The Met Office says there is a 60% chance of disruption due to snow in Pembrokeshire on Friday and into Saturday.
A severe weather warning has been issued with accumulations of up to 5cm possible at lower levels.
Snow is forecast to blow into much of Wales by Friday afternoon.
Carmarthenshire and Ceredigion also have 60% chances of disruption.
The Met Office website said: "Disruption to transport and power networks is likely and the public are advised to take extra care".
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