Conditional Loop, Values not adding to array

I am trying to read in a single value for WC(1). I would then like to use the initial value of WC(j) in a conditional loop. I get the first value of WC(j) to run smoothly (it meets the first condition in the loop), however, the first condition is supposed to establish the next value in the WC(j) array. However, it doesnt establish a value to the array it just says empty. Specifically in these lines: WC(j) = fc WCinit(j) = WC(j - 1)

When I step through the code, it will say fc=0.3 but WC(j) is empty even though I have set them equal to eachother. Since the WC(j) value is empty, it will only meet the 'else' condition of my loop.

It has the same problem with the next line of code, there is a value for WC(j-1) and it is set equal to WCinit(j), but WCinit(j) stays empty.

  Dim Month() As Double
  Dim WC() As Variant
  Dim WCinit() As Variant
  Dim NumMonth As Long, i As Long, j As Long

  Dim Precip() As Double
  Dim RefET() As Double
  Dim Runoff() As Double
  Dim Percolation() As Double

  Sub main()
    WaterBalanceReadMediterranean
    WaterBalanceMediterranean
    WaterBalanceReadPlains
    WaterBalancePlains
End Sub
Sub WaterBalanceReadMediterranean()
    NumMonth = 12

    ReDim Month(1 To NumMonth)
    ReDim WCinit(1 To NumMonth + 1)
    ReDim WC(1 To NumMonth + 1)
    ReDim Precip(1 To NumMonth)
    ReDim RefET(1 To NumMonth)
    ReDim Percolation(1 To NumMonth + 1)
    ReDim Runoff(1 To NumMonth + 1)

   For i = 1 To NumMonth

    Month(i) = Cells(4 + i, 1).Value
    Precip(i) = Cells(4 + i, 2).Value
    RefET(i) = Cells(4 + i, 3).Value
    Next i


For j = 1 To 1
      WC(j) = Cells(3 + j, 11).Value

     Next j

     Application.ScreenUpdating = True
  End Sub



Sub WaterBalanceMediterranean()

    Dim fc As Double
    fc = Cells(4, 7).Value
    NumMonth = 12
    i = 1
    j = 2

    Dim pwp,dz As Double

    Do
        If WC(j) >= pwp And (fc - WC(j - 1) + RefET(i)) < Precip(i) Then
            Runoff(i) = (Precip(i) - (fc - WC(j - 1) + RefET(i))) * 0.5
            Percolation(i) = (Precip(i) - (fc - WC(j - 1) + RefET(i))) * 0.5
            WC(j) = fc
            WCinit(j) = WC(j - 1)    
        ElseIf WC(j) >= pwp And (fc - WC(j - 1) + RefET(i)) > Precip(i) Then
            Runoff(i) = 0
            Percolation(i) = 0
            WC(j) = WC(j - 1) + Precip(i) - RefET(i)
            WCinit(j) = WC(j - 1)
        Else
            Runoff(i) = 0
            Percolation(i) = 0
            WC(j) = pwp
            WCinit(j) = WC(j - 1)
        End If
        j = j + 1
        i = i + 1
    Loop While j < 14


End Sub