Storm Forecast
Valid: Thu 01 Apr 2010 06:00 to Fri 02 Apr 2010 06:00 UTC
Issued: Wed 31 Mar 2010 21:21
Forecaster: GATZEN

A level 1 was issued for Romania and southern Ukraine mainly for excessive rain.

A level 1 was issued for the northern Adriatic mainly for excessive rain.

SYNOPSIS

A southern polar jet stream curves around a deep trough centred over western Europe and affects the Mediterranean. Some vort-maxima eject eastward into Europe while the main long-wave trough is generated by another impulse from the Atlantic Ocean. Over eastern Europe, weak mid-level winds are present in the range of refilling short-wave troughs. Mostly dry polar air masses will dominate the weather over Europe through-out the period except for the south-eastern portions.

DISCUSSION

Romania to southern Bulgaria

The polar air mass over Europe spreads eastward behind a cold front that becomes more and more orientated parallel to the southerly flow over eastern Europe. The cold fonr will therefore spread into the Black Sea region quite slowly, pushing the warm air mass to the east. Latest soundings indicate the presence of a deep mixed boundary-layer over the Balkans that will likely spread into Romania ahead of the cold front. Additionally, latest GFS predicts increasing low-level mixing ratios in the range of the southerly flow in the range of the cold front. This will likely result in diurnal instability with MLCAPE around 500 J/kg. This instability will likely be deep as a mid level trough will spread into the affected region during the day, resulting in equilibrium temperatures below -40°C from Romania to southern Ukraine.

Despite some cloud fields of overnights convection, some diurnal heating will likely build CAPE in the range of the cold front on Thursday. Given best low-level convergence and moisture along the cold front, initiation is expected in its vicinity around noon. With westerly low-level winds and weak southerly winds at mid levels as well as rather steep lapse rates in the initial state, back-building clusters of storms are expected that will slowly spread northward. Given the slow movement along the frontal boundary, the storms will be capable of producing excessive precipitation over some places, but the overall threat is weak due to the rather low moisture. Large hail is not likely given the weak vertical wind shear