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Weather guide Monday 12th to Sunday 18th January 2015

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TonyH

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[color=rgb(0,0,0)][font=Helvetica][b]Headline: Unsettled and often rather cold: wintry showers and longer spells of rain and (chiefly) hill snow; damaging gales late Wednesday into[/b][b] Thursday[/b][/font][/color]

[color=rgb(0,0,0)][font=Helvetica][b]Last weeks highlights[/b]

Fog persisted much of last Sunday over parts of the Midlands and by teatime Church Lawford had only managed 1.8c, in contrast Pembrokeshire was quite mild with Milford Haven at 9.2c maximum. After the quiet start plenty of mild, rather unsettled and windy weather in the past week. Orographic (hill forced rainfall) produced 66.6mm at Capel Curig on Wednesday although rainfall totals for the week away from Snowdonia were modest over West Wales and negligible across the Midlands. A very mild week overall with Friday was remarkably mild for January, highest reading being 16.1c at Pershore (some 9c above average) while most places reached above 13c. Long-standing records broken in places too, for example Coventry where the high of 14.5c on Friday pipped the 14.4c recorded in Janury 1944. Central Europe too experienced this remarkable Winter warmth, with 25c recorded in northern Italy and 22c in the Swiss Alps on Saturday! It was often windy from Thursday to Saturday but we were far enough south to escape the worst of the damaging winds experienced up north.

[b]The week ahead[/b]

A disturbed week to come as some deep lows cross the Atlantic bringing showers or longer spells of rain. Showers, wintry in nature at times too, as behind the frontal systems we will be in cold polar air-masses, and significant snowfall is likely over high ground above about 1000 feet, this perhaps coming down to lower ground too briefly from time to time especially later in the week, so a fair chance quite a few of us will have seen our first snow cover of Winter come next weekend albeit not sticking for long. Often windy this week, and there are strong indications of widespread damaging gales later Wednesday into Thursday.

Sunday afternoon is mostly dry, bright and breezy for the Midlands but is cloudier with some light showers for West Wales (WW) highs 7 to 9c, some places catching a passing shower, most likely Snowdonia. Wind picking up tonight as Atlantic fronts move in these bringing light rain to West Wales (WW) after midnight. A reasonably mild night but quite windy. Monday is then affected by a wriggling front across southern Britain which struggles to clear away SE. A mostly cloudy and windy day with rain at times, some heavy bursts, especially over South Wales and the South Midlands where the front slows down giving more prolonged rain afternoon into Monday evening. The rain should have cleared NW Wales and the NW Midlands by the end of the afternoon, with the winds easing too. Highs Monday a mild 9 to 11c. The rain eventually clears the South Midlands around midnight with some showers affecting WW by late night, and a local ground frost.

A showery westerly airstream for Tuesday, complications perhaps with a trough feature accentuating showers afternoon and this dragging in colder air which could turn the rain or showers wintry especially over high ground. Just the chance should the precipitation be heavy enough and winds light enough so that evaporative cooling takes place which would have the effect of bringing snow down to lower levels too during Tuesday afternoon, so one of those Winter days when a surprise snowfall cannot be ruled out for some areas, even giving a slight covering, but most likely this would be restricted to land above 200m. Maxima Tuesday 4 to 7c, but turning colder through the afternoon, and for the most part a rather windy day. A wintry mix of rain, sleet, hail and even snow showers keep going through the evening and night for WW but it becomes largely dry for the Midlands where there will be a widespread frost down to -2c in places, frost more patchy across WW but is likely inland where showers hold off.

Any remaining showers die out WW Wednesday morning, and for many it is a bright, dry and frosty start to the day with little sign of whats to come! The huge temperature contrast off the Eastern Seaboard of North America spawns a rapidly deepening low which is UK bound during Wednesday. This may be a very nasty low with the likely track taking it across Scotland during Wednesday night into Thursday. As the tightest isobars (pressure lines) and therefore strongest winds are nearly always found south of a low centre then England and Wales look like being pounded by gales, and potentially severe gales during Wednesday night, so for many areas damaging winds are likely between Wednesday evening and Thursday morning. Before that though most of Wednesday is dry bright and chilly, temperatures no higher than 4c away from WW coasts until evening, although set to rise further to 5 to 7c overnight. Winds though will strengthen through the afternoon as WW clouds over. Heavy rain and gale force winds then quickly move into WW early evening and onto the Midlands by midnight. The latest GFS model is showing a particularly nasty 950mbar low slowly crossing Northern Ireland Wednesday night with zones of severe gale force winds about its southern flanks. It could be that the gales ease later in the night only to pick up once more to severe gale during Thursday and worst affected would be Irish Sea coasts where gusts are likely to reach 80 to 90mph, even inland gusts would be over 60mph. At least the worst of the rain is gone by dawn Thursday!

Further showers or longer spells of rain during Thursday with hill snow, and winds could still be severe, although most models do indicate an easing of the gales during the day. A chilly day too Thursday, feeling cold given the windchill, highs 4 to 6c, but milder for Pembrokeshire at 8c. Winds may ease enough for a widespread frost on Thursday night. Friday and Saturday are controlled by low pressure to our north and NE so a rather cold NW flow to end the week bringing wintry showers. Maxima just 3 to 5c both of these days and so hill snow could well be building up above 1500 feet, even lower down some temporary accumulations of snow possible away from coasts, but a general kitchen sink mix of rain, sleet, hail, some snow and even a clap of thunder Friday and Saturday along with drier brighter intervals! Clear spells will permit widespread overnight frost and icy stretches as temperatures dip as low as -3c locally, more generally inland though -1c.

Next Sunday signs of a transient ridge giving a dry interlude ahead of wet and windy weather for Sunday night or Monday. This mix of weather looks like continuing through the rest of the month, although any prolonged cold snowy spell seems unlikely.[/font][/color]
[attachment=237810:PPVG89 windy rain times.png][attachment=237815:viewimage Mo lingering front rain.png][attachment=237811:PPVJ89 surprise snow chance feature TU.png][attachment=237812:ecmt850.072 wintry sh TU.png][attachment=237813:PPVL89 DL heavy rain gales later Wed.png][attachment=237814:ecmt850.096 gales heavy rain We night.png][attachment=237816:viewimage storm Th showery.png][attachment=237817:PPVO89 gales showery hill snow TH.png][attachment=237818:viewimage FR wintry showers r cold windy.png][attachment=237819:ecmt850.144 r cold wintry showers frosts FR SA.png][attachment=237820:ecmt850.168 wk R m dry Su.png][attachment=237821:viewimage chilly week mostly.png][attachment=237822:viewimage frequent rain spikes drying WEND.png][attachment=237823:mgram_Birmingham.png][attachment=237824:viewimage sub 980 TH R WEND.png]
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Thanks for a very interesting forecast ,always good to read your contribution ,lets hope we can get a good throw of the dice with any snowfall chances .

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