Forecast Update
Valid: Fri 28 Sep 2007 13:00 to Sat 29 Sep 2007 06:00 UTC
Issued: Fri 28 Sep 2007 13:20
Forecaster: TUSCHY

SYNOPSIS

Please refer to the outlook issued at Thu 27 Sep 2007 16:55!

DISCUSSION

...Parts of the Czech Republic, parts of Poland and NE Germany...

An upgrade became necessary due to increasing confidence of an enhanced tornado risk !

A well developed occlusion ( now over southern / central / northeastern Germany) with a large area of quite intense stratiform rain is forecast to constantly shift towards the north / northwest during the next few hours.
The airmass behind this front is characterized by dewpoints in the lower tens over the Czech Republic and mid-tens over Poland. Atmosphere now starts a gradual cool-down with rapidly steepening mid-level lapse rates and a broad area of low to moderate instability release will be the result.

The main concern will be the activity, which now develops just north of NE-Austria and over the Czech Republic in the prefrontal airmass just in the left exit region of an intense jet. Shear especially at lower levels remains strong (SRH-1 values at or above 200 J/kg, LL shear of 10-15m/s ) and in combination with low LCLs, an enhanced risk for several tornadoes will be a distinct possibility and even a strong tornado cant be ruled out. This threat is forecast to spread northward during the next few hours.
In addition, hail could reach our criterion in the stronger cells, especially where enhanced DLS and SRH-3 values of more than 200 J/kg overlap next to the front.


Some marginal modifications were done to the rest of the outlook area.