An in-line fluid phase process for blending low crystallinity polymer components (LCPCs) and high crystallinity polymer components (HCPCs) to form pellet-stable polyolefin pellets is provided. The in-line process for producing the blend includes providing two or more parallel reactor trains and one or more separators for product blending and product-feed separation; wherein the two or more reactor trains producting the LCPC and HCPC blend components operate under fluid phase bulk homogeneous conditions, and at least one of the reactor trains operates under supercritical conditions. The HCPC blend component is a high crystallinity polypropylene-based polymer. The LCPC blend component is a low crystallinity ethylene-based or propylene-based polymer. The resultant blend pellets exhibit a reduced tendency or an eliminated tendency to agglomerate during shipping, handling and storage.