Storm Forecast
Valid: Mon 21 Apr 2008 06:00 to Tue 22 Apr 2008 06:00 UTC
Issued: Sun 20 Apr 2008 22:01
Forecaster: GROENEMEIJER

SYNOPSIS

A mid-level low over France on Monday morning is expected to translate eastward, as will the strong southwesterly jet on its southeastern flank. An elevated mixed layer over the eastern Mediterranean and southern Balkans advects northward.

DISCUSSION

...Northern Dinaric Alps, Pannonian Plain and Transsylvania...

Insolation and gradually cooling mid-levels should lead to around 1000 J/kg of MLCAPE to form across the western parts of the Plain during Monday afternoon.

QG forcing, associated with the left exit of the upper level jet is progged to move over the northern Adriatic during the early afternoon and into the N Dinaric Alps during the late afternoon, before moving into the Pannonian Plain. Surface-based deep convective development appears likely during mid-afternoon over Slovenia, W Croatia and Bosnia. It is expected that more storms will form into Hungary and N Croatia during the evening. The highest storm coverage is expected in the north of the level 1 area, where storms will likely cluster into an MCS during the afternoon. More isolated storms will likely develop further south.

Given that deep-layer shear will be on the order of 25 m/s, the storms that develop, will probably include well-developed supercells capable of producing large hail, damaging winds and a few tornadoes.

Per current model guidance, the highest tornado threat would exist with storms that develop near and ahead of a convergence zone that is forecast to form in the level 2 area in the lee of the Dinaric Alps. There, 0-1 km helicity may exceed 250 m/s in places.

During the late evening and into the night, more storms are expected further east into eastern Hungary and Transsylvania. These will become more and more elevated in nature, and have a primary risk of large hail and severe gusts. As the Hungarian convective activity moves into the W Carpathians, a considerable flash flood risk may develop.

...Central Italy...

Although forcing for upward vertical motion will be weaker here, a few storms may form over the mountains of central Italy. If they do, they will develop in a strongly-sheared flow that may sustain an isolated large-hail producing supercell. This warrants issuing a level 1 for this area also.
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