3/17/2015: Latest predictions have good numbers for Seattle from darkness until 11pm or 1am. This morning was better. Tonight’s a little unpredictable.
From 3/17/2015 pm:
NOAA Kp index breakdown Mar 18-Mar 20 2015 Mar 18 Mar 19 Mar 20 00-03UT
7 (G3)4 2 5pm-8pm previous date 03-06UT 7 (G3)3 2 8pm-11pm previous date 06-09UT 6 (G2) 3 2 11pm previous date 2am 09-12UT 5 (G1) 3 2 2am-5am 12-15UT 4 3 2 5am-8am 15-18UT 3 3 2 8am-11am 18-21UT 3 3 2 11am-2pm 21-00UT 3 4 2 2pm-5pm Rationale: 18 March is expected to (G1-G3) storm conditions as the effects from the CME persist. Following the end of CME effects, geomagnetic activity should remain below G1 conditions for days two and three (19-20 Mar).
From 3/17/2015 am:
The greatest observed 3 hr Kp over the past 24 hours was 8 (NOAA Scale G4). The greatest expected 3 hr Kp for Mar 17-Mar 19 2015 is 8 (NOAA Scale G3). NOAA Kp index breakdown Mar 17-Mar 19 2015 Mar 17 Mar 18 Mar 19 00-03UT
25 (G1) 4 5pm-8pm previous day (PDT) 03-06UT 5 (G1)5 (G1) 3 8pm-11pm previous day (PDT) 06-09UT 6 (G2)4 3 11pm previous day - 2am (PDT) 09-12UT 6 (G2)3 3 2am-5am (PDT) 12-15UT 8 (G4)3 3 5am-8am (PDT) 15-18UT 7 (G3)3 3 8am-11am (PDT) 18-21UT 6 (G2)3 3 11am-2pm (PDT) 21-00UT 5 (G1) 3 4 2pm-5pm (PDT) Rationale: Geomagnetic storms reaching the G4 level are expected from the combined effects of recurrent and transient features on day 1 (17 Mar). Minor storm (G1) conditions are expected to linger into early on day 2 (18 Mar). Unsettled to active conditions (<G1) are expected for the remainder.
Aurora viewing from Seattle, basic info, tips, locations and resources.
What: Possible aurora. Slight greenish tinge, perhaps brighter columns or curtains in the sky, or a diffuse red glow. Do not be tricked by the normal red/yellow glow from downtown Seattle.
When: Use Timeanddate.com  to convert aurora prediction times from UTC to Pacific Daylight or Standard Time.
Where: Always look North for aurorae. When clouds are predicted over Puget Sound, so I recommend viewing from Lake Kachess just past Snoqualmie Pass, or even further East. There may also be chances from Sequim or north of Everett.
How: A digital camera with a long exposure will be better at detecting the slightest glow than your eye, but once it gets bright enough you won’t need the camera anymore.
Tips (from my Twitter stream):
- Alice’s Aurora Tip #1: Be patient, keep an eye on the data (see links below) until you see something. Then turn off the data and enjoy.
- Alice’s Aurora Tip #2: Look North. Be in a dark place.
- Alice’s Aurora Tip #3: Bring a digital camera or phone with a long-exposure setting. Long-exposure images gather more light than your eye with long exposures you may see the aurora first in a viewfinder, and with your eye as it brightens.
- Alice’s Aurora Tip #4: It is usually hard to see from Seattle, even when visible. Give your eyes a chance to adapt. Enjoy the stars too.
When Kp levels surpass 5 it is worth starting to check in. In Seattle, we hope for Kp levels of 6 or greater for the best chance to see the aurora. I explained Kp over here .
You should watch these forecasts for minute-to-minute updates:
The Ovation Model  – a prediction: bright green, yellow or red overlapping Seattle means go outside and look.
Soft Serve News  – a prediction: Kp over 5 means possible aurora for Seattle, but the higher the better. If it hits 6 go outside.
Current Activity  – a measurement: If the yellow/orange/red looks like it is overlapping the border between the US and Canada, the aurora might be visible from Seattle. Again, the closer the better.
Estimated Kp  – a prediction: Kp over 5 is good news. Remember the date/time along the bottom are in Universal Time so subtract 7 hours.
*NEW* Advanced Solar Wind Charge/Direction  – a measurement: scroll down. On the left under “Real Time Solar Wind” is a little speedometer thing labeled “Bz.” When this is pointed towards S/-50/Red we have better auroras in the Northern Hemisphere. When it is pointed the other way, the Southern Hemisphere has better aurora.
NOAA’s Space Weather Prediction Center  – lots of info in one place.
Cloudcover prediction for tonight at 11pm:
*NEW* Recommended Viewing Locations:
My general stargazing location recommendations .