Valid: Fri 27 Oct 2017 06:00 to Sat 28 Oct 2017 06:00 UTC
Issued: Thu 26 Oct 2017 14:10
An high-over-low blocking pattern is present over SW-Europe and results in a low-index pattern over most of Europe. A Rossby-wave over E-/NE Europe remains anchored with numerous impulses circling its western and southern periphery (affecting parts of Europe). The main feature of interest is a sharp upper trough over CNTRL- Europe during the start of the forecast, which races towards SE-Europe afterwards. An upper low over the E-Mediterranean begins to lift to the NE ahead of the approaching upper trough.
... Poland ...
A short-wave upstream of the main upper trough affects Poland during peak heating. Forcing and somewhat steeper mid-level lapse rates atop ML mixing ratios of roughly 6 g/kg result in weak CAPE along a SE-ward moving trough axis. Forecast soundings show a well and deeply mixed air mass with marginal CAPE, so strong gusts and graupel will be the main hazard. Temporal line-up of convection can occur, but the overall setup does not support a level issuance.
Sporadic elevated convection is possible along/ahead of the main upper trough (e.g. Alps and W-Balkan States), but the limited nature of activity precludes any lightning areas.
... E-Mediterranean ...
A moist air mass is incorporated in the cyclonic vortex with latest TPW readings in excess of 25 mm and warm SSTs. Cool mid-levels aloft bring SBCAPE readings to 1000 J/kg over the E-Mediterranean. Numerous convergence zones will be the foci for scattered slow moving storms with locally excessive rain and isolated large hail. A few waterspout reports are also possible. The risk diminishes betimes and exits our forecast domain to the E.