Extended Forecast
Valid: Sun 04 Aug 2024 06:00 to Mon 05 Aug 2024 06:00 UTC
Issued: Fri 02 Aug 2024 21:44
Forecaster: TUSCHY

A level 1 was added for NE Italy, N Slovenia and SE Austria mainly for isolated hail, strong to severe gusts and heavy rain.

A level 1 was added for parts of CNTRL Italy mainly for isolated hail, strong to severe gusts and heavy rain.

A level 1 was added for parts of the Ukraine mainly for isolated hail, strong gusts and heavy rain. A low-end tornado risk is possible.

SYNOPSIS

A building ridge from the Bay of Biscay towards the Norwegian Sea shunts of the westerlies and takes us back into a more blocked regime over W-CNTRl Europe. Numerous smaller waves/upper lows affect E-Europe in a relaxed mid-level flow regime.

A partially occluded cold front crosses Germany SE into Poland and approaches also the Alps during the end of the forecast. No other major frontal boundary is anticipated for this forecast period.

DISCUSSION

... Lightning areas including the level 1 areas ...

The prefrontal airmass ahead of the slowly E/SE ward sliding cold front features 500-1000 J/kg MLCAPE with mainly sub-10 m/s DLS over Poland. Hence pulsating sub-severe convection is forecast. An isolated (marginal) severe event is possible but driven by the orography/mesoscale.

We upgraded parts of NE Italy to Slovenia to SE Austria due to a better shear/CAPE overlap. 1000 J/kg MUCAPE support strong updrafts, which can organize in 15 m/s DLS. A few hail and strong to isolated severe wind gust events are possible next to isolated heavy rain. This activity weakens while moving deeper into Slovenia/Croatia.

Another level 1 upgrade was performed along the Apennines, where 1000-2000 J/kg MUCAPE overlap with 10-15 m/s DLS. Numerous passing weak waves from the NW induce temporal mid-level cooling/warming and NWP guidance is a bit divergent regarding the exact timing of those waves. If mid-level cooling and maximized diurnal heating overlap constructively we could see scattered CI with otherwise more reserved DMC activity. Any storm however could produce hail, strong gusts and heavy rain so opted to upgrade the orography for now.

Over the E-Ukraine, a moist inflow from the Black Sea pushes MLCAPE in the 1000 J/kg range in a 10-15 m/s DLS environment, so a few better organized storms with hail, heavy rain and gusty winds are forecast. Further NE better LL shear also adds a low-end tornado risk.

Elsewhere, meager CAPE/shear space precludes any level upgrade for now. A few waterspouts are possible over the Gulf of Bothnia/Finland and Lake Ladoga, where LLCAPE is somewhat enhanced.