Storm Forecast
Valid: Mon 04 Jul 2016 06:00 to Tue 05 Jul 2016 06:00 UTC
Issued: Mon 04 Jul 2016 03:40
Forecaster: VAN DER VELDE
A level 2 was issued for N Algeria mainly for large hail and severe wind gusts.
A level 2 was issued for N Spain mainly for large hail.
A level 1 was issued for S Romania mainly for excessive convective precipitation and large hail.
A level 1 was issued for NE Poland mainly for large hail.
A level 1 was issued for W Russia mainly for excessive convective precipitation.
A level 1 was issued for C Italy mainly for large hail.
SYNOPSIS
A low pressure center lies over NW Russia and Finland. Warm unstable air resides east of a sharp cold front extending south toward the western Black Sea. Cooler unstable airmass is present over southern Scandinavia and the Baltic region. A meandering westerly flow carries a new low with a frontal wave over the British Isles. A thermal low with unstable air formed over the western Iberian Peninsula. To its east, hot air is carried northward from Algeria into the Mediterranean, with very steep lapse rates.
DISCUSSION
...N Spain...
1000-1500 J/kg MLCAPE is forecast to develop according to GFS with little capping and 1500-2500 m high cloud bases, allowing strong updrafts to form. Presence of 10-15 m/s 0-6 km shear can further increase potential for large hail production, with organized multicells and isolated supercells possible. Eventually large hail and severe wind gusts can reach moderate coverage.
...N Algeria...
3000 m high cloud bases and weakly capped CAPE should be present over Algeria. At the coast a low pressure system develops with backed surface winds under strong 500 hPa winds, causing a large area of >250 mē/sē SREH and 25 m/s DLS. However, there is only small overlap between the shear and the unstable air, and in the most favorable case this would allow high-based supercells with large hail and severe wind threats. The activity will likely move over sea toward Sardinia at night.
...C Italy...
A situation with 10-15 m/s DLS and 1000-1500 J/kg MLCAPE allows organized cells with large hail. Initiation will probably be isolated. Mid level lapse rates are weak, but delta-theta-e over 20K supports severe downbursts.
...S Romania...
Instability remains in the wake of the Carpathian mountains during a cold front pass. Slow storm motion and weak shear at 12Z get replaced by 15 m/s DLS and circular hodographs with SSW-ward storm motion. If any CAPE remains, large hail may then occur.
...W Russia...
Good shear is present on the wrong side of the cold front. The warm side is starved of shear, with storm motion parallel to the front (N-ward) which increases the excessive precipitation threat from training storm clusters.
...NE Poland...
A slight chance of marginal large hail is present in the overlap zone between slight CAPE and 10-20 m/s DLS. In addition this area gets upper support from a shortwave trough.
...S Scandinavia...
Slow storm motion under the cold pool could locally spin up a spout-type tornado. Precipitable water is not high enough for a significant heavy rain threat though.
