Storm Forecast
Valid: Sun 22 Jul 2007 06:00 to Mon 23 Jul 2007 06:00 UTC
Issued: Sat 21 Jul 2007 22:08
Forecaster: DAHL

SYNOPSIS

Long-wave upper trough over central Europe remains the dominant feature this period ... with a plume of warm and partly moderately unstable air to its east. A perturbation at the periphery of the large-scale trough is accompanied by a small SFC low which will move from W Poland/W Germany into southern Sweden during the period, while undergoing some strengthening. W Europe will be affected by a digging short-wave trough which is rounding the base of the large-scale trough. SFC low attendant to it will boost the warm advection especially over France, but at this time it does not seem that the atmosphere will become sufficiently unstable to be supportive of deep convection.

DISCUSSION

... Poland ... W Belarus ... NW Ukraine ...

Focus for convective development will be along and ahead of the cold front trailing from the SFC low over the German/Polish border at the beginning of the period. CAPE may climb into the 1000 to 1500 J/kg range again. Deep shear will be strongest over S Poland and the NW Ukraine (20 m/s), decreasing towards the north to less than 15 m/s, per GFS 12Z. In this simulation, LLS will initially be rather weak but increase to 12 m/s over E Poland and W Belarus/NW Ukraine after about 18Z.

Expect multicellular storms capable of large hail and damaging wind gusts, with an increasing threat for supercells towards the south where shear profiles will be more favorable. Towards the evening, chance for a few tornadoes exists, though storms may rather quickly evolve into one or more MCSs, reducing the chance of isolated/tornadic supercells.

... NE Spain ...

It seems that NE Spain will continue to experience moist southerly/easterly LL flow, so that again strong CAPES should result. Deep shear remains very strong, so that well-organized storms, including supercells and bow echoes may occur. Main threats will be large hail and damaging winds. Currently, it seems that the coverage will be rather low, and a level-one outlook seems to suffice at the moment.