My green card expires in about 4 months and I applied for renewal but I have not received the new card yet. I need to travel outside the US for a family emergency. Can I still travel with the receipt notice

In many situations the receipt notice for the I-90 renewal extends the validity of the green card for a certain period of time. If your receipt notice specifically says your status is extended, airlines and border officers generally accept that along with the expired card. Before traveling, it is a good idea to confirm the extension period and carry a copy of the receipt notice and your expired card.