Tropical Storm ''Leon'' slightly intensified over the Philippine Sea and Tropical Cyclone Wind Signal Number One may be hoisted over portions of the Cagayan Valley and the northeastern portion of Bicol Sunday night or Monday morning.

In its 5 pm bulletin, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) said Sunday ''Leon'' is expected to ''gradually intensify in the next 24 hours and may reach severe tropical storm category and typhoon category on Tuesday.''

''Leon'' was located 1,000 kilometers east of Central Luzon and moving west at 20 kilometers per hour.

Pagasa said ''depending how close 'Leon' will be during its north-northwestward movement over the Philippine Sea'', its outer rainbands may affect extreme northern Luzon.

It could also influence '' the southwesterly windflow initially triggered '' by ''Kristine'' which may affect Visayas, Mindanao and the western section of southern Luzon, added Pagasa. DMS