Storm Forecast
Valid: Tue 21 Jun 2016 06:00 to Wed 22 Jun 2016 06:00 UTC
Issued: Mon 20 Jun 2016 21:05
Forecaster: DAFIS
A level 3 was issued for Ukraine mainly for severe wind gusts, large to very large hail and tornadoes.
A level 3 was issued for parts of Belarus, Ukraine and W Russia mainly for damaging wind gusts, large hail, excessive rainfall and tornadoes.
A level 2 surrounds levels 3 mainly for large hail, excessive rainfall, severe wind gusts and torndoes.
A level 1 was issued for parts of Russia, Belarus, Ukraine, Moldova, E Slovakia, E Hungary, Romania,Serbia, Bosnia and Herzegovina, Montenegro and NW Bulgaria, mainly for excessive rainfall and large hail. Also landspouts/tornadoes cannot be ruled out.
SYNOPSIS
A baroclinic zone in E Europe moves northeastwards during Tuesday, extending from Serbia towards Russia. A plume of very moist BL is found over NW Romania, W Ukraine, SE Belarus and Russia and models predict strong low level convergence. Furthermore, upper level configuration is prominent for supercell development over N Serbia, W Ukraine and in Russia, as a sub-tropical jet stream is gradually weakening during the night of Tuesday, but during the afternoon, it will increase the potential of severe weather events, as the dry slot that accompanies it will be over air masses with high equivalent potential temperature. Concerning the rest parts of the continent, a cold bubble is found in Central Mediterranean, but low instability is forecast in a moderate sheared environment. Another cold front is approaching NW Spain and a weak baroclinic zone in Germany.
DISCUSSION
.... West Ukraine ....
Latest model output indicates a wave crossing W Ukraine from SW to the NE. Ahead and during the passage of this wave, WAA and rich moisture will result in MLCAPE of 2000-2500 J/kg, maybe even more according to GFS. Those values are strongly fluctuating due to local moisture pools / areas with strong mixing so the magnitude of the instability release on a small scale is likely. Strong diabatic heating will help to remove the LL cap and initiation will be underway during the afternoon hour. We expect isolated to scattered thunderstorms to move in from the southwest and some of them to become supercells with damaging wind gusts, very large to extremely large hail and perhaps tornadoes within the most discrete cells. The possibility of tornadoes is of less concern in W Ukraine as the base of the clouds is expected above 1000 m, but strong rotating storms in the environment of 150-200 mē/sē SREH0-3km could create the favorable environment for tornadogenesis.
.... SE Belarus and Russia .....
Thunderstorms should develop in association with a frontal wave, propagating northeastwards along the front during the period. The cells that form should immediately become supercellular, main threat being large hail and damaging winds. It seems that the hail threat will be maximized where low-level moisture will be deepest, and very large hail, well in excess of 5 cm in diameter, may occur. As coverage increases, storms may merge into linear segments. In the evening hours, it seems that rich low-level moisture along with strong CAPE and quite favorable LLS profiles will coincide, which suggests that a threat for tornadoes will exist. Furthermore, large hail and damaging straight-line wind gusts are expected into this highly unstable and sheared environment. Very rich BL moisture and abundant moisture inflow into the thunderstorms will help to raise the threat for torrential rain and flash floods. Anticipated storm coverage and degree of severity necessitate a level-three threat.
Some 15 to 20 m/s DLS should overlap with weak to moderate instability over the rest of the level 1-2 areas. Diurnal heating as well as DCVA-forced ascent should aid in scattered convective development. Expect multicellular storms and isolated mesocyclones capable of severe wind gusts along with large hail. An isolated landspout / tornado could also occur north of level 3 area of Russia, especially in the late afternoon hours as LLS is expected to increase. In central - eastern parts of Ukraine, weak DLS should limit longevity of the cells and reduce the severe threat. In Serbia, Bosnia and Herzegovina we think that daytime driven thunderstorms will develop after 15z as initiation will be dependant on the local topography but thunderstorms will start to organize more and more along the convergence zone.
