Backup File Names Truncating

I'm performing a full backup of a database, and the file name that I am creating for the backup is truncating. This keeps happening and can't figure out why.

I have a stored proc that I run:

CREATE PROC usp_Backup_old_srvra_to_srvrb

AS

DECLARE @DOW varchar(10),
@Filelocation varchar(50)


--Get Day of Week and set backup file name
SET @DOW = DATENAME(dw,GETDATE())
SET @FileLocation = 'SERVERAE$MSSQL7BACKUP'+ @DOW + '__old_BKUP_SRVR_0418_0800.bak'

BACKUP DATABASE TEST
TO DISK = @FileLocation
WITH INIT,
STATS
RETURN (0)


The backup file that was created ended up being:

THURSDAY__old_BKUP_SR

Any idea why it didn't pick up the whole file name that I wanted?