Storm Forecast
Valid: Sun 29 Jul 2018 06:00 to Mon 30 Jul 2018 06:00 UTC
Issued: Sat 28 Jul 2018 13:01
Forecaster: TUSCHY

A level 1 was issued across parts of E/SE Europe mainly for excessive rain and a few large hail and severe wind gust events. An isolated tornado event is possible.

A level 1 was issued for E/SE Sweden mainly for excessive rain.

A level 1 was issued for parts of SW Italy mainly for an isolated large hail event.

SYNOPSIS

A deep cyclonic vortex over far NW Europe faces an anormal strong high pressure area over NE Europe. In between both vortices, southerly winds advect a warm and moist air mass far north. Over the W-Mediterranean, hot and stable air beneath a subtropical ridge prevents any DMC activity.

A cold front over S Norway and Sweden slides east and becomes quasi-stationary over N Norway/CNTRL Sweden. Elsewhere no substantial impact of a synoptic-scale front on DMC activity is expected.

DISCUSSION

... Level 1 areas over parts of E/SE Europe...

Deep confluent flow regime is characterized by weak to non-existent shear and deep moist profiles. Given weak CIN and temporal diabatic heating before noon, early and widespread CI is forecast. MLCAPE in excess of 1000 J/kg supports robust updrafts with a few large hail and severe downburst events during the discrete stage. On the mesoscale, enhanced LL shear, low LCLs and strong LLCAPE build-up could also support an isolated tornado event. Betimes however thunderstorms grow upscale into slow moving clusters with excessive rain the main risk. The overall activity weakens during the night.

...SW Italy...

A belt of stronger mid-level flow overspreads SW Italy, where SBCAPE aoa 1500 J/kg is forecast. Initiating convection could organize on a temporal scale with an isolated large hail threat. This activity weakens as it moves away from the orography and into a capped air mass to the S.

...Sweden...

Forecast hodographs show enhanced LL flow during the daytime hours with rather unidirectional shear and some veering above. In addition the wind speed above 700 hPa relaxes rapidly. Hence conditions would support training bands of showers/thunderstorms well onshore. Limited CAPE and thick cloud cover lowers confidence below the level 1 threshold. Still a few heavy rainfall events due to trainig convection embedded in a more stratiform rain event can't be ruled out.

A level 1 upgrade was performed over SE Sweden with SBCAPE in excess of 1000 J/kg and weak shear, so locally heavy rain becomes a risk. The level 1 was expanded to the NE along the coast with SBCAPE in the 400-800 J/kg range and supportive conditions for training convection.