Mesoscale Discussion

Mesoscale Discussion
Valid: Sat 25 Jun 2016 17:00 to Sat 25 Jun 2016 21:00 UTC
Issued: Sat 25 Jun 2016 17:00
Forecaster: PISTOTNIK

This MD is issued to highlighted an ongoing risk of scattered to widespread severe thunderstorms in a belt across east-central Europe.

12z soundings in the highlighted belt showed CAPE values between 1000 and 3500 J/kg and very high precipitable water values between 30 and 40 mm. A convergence line with a wind shift from SE-erly to W-erly direction is slowly moving eastward from Germany into Poland, the Czech Republic, and Austria.
Low-level moisture is maximized immediately ahead of this line and likewise in a belt from SE Austria into N Bosnia-Herzegovina and Serbia, where latest surface observations show 2m dewpoints up to 23C. Hence CAPE may locally even exceed 4000 J/kg.

In the last few hours, scattered intense pulse storms have already formed near the convergence line and over orographic features ahead of it. Numerous events of large hail, flash floods and severe wind gusts have already been reported.
Despite weak vertical wind shear, reports show that today's storms under such CAPE values may even produce severe events which approach or exceed our "extreme" criteria, e.g. 5 cm sized hail in Halfterhaeuser (Saxonia, E Germany), possible F1 wind damages in Kosowo and Tupadly (W Poland), and a measured wind gust of 31 m/s in Innsbruck (Austria).

Further to the east, a mostly cloudless sky suggests that a capping inversion is still in place. However, any outflow boundary sent into this air mass can easily trigger secondary convection. Despite a partly erratic propagation so far, the dominant storm motion is from SW to NE. It is therefore likely that also previously calm regions of Serbia, inland Bosnia-Herzegovina and Croatia, SW Hungary and E Austria will be affected in the next couple of hours.

Activity is still in its upswing and the threat of large hail, severe cold-pool driven downbursts, and excessive precipitation remains enhanced. Especially with backbuilding storms or large clusters, flash floods will turn into the main risk and even a few life-threatening events in hilly terrain cannot be ruled out.

Storms will likely continue when this MD expires (21z), and their severe weather risk will only gradually decrease.

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