MetService has issued severe thunderstorm watches for parts of both islands on Boxing Day, with the upper North Island facing a risk of heavy downpours and the lower South Island bracing for large hail.
The forecaster said a cold, unstable airmass was affecting the South Island, with a risk of thunderstorms for Christchurch, Dunedin, Clutha, Canterbury Plains, Canterbury High Country, North Otago, Central Otago and Southland this afternoon and evening.
Those storms could become severe with hail larger than 20mm in diameter, which MetService said could cause significant damage to crops, orchards, vines, glasshouses and vehicles.
Meanwhile, a complex weather trough was expected to move across the upper North Island, bringing a risk of severe thunderstorms with heavy rain to Northland, Auckland, Coromandel Peninsula, the western Bay of Plenty and Rotorua from 2pm to 8pm.
Downpours could bring between 25mm and 40mm of rain per hour, the forecaster said, with conditions potentially causing surface or flash flooding, particularly in low-lying areas near streams and rivers.
A separate thunderstorm watch applies to the eastern Bay of Plenty and far north of Gisborne from 7pm to 11pm.
Heavy rain watches were also in place for Wellington until 3pm and the Tararua Range until 5pm. MetService said there was a moderate chance these could be upgraded to warnings.
A further heavy rain watch covers the Bay of Plenty east of Whakatane from 7pm Friday until 6am Saturday.
MetService was due to provide its next update by 2pm for the South Island thunderstorm watch and by 8pm for the North Island conditions.
Full warnings and watches as of 10am
Severe Thunderstorm Watch
Area: Christchurch, Canterbury Plains, Canterbury High Country, North Otago, Central Otago, Dunedin, Clutha, Southland
Period: 7hrs from 1pm - 8pm Fri, 26 Dec
Forecast: A cold unstable air-mass affects parts of the South Island today. For coastal Canterbury from the Banks Peninsula southwards, eastern Otago and Southland there is a moderate risk of thunderstorms. These storms may become Severe this afternoon and evening with hail, larger than 20mm.
Area: Northland, Auckland, Great Barrier Island, Coromandel Peninsula, Bay of Plenty, Rotorua
Period: 6hrs from 2pm - 8pm Fri, 26 Dec
Forecast: A complex trough embedded in a moist unstable air-mass is expected to move east across the upper North Island today. For Northland, Auckland, Coromandel Peninsula the western Bay of Plenty and Rotorua there is a moderate risk of thunderstorms with heavy rain associated with the trough this afternoon and evening. There is also a moderate risk of Severe thunderstorms with downpours bringing hourly rainfall amounts of 25 to 40 mm.
Area: Bay of Plenty, Gisborne
Period: 4hrs from 7pm - 11pm Fri, 26 Dec
Forecast: A complex trough embedded in a moist unstable air-mass is expected to move east across the upper North Island today. For the eastern Bay of Plenty and the far north of Gisborne there is a moderate risk of thunderstorms with heavy rain associated with the trough this evening and at night. There is also a moderate risk of Severe thunderstorms with downpours bringing hourly rainfall amounts of 25 to 40 mm.
Heavy Rain Watches
Area: Bay of Plenty east of Whakatane
Period: 11hrs from 7pm Fri, 26 Dec - 6am Sat, 27 Dec
Forecast: A period of heavy rain, with localised downpours and thunderstorms possible. Rainfall amounts may approach warning criteria, especially about the ranges. Moderate chance of upgrading to a Warning.
Area: Taranaki Maunga
Period: 9hrs from 10am - 7pm Fri, 26 Dec
Forecast: A period of heavy rain, with thunderstorms possible. Amounts may approach warning criteria. Low chance of upgrading to a Warning.
Area: Tararua Range
Period: 7hrs from 10am - 5pm Fri, 26 Dec
Forecast: A period of heavy rain, and amounts may approach warning criteria. Moderate chance of upgrading to a Warning.
Area: Wellington
Period: 6hrs from 9am - 3pm Fri, 26 Dec
Forecast: A period of heavy rain, and amounts may approach warning criteria. Rain easing from the south late morning and afternoon. Moderate chance of upgrading to a Warning.
SHARE ME