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With a post on its Facebook page, the Lombard Meteorological Center warns with a warning of heavy and abundant rains:
Dear weather lovers! As anticipated last week, we are about to witness a meteorological impact on Bel Paese. We comment on the general evolution and detail the first forecast notice, valid from the afternoon of Thursday 24.
As usual, the hope is that everything goes well, but the only way to improve things is to be vigilant and prepared. To be more explicit: be careful and don’t lie, it is a potentially dangerous situation.
An impressive North Atlantic disturbance, which in high latitudes has just been propelled by a pulse of cold air fished even from North Greenland, will make a majestic lunge in the Mediterranean meridian on Friday, September 25, 2020. And it will be a panorama satellite of great occasions.
As you can guess, given that the shy but long-tailed summer has just ended here, the thermo-hygrometric contrasts within this disturbance will be locally extreme.
After the current phase of fatigue of prodromal instability, calm (or almost) that will last about 24 hours, starting on Thursday afternoon a phase of strong instability will take shape, with scattered showers / storms and locally very intense storms, whose main, If not the only one, criticality is represented by the enormous amount of precipitation concentrated in a short time in restricted areas (therefore, risk of flooding in the plain and hydrogeological risk in the pre-Alpine foothills).
The attached map is an attempt to summarize the evolution and phenomenology from one area to another. Please do not take the subdivisions of the area literally, they are only indicative.
There are basically two areas that we think we need to pay special attention to.
The first, the one that raises the greatest concern for the aforementioned hydraulic / hydrogeological risk, is found in the sectors of the altiplano and western foothills (Novarese, Varesotto, Alto Milanesa, Brianza, Luganese, Lario and Orobie Bergamasche), where a persistent confluence Los vientos from the east in the lower strata could determine semi-stationary storm lines, with very significant accumulations (up to 150 mm in 6 hours). During the night the phenomena will gradually move towards the east, but with less stationarity characteristics (which, in these cases, is a salvation).
The second Lombard area to watch is that adjacent to Emilia, between the upper Oltrepò Pavese and the low plains of Lodigiano, Cremonese and especially Mantovano. In these sectors, isolated strong thunderstorms could be unleashed in the middle of the afternoon (in “flight” towards Bresciano-Gardesano), so in the middle of the night the entry of a massive storm line rising from the Ligurian di Levante (Lunigiana and Versilia below check).
The general situation will only be mitigated in the middle of the night of Friday 25, to then make room for a window of precipitating temporary calm. However, already in the early hours of Friday afternoon, the strong instability in the region will reactivate again, with scattered showers and storms, forming hail locally (unlike on Thursday when the risk of hail seems very low or almost nil) . Also on Friday afternoon, the influx of abundant cold air high up from the northwest is likely to push the snow in the eastern Rhaetic Mountains to mid-altitudes (around 1500 m). However, we will detail this second phase in a later notice.
Later, for the night of Saturday 26, the peremptory rotation of the currents of the northern quadrants will determine the depletion of precipitation from the western sectors, with progressive transfer of very fresh air (and relatively drier, with gusting ventilation) in the store. Po Valley.
The weekend will pass under variable skies, mostly dry, with sun interrupted by scattered clouds, in a thermohygrometric context … subverted from the standard we have been used to for months. Temperatures at sunrise, especially as of Monday 28 (around 8-10 ° C at the bottom of the valley), will require heavy clothing, while in the central hours of the day the possible availability of sun will push (with difficulty) the thermometer around 18-19. ° C. In the high mountains it will be very cold.
For those planning an outdoor wedding reception for this weekend, we recommend adapting the dress to the context.
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