During periods of below freezing temperature, liquid water in the pack will refreeze thereby increasing the solid water content. The potential amount of refreeze during a given time interval is calculated using a temperature index method similar to snowmelt.

REFRZP = the amount of refreeze (mm);
KF = the refreeze factor which is usually set equal to KM.

The actual refreeze, REFRZ (mm) is set equal to either REFRZP or the current LWC, whichever is less. Then the water balance of the pack is updated as follows.

The snow pack dry density RHO is then updated.