Storm Forecast
Valid: Mon 14 Jul 2025 06:00 to Tue 15 Jul 2025 06:00 UTC
Issued: Sun 13 Jul 2025 22:56
Forecaster: PISTOTNIK

A level 2 and level 1 are issued for parts of Russia, S Finland, south-central Sweden and south-central Norway mainly for excessive convective precipitation, and to a lesser degree for large hail and severe convective wind gusts.

A level 1 is issued for S Germany, Austria and NE Italy mainly for excessive convective precipitation, and to a lesser degree for large hail and severe convective wind gusts.

A level 1 is issued for parts of Poland, Lithuania and Belarus mainly for excessive convective precipitation, and to a lesser degree for large hail and severe convective wind gusts.

A level 1 is issued for far-south Sweden and parts of Denmark mainly for excessive convective precipitation.

A level 1 is issued for parts of Romania, Moldova and the W Ukraine mainly for severe convective wind gusts.

SYNOPSIS

A blocking anticyclone extends from Iceland to W Russia. South of it, a chain of low pressure systems stretches from the North Atlantic around 55N to the British Isles, the North Sea, the southern Baltic region and Belarus. The strongest and most baroclinic cyclone is placed just NW of Ireland, whereas the rest of the zonal low-pressure trough further east is rather shallow and largely barotropic. Most of W and central Europe are placed under a moderate westerly mid-level flow, which increases further west at the flank of the British cyclone, bringing unsettled and moderately warm conditions in a modified maritime polar airmass.
Anticyclonic, warm to hot weather prevails in the Mediterranean region, the Balkans, Turkiye and Russia, from where a stream of very warm air extends also far NW-ward into central Scandinavia.

DISCUSSION

... W Russia, Estonia, S Finland into south-central Sweden and south-central Norway ...

Plentiful daytime heating creates CAPE on the order of 500 to 1500 J/kg in the tongue of warm air that wraps from the SE around the forward side of the low-pressure channel. Locally higher CAPE is possible along convergence zones or in areas where vertical mixing is temporarily suppressed.
Isolated, partly elevated and non-severe storms may already be active in the morning or left over from the previous night. Widespread surface-based initiation is expected from noon onward, mostly triggered by the airmass / insolation gradient along the almost stationary cold front. Travelling vorticity maxima aloft, sea breeze fronts and outflow boundaries are other possible sites of initiation.
Due to a front-parallel motion from ESE to WNW and mostly weak vertical wind shear, excessive precipitation is clearly the main hazard, especially in case of training storms and several large, side- or backbuilding clusters that may emerge. In addition, large hail is possible in initiating stages and with more discrete storms that manage to propagate into the warmer air towards the north, and severe wind gusts at the leading edge of large clusters. Regionally speaking, the hail and wind hazards are relatively highest in Russia, where steeper lapse rates are present, but at least isolated events cannot be ruled out near the backward (southern) rim of the CAPE reservoir in south-central Sweden and Norway, which could partly overlap with enhanced vertical wind shear.
Convection will gradually weaken but not fully decay overnight, and especially the excessive rain hazard is still enhanced then.

... central Europe between Switzerland, Denmark, far-south Sweden, Lithuania and Hungary ...

The maritime airmass features low to moderate CAPE up to 1000 J/kg, based more on decent low-level moisture than on steep lapse rates. Scattered and mostly daytime-driven thunderstorms are expected especially ahead of two short-wave troughs that cross the N half of Poland and Belarus, and the S half of Germany, the Czech Republic and the Alpine region, respectively. Storm coverage will be lower in the subtle mid-level ridge between these two troughs, i.e. from N Germany towards Hungary.
Deep-layer shear below or around 10 m/s keeps thunderstorm organization low. Isolated to scattered excessive rain events appear likely, along with the odd large hail instance with storms intiating in pockets of higher CAPE, especially towards the Alpine region where vertical wind shear is a tad stronger. While the hail and wind hazards are limited by the moist airmass and poor lapse rates, it is worth mentioning that some convection-resolving models show the evolution of a cold-pool driven convective line from S Germany into Austria which would augment the wind hazard a bit. However, neither this scenario nor the primary hazard of excessive rain appear likely enough to upgrade this region to a level 2.
Low model consensus does not allow pointing to more details at the time of writing.

... N Italy into N Balkans ...

The southwestern one of the two short-wave troughs mentioned above only grazes the southern side of the Alps. More plentiful CAPE, probably exceeding 1000 J/kg, along with moderate vertical wind shear would allow some better organized storms, but the model pool largely agrees that the robust capping inversion will hold over the lowlands. Nonetheless, the level 1 is extended a bit southward in the Veneto and Friuli regions in case a few mountain storms can yet descend into the coastal plains along outflow boundaries in the evening. In that case, more concentrated swaths of large hail, severe wind gusts and excessive rain could occur. This convection might also affect Slovenia or even parts of Croatia and Serbia overnight, but limited CAPE in the drier airmass makes severe weather less likely.

... Romania, Moldova, W Ukraine ...

Isolated to scattered afternoon storms are expected to initiate over the Carpathian mountains in a hot and dry, deeply mixed airmass. The coverage of storms and their degree of propagation towards the east is somewhat unclear, as the dry air and a lack of synoptic lift support will make convective initiation and sustenance difficult. However, a level 1 seems to be warranted, since any of these storms could bring at least localized severe downbursts thanks to strong evaporative cooling.