Forecast Update
Valid: Sat 06 Jan 2007 18:00 to Sun 07 Jan 2007 06:00 UTC
Issued: Sat 06 Jan 2007 17:33
Forecaster: TUSCHY

SYNOPSIS

Please refer to the outlook, issued at Fri 05 Jan 2007 17:16 !


DISCUSSION

... Parts of extreme E-France / Belgium / SE Netherlands and parts of W / CNTRL Germany...

Models came into better agreement regarding the expected thunderstorm evolution. GFS and NMM continue to show a plume of low-end instability over the area of interest.
Current thinking is that indicated wrap-around moisture and intersecting dry slot, combined with some forcing and mid-level cooling will be enough for those CAPE values to get realized.
850hPa thermal axis is forecast to shift towards the east as a result of some CAA from the WNW.
Focus for an isolated thunderstorm threat will be present along the eastward moving, but continuous weakening cold front.
Another area for enhanced convective activity will possibly arise behind the cold front, where boundary layer moisture below 850hPa will diminish only very slowly.
Time - frame for best thunderstorm activity should be between 22Z and 04Z, where parameters will be in place.
Difficult to determine the exact tornado threat. Kinematic parameters are fine and veering in lowest levels is pretty strong. GFS steepens the LL lapse rates in the area of interest, but
forecast soundings still indicate weak capping at lowest levels. Not much cooling needed for low-end SBCAPE release and hence a risk for an isolated tornado / severe wind gust can't be ruled out in the highlighted area.
Thunderstorm coverage will be on the lower-end side so no higher probabilities warranted.

Storms should undergo a weakening trend due to diminishing forcing on their eastward track.