To catch the aurora in the Northeast, two things need to cooperate: Space Weather and Earth Weather.
Regardless of the forecast, there is still one thing you need to do to be successful: Go.
Space Weather Environment
Space Weather is the solar wind conditions which affect the earth's magnetosphere. When a strong solar wind collides with earth, it agitates the magnetosphere, increasing auroral activity. Auroral activity is measured in a value called Kp.
The NOAA and others take measurements of the solar wind which is used to create Kp forecasts. Below are some of the most useful forecasting tools. To see the lights in any part of New England, a Kp value of 6 or above is necessary, during the times when we're in darkness; approximately 0100 - 0010 UTC.
3-day Kp Forecast
Kp is an indicator of auroral activity.
Under "NOAA Kp Index Breakdown" is the predicted Kp value in 3-hour windows for the next 3 UTC days.
In the Northeast, we want to see Kp values over 7 during 9pm-2am (Eastern Time).
This corresponds to 01-10UT in the breakdown.
Tonight's View Line Forecast
This is a graphical representation of the Kp forecast for tomorrow. It shows a prediction of the intensity and location of the aurora borealis tonight, in the green oval centered on the north pole. This oval is called the Auroral Oval.
Green represents low intensity, yellow represents medium intensity, and red indicates high intensity auroras predicted.
The red line below the oval indicates the View Line. Locations north of this line have a chance to see the aurora on the northern horizon.
Remember that this image represents a prediction; actual geomagnetic conditions can always under- or over-perform!
The "30-Minute" forecast is a prediction of where the aurora will appear in the next 30-90 minutes. The colors represent the intensity predicted for the UTC time listed in the top left corner.
In the top right corner, you can see the "Forecast Lead Time", which tells you how far in the future the model is predicting. The faster the solar wind, the shorter the lead time.
Unlike the viewline forecast, the 30-minute forecast uses real-time data from near-earth spacecraft. This makes it a very good indicator of what you can expect in the next 30-90 minutes.
You can click on the image to see a 24-hour animation of the model.
Real-Time (30-Minute) Forecast
Current Planetary Kp
These charts are real-time reports on the current space weather environment, when chasing the lights, the bottom chart of the current Kp index will be the most useful.
The Solar X-Ray Flux is used to look for Coronal Mass Ejections, which can cause Solar Storms a few days later.
The Solar Proton Flux is a measurement of particles which can indicate the arrival of a Coronal Mass Ejection.
The Geomagnetic Activity is a measurement of Planetary Kp. When you see values getting higher than 6 on this chart, it's time to go looking for lights!
Earth Weather Environment
12-hour Cloud Cover
This is the NWS prediction for cloud cover in 12 hours. If you're planning an aurora chase, this map shows the predicted cloud cover for tonight.
When evaluating this map, it's important to look for the best combination of clear skies in the forecast, and dark skies in the light pollution map. Where these two areas line up is your ideal spot to catch the northern lights!
Real-Time Cloud Cover
This is a real-time satellite image of where the clouds are in our area. The clearer, darker spots indicate clear skies and minimal cloud cover. You can click on the image to see a loop of the imagery.
This is especially useful if you're waiting on the sky to clear and trying to identify what areas are clearing first. In this case you'll see dense white clouds in the image breaking into darker patches of open sky. You can also compare this against the forecast models to see if the predictions are on track.
Sometimes, you'll see clearing in a predictable pattern such as clearing first from west to east, or clearing faster in areas downslope of mountains.