Semyan.com Seattle Weather

Pressure Observations from the UW
520 Bridge - Wind Readings

Pressure Gradients - Ferry Observations
Wind Map - Westpoint Conditions

5 Day Outlook from the National Weather Service

Friday Night

Clear
Hi 87°F
Lo 59°F
PoP 0%
Independence Day

Mostly Sunny
Hi 87°F
Lo 59°F
PoP 0%
Saturday Night

Mostly Clear
Hi 87°F
Lo 61°F
PoP 0%
Sunday

Partly Cloudy
Hi 87°F
Lo 61°F
PoP 3%
Sunday Night

Mostly Cloudy
Hi 69°F
Lo 58°F
PoP 12%
Monday

Mostly Cloudy
Hi 69°F
Lo 58°F
PoP 17%
Monday Night

Mostly Cloudy
Hi 68°F
Lo 56°F
PoP 17%
Tuesday

Mostly Cloudy
Hi 68°F
Lo 56°F
PoP 17%
Tuesday Night

Mostly Cloudy
Hi 72°F
Lo 55°F
PoP 17%
Wednesday

Mostly Cloudy
Hi 72°F
Lo 55°F
PoP 17%
Data From: Sat, 04 Jul 2009 12:06:58 GMT
Lake Union Weather Conditions

Current Seattle Radar - Base Reflectivity
4 Km Infrared Satellite
4 Km Infrared Satellite
4 Km Water Vapor Satellite
4 Km Water Vapor Satellite

7 Day Forecast for Seattle - NWS

Red Flag Warning

Independence Day: Sunny, with a high near 85. Calm wind becoming northwest between 4 and 7 mph.

Tonight: Clear, with a low around 57. North northwest wind between 5 and 8 mph.

Sunday: Sunny, with a high near 84. Calm wind becoming northwest around 5 mph.

Sunday Night: Mostly cloudy, with a low around 58. North wind 9 to 17 mph becoming south.

Monday: Mostly cloudy, with a high near 72. South southwest wind between 8 and 16 mph.

Monday Night: Mostly cloudy, with a low around 56.

Tuesday: Partly sunny, with a high near 68.

Tuesday Night: Mostly cloudy, with a low around 54.

Wednesday: Partly sunny, with a high near 72.

Wednesday Night: Mostly cloudy, with a low around 55.

Thursday: Partly sunny, with a high near 72.

Thursday Night: Mostly cloudy, with a low around 55.

Friday: Partly sunny, with a high near 73.

   Marine Forecast - NWS Zone Forcasts
Puget Sound and Hood Canal- 231 AM PDT Saturday jul 4 2009

Today: Northwest wind 5 to 15 kt, except southwest over the south sound. Wind waves 2 ft or less. Patchy morning fog over the far south sound.

Tonight: Northwest wind 10 to 15 kt, except southwest 5 to 15 kt over the far south sound. Wind becoming light by midnight. Wind waves 2 ft or less, subsiding.

Sunday: Light wind, becoming northwest 5 to 15 kt in the afternoon. Wind waves building to 2 ft or less.

Sunday night: Variable wind 5 to 15 kt, becoming south 20 to 30 kt by midnight. Wind waves building to 3 to 5 ft.

Monday: Southwest wind 15 to 25 kt, easing in the afternoon. Wind waves 2 to 4 ft, subsiding. A chance of showers.

Tuesday: Southwest wind 10 to 15 kt. Wind waves 1 to 2 ft.

Wednesday: Southwest wind 5 to 15 kt. Wind waves 2 ft or less.


Admiralty Inlet- 231 AM PDT Saturday jul 4 2009

Today: Light wind, becoming northwest 10 to 15 kt this afternoon. Wind waves less than 1 ft, building to 1 to 2 ft.

Tonight: Northwest wind 10 to 20 kt, easing after midnight. Wind waves 1 to 3 ft, subsiding.

Sunday: Northwest wind 5 to 15 kt. Wind waves 2 ft or less.

Sunday night: Northwest wind 5 to 15 kt, becoming south 20 to 30 kt about midnight. Wind waves building to 3 to 5 ft.

Monday: South wind 20 to 30 kt, easing in the afternoon. Wind waves 3 to 5 ft, subsiding. A chance of showers.

Tuesday: South wind 10 to 15 kt. Wind waves 1 to 2 ft.

Wednesday: South wind 5 to 15 kt. Wind waves 2 ft or less.


Forecast Discussion - NWS - Glossary
300 AM PDT Saturday jul 4 2009

Synopsis: Sunny and warm weather will continue through the holiday weekend, with areas of morning low clouds and fog confined mainly to the coast. An upper trough will move into the region Sunday night and Monday for a transition to cooler weather with a chance of showers for next next week.

Short Term: An upper level ridge remains over the pacific northwest with 500 mb heights over Western Washington around 5800 meters. There have been some changes at low levels that will make the forecast for the next couple days slightly tricky. The surface gradients turned weakly onshore Friday evening and a shallow layer of coastal stratus has been moving inland slowly overnight, mainly through the chehalis gap and to a lesser extent down the Strait of Juan de Fuca.

In the interior the stratus will probably remain limited to the southwest part of the Puget Sound region -- ie shelton and perhaps bremerton -- with only patchy coverage in the strait and north interior. It should burn off relatively quickly. But more importantly the influx of shallow marine air should have at least a minor effect on high temperatures across the interior lowlands. In general the models have underestimated the strength of onshore gradients. The bottom line is that we are likely to be not quite as warm as Friday across the interior lowlands.

The upper ridge axis will move east toward the northern rockies tonight, and the upper trough currently just outside 140w will approach the pacific northwest coast Sunday. Low level onshore flow will probably remain only weak, but the 500 mb heights will fall to around 5750 meters as cooler air moves in aloft. Temperatures over the lowlands will be similar or only slightly cooler on Sunday, but the cooler air aloft with the trough will destabilize the air mass for a low chance of showers in the Cascades.

It should be mentioned that the guidance is not unanimous with the idea of slight cooling each day this weekend. In particular the nam mos is forecasting temperatures over the interior to be about the same as Friday for both days this weekend. The models remain in general agreement that the upper trough will reach the area Sunday night. Upper level heights will crash further, resulting in a sufficient increase in onshore flow for a moderate to strong onshore push. By Monday the pattern change will be more or less complete -- an upper trough will be settling over the region and low level flow will be onshore for cooler weather and a chance of showers.

mcdonnal

Long Term: The longer range models agree that the upper trough will be parked over the region for the extended forecast period Tuesday though Friday. The current broad brush forecast looks good. There will be more clouds than Sunday along with a chance of showers. Onshore flow will continue with a fairly strong marine influence, and temperatures will be a little below normal.

mcdonnal

Aviation: An upper ridge will remain over the region thru tonight. Increasing southwest flow aloft. Light onshore flow today will become flat or weak offshore overnight.

stratus/fog Now blanketed the coast, and has made it as far east as the far south sound. The depth of the marine layer was fairly shallow or between 1k and 1500 ft deep. expect the low clouds/fog To dissipate or retreat offshore between 18z and 20z, sooner over the interior.

Ksea, continued vfr conditions. low clouds/fog Should remain well south and west of the terminal. Expect light and variable winds, becmg northwest in the afternoon.

Marine: Light onshore flow will prevail over the area today. The flow will become weak offshore overnight but this will be brief. Expect light onshore flow to return Sunday afternoon, with a strong marine push occuring Sunday night. It is possible that there will be a brief period of wind gusts near 35 knots with the push as it surges north across the Puget Sound, Admiralty Inlet, and the northern inland waters. Anticipate moderate onshore flow across the area on Monday.

Watches/Warnings/Advisories: Wa, red flag warning in effect for the entire area until midnight Sunday night. Pz, Small Craft Advisory for winds in effect for the central and eastern Strait of Juan de Fuca from 3 PM this afternoon until midnight tonight.


Current/24 HR Pacific Surface Analysis from the
NOAA Ocean Prediction Center

Current Surface Analysis

24 hr Surface Forecast

Current 500 mb chart from the
NOAA Ocean Prediction Center

Current 500 mb Chart


Disclaimer: this data comes from various NOAA, Accuweather, and Washington DOT web sites. It may be woefully out of date or inaccurate. As always, use common sense and verify conditions before making any decisions regarding boating, aviation, hiking, or any other weather dependent activities. If you find any errors, please email me at semyan@hotmail.com.