Storm Forecast
Valid: Sun 20 Jan 2008 06:00 to Mon 21 Jan 2008 06:00 UTC
Issued: Sat 19 Jan 2008 22:04
Forecaster: DAHL

SYNOPSIS

Strong westerly upper flow remains in place across central portions of Europe, with the associated, reasonably stationary, low-level frontal zone extending from the British Isles into east-central Europe. An Atlantic upper trough will approach the British Isles late in the period, supporting cyclogenesis over the S UK towards early Monday morning.

DISCUSSION

... western British Isles ...

GFS hints at the development of weak instability ahead of the Atlantic upper trough which is simulated to reach the western British Isles early on Monday. Later evolution of the model results will be awaited before pinpointing the (severe) thunderstorm threat in this regime, since the presence of CAPE in such an air mass comparatively far ahead of the upper trough is somewhat unusual. If positive CAPE indeed develops, some threat for severe wind gusts and possibly an isolated tornado or two will exist. An upgrade may be necessary on Sunday if the latest GFS scenario indeed materializes.

... southern Norwegian Sea ...

Chance of sporadic lightning persists over the southern Norwegian Sea in the polar air mass, especially amidst the upslope flow regime of the western Norwegian Mountains. However, lightning should remain too isolated to necessitate a thunderstorm area.

... southern Ionian Sea ...

Weak CAPE is simulated to persist over the southern Ionian Sea, becoming increasingly shallow during the period as a result of increasing mid-/upper-level ridging. However, GFS does not come up with convective precipitation in the region where CAPE is reasonably deep, which matches the latest observations, which suggest that region of deep convection is already moving southward beyond the forecast area boundary. Altogether, threat for significant thunderstorm activity seems to be too low for a thunderstorm area.