Storm Forecast
Valid: Sat 16 Aug 2008 06:00 to Sun 17 Aug 2008 06:00 UTC
Issued: Fri 15 Aug 2008 15:23
Forecaster: DAHL

SYNOPSIS

Deep upper longwave trough is covering most of Europe, with a compact perturbation at its eastern periphery moving from the N Balkans into N Poland during the period. Another upper vort max will cross the Iberian Peninsula and the western Mediterranean on Saturday. Quite moist and unstable air is present east of the trough over E/SE Europe as well as over the southern Mediterranean. The associated cold front should stretch from the Baltic Sea southwards into the southern Adriatic and then westward into the N Maghreb States on Saturday afternoon per model guidance. Weak SFC low should persist across Poland into the N Balkans E of the cold front, undergoing some strengthening late in the period. Otherwise, SFC conditions are rather quiescent.

DISCUSSION

... E Poland ... S Baltic States ...

Some uncertainty exists about the degree of instability ahead of the cold front given anticipated extensive convective debris and fronal cloudiness. However, where breaks in the clouds occur, CAPE on the order of 1500 J/kg may materialize. Deep shear will remain conducive to well-organized convection. At least locally, 10 m/s LLS are simulated to exist, hinting at an increased chance of tornadoes. Storms should initiate over central Poland during the afternoon hours, possibly along mesoscale boundaries like outflow boundaries from previous convective activity, and along the main synoptic-scale thermal boundary. Expect storms to rapidly develop into supercells, capable of very large hail and damaging wind gusts. Tornadoes may also occur, though maxima of LLS are simulated to be somewhat patchy. Storms will likely merge into one or more large MCSs in the evening/night hours.

... N Baltic States ... W Russia ...

Farther NE across the Baltic States and extreme W Russia, DLS should be somewhat marginal with only 10 m/s. However, strong LLS along the warm-frontal boundary suggests that at least copmparatively short-lived supercells with a threat for tornadoes will be possible. Large hail and severe wind gusts may also occur with these storms.

... Ireland ...

Comparatively shallow polar-air convection will likely accompany the upper low that is simulated to cross Ireland on Saturday. Though cells will likely fail to become well-organized, about 10 m/s LLS suggest that a brief funnel/tornado or two could occur. Threat seems to be too low for a categorical outlook.