A strong upper level ridge with low level offshore flow will result in one more sunny and warm day today. Record high temperatures are likely. Marine air will surge inland tonight into thursday resulting in an increase in clouds and moisture and much cooler high temperatures. Light rain will spread northeast across the area on friday. There will be a chance of showers on saturday followed by drying to sunday. Temperatures friday through the weekend will be near normal.
A strong ridge of high pressure at the surface and aloft over southeastern british columbia is expected to move off to the southeast and slowly weaken tonight and thursday. Strong easterly flow continues to produce dry conditions across the area this morning with a wide range of temperatures. Places exposed to easterly flow (such as seatac airport) are still in the mid 60s at 2am! places that are sheltered to the wind have radiated out nicely and some colder locations are in the upper 30s to mid 40s. Temperatures this afternoon will again exceed record values. The record high at seatac airport today is 69 degrees (we are only 3 degrees shy of that early this morning) and highs today will likely top out in the mid and upper 70s. Easterly pressure gradients will be gradually relaxing this afternoon, so the temptation to match temperatures that we saw on tuesday was avoided.
As easterly flow decreases, expect a thermal low to develop on the north-central oregon coast and to surge into sw washington this afternoon. By late afternoon, expect north bend or to seattle pressure gradients to go over +4mb, the point at which marine air surges inland. The nam seems to do a reasonable job in capturing the development of a stratus deck at the top of a deepening marine layer early thursday morning and in keeping temperatures in the mid 50s to lower 60s thursday afternoon. While temperature forecasts will be on the top end of the guidance envelope for today, they will be on the lower end of the guidance envelope for thursday with the influx of marine air. Despite the marine air, it appears that it will stay dry on thursday across the area.
A nw/se oriented front will lift across the area friday afternoon and evening, bringing some light rain to the area. Light ne flow ahead of the front will allow temperatures on friday to top out near the 60 degree mark before precipitation moves in. Albrecht
A weak upper level trough behind friday nights front will give showers to the area on saturday. The showers will gradually come to an end saturday night as high pressure aloft builds into the area and surface high pressure builds northward into british columbia. Sunday now looks dry with low level ne to e flow increasing ahead of the next negatively tilted frontal system that will be approaching from the southwest. Temperatures aloft wont be as warm as they have been the past few days, so expect high temperatures on sunday to stay in the mid 50s to lower 60s. Rainfall associated with the next frontal system will move into the area on monday. Albrecht
River flooding is unlikely over the next seven days.
Wa...none. Pz...small craft advisory until noon pdt today for central u.s. waters strait of juan de fuca-coastal waters from cape flattery to james island 10 to 60 nm-coastal waters from cape flattery to james island out 10 nm-west entrance u.s. waters strait of juan de fuca.
Offshore flow will persist through this evening. breezy winds near the gaps of the coastal terrain - strongest easterly winds will be along the central strait of juan de fuca through this morning. Light onshore flow developing on thursday ahead of a weakening front spreading into the region on friday. westerly swell 10 to 11 feet will begin to affect the coastal waters friday night rising to 12 feet at 16 seconds saturday.
Low level offshore flow will continue today, with vfr conditions for all terminals. Easterly winds have started to ease over the last 2 hours, however should pick up again for terminals along the southern portion of the sound near 18z. The air mass will remain dry and stable, with southerly-southeasterly flow aloft.
Ksea...vfr conditions with easterly winds 10-15 knots. Winds expected to pick up again near 18z, with gusts up to 25 knots possible at times. 14