CONVECTIVE FORECAST
VALID 06Z SUN 18/01 - 06Z MON 19/01 2004
ISSUED: 17/01 22:31Z
FORECASTER: DAHL

General thunderstorms are forecast across the western and central Mediterranean Regions ... and over the N Balkan States.

General thunderstorms are forecast across SW Norway.

SYNOPSIS

Digging upper trough ATTM over the Biscay will close off into an elongated cut-off low ... covering the NW Mediterranean Sea towards the end of the forecast period. Associated SFC low is expected to weaken after Sunday 12Z ... and to rermain centered over the NW Mediterranean Sea. Nearly stationary warm-frontal boundary will extend across N Italy ... the N Adriatic into the N Balkan States ... while the cold front will move into the central Mediterranean Sea during Sunday. Over the north Atlantic ... short-wave trough will move SE and cross S Scandinavia during the period. Associated SFC low is FCST to reach the the Baltic Sea by Monday 06Z.

DISCUSSION

...Mediterranean...
Indications are that pre-frontal air mass will be weakly unstable ... and that TSTMS may accompany the cold front. TSTMS over ATTM over N Spain W of the SFC front appear to be elevated. Chance appears to exist that TSTMS will become SFC based as the front strengthens and encounters the relatively warm Mediterranean Sea early Sunday morning. 0-6 km shear in excess of 70 knots will be present ... with 850 hPa flow of 40+ knots. Short-line segments and bow echoes may occur in this environment ... though low-level SRH is not particularly high ... anomalous propagation due to the strong shear may promote updraft rotation ... with an attendant threat for large hail and a tornado or two. Situation should be monitored for possible squall line development along the cold front ... and an upgrade to SLGT may be necessary if well-organized storms indeed form along the cold front.

TSTMS are also expected along and N of the warm frontal boundary over N Italy ... the N Adriatic into the Balkan States ... majority of the storms will likely be elevated and pose less of a severe wind threat ... however ... if storms root down into the PBL ... a few severe-wind events may occur. Also ... given strongly backed low-level flow INVOF the warm front ... SFC-based storms will have fair chances of becoming supercellular with a threat of marginally severe hail and maybe a brief tornado or two.

Allover severe-weather threat appears to be rather conditional ... and a SLGT is not warranted ATTM. Situation will be watched and an upgrade may be necessary.

...SW Norway...
A few lightning strikes may occur primarily at the Norwegian SW coast in strong upslope flow regime ahead of vigorous vort max ... this convection will likely augment the strong/severe mesoscale gradient flow by vertical momentum transfer.

#