Storm Forecast
Valid: Wed 03 Dec 2014 06:00 to Thu 04 Dec 2014 06:00 UTC
Issued: Tue 02 Dec 2014 22:06
Forecaster: PUCIK

A level 1 was issued for parts of N Norway mainly for severe wind gusts.

A level 1 was issued for N Morocco mainly for excessive precipitation.

A level 1 was issued for parts of central Italy mainly for excessive precipitation and tornadoes.

A level 1 was issued for W Greece mainly for excessive precipitation and to the lesser extent for large hail.


SYNOPSIS

While stable conditions remain over much of central and eastern Europe owing to the area of high pressure, both northern and southern Europe are under an active weather pattern. Scandinavia will be situated under strong westerly jet-stream with windspeeds over 50 m/s at 500 hPa level. To the south, a short-wave trough will dig towards southern Iberia and northwestern Africa, while another short-wave will rotate towards Greece and the Aegean. Both short-waves are connected to a large area of low geopotentials over southwestern Europe.

DISCUSSION

... N Norway ...

A short-wave is forecast to cross the region on Wednesday morning to noon hours with heavy precipitation enhanced orographically on the coastline areas. It seems that a modest overlap of marginal low level moisture and steep lapse rates will be present with CAPE values around 100 - 200 J/kg possible. Some linearly oriented low-topped multicells will be possible, perpendicular to the strong low level flow (reaching up to 25 m/s at 850 hPa level), with attendant threats of severe wind gusts. A marginal Lvl 1 is issued for the region with the highest threat.


... N Morocco ...

Yet another round of heavy rainfall, much of it associated with DMC, is forecast for this region. With the passage of a short-wave, marginal instability build-up is forecast. In northwesterly flow, perpendicular to the coastlines, repetitive rounds of storms will be possible, posing the risk of excessive precipitation. Because of the rather modest low-level moisture and absence of low-level jet, only Lvl 1 is issued.

... Central Italy ...

A strong low-level convergence is forecast in conjunction with a low pressure system that will be situated in the area. Thus, rather widespread initiation of convection is forecast. Even though CAPE values will be rather low, advection of moist airmass from south along with moist vertical profile and low LCLs will prove enough for an excessive precipitation event. Furthermore, enhancement of low level shear and SREH on the eastern and northeastern flank of the surface low, especially along the coastlines, may result in a tornado event in the area.

... Greece ...

Passage of a short-wave trough along with a cold front that is forecast during 18 to 00 UTC timeframe will likely result in a widespread DMC initiation. Around 15 m/s of 850 hPa flow will feed the multicells redeveloping over the coastline areas. In rather moist airmass with CAPE values up to 1000 J/kg, training pattern of cells may locally produce excessive precipitation, which should be the primary severe weather threat. With strong DLS exceeding 20 m/s and steep mid level lapse rates, large hail may occur in case that supercells develop. Threat will slowly diminish after Thursday 00 UTC.