Good Erev Shabbat:
Heavy rain is expected during the next couple of days.
Because temperatures should be unusually cool at 500 mb, and comparatively warm at lower levels, we can expect very strong storms, including thunder, lightning and hail.
The latest 4 km WRF forecast has the heaviest rains located over the central part of the country, including the Jerusalem mountains. There is the potential for flash floods in heavier storms.
Showers should arrive towards morning, and continue through the day. The potentially heavy rain should arrive Motzei Shabbat with the passage of the 500 mb trough (and its very cold air).