Forecast type:Day1 Outlook
 

Synoptic and convective discussion:

...Synopsis...

A large-scale westerly flow/high index pattern prevails over much of Europe from the North Atlantic with enhanced speed maxes within attendant troughing. Two primary shortwave troughs move ENE over CNTRL/NE Europe. A small 320K PV+ maxima drifting from CNTRL Italy toward Greece -- also visible in the 500mb geopotential field as a mesoscale pressure perturbance -- where it will augment the convective potential over Peloponnese.

A flattened barotropic subtropical ridge remains in place across the S Mediterranean Sea and N Africa.

A potent eastward moving cold-core vortex with an associated 60+kt mid-level jet will reach Ireland Sunday morning. After that, it will open up and eject as a stout shortwave trough into Benelux Monday morning. Strong DPVA maxima amid the exit region of the cyclonically curved jet-stream with a lot of rising motion/upper-level ageostrophic divergence is forecast to overspread most of W Europe with its maxima over Benelux, W Germany and N France. 

At the surface, a cold front, draped from the aforementioned low, will move from W Europe east/northeast with its strongest portion from NE France across S Germany Sunday evening/night. 

...England/W Europe...

Although the strongest height falls there is forecast Sunday afternoon/evening, guidance agrees that it still seems adequately-timed with peak heating and differential temperature advection which will be the key in a buoyancy build-up. Simulations show rather skinny CAPE profiles within moderately strong deep-layer shear with straight-line hodographs. Daytime heating may be limited by cloud cover shifting from the west but there should be a window of stronger insolation over England Sunday afternoon.

800-1000J/kg MUCAPE maxima and 40-50kt deep-layer shear will be adequate for several thunderstorms to initiate along an occluded front or convergence zones and organize into small supercells given strong upper-level ventilation. A few spin-ups from local vorticity sources ingested into updrafts where strongest LL buoyancy will be present are probable. 

Storms may eventually organize into small lines as the day progresses with an augmented wind gust threat. They should be active even after the sunset given ample upper-level forcing and cold-core nature of the convection especially across Benelux where one or two stronger supercells could produce isolated large hail and strong wind gusts.

...S Germany, Czech Republic...

The eastward shifting cold front forming within a passing low-level wave along a SW-NE oriented baroclinic wave will be the main source for CI Sunday evening/night. Guidance shows slightly different scenarios regarding the convective evolution, but it agrees on storm activity along the wave/front Sunday night Monday morning. The presence of meager buoyancy will be dependant on LL advection/pooling of moisture under the mid-level cold trough before somewhat warmer ridging over France. The southern portion of the DPVA bullseye passing from W will also play a major role in generating of upward motion.

Discrete cells may fail to resist the very strong shear and upper-ventilation for organization into supercells as they will loose mass quickly.. Perhaps a few storm interactons and mergers will be able to resist this environment (low instability and strong shear) and become full fledge supercells capable of large hail and severe wind gusts. This interaction may also lead to more outflow producing storms with cold-pool initiation and produce isolated damaging wind gusts and heavy precipitation given saturated profiles. This scenario seems more reasonable for now. The activity should continue into Czech Republic or N Austria Monday morning.