Storm Forecast
Valid: Mon 28 Aug 2006 06:00 to Tue 29 Aug 2006 06:00 UTC
Issued: Sun 27 Aug 2006 22:27
Forecaster: DAHL

SYNOPSIS

Quite strong Atlantic upper jet is propagating southeastwards across France and the N Mediterranean ... at W/SE periphery of large-scale European upper trough. Nose of the jet streak is expected to reach the northern Balkans by early Tuesday morning. Weak frontal wave is simulated to accompany the left-exit region of the jet streak. Large-scale SFC low ... associated with mean long-wave trough ... will shift towrds SW Scandinavia. E of this low-pressure area ... weakly unstable warm/noist air is present over E and SE Europe.

DISCUSSION

NE France ... Benelux States ... S and W Germany

Main challange will be convective scenario associated with intense jet streak nosing into NE France and W/S Germany during the day. Available models do not resolve focused SFC convergence over S Germany in association with the DCVA-related ascent accompanying the jet streak. However unresolved meso-beta-scale SFC convergence lines may still be imbedded in the flow.

Lack of CAPE may also be an issue ... with profiles expected to be essentially neutral. Towards 18Z however ... model soundings suggest substantial drying at mid-levels associated with a dry slot. Though the details of the convective evolution remain unclear ATTM ... it seems that some convective threat exists ... maybe in the wake of extensive stratiform precip associated with WAA ahead of the frontal wave in the early evening hours.

Deep shear will be quite strong over S Germany increasing southward toward the axis of the upper jet ... with 20 to 35 m/s DLS. LLS will be maximized over W Germany per GFS 12Z ... with up to 15 m/s. Small/shallow supercells may occur anywhere across W and S Germany ... though they may be most likely over SW Germany where both, strong DLS and LLS will overlap. Slight tornado threat may extend into the UK ... but coverage should be too low for an inclusion into the level one area.

Considerable uncertainty exists with this forecast ... and an update may be required tomorrow. However ... given favorable shear ... at least neutral thermodynamic profiles and strong vertical motion ... some severe threat seems to exist. Main threat may be brief tornadoes and damaging winds ... as well as marginally severe hail.

Extreme N Turkey ... Black Sea

Scattered TSTMS will likely form along and ahead of frontal boundary over the E Balkans and the Black Sea. LL moisture depth seems to vary ... and is likely not well resolved by the available sounding data. Indications are that at least across portions of the
pre-frontal environment ... some CAPE will exist.

It seems that bulk of activity will be slightly removed from the best shear profiles ... though storms over N Turkey and the Black Sea should have sufficient shear to become multicellular and possibly mesocyclonic. Main threat should be severe wind gusts and large hail.