Storm Forecast
Valid: Tue 08 Jul 2025 06:00 to Wed 09 Jul 2025 06:00 UTC
Issued: Mon 07 Jul 2025 17:30
Forecaster: TUSCHY

A level 2 was issued for parts of E-Croatia/N Serbia into SE Poland/W Ukraine mainly for severe to damaging gusts, large hail and heavy rain.

A level 2 was issued for parts of NE Belarus into NW Russia for severe gusts, large hail and heavy rain.

A level 2 was issued for parts of the Adriatic Sea mainly for severe gusts.

A level 1 surrounds all level 2 areas for similar hazards but with lowered probabilities. In addition we see a regionally augmented tornado threat (see text).

A level 1 was issued for parts of E France mainly for an isolated tornado risk next to strong to isolated severe gusts.

SYNOPSIS

An unseasonable low geopotential height field covers most of CNTRL Europe in response to a broad trough, which starts a cut-off process while drifting towards E-CNTRL Europe. IFS-ENS agrees in the evolution of a broad/diffuse LL vortex somewhere over Slovakia/Hungary, which lifts towards E Poland/W Belarus during the overnight hours. Ongoing strong member spread with kind of bifurcating solutions point to ongoing uncertainties regarding where and when this vortex evolves and intensifies. Today's convective activity probably also adds to those uncertainties as vigorous convection should induce adjustments to the positive PV tower of the mid-level wave, which gets reflected by latest NWP corrections towards a more amplified solution. The diggig jet configuration places the strongest mid/upper jet from France towards CNTRL Mediterranean, whereas some softening of the wind field is forecast over E-CNTRL Europe. Still enough CAPE shear overlap exists for an organized DMC risk over a broad area.

The evolving depression over E-CNTRL Europe causes structuring synoptic-scale fronts, which frame an unstable warm sector. This sector covers most of SE Europe into far NW Russia.

DISCUSSION

... Slovenia, Croatia, Bosnia and Herzegovina to Hungary and Slovakia, N-Serbia and parts of Romania into W Ukraine and parts of Poland ...

The structuring depression and attendant cold front serve as main foci for scattered to widespread CI from SW to NE.

First thunderstorms most likely continue from the previous night and some uncertainties exist if parts of Slovenia and W Croatia still see thunderstorm activity during the start of the forecast. The activity over Slovenia into W Croatia probably starts more elevated but rapid BL mass modification is forecast and near surface based activity is likely before noon, as a growing MCS shifts E/NE. Heavy rain and isolated large hail will be the main issue, before the gust risk increases rapidly as BL becomes more unstable.

Thereafter the MCS shifts E into a very favorable CAPE/shear space with 1000 to 2000 J/kg MUCAPE, 20 m/s DLS and 15 to 20 m/s 0-3 km shear. Combined with diurnal BL destabilization, we expect the MCS to turn severe rapidly with scattered to widespread severe gusts forecast due to a deepening mixed BL, especially towards N Serbia and into W Romania. Large hail and heavy rain also accompanies this line.

Beside the MCS event, healthy background QG lift along the path of the NE ward lifting mid-level wave and ahead of the intensifying cold front all point to the chance of a few discrete cells ahead of the MCS, which most likely affect E Hungrary into far NW Romania with large hail, severe gusts and heavy rain. The MCS probably snares the discrete activity betimes, as it enters the W Ukraine during late afternoon into the evening. There NWP guidance indicates an increasing cap issue depending on how fast this convection appraoches this area. We expanded the level 2 into parts of the W Ukraine to account for a more progressive MCS event than currently forecast given the dynamic background environment.

The tornado risk seems to be hampered by rather high LCLs but nevertheless an isolated event cannot be ruled out, especially from N Serbia into E Hungary, where BL moisture peaks.

During the night, a large convective clusters moves into Belarus and causes some flooding issues due to healthy rainfall amounts. Some small hail is not ruled out with stronger cores.

A local level 3 upgrade over far SE Hungary into NW Romania was considered, but the lingering uncertainties of the exact path of any long-lived severe bow echo event (embedded in this extensive MCS) remain too large to pinpoint any area of most extreme gust potential. However we expect rather widespread coverage of severe gust reports in this level 2. In addition, we expanded the level areas well into Romania to account for cold pool driven activity with a gust risk to affect areas far E.

Next to the DMC event, a starting heavy rain event unfolds over parts of CNTRL/E Poland into far E Czechia and N Slovakia, where 12 h rainfall amounts of 50-100 l/qm occur. Next to flash flooding, the general flood threat increases with the extensive coverage of healthy amounts. An intensifying deformation band along the evolving vortex has plenty of MUCAPE inflow for an ongoing thunderstorm risk in the otherwise more stratiform rain event (especially along the E fringe of the deformation band). Mentioned issues with the placement of the depression and probably only regional thunderstorm activity preclude an upgrade for now so we just issued a broad level 1 area.

...E Belarus into NW Russia ...

Another corridor with a favorable CAPE shear space exists ahead of an eastbound surging cold front, which turns quasi-stationary betimes in the highlighted area, before moving back N/NW as a warm front.

The warm sector offers 1000-2000 J/kg MUCAPE with 20 m/s DLS and 15 m/s 0-3 km shear, which increases to values in excess of 20 m/s along the frontal zone (into NW Russia).

Beyond noon, scattered thunderstorms initiate along the front with a mix of line elements and semi-discrete convection. Large to very large hail (probably up to 5 to 8 cm in diameter) and swaths of severe/damaging gusts are forecast. This activity weakens beyond sunset as strongest shear exits to the N and BL stabilization induces a gradual decline of MUCAPE.


... N Adriatic Sea and surrounding areas ...

With the approach of another strong mid-level wave, an uptick in convection is forecast during the evening hours. A growing nocturnal cluster of organized multicells and a few supercells is forecast with severe gusts, some hail and heavy rain. In addition, lowered LCLs induce a nocturnal mesocyclonic tornado threat. We added a confined level 2 for a rather widespread nocturnal offshore/coastal wind event.

... E-France ...

A marginal level 1 for the noon/afternoon was added as lines of strong thunderstorms push SE. Strong DLS is present and we could see some shallow rotating updrafts with an isolated tornado and gust risk. Small hail is also forecast. This activity weakens until sunset.