Storm Forecast
Valid: Wed 03 May 2017 06:00 to Thu 04 May 2017 06:00 UTC
Issued: Wed 03 May 2017 07:02
Forecaster: PUCIK

A level 1 was issued for Serbia, E Hungary, E Slovakia, W Romania, SW Ukraine and extreme SW Poland mainly for large hail and severe wind gusts.

A level 1 was issued for Algeria mainly for large hail and severe wind gusts.

SYNOPSIS

Main macrosynoptic features of the day at mid and upper troposphere are a ridge stretching over the NE Atlantic and a pair of two lows, the first one located over N Russia and the second one centered over E France and BENELUX. At the surface, an extensive high pressure system covers basically the whole N-ern part of Europe with prevailing easterly surface flow over much of Central and W Europe. An ill defined, shallow low is situated over the Mediterranean. Isolated to scattered tstms will be associated with the low over W and Central Europe, especially at its forward flank, where the most abundant lower tropospheric moisture is observed.

DISCUSSION

... Serbia, E Hungary, E Slovakia, W Romaina, SW Ukraine, extreme SE Poland ...

At the forward flank of the low at mid and upper troposphere, models simulate strengthening of the S-ly flow at the 500 hPa, reaching 15 to 20 m/s. At the same time, a subtle short-wave will approach the region as it rotates around the low. Surface observations show modest dewpoints in the area, ranging from 10 to 15 deg C. 00 UTC Szeged sounding showed around 20 m/s of DLS along with marginal CAPE. With surface heating and perhaps some additional moisture advection from east, several hundreds J/kg of MLCAPE seem plausible by the afternoon hours. GFS shows higher CAPE values, but these are a result of 16 deg C dewpoints which are highly questionable at the moment. Nevertheless, first cells, likely elevated, are already ongoing over the region. Coverage of tstms is expected to increase towards the afternoon and evening, especially along the weak wavy frontal boundary. With moderate to strong DLS (15 to 20 m/s), well organised multicells will be the primary convective mode, with some supercells possible as well. Large hail will be the primary threat, with severe wind gusts as a secondary threat materializing especially if a larger cluster (MCS) forms. With the approach of short-wave from south, tstm activity may be ongoing quite late into the night.

... Algeria ...

A plume of steep lapse rates will advect over modestly moist airmass with dewpoints around 12 deg C, resulting in a few hundreds J/kg of MLCAPE. With around 15 m/s of 500 hPa flow, conditions seem quite favourable for a few well organised multi or even supercells, capable of large hail and/or severe wind gusts. Storms will initiate especially along the local topographic features, such as the Atlas mountain range.