Storm Forecast
Valid: Tue 30 Jun 2026 06:00 to Wed 01 Jul 2026 06:00 UTC
Issued: Mon 29 Jun 2026 12:59
Forecaster: TUSCHY
A level 1 was issued for parts of CNTRL Europe mainly for heavy to excessive rain, hail (isolated large) and a regionally augmented gust risk. An isolated tornado risk could evolve over NW and E-CNTRL Germany.
A level 1 was issued for the W Balkans, Italy and N Algeria/Tunisia mainly for a local heavy to excessive rain, large hail and severe gust risk.
SYNOPSIS
As the blocking ridge over E Europe weakens, a trough approaches CNTRL Europe from the NW. And attendant cold front gets pushed E but on a slow rate. A lingering cut-off over Greece lifts slowly N ahead of rising geopotential heights over SW Europe.
DISCUSSION
... Italy ...
An ongoing marine heatwave with SST anomalies in the +5 to +7k range and no real airmass modification during the past few days/weeks caused an offshore plume with very high/deep BL moisture as BL mixing ratios regionally soar into the 16 g/kg range. Long lasting subsidence caused a broad area with steepened mid-level lapse rates, although a warm low tropospheric layer keeps the cap alive during the day. Main area of concern for CI remains the interface of onshore moving sea breeze fronts with the local orography. MUCAPE in excess of 3000 J/kg but very weak shear support numerous intense updrafts with bursts of very heavy rain, isolated (even large) hail and strong to severe downburst gusts (on a very local scale). Hence a level 1 was added for the mainland but also for Corse/Sardegna. CI will be from noon onwards and convection weakens beyond sunset.
... Parts of N Algeria into Tunisia ...
A very similar setup compared to the Italian one is forecast, which is described above. Numerous intense pulsating thunderstorms bring a local flash flood, large hail and severe gust risk as MUCAPE up to 3000 J/kg overlaps with 5 m/s DLS or less.
... Alps to Germany, Czechia into Poland and E towards Romania ...
Finally some marginal better defined dynamics come into play as a broad mid-level wave over NW Europe shifts E and approaches Benelux/NW Germany until 06Z. In addition, a residual weak wave/positive IPV maximum over S Germany gets steered NE ahead of the approaching trough and serves as lead impulse, which crosses Czechia NE during the day.
Finally, a cold front gets pushed east during the day but with applied brakes (e.g. approaching S and E Germany during the overnight hours into Wednesday). In addition, an upper speed maxmimum over Scandinavia places its divergent right entrance region towards Germany during the overnight hours, improving chances for larger thunderstorm clusters.
The airmass over S Germany/Czechia and along the Alps features very high PWATs in the 40 mm range with some regional drying at mid-levels noted on a regional scale (which could induce enhanced downdraft speed). This moisture pushes MUCAPE in the 1000-2500 J/kg range with peak values along the Alps and further NE towards Czechia. DLS is in the 10 m/s range for most places but increases locally to peaks in the 15 m/s range f.ex. from SW Germany towards SW Poland.
Fist expect scattered CI along the orography along the Alps beyond noon. Deep moisture and slow storm motion induce a heavy to local excessive rainfall risk with isolated flash flooding not ruled out. This is also valid for firing convection over SW into E-CNTRL and far SE Germany and Czechia. Isolated hail is not ruled out and storm dynamics could even offer a large hail risk on a spotty scale.
Better DCAPE/BL mixing over NE/E Austria support growing cold pools and a northward pushing MCS could bring strong to severe gusts from NE Austria into S Czechia. A level 2 upgrade was anticipated mainly for clustered reports, but confidence in the exact track of any MCS (and attendant RIJ path) remains too diffuse for upgrading that far out. Swaths of strong to severe gusts spread deep into CNTRL/E Czechia thereafter. Hail (isolated large) and heavy rain will be another issue. We could also see a progressive MCS event along the periphery of the lifting lead impulse and this MCS could cross Czechia NE into Poland with swaths of severe gusts, hail and heavy rain. This would also be a cold pool driven event with not much background support (e.g. stronger winds within the H7 layer for RIJ enhancement) so a level 2 upgrade was not yet performed. We cannot rule out confined swaths of gusts in the level 2 range however.
During the evening onwards, improved forcing from the W beneath divergent upper levels increases the odds for numerous large clusters to evolve over S/CNTRL into E Germany. Heavy to locally extreme rainfall amounts are forecast as this convection tracks east, attached to a very moist/unstable inflow from the SW.
Please be aware of the following lingering issues:
a) There are some hints in EPS data for better defined cold pools, especially with some mid-level drying forecast. This would induce a more foreward propagating MCS event with a temporal gust risk, before CIN increases during the night. Don't see this risk too enhanced for now with deep moisture in place, but this needs to be monitored in nowcasting.
b) We could see an evolving severe risk for organized DMC activity over CNTRL Germany from late afternoon onwards as the unstable moisture plume interacts with improving kinematics from the W. Forecast soundings from ID2/ID05 reveal some nice hodographs and UH tracks with an increase in coverage and intensity. This scenario becomes more likely and could switch into a confined severe thunderstorm event, including a few supercells mainly for CNTRL into E-CNTRL Germany. Updraft dynamics could cause extreme rainfall rates with those storms next to some gusts and hail. In addition, an isolated tornado event is possible but depends heavily on exact timing of activity and thermal BL stratification.
Due to ongoing uncertainties with timing, coverage and placement of any organized DMC activity we did not upgrade to a level 2. In addition, even with organized convection, long/thin CAPE profiles could limit hail size and a more stable BL could lower the gust risk with rain the main hazard for now. This event needs to be monitored closely in nowcast.
... S Poland to Romania ...
We expanded the level 1 to cover numerous intense pulsating thunderstorms along the orography, which see ample of MUCAPE up to 3000 J/kg but very weak shear. Large hail, heavy rain and severe gusts on a local scale are possible. Small cold pool driven clusters are certainly possible with confined swaths of severe (wind/hail) and therefore we broadened the level 1.
... NW Germany into the Netherlands...
Thunderstorms over NW Germany need to be monitored closely during the afternoon into the evening hours for some rotation probabilities including a tornado risk. Kinematics improve and support rotating updrafts with the most striking signature being abundant 0-3 km CAPE build-up. Hence very robust low/mid-level updrafts could cause a few non-mesocyclonic tornado events next to some hail. Main caveat remains a regional drying trend in the CAPE layer, which could lower ECAPE magnitude. Still a level 1 was added and expanded into NE Netherlands, which could also reside in this stratification.
... W-Balkans ...
High based convection along the orogrpahy poses a risk of damaging gusts and isolated hail, which prompted the issuance of a level 1 area.
