7-day VFR cross country weather planning

My wife Bette and I started taking flying lessons together in January 2004. Her main goal of these lessons was to be comfortable flying in a small plane and feel confident enough to take over the controls in an emergency if necessary. She has accomplished both of these goals and we often fly together to visit family for holidays.

As you can imagine, planning a holiday trip exposes us to weather over a relatively long period of time and opens up the possibility of being stranded far from home when we both need to get back to work on time. So far we have had a good success record and I wanted to share some tips how we do that with you. Planning, awareness, and schedule flexibility are the keys to having a good visit and making it back to work on time.

The graphical NOAA forecast map provides a lot of information over a 7-day period.

Bette’s dad winters in Hilton Head, SC (a coastal island near the GA-SC border). A 400nm trip from Fredericksburg, VA (EZF) to Hilton Head Island, SC (HXD) is fair game for Thanksgiving, Christmas, or Easter. In the past two years we have completed this VFR trip successfully five times. How have we done so well on such a long trip VFR when the weather is so unpredictable? We have a multi-level system and we follow it. It is not perfect but it works.

1. We always plan to fly as a backup to driving the car, and make our final decision to fly instead of drive based on the probability the departure trip and return trip can both be accomplished. This is a good plan for us because we have to load the car anyway, whether we fly or drive. If we fly, we load the car to go to the airport and if we drive, we load the car for the road trip. You load the car either way.

2. Decide to fly only if you know the weather will be acceptable for both the departure trip and the return trip. This means we need to see a picture of the forecast weather for the next 7 days. I use the NOAA 7-day Graphical Forecast map to see the whole week on one screen. This map has many interactive features that can be used to identify VFR weather several days in advance. I’ll explain in detail in a minute.

3. Plan for flexibility into your departure and return dates and choose the day to fly based on the weather, not your schedule. After you have been using the 7-day tool for a while, you will realize that the forecast is usually 80% right, but not always right at the right time. Weather formations change and move over time. The 7-day forecast usually predicts these formations fairly well, but the timetable might be off by a day or so. If it is raining now, and good flying weather is predicted in two days, that good weather might take three days to appear, or it might show up a day early.

You must be able to adjust your flying schedule to meet the weather if you want to fly the trip and be safe. For a family trip that has only one hard date event, (like Thanksgiving) that is probably doable. If there are two or three hard date events, it might not be. We drive the car if there are multiple hard dates that must be met.

4. It is ok for your airplane to sit in the rain while you are enjoying your destination. The weather does not have to be good for your entire visit; it only has to be good on the days you are actually flying. We often fly to HXD just before the weather turns sour, enjoy our visit, and then fly home after the weather has cleared up. The 7-day graphic forecast is a great tool for predicting these weather windows, good or bad, and planning our trips around them.

So to recap our simple long-term VFR system:

1. Plan to drive and decide to fly as a backup.
2. Fly only if the weather will be good for both the departure and return trips.
3. Drive the car if multiple hard date events are scheduled.
4. Accept the bad weather while at your destination and plan your flying in the good weather windows.

The NOAA 7-day Graphic Forecast Map has several features to help predict good VFR weather several days in advance. Be aware that the good weather windows might be off by 12, 24, or 36 hours and plan your flying accordingly. I always use the expanded weekly view so here is how it works.

The forecast cloud cover map is useful for VFR flight planning.

Pull up the screen and look at the map on the right. If you haven’t scrolled over one of the controls to the left, the map might be empty with some little circles in it. If you scroll over the coastline at the bottom, a little window will pop up for St. Simons Island, GA, and if you scroll up the coast to the top a window for Dover, DE will pop up. That is a pretty large area. You can change the area of view by clicking the Go to Region at the top left of the map. There you can select Cont US, or regions, or eastern and western states by state.

If I am doing planning for a short flight, I usually look at Maryland because EZF is about in the center of it. I usually start my flight planning 7 days out by using these maps to get a feel for the expected weather.

The data table to the left of the map includes columns for High/Low temp, 12-hr Probability of precipitation, and 3-hr weather forecast. Scrolling over any one of these with the cursor fills in the map to the right with the desired information and includes a color scale at the top to help you interpret the information presented. If these are the only data tables, click on Expand at the top of the table just below the tabs. The expanded table adds columns for hazards, temperature, dew point, wind speed and direction, wind gust, sky cover, amount of precip, snow and ice, wave height, apparent temp, and humidity. As a pilot, you will want to look at most of the first eight of them. As you scroll down the table, you will notice the 3-hr windows become 6-hr windows after the first three days.

In planning for VFR XC flights I always look at the temp/dew point spreads and try to plan for 20 degrees difference or more on all my flights if I can. That should give me cloud bases of at least 4000 feet or greater. While for shorter flights I could take less on some days, I find that temp-dew spreads from 10-15F are sometimes unreliable predictors of actual cloud base height over the course of a flight (especially near large bodies of water), but I have never had trouble if the temp-dew spread is over 20.

Another thing I look at is wind. I am more likely to fly in higher winds than some pilots, but gusty winds can be very bumpy and can make for an uncomfortable ride. If I have a choice between two days and one of them has bumpy wind and the other has smooth wind, I am likely to opt for the smooth.

There is so much information that you can derive from this graphic forecast map tool that I use it exclusively for long-term VFR flight planning. When the time ticks nearer the actual flight, regular aviation weather tools kick in with more detail available. I also always get a weather briefing from Flight Service so I can ask questions about my flight if I need to. Sometimes I ask a lot of questions.

So does having all these tools and rules mean I fly more often? Sometimes yes and sometimes no. We went for nearly a year and a half with no flights to HXD. The weather forecast tools told us that we would not be able to complete both departure and return flights in the time frames we wanted to complete our trips. We drove instead and didn’t have any problems. But we have also been able to complete some of our flights in good weather windows that either opened or closed within three hours of being in the air. That is admittedly cutting things close, but we were good VFR all the way and had pleasant, safe trips each time. Isn’t that what it is all about?

Have Fun. Fly Safe.

This is Pete’s second article for Air Facts. Based in Spotsylvania, Virginia, he previously made “a case for his airplane” by writing about his 1968 Cherokee PA28-140. 

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Pete Hodges

Pete Hodges grew up on a farm and has been around all types of machinery since he could walk.When he was 12 he got his first ride in a small airplane at a local EAA fly-in.Watching the pilot manipulate the controls and seeing the cables and surfaces move gave him an instant “I can do this” understanding of how an airplane flies.He took several lessons in ‘79 and in 2004 he and his wife took lessons together, passed his check ride and bought their first airplane, a ’68 Piper Cherokee.He is also rebuilding a Coot Amphibian to hopefully use on the Chesapeake Bay.

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