Storm Forecast
Valid: Sun 20 Aug 2006 06:00 to Mon 21 Aug 2006 06:00 UTC
Issued: Sat 19 Aug 2006 22:03
Forecaster: DAHL

SYNOPSIS

Main upper trough remains anchored over the North-Sea region ... with rather vigorous vort max rounding the base of the trough in the early morning hours ... thereafter lifting NEWD across Poland into the Belarus by early Monday morning. As Plume of warm air is advected into E central Europe E of the Alps ahead of the vort max ... weak cyclogenesis is expected over S Poland in the early afternoon hours.

DISCUSSION

W Mediterranean ... central Italy

LL moisture seems to recover slowly as EML has overspread the central portions of the Mediterranean and Italy ... thus limited deep vertical mixing. As a result ... CAPEs on the order of 1000 J/kg should be present ahead of main baroclinic zone over the W Mediterranean and Italy on Sunday.

Shear profiles remain quite strong across this region ... with about 30 m/s DLS ... and 15 m/s 0-1 km shear. Though main large-scale UVV regime is not expected to overspread the LL front until late in the night ... GFS advertises precip along the front in the afternoon and evening hours. This may be a reflection of rather isolated evolution in response to increasing capping and limited large-scale ascent.

Any storm that forms ... will likely become supercellular ... capable of producing entire facet of severe weather ... large hail ... damaging winds and tornadoes ... though the tornado threat may be somewhat limited by anticipated strong cap. ATTM ... upscale growth into large MCS is not expected given large CINH and only weak large-scale forcing for ascent. An upgrade to level two may be considered on Sunday however if TSTM coverage happens to be larger than currently anticipated.

Poland

Another focus for severe evolution should be the frontal wave which is expected to develop over Poland during the day ... and move into Belarus in the late evening/night hours. CAPEs should be somewhat marginal ... possibly on the order of 500 to 1000 J/kg ... as will be deep-layer shear ... but strong LL shear will likely promote isolated severe evolution. Threat should primarily be tied to small supercells ... capable of producing large hail and damaging winds. Backed SFC flow and rather strong LLS may also promote a few tornadoes.

Otherwise ... have included Austria ... E Switzerland and extreme S Germany in the LVL1 as isolated large-hail events could occur in weakly unstable and strongly sheared air mass. Threat should be somewhat marginal however.