Storm Forecast
Valid: Thu 01 Sep 2016 06:00 to Fri 02 Sep 2016 06:00 UTC
Issued: Wed 31 Aug 2016 22:40
Forecaster: GATZEN

A level 1 was issued for northern Morocco and Algeria mainly for large or very large hail and severe wind gusts.

A level 1 was issued for portions of the Balkans, Italy, and Spain mainly for excessive rain.

SYNOPSIS and DISCUSSION

Weak mid-level flow is expected across southern Europe. Two mid-level troughs centred over Iberia and the Balkans will slowly move east. Northern Europe is affected by a strong zonal flow with a short-wave trough crossing northern and central Scandinavia.

Low-level moisture increases to the south, where it overlaps with steep lapse rates centred below the cut-off lows with cool mid-level air. Land-sea-breezes and mountain circulations will act as sources for low-level lift to initiate storms. As vertical wind shear is weak, organized storms are not expected. However, slow moving storms can produce local flash floods. Stronger vertical wind shear evolves due to onshore flow across northern Africa. Although initiation is unsure, every storm that moves from the Atlas mountains to northern Morocco and Algeria can turn into a supercell capable of producing large hail and severe wind gusts.

Almost no thunderstorm activity is forecast over northern Europe, given stable lapse rates over many places. Best potential exists of Scandinavia, where progressive troughs lead to low-level stretching. Additionally, low-level moisture increases ahead of a cold front that enters Finland during the day. Over central Finland, there might be some overlap of this moisture with steeper lapse rates, allowing for weak CAPE. In association with low LCL heights and strong low-level shear exceeding 10 m/s in the lowest km, a tornado cannot be ruled out, especially when some breaks in the clouds allow for stronger low-level heating.