Super Cooled Jet Fuel

[KC2555]

Could someone please explain the following situation? My husband was on a Southwest flight that connected through Austin late last Friday afternoon (SW# 2137, AUS to BNA, scheduled departure 5:05 pm). Although the air temp was around 50 degrees F, the flight was delayed to be redirected for de-icing. The flight deck reported to the passengers that "super cooled jet fuel had been loaded in and had caused ice to form on the wings". I realize that jet fuel freezes at a lower temp than water.  However, I am wondering how jet fuel ends up being super cooled when the ambient air temp is far above freezing. Is there a specific pre-flight protocol that checks for ice on the wings regardless of ambient air temp? Is this done only if the fuel is known to be super cooled? Or did someone just happen to notice the ice formation? Hopefully, not the last choice. We fly a lot and I have just never heard of this situation before and am hoping someone can enlighten me. Thanks.

[JetScan1]

I am wondering how jet fuel ends up being super cooled when the ambient air temp is far above freezing.

I suspect what they meant was the fuel that was already onboard from the previous flight was cold soaked to below freezing (32F) while the aircraft was at cruise altitude where the temperature is typically between -50C and -60C.

[porterjet]

To follow up on Setscan's comment. If the incoming flight was at altitude for several hours the fuel would have slowly cooled towards the ambient temperature, -50 to -60. If it was fairly humid in Austin, combined with fuel that was still at, say -20, ice may have started forming on the wings hence the need to deice. Condensation on the bottom of the wings is fairly common when the airplane has been at high altitude for a while then descends into warm humid air on the ground. Where there is air in the tank's you don't get the condensation, it is only where there is fuel.