CONVECTIVE FORECAST
VALID 06Z SUN 23/05 - 06Z MON 24/05 2004
ISSUED: 22/05 17:00Z
FORECASTER: DAHL

General thunderstorms are forecast across south and east Europe.

General thunderstorms are forecast across NE Germany ... Poland ... Baltic States.

SYNOPSIS

Upper low centered over the Baltic Sea early Saturday evening ... will make slow eastward progress during the period ... and is expected to amplify as short wave is rotating about its periphery. Slightly meandering southern upper frontal zone will extend from Morocco across the central and eastern Mediterranean Sea. At low levels ... polar air mass will continue to progress southwards ... overspreading the N Mediterranean regions on Sunday. Weak SFC low over Iberia will strengthen ahead of SRN stream upper upper low ... hampering intrusion of the polar air into Spain and Portugal. Weak low pressure area/theta-e plume will persist/spread north ahead of main upper trough over E Europe/W Russia.

DISCUSSION

...E Europe ... W Russia...
TSTMS will likely form in weakly plume of unstable air mass over E Europe/W Russia ahead of upper trough ... indications are that deep/dry CBLs will be present again ... promoting strong evaporative cooling of the downdrafts. Also ... deep-layer shear is progged to increase along the theta-e plume ... to 15 to 20 m/s ... altogether creating favorable environment for strong outflow winds ... which may briefly/isolated approach severe levels. An isolated marginally severe hail event may also occur. However ... mid/upper cloudiness associated with large-scale vertical motion regime may inhibit diabatic SFC heating ... and somewhat limit TSTM coverage. This setup does not warrant a SLGT ATTM.

Farther south ... weak capping ... solar heating combined with mountainous terrain ... and DCVA overspreading the area during the day ... will likely promote another round of TSTMS over the S Balkan States. About 15 m/s deep-layer shear ... and MLCAPE substantially less than 1000 J/kg are expected ... but a few strong wind gusts and some hail ... maybe approaching severe levels may occur given deeply mixed sub-cloud layers.

...Iberian Peninsula...
It looks that profiles have moistened some over Iberia at low levels ... possibly owing to the last days' precip. Though Saturday's 12Z soundings ... taken while air mass was convecting ... do not reveal much CAPE ... pre-convective environment on Sunday may be characterized by MLCAPEs in the 500 to 1000 J/kg range ... with very weak capping. TSTMS should initiate around mid day ... over S Spain which will be overspread by large-scale UVVs ahead of approaching upper low ... and spread northwards across most of Spain and Portugal as solar heating erodes CINH. Given expected large TSTM coverage ... chances exist that some storms encounter outflow boundaries such as to ingest high SRH's ... and a brief mesocyclone or two may develop. These will primarily pose a threat for large hail and damaging wind gusts.

...central Mediterranean...
Weakly unstable profiles will likely develop over the central Mediterranean ... mainly across the S Italian Peninsula. As vort max crosses the region towards the afternoon ... a few TSTMS may initiate. Low-level moisture looks to be quite sparse though ... and despite about 20 m/s deep-layer shear ... confidence in long-lived TSTMS is quite low ATTM. However ... dry environment may support strong outflow winds.

...NE Germany ... Poland ... Baltic States...
Shallow TSTMS will likely develop with diurnal heating in uncapped/mixed polar air mass. Low WBZ heights will likely promote small hail with the stronger cells ... but severe threat should be negligible with this activity.

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