Storm Forecast
Valid: Sat 31 Jul 2010 06:00 to Sun 01 Aug 2010 06:00 UTC
Issued: Sat 31 Jul 2010 03:42
Forecaster: VAN DER VELDE

A level 2 was issued for the central Balkan mainly for large hail and severe convective wind gusts.

A level 1 was issued for Balkan, Hungary, Slovakia, E Poland and E Baltic states mainly for large hail and local excessive rain.

SYNOPSIS

A low pressure area is situated over Scotland and southern Norway. The accompanying cold front will drag slowly over N France, Benelux, Denmark and NW Germany, with most-unstable parcel equilibrium level temperatures marginally cold enough in the GFS model for some thunder (locally -15°C). Embedded convection in the front may train a bit and enhance rain rums.
A stationary front with an unstable warm airmass lies over the Baltics, Poland, Balkan and Italy. A negatively tilted mid-level trough and PV maximum moves from Italy and Adriatic into Serbia and surroundings.
A positively tilted mid-level trough moves into the Iberian Peninsula where it destabilizes the airmass by lifting, which should result in more active convection during the Sunday.

DISCUSSION

...central Balkan...

While MLCAPE is with a predicted 800-1000 J/kg relatively modest for the region, the synoptic/mesoscale dynamics are strong and favorable wind shear is present for supercells and multicell clusters/MCSs: 15-25 m/s 0-6 km shear. The largest circular hodographs in GFS are predicted for the eastern half of the level 2 area. Large hail and severe wind gusts are likely.

...Hungary, Slovakia, Poland, Baltics...

Slightly enhanced shear could organize multicell clusters which can produce isolated large hail. The storm motion and shear vectors are predicted to be along the front (west) and convergence line (east side of moist plume). It could enhance local rain sums by training of storms. An chance of severe local gusts is not excluded.