Issued at: 10:53 on Thursday 12 November 2015
Valid from: 15:00 on Saturday 14 November 2015
Valid to: 03:00 on Monday 16 November 2015
A frontal system is expected to become slow-moving across parts of northwest Wales, northwest England and southwest Scotland. Rain associated with this feature is expected to become heavy and persistent, especially over hills exposed to the strong westerly flow.
Flooding is possible either from standing water or from rivers which have remained high after the large rainfall totals seen in these areas over the last few days.
Chief Forecaster’s Assessment
A strong, moist westerly flow is expected to develop during Saturday and last through Sunday before clearing to the southeast on Monday. A frontal system aligned within this flow is expected to bring a period of heavy and persistent rain, this aided by tropical air being entrained into the system. Many parts of the warning area are likely to see 70-100 mm of rain, with some of the more exposed parts of north Wales and northwest England possibly seeing as much as 150-200 mm through the period. This amount of additional rainfall falling on to already saturated ground is likely to lead to flooding, either from standing water, or from rivers bursting their banks.
There is some uncertainty in the exact areas likely to be affected by the heaviest rain, perhaps more especially southwest Scotland. As such, this warning will be kept under review to hone areas most at risk of the heaviest rain, and to potentially escalate to an Amber, should significant impacts become more likely.