The stage could be wet. A strong cyclonic potential vorticity anomaly will be swinging across France tomorrow, with rain sweeping into the western Alps during the race.
GFS dynamic tropopause pressure (red contours), surface wind
(grey vectors) and 6-h accumulated precipitation (color filled
every 5 mm after initial .25 mm contour) at 1200 UTC 19 July 2011.
Source: Don Murray/ESRL.