I'd be well excited about this apart from the fact that I'm supposed to be going on holiday, and I'd rather be skiing in the Alps than waiting for a charter flight to try and figure out how it's going to leave Gatwick!
Anyway, Heathrow:
FT 032300 032259Z 0400/0506 33005KT 9999 FEW038 PROB30
0404/0411 5000 HZ BECMG 0411/0414 18010KT BECMG
0418/0421 3000 -SN BKN006 BECMG 0421/0424 1200 SN
BKN002 PROB40 0421/0506 0500 SN VV/// -
This means between 1800 and 2100 on the 4th it will be 3000m visibility in light snow, becoming from 2100 to midnight 1200m in snow, with a 40% probability (which we regard as being likely for planning purposes) of between 2100 on the 4th and 0600 on the 5th of 500m in snow with no vertical visibility upwards. Ie if you look straight up you will not be able to see anything for the snow.
Gatwick:
FT 032300 032259Z 0400/0506 33004KT 9999 FEW030 PROB30
0402/0411 6000 BECMG 0410/0413 17010KT BECMG
0419/0422 3000 -SN BKN004 TEMPO 0421/0505
18015G25KT 0800 SN BKN001 -
Between 1900 and 2200 on the 4th it will be 3000m vis in light snow and temporarily for a period between 2100 and 0500 on the 5th it will be quite windy (15 knots from the south with gusts up to 25 knots) and 800m vis in snow, broken clouds at 100ft.
Anyway, whatever the weather, I'm off to work now, for a lovely (not) 9 hour flight. Because its all glamour, this job!