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Flying VFR in rain: how much is too much?

Looking for the forcast for the weekend ahead (not yet settled), I can see isolated but big patches of rain but I still think of flying VFR in/around them, what are the things to watch out for? How long one would call it off?

Cloudbase is forcasted high 5000ft but visbility “looks” crap (2-3km) and no frontal/thunder activity (high pressure day)

Ps: flew in both high/low pressure rains before but not longer than 20min around local areas (so many way outs)

ESSEX, United Kingdom

What is your forecast source ? GFS/ECMWF models ?

Look at the visibility as you fly, and be prepared to divert if it’s approaching your limits. I’d accept less in a heavy shower, which I’d be quickly through. But the vfr limits in the UK are ridiculous – I’d need much more. See what? A white cottage against dark moor, or cloud to the ground against grey cloud?
And avoid flying just under the cloud. It can form lower.

Maoraigh
EGPE, United Kingdom

I use windy it has all models on it nems, gfs, ecmwf, icon

Yes, 2km is way bellow what I need to navigate/fly in unfamiliar places but does the job with a gps backup for local flights OCAS (I know every white cottage around !)

ESSEX, United Kingdom

I do use windy too.
From past experience, the rain areas forecasted are more a sign of probable rain than a prediction of where precisely it will rain. And a 5000ft ceiling becomes usually a 2000ft one.
I mainly use the low clouds and the rain page. If there is more than small spots, I cancel any cross country flying.

Yes, long-term forecasts tends to be pessimistic about the extent of rain/clouds, GFS is quit ok-ish for long-term forecasts of synoptic charts over huge areas but I rarely look at GFS data for medium/short term forecasts,

Less than 3 days, I tend to use ECMWF/NASA on met-check as they give accurate synoptic/rain contours but sometimes they may give very unstable outlooks in each update for the last 48h run-up

https://www.metcheck.com/WEATHER/nasa_geos5_charts.asp
https://www.metcheck.com/WEATHER/ecmwf_charts.asp

On the day nothing better than the “weather stone”

ESSEX, United Kingdom

I think the answer to post #1 is that it depends on

  • does your plane leak
  • can you fly on instruments
  • can you be 100% sure there are no CBs (a strike will likely cost you ~20k and that is the best outcome)

The min vis for VFR is now 1500m which is basically soup, and unless you are scud running at 500-1000ft AGL you can see sod-all, especially not for navigation purposes. Visual nav is almost impossible in 3k-5k vis. And any scenario where there is no visible horizon (which could be 10km vis) needs instrument flying ability even if it is “legally VFR”.

For comparison, if you fly an IAP with an 800ft MDH (EGKA 20) and if the vis is 1500m, you will only just see the runway at minima.

Forget forecasts 6-7 days ahead. They are mostly fiction.

Administrator
Shoreham EGKA, United Kingdom

I don’t use GFS anymore. I use ECMWF for long term and ICON then. ICON becomes very reliable 48hrs before.

I agree.

GFS (Gramet etc) is great when the forecast is right

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

does your plane leak

Yes. Having long legs and the seat all the way back means the water drips on my shoulder and down my neck.

Landing at Lyon Bron I went thorough some rain that was very dirty (Saharan dust storm?) and left streaks on the perspex, which didn’t help visibility.

EGHP-LFQF-KCLW, United Kingdom
39 Posts
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