ZitatA level 2 was issued for SE-ernmost Germany, N-ern Austria, the Czech Republic and SW-ern Poland, and a level 1 for the rest of Poland for severe wind gusts, large to very large hail, and to a lesser extent for excessive precipitation.
Rich low-level moisture with dewpoints in the upper tens and even lower twenties are present at 06 UTC, while another "Alpine plume" with steep lapse rates will be advected over the Czech Republic and Slovakia into Poland at mid-levels. Moderate to strong instability with CAPE between 1000 and 2000 J/kg can hence be expected to build up, overlapped by moderate DLS of 15-20 m/s.
Main uncertainty is the behavior of the low-level wind field and the coupled evolution of boundary layer moisture depth. Overnight's thunderstorm activity over Germany has spilled an outflow with northerly winds into Austria and surrent thunderstorms across the Czech Republic. Current thinking is that this wind regime will subside again until noon and turn into a messy set of meso- and small-scale circulations over the Czech Republic, and into more pronounced Northerly to Northeasterly upvalley circulations with according "moisture piling" along the Northern Alpine rim.
Convective activity is forecast to weaken across the Czech Republic in the following hours. Due to moderate to strong capping and the absence of synoptic-scale forcing, convective initiation will again happen rather late. First isolated storms can be expected in the afternoon hours, igniting over orographic features and with a good chance to turn into multi- and supercells with a threat of large or even very large hail and local downbursts. Storm coverage should significantly increase towards evening, as the existing gust fronts / outflow boundaries will continue to trigger secondary convection. The forecast models largely agree on the formation of another MCS over SE-ernmost Germany, moving into the Czech Republic in the evening and across Central and Eastern Poland overnight. Severe wind gusts will be the main threat, but large hail and excessive precipitation are possible as well. A level 2 was drawn in order to account for a possible outbreak of severe weather with this feature.
Eastward channeling of the outflows along the Northern Alpine rim and the accordingly strong low-level convergence will probably be sufficient to initiate further storms over Northern Austria, where also a bow echo with widespread severe wind gusts may evolve in the evening hours and propagate eastward towards the warmer and moister air masses. The breaking of the cap and convective initiation or sustenance becomes somewhat questionable the further South and East it gets, but the threat seems to be robust enough to extend a level 1 into Slovakia.
Along the Northern edge of the area, i.e. over Eastern Germany and Western Poland, DLS increases to even 20-25 m/s, while CAPE decreases. Exact position of the frontal boundary is unclear and initiation becomes much less likely on its cool side, but a level 1 area includes these regions in case more instability will build up again and enable scattered multi- or supercell storms with a threat of large hail or severe wind gusts.
Mit Sturmböen und starker Bewölkung hat es in der Früh begonnen - nun ist es wolkenlos bei bei 27,9 Grad und windstill in St.Oswald im südl. Waldviertel
Momentan hat bei Uns 22 Grad bei 79 % Luftfeuchte, der Luftdruck liegt bei 950 hPa der Windchill bei 22 Grad. Wind kommt von Nordwest mit 5-9 km/h. Lassen Wir uns überraschen wie sich das Wetter entwickelt ;)
