SQL Server 2012 :: Insert Rows Based On Number Of Distinct Values In Another Table

I have a table with PO#,Days_to_travel, and Days_warehouse fields. I take the distinct Days_in_warehouse values in the table and insert them into a temp table. I want a script that will insert all of the values in the Days_in_warehouse field from the temp table into the Days_in_warehouse_batch row in table 1 by PO# duplicating the PO records until all of the POs have a record per distinct value.

Example:

Temp table: (Contains only one field with all distinct values in table 1)

Days_in_warehouse
20
30
40

Table 1 :

PO# Days_to_travel Days_in_warehouse Days_in_warehouse_batch
1 10 20
2 5 30
3 7 40

Updated Table 1:

PO# Days_to_travel Days_in_warehouse Days_in_warehouse_batch
1 10 20 20
1 10 20 30
1 10 20 40
2 5 30 20
2 5 30 30
2 5 30 40
3 7 40 20
3 7 40 30
3 7 40 40

How can I update Table 1 to see desired results?