Storm Forecast
Valid: Tue 04 Mar 2008 06:00 to Wed 05 Mar 2008 06:00 UTC
Issued: Mon 03 Mar 2008 23:08
Forecaster: VAN DER VELDE

SYNOPSIS

An Atlantic cold upper trough with associated unstable airmass moves into Europe. Its southern apex with enhanced ascent is going to affect northeastern Spain and southern France before settling as an upper cut-off low over the central Mediterranean Sea in the next few days. A secondary upper shortwave trough in the northwestern flow is projected by GFS to reach the Benelux countries and northern Germany in the early evening, possibly with a short episode of clustered showers, though then only modest instability remains.
A small depression / polar low is predicted for central Norway, with GFS depicting a curl of CAPE sinking quite deep inland.
The drawn thunderstom areas appear to be where instability and mesoscale lift factors appear best, but isolated lightning activity may for the rest occur anywhere in the cold airmass.

DISCUSSION

SW France, N Spain:

An area of strong flow and resulting strong vertical shear vectors (15 m/s over 0-1 km, nearby jetstreak produces >35 m/s over 0-6 km) , and good instability. This raises chances of an isolated tornado event within the area in the morning hours as well as strong gusts, though not likely severe gusts (around 20 m/s possible).

Central Norway:

Low-level shear >15 m/s and deep layer shear >20 m/s are both favourable to low-level updraft rotation and tornadogenesis in the coastal zone during the evening. Intense snowfall is more likely to become a problem, and severe gusts can occur within the strong gradient at the west flank of the low.