Storm Forecast
Valid: Wed 03 Jul 2019 06:00 to Thu 04 Jul 2019 06:00 UTC
Issued: Tue 02 Jul 2019 21:29
Forecaster: PUCIK

A level 1 was issued across Massif Central and the Alpine range mainly for excessive rainfall, large hail and severe wind gusts.

A level 2 was issued across Romania mainly for large to very large hail, excessive rainfall and severe wind gusts.

A level 1 was issued from Serbia towards the Black Sea mainly for large hail and severe wind gusts.

A level 1 was issued across parts of Russia mainly for large hail and severe wind gusts.

SYNOPSIS

A strong zonal flow will continue over much of Central - NEurope with several embedded short-wave trough quickly moving towards Russia during the day. Flow weakens towards south, where a frontal boundary will stretch from France through S Germany, Hungary, into Romania, Moldova and S Ukraine. South of the frontal boundary, abundant lower tropospheric moisture will overlap with steep mid-troposheric lapse rates, yielding an extensive zone of moderate to high CAPE values from S France through N Italy towards Serbia, Romania, Bulgaria and the Black Sea coastline. Convective activity will be confined especially along the main mountain ridges south of the front - the Pyrennees, Massif Central, Alps and Carpathians.

DISCUSSION

... The Alpine area ...

NWP simulates widespread convective initiation over the area by early afternoon hours in the upslope flow of moist airmass with dewpoints between 16 and 20 deg C. In combination with lapse rates around 6.5 K/km, 1000 to 2000 J/kg of MLCAPE will be widely available on the Alpine foothills. DLS is forecast to reach 10 to 15 m/s, allowing for numerous multicell clusters, increasing towards east, where the values may even exceed 15 m/s, increasing potential for a few marginal supercells. The primary threat will be excessive precipitation, owing to mean wind around 5 m/s, followed by large hail from stronger and better organised cells. Isolated wet downbursts are not ruled out, particularly with storms forming towards south of the area, where well mixed boundary layer will be present.


... Romania ...

South of the frontal boundary, very moist airmass, combined with the lapse rates around 7 K/km, increasing towards south, will contribute to high MLCAPE values, locally reaching 2000 - 3000 J/kg. Widespread initiation is forecast by models, albeit the timing is uncertain. It is likely that an early morning activity and its outflow boundaries may impact the evolution especially over the northen part of the area. By 15 UTC, numerous storms will have formed or reached the southern part of Carpathian range. In DLS around 15 m/s, well organised multicells, or even brief supercells will be possible, capable of large hail, excessive rainfall and some severe wind gusts. Especially if storms manage to detach from the mountains and continue towards environment of very steep lapse rates, very large hail will be possible as well.

... Russia ...

A shallow, but fast-moving short-wave will cross the area, enhancing the wind at mid to upper troposphere. Forecast hodographs show more than 20 m/s of DLS and given their linear nature, splitting supercells and some line segments are expected. Due to the modest lower tropospheric moisture, MLCAPE on the order of few hundreds J/kg is forecast, limiting the updraft strength. Due to the moisture discrepancy in NWP, true extent of MLCAPE will likely impact the overall severity of scenario. Nevertheless, a lvl 1 for isolated large hail and severe wind gusts is issued.