Key Takeaways:
- Rainfall is expected to intensify from Sept. 25–27, with heavy to very heavy rain forecast in several provinces
- Gandaki and Lumbini face the highest risk, with extremely heavy rainfall possible at isolated locations
- The system could trigger floods, landslides, soil erosion and rising river levels, affecting transport and livelihoods
- The high Himalaya may receive heavy snowfall, prompting caution for climbers and mountain travelers
A developing weather system over the Bay of Bengal is expected to strengthen in the coming days and bring increasingly heavy rainfall to Nepal, with the most intense spell forecast between September 25 and 27, according to the Department of Hydrology and Meteorology.
The department said a low-pressure area over the central-western Bay of Bengal is likely to intensify into a deep depression and move west-northwestwards. The system is currently influencing Nepal's weather along with the ongoing monsoon and a partial influence of westerly winds.
Meteorologists have forecast heavy to very heavy rainfall in many areas of Gandaki and Lumbini provinces, with the possibility of extremely heavy rainfall at one or two locations. Heavy rain accompanied by thunderstorms and gusty winds is also expected across parts of Koshi, Madhesh, Bagmati and Sudurpashchim provinces, while some areas of Karnali Province could also receive intense rainfall.
The department warned that the weather system may increase the risk of floods, landslides, soil erosion and debris flows. Rising water levels in rivers and streams could affect low-lying settlements and urban areas, while transport, aviation, agriculture, tourism and construction activities may also face disruptions.
In the high Himalayan region, heavy snowfall is possible, prompting authorities to advise caution for climbers, trekkers and others travelling in high-altitude areas.
For Tuesday, generally cloudy conditions are expected in the Himalayan and hilly regions, while the Terai is forecast to remain partly cloudy. Moderate rain or snowfall accompanied by thunder and lightning is likely in parts of Koshi, Bagmati and Gandaki provinces, with heavy rainfall possible at one or two places in the hilly areas of Koshi, Bagmati, Gandaki and Lumbini.
Kathmandu is expected to record a maximum temperature of 28–30°C with a 60 percent chance of rain during the day. The capital may receive moderate rain and thunderstorms at night, with temperatures falling to 18–20°C.
The weather department said it is continuing to monitor the Bay of Bengal system and will issue additional alerts and updates as the situation develops.