If I'm reading it right, it's coming from the fabric at the top of the windshield (in addition to lower down)? I'd be suspecting a leak at the cab to cabover junction or in the cabover itself (corners, clearance lights, windows).
Jim, "Mo' coffee!"
'06 Tiger CX 'C Minus' on a Silverado 2500HD 4x4, 8.1 & Allison (aka 'Loafer's Glory')