Extended Forecast
Valid: Wed 11 Jun 2008 06:00 to Thu 12 Jun 2008 06:00 UTC
Issued: Mon 09 Jun 2008 20:59
Forecaster: SCHLENCZEK
SYNOPSIS
High pressure builds over the North Atlantic while an upper longwave trough over Scandinavia will shift eastward. A well-defined cold front that stretches from the Baltic States via southwestern Poland and central Germany towards the North Sea is forecast to move southeastward. An upper level cut off low over Spain with a 40 m/s upper jet streak over the Balearic Islands will move eastward. Some vorticity maxima embedded in the jet stream will travel northeastward. Another upper level disturbance over the eastern Mediterranean will leave the forecast area during the day.
DISCUSSION
...Western Mediterranean, northern Algeria...
In the vicinity of a 35 m/s jet streak at 300hPa, some hundred J/kg of CAPE may form during the day. As the upper level vort max overspreads the region, deep layer shear is forecast to increase to about 20 - 25 m/s. Enhanced SRH with values up to 400 J/kg hints at possible mesocyclones. Well-organized multicells and supercells may evolve, capable of producing large hail and severe gusts. Some uncertainties with respect to the region where moderate CAPE and strong DLS will overlap remain but a level-one threat seems to be warranted, though.
...Austria, southern Germany, Switzerland, S-central France, northern Italy...
During the afternoon, about 1 kJ/kg MLCAPE is expected to form and thunderstorms will evolve in a weakly sheared environment. Weakly organized multicells are capable of producing isolated large hail and heavy rain that may lead to local flooding. Thunderstorm activity will rapidly decrease after sunset.
...Southern Sweden, Baltic States...
In the wake of the trough, upper-level cooling and diurnal surface heating will create some low-end instability. Weakly electified thunderstorms and showers with small hail and gusty winds may develop. Locally enhanced LLS and good LL buoyancy may provide a slight chance for an isolated tornado but a threat level is not warranted at the moment.
...British Isles...
Some low-end instability in the vicinity of the jet axis may allow showers and thunderstorms. Deep layer shear around 20 m/s and strong QG forcing are expected and multicells may organize into a few convective lines that could produce marginally severe gusts. Given great uncertainties with respect to the instability, a threat level is not introduced but may be issued later on.
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