface winds are trending lighter but will flip to the northwest in the afternoon to around 8-12 kt. Early indications for Monday morning have 40-60% chance of IFR/LIFR conditions for the immediate coast, and east out to the Kitsap area. Probabilities for any ceilings elsewhere remain low at this time.

KSEA...MVFR stratus is scattering to VFR and is forecast to remain in place throughout the day. Southwest winds trending lighter this morning before switching to the northwest from 18Z-21Z around 8-12 kt before turning more northeast around 5 kt late.

HPR/41

MARINE

A trough remains along the coast with an upper low in BC. Down at the surface, a stationary front with surface low pressure remains in eastern WA, with high pressure over the coastal waters. No headlines in place currently across area waters. The pushes through the strait will become much weaker going through midweek, and odds right now are in favor of winds and gusts remaining below 20 kt through the remainder of the week. Coastal waters may also see wind gusts approach 20 kt towards the end of the week on Thursday and Friday with another low system tracking through the waters.

Seas for the majority of the forecast will remain at 4-6 ft, with the system Thursday/Friday increasing seas to 7-8 ft with periods around 6-8 seconds.

HPR/41

FIRE WEATHER

The lack of offshore flow through the middle of the week will keep fire weather concerns at a minimum. Warming temperatures late week will begin to increase the fire weather risks going into the weekend. An upper trough arriving around midweek will need to be monitored in the days ahead for potential convection and associated risks of lightning strikes with fuels now running quite dry.

SEW WATCHES/WARNINGS/ADVISORIES

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