CONVECTIVE FORECAST
VALID 06Z SAT 27/03 - 06Z SUN 28/03 2004
ISSUED: 26/03 22:58Z
FORECASTER: DAHL

General thunderstorms are forecast across S Iberia ... S-central Mediterranean Sea ... Aegean and adjacent States.

SYNOPSIS

Relatively intense southern frontal zone is stretching from extreme NW Africa across the Mediterranean into the Black Sea ... with several relatively poorly defined vort maxima embedded. Three upper cut-off lows are present N of this frontal zone over SE-central Europe and SW Europe. At low levels ... cold air and high pressure dominate most of central and W Europe ... weak cyclogenesis is progged ahead of weak vort max over the Ionian Sea early Saturday morning.

DISCUSSION

...Aegean ... Greece ... S Bulgaria...
LGIR, Crete, Friday 12Z launch reveals plume of mid-level steep lapse rates which is likely to originate from the N Sahara Desert ... and also shows substantial lack of low-level moisture ... which is supported by various regional soundings. However ... LIEE and LIBR 12Z and 18Z ascents show increasing low-level moisture at the NW edge of the Saharan EML ... the origin of this moisture is quite uncertain ATTM. GFS is simulating weak CAPE over Greece ... S Bulgaria and the Aegean Sea during Saturday afternoon/evening ... which happens to coincide with the NWRN edge of the EML plume. Despite the uncertainty regarding the moisture distribution ... indications are that CAPE may indeed be present over Greece and Bulgaria towards the afternoon ... possibly aided by insolation.

Current thinking is that a few TSTMS will initiate toward midday/early afternoon ahead of weak vort max along low-level baroclinic zone over N Greece and S Bulgaria. Substantial uncertainty as to the low-level moisture exists ... but given about 25 m/s deep-layer shear ... small severe TSTM threat appears to exist. Situation will have to be monitored ... and if more favorable low-level thermodynamic fields than currently expected turn out to materialize ... an upgrade may be needed.

...SW Iberian Peninsula...
Upper low off the Iberian W coast ... is progged to promote SFC cyclogenesis E of Portugal and Morocco ... and push steep lapse rates into S Spain. Low-level ELY flow looks to be quite dry ... and uncertainties not too dissimilar from those in the central Mediterranean exist. Shear will likely be adequate for a few severe TSTMS ... but threat is quite conditional ... depending on the presence of sufficient low-level moisture.

Farther east ... a few elevated TSTMS may accompany the northward progression of high theta-e's from N Africa over the S-central Mediterranean during the night/early Sunday morning.

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