Snow maps show 18 counties buried in hours as 30cm blizzard hits in hours - full list

Britain is bracing for a sudden late-winter hit as new weather maps indicate 18 counties could be buried with up to 30cm of snow possible in some areas. High-resolution forecast charts show a deep low-pressure system sliding across the south of the UK overnight and into tomorrow (February 19).

As milder, moisture-laden Atlantic air rides over colder air already in place, rain is expected to rapidly turn to sleet and then heavy snow before the morning commute. The weather pattern is capable of producing very fast-settling snowfall, with short bursts of 2-4cm per hour likely in the heaviest band. Because temperatures will be near or below freezing when it arrives, snow is expected to stick quickly - even on untreated roads in towns and cities. Snow is forecast to develop during the early hours and spread west to east across Wales, the Midlands and northern England before reaching eastern England later in the morning.

The Met Office warning on its website states: "Whilst there is some uncertainty in the details, there is the potential for an area of rain and snow to affect parts of Wales, central England and into the southern Pennines during Wednesday evening and overnight into Thursday."

The most disruptive conditions are projected between around 3am and 9am, raising the risk of dangerous rush-hour travel as snow settles on untreated roads and visibility worsens.

Forecast charts show a sharp rain-snow boundary, meaning some places may see rain before temperatures fall quickly enough for it to turn to snow, creating a risk of a "flash freeze" as wet surfaces ice over. Temperatures close to freezing should allow snow to settle even at low levels.

Accumulation maps suggest 3-8cm widely, 5-10cm in some towns, and 15-30cm over higher ground across the Pennines, Peak District and north Wales. Strengthening easterly winds around the low-pressure system could also cause drifting and brief white-out conditions on exposed and rural routes.

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Forecast charts show the snow band tracking across Wales, the Midlands and northern England, with several counties at risk of accumulating snowfall within just a few hours.

North West & North

• Cumbria

• Lancashire

• North Yorkshire

• West Yorkshire

• South Yorkshire

• County Durham

• Northumberland

Midlands

• Derbyshire

• Nottinghamshire

• Staffordshire

• Leicestershire

Wales

• Gwynedd

• Powys

• Denbighshire

• Conwy

East of England

• Lincolnshire

• Norfolk

Forecast model charts indicate a wide range of totals depending on elevation. WXCharts accumulation maps suggest around 3-8cm could fall quite widely, with 5-10cm possible in some towns and cities.

Over higher ground - particularly the Pennines, Peak District and north Wales - the charts show the potential for 15-30cm in places, with drifting making it deeper locally.

The Met Office has issued related guidance in its weather warning, saying accumulations of 2-5cm are possible above around 150-200m, with 10- 15cm over higher routes, especially across parts of Wales and the southern Pennines.

Forecasters also warn strong easterly winds accompanying the system could lead to drifting snow and reduced visibility in exposed areas, increasing the likelihood of disruption even where totals are relatively modest at lower levels.

Because the snow band is narrow, neighbouring areas may see very different conditions, with some locations experiencing only sleet or rain while others wake up to several centimetres of lying snow.

Long-range forecast charts suggest the wintry conditions may not be the last of the cold weather. Later model projections into early March show colder air trying to push southwards from the north, with the strongest signals across Scotland and higher parts of northern England.

Some weather maps indicate a return to overnight frosts and the potential for further wintry showers, particularly over hills, although confidence is much lower at this range.

Meteorologists stress charts at this distance can change significantly and should be viewed as an early indication rather than a firm forecast.

At this stage the signals point more towards a stop-start start to spring, with milder interludes mixed with brief colder snaps rather than a prolonged freeze.