Notes on Developing Cold Fronts
Percentage Forecasting:
Thanks to the milder climate over the last ten to twenty years, snow can be quite a marginal event in Blackheath so lets try this percentage system below for snow shower forecasting. Settled snow is generally too hard to predict accurately for the upper mountains although occasionally it is possible.
5% to 10% chance = unlikely to see much snow.
10% to 20% chance = very slight chance of snow.
20% to 30% chance = slight chance of snow.
30% to 40% chance = slight to moderate chance of snow.
40% to 50% chance = moderate chance of snow.
50% to 60% chance = moderate to good chance of snow.
60% to 70% chance = get out the skis.
70% to 80% chance = get out the snow plow.
80% to 100% chance = I'm lying and drinking too much green cordial.
This is just a basic guide but it might be a quick way for you to check on the chances of seeing snow in our area. I will try to use them more in my forecasts.
Saturday 4-7-09, Midday: Fingers crossed we get some stronger fronts into mid and late July. Apart from a weakish system this Monday/Tuesday there is not a lot of potential on the charts at present.
Thanks for the regular trickle of emails that come my way, sorry I can't answer them all personally, I quite often just don't have the time. I do read them all though. I know there are people from all walks of life that enjoy this site, so whether you are young, old, unwell or just middle aged and creaky like me, its a pleasure to bring this little piece of cold climate fun your way. It wouldn't be much fun if I was just here, talking to myself. Although it wouldn't be the first time.
NB: The forecasts and outlooks above are informal considerations presented by blackheathweather.com. Please refer to the main page for official BoM forecasts.
Debunk The Myth
I often hear it said in Blackheath that we didn't get snow because it was too windy. There is no scientific basis to this at all. Its just that most cold fronts come from a SW direction and are usually windy and bring more snow to the Oberon Plateau than they do to the Blue Mountains. Its not because its too windy that we don't get snow its because we are downwind of the Oberon Plateau and during most cold fronts they 'steal' most of our snow. Without wind, the cold air from down south wouldn't get here in the first place. So snow lovers, tell your mates that its not the wind that prevents the Blue Mountains from getting snow at all, its the Oberon Plateau in most situations.
NB: We still can get nice snowfalls from the SW but you need cold upper levels (at least minus 27C at 500hPa) and good mid level moisture at 700hPa to create a nice moist and unstable mix. Don't forget it was very windy from the SW during the 19-6-07 fall and cold upper level air and good moisture in the lower levels was the reason we got such good snow.
