Message from the Met Office Advisor - Significant rainfall event Wednesday to Friday


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PLEASE SEE THE MESSAGE FROM TEH MET OFFICE - LOTS OF RAIN ABOUT

Unfortunately we are now entering that time of year when the most disruptive rainfall events across Cumbria & Lancashire have historically taken place. All these events have had one thing in common – a slow-moving weather front becoming anchored over or just N of Cumbria with copious supplies of very mild, moisture-laden air being pumped up across the Cumbrian Fells on a brisk SW’ly airflow, the topography then enhancing the rainfall via a combination of orographic enhancement and convergence of the airflow by the topography. The scenario is set to repeat itself throughout tomorrow and perhaps for a good part of Thursday and Friday as well although, as we head into Thursday and Friday, there is more uncertainty as to the exact orientation and position of the rain band.

General Weather Sequence:

The rain is set to arrive in Cumbria later tonight and basically then sits over much of the county throughout tomorrow and into tomorrow night. Some heavy pulses of rain are inevitable, especially across the southwestern two thirds of the county. Into tomorrow night and doubts begin to arise concerning developments which could result in the rain band being temporarily displaced northwards more into southern Scotland than across Cumbria. However, it should be noted that there remains the potential for further appreciable rainfall during Thursday with the offending weather front never too far away. By the time we reach Friday the more persistent rain should eventually start to clear to the east but we remain in a very unsettled phase of the weather with further rain/showers inevitable over the course of the weekend.

Tomorrow’s rain is likely to start impacting upon traffic across Cumbria from mid to late morning onwards and through the overnight period with appreciable standing water on the roads leading to localised disruption.

From a Lancashire standpoint, some of tomorrow’s rain will invariably spill across the Cumbria border into parts of N Lancashire with even one or two heavier interludes possible here, although amounts should in general be a good deal lower than in central Cumbria. However, with further rain here too during Thursday and Friday some impacts could start to show their hand over time.

Severe Weather Warning Status/Flood Risk:

Given the extended nature of the impending rainfall event but also the uncertainty regarding developments and the exact location of the rain area through Thursday and Friday, separate medium impact yellow rain warnings have been issued this morning, the first (an update from yesterday’s) covering just Wednesday with a second warning covering Thursday and Friday. Both are attached above. The Wednesday warning sees an increased likelihood of medium impacts from very low to low (medium impacts includes the likes of flooding of properties and sig travel disruption) whilst that for Thursday and Friday keeps the likelihood of medium impacts at very low due to ongoing uncertainty in amounts/distribution of rain. Both warnings have the potential to be escalated further, pending new forecast data over the next 24 to 36 hours.

This morning’s Flood Guidance Statement shows Cumbria on low flood risk (yellow) from tomorrow through Friday, the flood risk derived from both river and surface water contributions with the flood risk assessment aligning with the severe weather assessment in the Met Office warnings. For Lancashire the flood risk assessment is for a low likelihood of minor flooding impacts tomorrow (green), escalating across the NE’ern half of the county to a very low likelihood of significant impacts (yellow) by Thursday and Friday. Again this ties in with the Met Office warnings, the flood risk being a mixture of river and surface water contributions.

Beyond Friday and as already alluded to above, the unsettled spell of weather will continue over the weekend with further rain/showers and perhaps some more persistent rain later in the weekend. This rain looks to carry somewhat less disruptive potential than that during the Wed-Fri period but on the other hand winds could become more of a feature by then so still plenty to think about.


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