Storm Forecast
Valid: Sat 16 Dec 2017 06:00 to Sun 17 Dec 2017 06:00 UTC
Issued: Sat 16 Dec 2017 01:00
Forecaster: TASZAREK

A level 1 was issued for part of W Balkan Peninsula coast mainly for excessive precipitation.

SYNOPSIS and DISCUSSION

A broad long-wave with low centered over Baltic Sea covers N, CNTRL and parts of S-CNTRL Europe. From west and east the trough is surrounded by jet streaks with high shear values. Most of the trough consists of an arctic airmass with steep lapse rates, especially over sea surface. Marginal CAPE develops on the rear side of the trough along W Norwegian coast and North Sea, mainly over sea surface. Although low-level moisture is poor (2-3 g/kg MIXR), a low-topped convection with a small potential for lightning may develop. Most of the convective cloud tops within this area will reach the temperature of -30°C but weak updrafts will limit lightning activity to only occasional events. Another area where convection may develop is a peak side of the long-wave (S-CNTRL Europe) with vorticity maxima traveling eastward. Lapse rates are expected to enhance due to synoptic-scale stretching and along with 5-6 g/kg MIXR over sea surface will provide ML CAPE up to 200-400 J/kg. Thunderstorms are expected to develop within PVA around noon hours in N section of E and W Italian coast and later in the S section. Although vertical wind shear will be strong, weak instability should limit severe weather potential. Minor severe wind gusts events however cannot be ruled out within 1 or 2 stronger cells. A risk of excessive precipitation covers W Greece, Albania, Montenegro and parts of Croatia, mainly due to superimposing stratiform and convective precipitation, and the support of orographic lift. Thunderstorms over these areas are likely to maintain until nighttime hours.