Extended Forecast
Valid: Sun 23 Mar 2008 06:00 to Mon 24 Mar 2008 06:00 UTC
Issued: Fri 21 Mar 2008 19:58
Forecaster: TUSCHY

SYNOPSIS

Highly amplified streamline pattern will be present as huge longwave trough runs from the Greenland Sea to N-Africa ! This feature is part of a split-flow regime over the N-Atlantic, where stout ridging will be present.

This constellation means that many parts of Europe will see cold conditions with mainly daytime driven convective activity. Downstream of this trough, a warm airmass spreads north-northeastwards, affecting the extreme eastern parts of our forecast area.

... Central Mediterranean...

The focus for thunderstorm initiation will be a southeastward racing cold front. GFS had persistent signals of low-end to modest instability release along and just ahead of this frontal boundary. This region would be just under a strong mid-/upper-level streak with winds at 850hPa reaching 25m/s so there is a distinct risk for severe wind gusts. The main negative fact for a more widespread severe weather event looks like to be the alignment of the surface front in respect to the background flow as angle of intersection is quite shallow. Such a constellation favors a complex of storms, possible training with a lower chance for more discrete cells. Another point is the final strength of the developing surface depression SE of the Alpes, which shows still run-to-run inconsistency. We already issued level areas where confidence is high that environment becomes favorable for a severe weather risk but modifications may become necessary in later outlooks.
Despite the main risk being a severe wind gust and isolated large hail threat, tornadoes could be a topic, too mainly along coastal areas of the eastern Adriatic Sea and over parts of central Italy.

The thunderstorm area may have to be expanded northeastwards as degree of instability well inland becomes more clear.

In the range of the upper-level trough, convection should increase during the day but lack of moisture and limited instability preclude any highlighted areas for the moment.