Valid: Wed 18 Feb 2015 06:00 to Thu 19 Feb 2015 06:00 UTC
Issued: Tue 17 Feb 2015 21:24
A level 1 was issued for S Sicily and parts of S Algeria coastline mainly for the excessive precipitation.
Blocking pattern will continue also during Wednesday with high geopotentials covering much of W and Central Europe. A slight change in a form of approaching trough from the Atlantic is forecast in the following days. Conditions will be mostly hostile to DMC with stable and dry airmass dominating over the continental Europe. The only exception should be the S Mediterranean and perhaps the SW Black Sea (both regions discussed below).
... Southern Mediterranean, S Sicily towards Algeria coastline ...
In E-ly to NE-ly flow, low geopotentials have spread over the area with a center of the mid-tropospheric low over Tunisia. This low is forecast to slowly fill in during the forecast period, slowly moving towards Algeria. To the north of it, easterly flow will persist with a subtle frontal boundary and a tongue of moister airmass. At the time of writing the forecast (Tuesday 21 UTC), precipitation was ongoing over Sicily with moderate intensity under the persistent easterly flow. Surface dewpoints in the coastal stations reached around 10 deg C. During Wednesday, aforementioned frontal boundary should progress southwards with colder and drier airmass behind it. Thus, it is likely that the rainband will move southward during the day and slowly lose in intensity as the low fills in. Nevertheless, will keep Lvl 1 for excessive precip. for S Italy with a potential training pattern event as convection may be embedded in the rainband.
Another Lvl 1 is issued for parts of Algerian coastline where persistent NE-ly flow will impinge on the coastline. In the environment of marginal instability and flow parallel to the orientantion of rainband, training pattern with excessive precipitation may occur as well. Also here, rainband is expected to weaken as the low fills in. It will move W-wards during the day, in accordance with the movement of the low.
... S Black Sea coastline ...
As was already mentioned in the forecast for yesterday, impressive setup for the sea-effect snow is ongoing over the southern parts of the Black Sea coastline. In 850 hPa flow of around 15 m/s, banded showers will form in an arctic airmass that has been advected over the region. Even though CAPE values will be very small and most likely confined to the lower levels, CAPE will be likely realised in the graupel forming (charge separation) zone as 850 hPa temperatures dipped towards - 15 deg C. Thus, a few weakly electrified cells are quite possible in this setup, besides very high snowfall rates in any of the showers impacting shoreline.