A second day of disruption is expected in mid and north Wales on Friday, following more heavy snowfall last night.
The Met Office upgraded its weather warning to orange on Thursday and it will run until 09:00 GMT.
A second yellow warning for snow and ice is in effect until 14:00 GMT when storm Larisa hits the UK.
Nearly 300 schools across Wales are closed on Thursday and more than 270 have confirmed they will close on Friday.
More than 60 homes in Merthyr Tyfdil were left without power on Friday morning, and the National Grid expects the problem to be fixed by 10:30 GMT.
Up to 30 cm (12 in) of snow is expected in some places, closing some major roads on Friday morning, including:
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The A55 westbound between Junctions 36A and 35 in Broughton, Flintshire
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The A542 Horseshoe Pass, Denbighshire in both directions between Llangollen and Pen-Y-Stryt
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The A543 in both directions at Pentrefoelas, Conwy
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The A4086 in both directions from Capel Curig, exit Caernarfon to The Royal Victoria Hotel, Llanberis, Gwynedd
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The A458 in both directions from Criggion Lane, Garreg Bank, to The Church, Middletown in north Powys
Traffic Wales has also warned of extremely difficult driving conditions on the A548 in both directions between Buttington and Middletown in Powys due to snow, while delays are also expected on the A55 and A470 in both directions.
Katie Wilby, from Flintshire council, told Radio Wales Breakfast: “The conditions are quite challenging. We’ve had gritter crews plowing and spreading all night. We’ve brought in extra vehicles.
“There was quite a bit of snow last night. We’ve seen 8 to 15 inches of snow in places, especially on high ground, but I think most parts of Flintshire saw snow this morning and will be waking up to snow.
“It’s coming down just as fast as we’re clearing it right now, so it’s really tricky.”
Ms Wilby added that the authority spread about 360 tonnes of road salt this morning and covered 2,360 kilometers by road in 36 hours.
She said some disruption should be expected, adding: “We are working very hard to keep the roads open, but I would advise people not to travel unless absolutely necessary.”
Helen Kynaston from the Newtown Community Cafe in Powys: “It snowed very early this morning.
“Yesterday was a big challenge and we only had a handful of customers, but our chief managed to get in. It took my neighbors and I about 45 minutes to dig [us] out.
“We made the bowling club really nice and warm and we had requests from our regulars who were really struggling, so we delivered to them, which we don’t normally do on a Thursday.”
Meanwhile, Tanat Valley Coaches’ Brian Dulson said the company has had to cancel its Powys services for a second day.
He said: “Still pretty heavy in the last few hours. Our local schools are closed.
“Everywhere the snow is really bad, so it’s annoying to turn off the buses, because when you get stuck in the snow, it’s annoying. We have small lanes and side roads, our routes are not just on the main roads. “