Storm Forecast
Valid: Sun 31 Mar 2024 06:00 to Mon 01 Apr 2024 06:00 UTC
Issued: Sat 30 Mar 2024 23:03
Forecaster: PUCIK/KUZMENKO
A level 1 was issued across NE Spain mainly for tornadoes and severe wind gusts.
A level 1 was issued across S-central France to BENELUX and W Germany mainly for tornadoes and severe wind gusts.
A level 1 was issued for SW and central Germany mainly for large hail and severe wind gusts.
A level 1 was issued for the Alps mainly for heavy rainfall.
A level 1 was issued across N/NE Italy mainly for severe wind gusts, tornadoes and to the lesser degree for large hail.
A level 1 was issued across S Sweden mainly for large hail and heavy rainfall.
A level 1 was issued across Lithuania, Latvia, Estonia, N Belarus and W Russia mainly for large hail, severe wind gusts and tornadoes.
A level 1 was issued across Morocco mainly for severe wind gusts and tornadoes.
DISCUSSION
IMPORTANT: A dense dust situation is currently affecting large parts of Europe. The areas experiencing dust should count on reduced solar insolation and overall lower temperature maxima compared to the model forecasts. In such case, the models will overestimate CAPE and underestimate CIN.
... NE Spain ...
In conjunction with the passage of a sharp short-wave trough and a frontal wave, a window for isolated severe weather events will develop between 15 and 18 UTC. While CAPE will stay rather marginal, strong wind field and shear are forecast in the lower troposphere, enhancing the threat of tornadoes and severe wind gusts.
... central France to BENELUX and NW Germany ...
A pronounced left exit region of a jet will cross the area during the day. In conjunction, a trough in the lower troposphere will develop with an enhanced low-level wind field ahead of it. Isolated to scattered storms will initiate near the trough and spread N. Model soundings show limited CAPE with low LCLs. Hodographs show strong low-level shear with 0-1 km bulk shear exceeding 10 m/s and 0-500 m SRH locally exceeding 100 m2/s2. ICON-D2 ensemble simulates a number of swaths with high vorticity in the lower levels, suggestive of strong rotation and potential for tornadogenesis. Besides tornadoes, severe wind gusts may also occur.
... central Germany ...
While the synoptic influence will be the same here, the environment for the storms will be different, featuring steeper lapse rates and more abundant CAPE. Deep-layer shear will support both short linear segments and supercells; primary threats will be large hail and severe wind gusts. Storms will spread NE during the day and diminish in the evening.
... S/SE France, Liguria, Alps ...
A heavy rainfall episode is forecast across the area in two waves. The first wave will be connected to the short-wave crossing the area in the morning hours. The second wave will be connected to the second short-wave arriving in the late afternoon to overnight hours. While the majority of rainfall will be driven by the combination of strong synoptic-scale and orographic lift, forecast soundings suggest embedded convection may enhance rainfall rates and thus Lvl 1 is introduced. On Sunday morning, strong low-level shear may result in a tornado threat over S France.
... N/NE Italy ...
The arrival of the short-wave trough in the morning and strong cross-mountain flow is forecast to cause the development of a mesoscale low in the wake of the Apennines. According to the high-resolution models, isolated supercell(s) may form ahead of the low in an environment of strongly curved hodographs and 0-3 km bulk shear exceeding 20 m/s. Combining these with low-level shear above 10 m/s and 0-500 m SRH above 100 m2/s, tornadoes and severe wind gusts can be expected. While poor CAPE below -10 deg C may limit hail threat, it can't be ruled out with supercells. Strong low-level shear and high low-level CAPE are also forecast with the cells developing near and N/NE of Milan, suggesting tornado risk also there.
... Lithuania through Latvia, Estonia, N Belarus into W Russia ...
A rather rare setup, given the time of the year, is shaping up across the region. A warm front will cross the area during the day with advection of steep mid-tropospheric lapse rates and moister airmass in its wake. Dewpoints are forecast to reach or slightly exceed 10 deg C. While all models agree to this, such dewpoints are currently not found anywhere in the vicinity of the region. Thus, forecasters should closely monitor the dewpoint trends in the morning hours. In the model simulations, substantial CAPE for the time of the year will develop with MLCAPE values reaching 1000 J/kg.
Strongly curved hodographs with 0-6 and 0-3 km bulk shear exceeding 15 m/s and 0-3 km SRH exceeding locally 250 m2/s2 are simulated. Strong low-level shear is forecast as well, with 0-1 km bulk shear between 8 and 15 m/s with 0-500m SRH generally over 100 m2/s2. Low-level shear is forecast to increase further towards the night, but at the cost of storms likely being elevated with an inversion developing between 1 to 1.5 km AGL.
Well-organized storms, including supercells, can be expected in such an environment, posing a variety of hazards. Large hail is likely given much of CAPE below -10 deg C isotherm. Tornadoes will be possible with any surface-based supercell given the strong low-level shear. Severe wind gust threat will be enhanced by steep low-level lapse rates.
One uncertainty in the situation is the degree of CAPE due to the dewpoint values and the questionable dust situation. Another uncertainty is the lift and where or if the storms will form. Storms will be initiated either along a progressing warm front (which may yield some elevated storms in the morning already) or a weak, ill-defined cold front near the surface over the W part of the area. Furthermore, models agree on the initiation close or after sunset when the storms would be mostly elevated. With these uncertainties, a broad Lvl 1 is issued and no Lvl 2 is introduced. Particularly the southern half of Lvl 1 may not see storms at all. The most likely corridor of severe weather will be between NE Latvia, E Estonia, and W Russia.
... S Sweden ...
Moderate bulk shear, exceeding 15 m/s in the 0-6 km layer is forecast to combine with decent CAPE in and above the hail growth zone, suggesting a risk of large hail in the stronger updrafts. Storms will cross the region in two rounds. The first round will be associated with a warm front and storms will be elevated at this stage. The second round of storms will follow in the late afternoon hours from Denmark.
... Morocco...
Low-topped supercells and/or multicells will are expected since the morning hours. The low cloud bases and strong low level shear point towards possible formation of tornadoes, Hodographs will remain rather straight, which may limit the amount of streamwise vorticity in the inflow. Given 25 m/s of flow at 500 m AGL, severe wind gusts will likely be the main hazard.
