Storm Forecast
Valid: Wed 30 Mar 2016 06:00 to Thu 31 Mar 2016 06:00 UTC
Issued: Wed 30 Mar 2016 06:21
Forecaster: PUCIK

A low-end Lvl 1 was issued for NE Hungary and NW Romania mainly for large hail and severe wind gusts.

SYNOPSIS

Major synoptic-scale features on the weather maps are two troughs. The first one is located over the Atlantic and is highly amplified, its base reaching towards the S Iberia. As trough progresses eastwards, SW-ly flow on its forward flank advects EML from Sahara over Iberia and also S France. Scattered DMC is observed in the core of the trough, where cold mid-tropospheric temperatures contribute to steeper lapse rates. The second trough is currently located over Belarus and Ukraine, also moving eastwards. In between of the troughs, strong zonal flow is observed.

DISCUSSION

... SW France ...

Strong SW-ly flow at mid to upper troposphere should result in the high values of DLS (over 25 m/s), with over 15 m/s of bulk shear in the 0-3 km layer. Such values are conducive for well organised convection, including supercells. According to the model output, EML should reach this region around 12 UTC and in conjunction with the increase in the low-level moisture should result in marginal latent instability build-up. MLCAPE values should not exceed 400 J/kg and it is very likely that there will be a capping layer with CIN values around -100 J/kg. Due to the lack of strong QG forcing as axis of the trough is still far west, it is not probable that convection would initiate in this setup. Lvl 1 was considered for possibility of marginally large hail occuring with supercells, but chances seem too low at the moment.

... NE Hungary to NW Romania ...

A borderline Lvl 1 situation will develop over the region as up to 400 J/kg of MLCAPE are simulated by models along with high values of DLS, exceeding 30 m/s and 0-3 km shear reaching 15 m/s. Isolated to scattered DMC is forecast to initiate in this setup. If it can sustain itself against the strong vertical wind shear, then supercells can form with a threat of large hail and severe wind gusts. However there is a distinct possibility that updrafts of the growing convection will be entrained with dry air due to the strong storm relative flow. In such case, despite strong DLS, DMC would not be able to attain a well organised state.

... Ukraine ...

In the core of the trough and cold mid-tropospheric temperatures (below -30 deg. C at 500 hPa level), MLCAPE values should reach 100 to 500 J/kg. At the same time, DLS values should stay between 10 to 15 m/s. This setup will allow for scattered initiation and DMC will organise into multicell clusters. The stronger ones will be capable of (non-severe) hail and perhaps gusty winds. Threat seems to be too low to warrant a Lvl 1.