A familiar story in some of the UK’s wetter and windier spells looks to play out over the coming days. A lobe of the tropospheric polar vortex dropping south over North America, likely due to a recent stratospheric wave reflection, is leading to exceptionally cold arctic air pressing down across central and eastern USA. This in turn creating a steep thermal gradient against warmer tropical air to the south, leading to a strong trans-Atlantic jet stream heading to Europe, albeit a southerly tracking one that heads into Spain and/or France, with the the UK on the cool but cyclonic side of the jet stream, with low pressure often close by.
Areas of low pressure look to continually spawn along the jet stream which will act as a conveyor bringing them towards the UK, from the west and southwest, but tending to stall near the UK as they come up against blocking high pressure that persists to the northeast over Scandinavia. The blocking high to the northeast did, for a time, look to bring much colder air across the UK from this weekend, but now it looks to only bring cold air to Scotland, where we could see a fair bit of snow over the hills in the coming days, with snow possible on higher ground of the northern Pennines too.
But for much of England and Wales, the main weather concern over the coming days will not be snow but rather much more rain falling on already saturated soil in the south and west in particular. Parts of southern and western UK, along with higher ground in the north, could see over 100mm between now and Friday.
Because areas of low pressure moving in from the Atlantic will be blocked in progress eastwards, they will instead swing north across the UK. This direction of track and quick succession of lows from low latitudes off a southerly tracking jet stream tends to be the antecedent to bring areas of heavy and persistent rain across the south and west of the UK, due to picking up more warmth and moisture than lows emanating from further north in latitude.
Models have increasingly been showing some large rainfall totals over the coming few weeks for southern England and Wales. Large parts of southern England (mostly south of the M4) and Wales have seen over 100mm so far this month, with a lot more to come. With the ground already saturated and river levels currently already running high, there is a growing risk of flooding as we head towards the start of February.
UK Met Office yellow rain warnings in force for N. Ireland, Wales and S England for early next week
Also for next week, as well as more rain on the way, we are keeping an eye on the tendency for some models to develop one or two deep lows that could affect southern UK with gales. GFS has shown a deepening low swinging in across the southwest Tuesday, bringing gales to southern and southwestern coastal areas and perhaps inland across the southwest. There is also potential for another deepening low for Thursday night too moving in from the southwest, but uncertainty over this for now.
So looking rather unsettled to see out January, with plenty more rain on the way and some hill snow in the north, particularly for the Scottish Highlands. But there is also a risk of strong winds too.
Sunday is looking cloudy for many in the morning across England and Wales, with showers in places, but these tending to fade into the afternoon, with many places becoming drier and brighter.
Monday looks mostly fine and bright or sunny for many, though showers in the northeast, while a band of rain and strengthening winds moving in across the southwest in the afternoon then looks to move north and east overnight, turning heavy and persistent from the south across England.
Heavy rain spreads north across the UK on Tuesday, turning to snow over higher ground in the north as it meets cold air moving in from the east from Scandinavia, drier and brighter conditions following, but with coastal showers. More wet and windy conditions may return across the south overnight, with coastal gales.
Further bands of rain spreading northeast at times for the rest of the week, sunny spells and showers for some in between these bands, windy at times too, with coastal gales possible. Further hill snow over Scotland possible, with colder air feeding in from the east here. Temperatures will generally be around average, but will feed cold in the wind.
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