CONVECTIVE FORECAST
VALID Sun 27 Nov 06:00 - Mon 28 Nov 06:00 2005 (UTC)
ISSUED: 27 Nov 01:20 (UTC)
FORECASTER: DAHL

SYNOPSIS

Entire Europe is covered by one large upper trough ... which remains centered over the Benelux States and NW Germany ... exhibiting various vort maxima at its broad periphery. These will mainly affect the Mediterranean regions during the period. Extensive SFC low pressure system is likewise covering much of Europe ... with deep polar air advecting across central into SW Europe/extreme N Africa ... and increasing WAA across the central and E Mediterranean ... spreading into E Europe.

DISCUSSION

...SLGT area...
It seems that there will be three foci for convective development ... the easternmost will be associated with weakly unstable air advecting northwards across Greece and the Aegean into SE Romania. Degree of instability remains uncertain owing to lack of radiosonde data ... but indications are that steep mid-level lapse rates associated with convectively mixed Saharan air may be in place ... though instability should nonetheless be rather weak given only modest LL moisture. However ... kinematic profiles will be sufficient for severe evolution with deep shear in excess of 20 m/s and LLS of 10+ m/s ... which may locally be augmented by topographic features. This suggests that isolated severe TSTMS may occur ... posing threats for severe outflow winds ... large hail and isolated tornadoes.

Farther west ... TSTMS should continue along main frontal boundary. Thermodynamic profiles should be quite weak ... with essentially neutral lapse rates. It seems that mesoscale forcing for UVVs will weaken along the front ... and that bulk of activity may occur along upslope flow regime along the W slope of the Dinaric Mountains. Shear should be more than sufficient for isolated severe ... including marginally severe hail ... damaging straight-line winds and possibly a few brief tornadoes.

...W Mediterranean...
In the wake of the frontal boundary in the deep polar air ... cellular convection should continue to spread east. A mesocyclone or two cannot be ruled out ... with an attendant hail/wind/tornado threat. But limited large- and mesoscale forcing for ascent as well as weaker shear than farther E should keep severe threat rather isolated/brief ... and a SLGT does not seem to be warranted.

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