Predicting summer afternoon thunderstorms?

[mcmanigle]

General question and specific question:

General: Isolated scattered PM thunderstorms are par for the course in the mid-Atlantic summertime. How do you decide, say 24 hours in advance (no radar yet) whether a forecast of "thunderstorms in vicinity" is going to cancel your cross-country, or whether they'll be the standard stuff you can pick through?

Specific: I have to get in the vicinity of OYM (central PA) from RDU (central NC) on Saturday morning, so likely departing tomorrow (Friday) afternoon around 3pm. Backup is commercial tickets which have been purchased RDU -> PIT at 3:28pm plus a car rental and 3-hour drive. I need to decide around noon. Ultimate fallback if I decide "go" and then can't actually do it is the 9-hour direct drive overnight, which I'd like to avoid. Passengers are likely, and I'm not night-current, but am IFR current. Plane is a 182 (300 HP) without O2, with Stratus weather but nothing fancier.

Categorical outlook shows the whole east coast in a TSTM area, but nothing higher-prob. Prog chart shows "chance" rain and T-storm, and a cold front, but nothing "likely". TAFs predict TS in vicinity, but high ceilings and light winds.

All-in-all, my read is that this is likely to be minimal isolated t-storms which could be steered around. But I won't have radar yet when I have to make the call, and getting it wrong means a really long drive, so I'd like to hear any tips you have.

 

[petrolero]

The classic GA conundrum. Bottom line is that if it's really important for you to be someplace, don't rely on a small airplane.

 

[RudyP]

Look up the NAM simulated composite reflectivity for the time of your trip. Unless it shows a big, impenetrable line, I'd be ok with a forecast for scattered stuff.

 

[brian]]

Yep, same problem here in the South. Go early. Sometimes waiting a little bit helps as well as most summertime thunderstorms move off and dissipate unless there is something to keep them alive (e.g. a front).

 

[frfly172]

Watch the evening weather ,on the local TV station,be aware of fronts and there movement. Fly early ,and stop often to check the weather as you go. If you must land and let the storm go over you.

 

[wilkersk]

Read Richard Collins' "Thunderstorms and Airplanes". Also "Weather Flying" by R.N. Buck & R.O. Buck is another great book on the subject.

 

[Unit74]

Yep...off at dawn, down by 2pm. After that, roll the dice and hope for 7s

 

[Jimmy cooper]

The weather channel is describing weather for the time you describe as a real toss up. I'd go commercial. Lots of forest and nothing in central pa. Yes, off at dawn, etc, maybe. I would not do it but I'm very conservative having had the s...scared out of me in a mooney twice doing this type stuff.

 

[sourdough44]

XM weather really earns it's keep under the asked about conditions.

 

[bflynn]

The real answer is that you don't predict them. Afternoon thunderstorms might be expected or sometimes not expected. But 24 hours out, you cannot predict where they might be.

Fly early, land early.

 

[Unit74]

XM weather really earns it's keep under the asked about conditions.

Too bad it's at least 15 min old when it arrives.

 

[rbridges]

Best advice is to fly early if possible. Crystal clear skies turn into afternoon Tstorms in Georgia during the summer. I have a stratus and stormscope. ATC has helped me go around some stuff but I prefer to avoid it altogether.

 

[cgrab]

Borrow a stratus and tablet to get weather through ADS-B in. You won't trigger a tower without ADS-B out but int he east there is allot of othetr flying and you will probably get enough reports.

 

[AggieMike88]

Even better than any of the above....

Convince Scott Dennstaedt to travel with you and let him do the predictions.

 

[Fearless Tower]

Too bad it's at least 15 min old when it arrives.

Not always. sometimes better, sometimes worse, but in my experience it tends to be more up to date than ADS-B.

 

[sourdough44]

Too bad it's at least 15 min old when it arrives.

I was just throwing it out, doesn't sound like the OP has it. Especially in hazy conditions it can be hard to see the best way to avoid. Even if you can see somewhat, it's nice to see beyond to where the route makes the most sense.

Here's some words(from XM) on the age of the radar return displayed in the cockpit. The 'time stamp' shown isn't necessarily the actual age of the return. Even with a lag, still a big help.

The timestamp shown on a NEXRAD display underestimates the age of the information shown. Parts of the image may be three to four minutes old, or more, before the information is transmitted to the pilot. There is no easy way to tell what came from the early part of the sweep and what's from the latest. The NTWB notes that in some extreme cases, the delay could exceed 15 to 20 minutes.



Due to latency, a cell may have advanced five miles from the position noted on the NEXRAD display, though two miles of movement is more typical.

 

[petrolero]

Even better than any of the above....

Convince Scott Dennstaedt to travel with you and let him do the predictions.

Scott travels with all of us... in foreflight.

 

[James331]

When I lived in the south this was what I was told, it basically didn't get me to scrap any flights, but did make me rethink some stuff.

T-storms probable if dew point over 17c and 10c or less spread

 

[JustinD]

Being down in FL this has always been a classic problem for me. Since I've lived in Florida for about 20 years it's just a known fact that it will more than likely thunderstorm in the afternoon sometime after 3pm (where I live at least) If I absolutely have to be somewhere or need to return home in the afternoon I won't fly or rely on it. I plan all my long stuff in the morning. For instance If I'm visiting a friend in the keys I'll plan on leaving in the morning and returning in a morning, If it's just a day trip down to visit my family and I have to be back home that afternoon I often times won't rely on flying as the summer time thunderstorms are all too common.

 

[ahkahn]

Traveling with a Stormscope and ADS-B (or XM) would be a must for me under these conditions. I got into some trouble the day after I sold my Stratus 1 awaiting my Stratus 2S by getting caught up in a cell. Won't fly without it again!

 

[Vf6cruiser]

Leaving at 3pm will be in the thick of it........and your scenario didn't sound that bad until "cold front" stuck its face in there. That could turn the whole thing into junior rodeo time. Let the guys with the sidesticks and ottopilots do this run...........your 182 will look a lot better with the wings still attached.

 

[Geico266]

The classic GA conundrum. Bottom line is that if it's really important for you to be someplace, don't rely on a small airplane.

Bull Pucky!

Read the storms with in-flight weather. Leave early, dark 30, to avoid storms.

 

[BillyBH]

Living here in south Florida, there is a period from June through mid-October that it is either too hot or too clobbered by existing or potential thunderstorms. That's when you schedule your major work on your airplane. The rest of the year, mid-October continuing through the end of May are generally gorgeous down here. Seven out of twelve...not bad.

 

[JCranford]

I'm having the same issue. Supposed to fly Friday from Dallas to San Antonio. Weather here looks good so far and weather in SA looks mostly cloudy, 20% chance of storms in the vicinity.

I figure I get up early, check the weather and make the call. If I had to base a decision on what I know right now, given that the 'mostly cloudy' was high enough, I would call a 'Go'.

 

[petrolero]

Bull Pucky!

Read the storms with in-flight weather. Leave early, dark 30, to avoid storms.

You can only read the storms the day of the flight. If they are unflyable then it's too late to hop an airliner. So if you absolutely gotta be someplace on time, don't rely on a small airplane. And OK I'll add "unless you have a really strong sense that the wx will be OK."

I agree with leaving at the butt crack of dawn - gives you the best shot. But anyone who's had a no-go knows what I mean.

 

[brian]]

yep - check out this VFR day with "High pressure in control" (or something like that from the FS guy).

My A.... wait, is that a thunderstorm? why yes, that is a thunder storm (Actually 3 in the area.)

Pfft - was about 3:30PM on the Arkansas / Oklahoma border. You can almost set your watch that there will be a thunderstorm over by Fort Smith on any VFR day with high pressure an no significant weather - just after lunch. Ok, maybe it's just my bad luck.