Storm Forecast
Valid: Sun 10 Feb 2019 06:00 to Mon 11 Feb 2019 06:00 UTC
Issued: Sat 09 Feb 2019 13:29
Forecaster: TUSCHY

A level 1 was issued for severe wind gusts and an isolated tornado threat for parts of E France, Luxembourg, S-Belgium and SW Germany.


SYNOPSIS

A progressive flow pattern takes another upper-level trough to CNTRL Europe. Constant amplification towards N-Italy is anticipated. Ahead of this trough a strong depression crosses Benelux, N-Germany and the S-Baltic Sea and attendant warm/cold fronts bring unsettled conditions to most parts of W/CNTRL Europe. During the night a digging upper jet results in falling heights/surface pressure south of the Alps.
Over E-Europe ongoing split-flow regime transforms into a building ridge, which suppresses thunderstorm probabilities.

DISCUSSION

... France, S Belgium, Luxembourg, SW Germany and Switzerland ...

Isolated to scattered thunderstorms erupt in the well mixed postfrontal air mass during the daytime hours as mid-levels continue to cool and along the cold front. Additionally a low-tropospheric post-frontal wave crosses that region beyond noon from NW to SE and pushes SRH-1 values in excess of 200 m^2 s^-2. Despite low SBCAPE values, temporal diabatic heating may cause adequate LL lapse rates/mixing for strong/severe wind gusts and an isolated tornado risk. This risk seems to be augmented along any line segment of enhanced convection especially over E France/W Switzerland into SW Germany during cold front passage. We added a level 1 due to the wind risk (60 kn at 850 hPa overlapping with steep LL lapse rates due to strong CAA) and an isolated tornado threat. Hail, although possible, should stay isolated in nature and sub-severe.

... N-Italy ...

Ongoing mid-level CAA / steepening lapse rates in a 750-500 hPa layer cause some elevated CAPE during the overnight hours atop a resistant cap. Enough mid-level shear is forecast for a marginal hail threat with the maximized risk residing around the Ligurian Sea and later-on over the N-Adriatic Sea.

... Far E Mediterranean ...

An eastward moving upper trough causes moderate offshore CAPE with cold mid-levels atop warm SSTs. Scattered thunderstorms bring heavy rain and graupel with the risk decreasing during the night. Could be a marginal level 1 rainfall setup along the coastal areas, but weak signals in model data preclude a level issuance for now.