You run out of petrol?

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres

Shorts, Surely with 850s between -7 and -9 for two days in an ENE flow, nothing can go wrong?

Lack of moisture? I'll pre-empt the 'small scale features embedded in the flow', and it's a valid one, but also not one to pin your hopes on. So, in answer, plenty can go wrong and will for many, in terms of useful snowfall. Someone may well hit the jackpot. Fingers crossed. 

Indeed - it was all very tongue in cheek.

Actually, on the theme of GEFS entertainment, I thoroughly recommend a browse through the set tonight whilst you're chilling out on your hot chocolate. As amusing a set as I've seen all winter. On one member I think we get -14 uppers in.

For standard lake effect, temperatures are not the only factor. All of the following must be satisfied.

Temp Gradient: >13C with >15C preferable as in my lake effect potential charts.

Wind direction: Ocean upwind at 850 level.

Wind Speed: Moderate with low speed sheer. Light winds generate weak coastal activity, whereas strong winds may prevent good vertical motion.

High Inversion level: If the convection layer is too shallow the lake effect will not happen, check skewt diagrams to make sure.

Low directional sheer: Less than 30 degrees to 850 with under 15 degrees preferable.

Fetch: At least 50km with 80km preferable. 

Cold air advection: WAA inhibits convection, weak WAA can give activity, strong will definitely not. 

I reckon people usually only check the first two, and perhaps they don't even check properly at the 850 level. Its quite possible for the first two factors to be in place but all the others working strongly against.

Indeed, but the flow isn't very strong, so for snow inland you'll need the virtually unforcastable troughs etc

A great chart and it is 18 hours away.  Wet snow for many in the  far east and the west.  A somewhat reduced wishbone effect tomorrow due to low pressure and strong winds.  Good with altitude:

What could possibly go wrong

The GFS ens tell an uncertain story beyond day 5: Low confidence beyond Feb 4th

reload from the North maybe ??

Still to this day I am not 100% sure Matty. My thinking now is that although all the 850Hpa parameters were favourable the lower level from say 900hpa to surface level was pulling in a drier continental feed capping the shallow convection potential. The Met Office were indeed correct and all we got was occasional snow grains.

This time looks better. 

Now what does this tell us

NAVGEM and CMA both very good this morning. GEFS shows the same big split between continuing cold and milder from late next week.

http://www.wetterzentrale.de/pics/Rnvg1801.gif

0z ECM ensembles - there's a lessening of the cold into the weekend, but given the average February high in Reading is 8C it's still below normal.

He/She has no roof? 

I'm taking a short breather from in-depth model watching, but figure it's worth noting that the model output does seem to be edging towards the idea of dropping a new trough down into Europe in 7-8 days time, which is in line with my attempt on Thursday at foreseeing the direction of travel based on those background drivers (MJO, GWO etc.).

Not sure it's going to happen far west enough for us though - unless the momentum in the 4-7 day range is reduced, preferably in combination with better amplification in the western North Atlantic to help the mid-Atlantic high build north instead of toppling east. The NAVGEM 00z does a good job of showing this idea.

I'll be paying close attention to the model output for Tuesday-Wednesday once the weekend has passed. In the meantime all I have to chase is the potential for a dusting of snow tomorrow morning.

The 00z GEFS control run has enough amplification upstream to keep much of England in the freezer through to around 10th February.

Essentially, we're hoping that the models are flattening the high too fast - a classic situation with longer range charts.

That new trough diving down into Europe is being attempted by most output this morning. It needs watching closely. It would tie in nicely with those that based their February predictions of the cold pattern backing west with each attempt.

My CET prediction has been based on this not occuring but you really wouldn't rule out an easterly developing towards mid month.

Interesting times.

Op a warm outlier for Feb 7 a change is distinctly possible on the 12zs.

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS

THE CURRENT GENERAL SITUATION A cold Northerly flow will blow down across the UK over the next 48hrs with various showery troughs feeding South at times too.

MODELS-2 WEEK HEADLINE Remaining cold with some snow showers especially near northern coasts. Becoming dry and possibly less cold in the North later.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Forecast shows the deep trough in the flow across Europe currently remaining for another week or so before signs of the trough lifting out somewhat to a WNW to ESE flow just South of the UK later in the period.

GFS OPERATIONAL The GFS operational today shows cold weather hanging in across much of the UK, particularly the South as pressure builds towards and over the NW later next week tilting the winds towards the NE and replacing the current wintry showers in the North more towards the East and SE later next week. Frosts and dry bright weather will be endorsed elsewhere later next week. Then in week 2 the High over the NW finally sinks SE across the UK and on into Europe with milder SW winds for all then last to reach the SE.

THE GFS CONTROL  The GFS control run is even more dogged in maintaining cold in parts of the UK with the South never leaving cold through much of week 2 either as High pressure is held over the North and cold East winds blow for longer over the South with some wintry showers in places. the end of the run sees all areas more unsettled but certainly not warm as cold pockets of air remain close to or over the UK.

THE GFS CLUSTERS The GFS Clusters show a 760/40 split in High pressure ending up in a position to the NW or West of the UK in 15 days time with further cold weather in North or NE winds across the UK. The 40% takes up options around milder Westerly winds taking control with High pressure to the South and SE.

UKMO UKMO this morning continues to show cold weather across the UK next week as High pressure to the West of the UK edges in closer to the West and North early next week. Wintry showers look like becoming less prevalent away from the SE as winds fall lighter but with sharp frosts at night almost everywhere.

THE FAX CHARTS The Fax Charts continue to show a complex pressure pattern under cold and unstable North winds. There are various troughs featured moving South in the flow but this morning they are shown to be mostly away from land either to the West or East of the UK probably meaning a lot of dry, bright and cold weather away from windward coasts where sleet or snow showers continue likely.

GEM GEM today shows High pressure gradually taking control of the weather as we move through the latter part of next week as a ridge extends East from it across the UK sinking South later. So wintry showers early in the week should be replaced by largely dry, bright and cold weather with hard frosts for many before milder air reaches the North on strengthening Westerly winds later.

NAVGEM NAVGEM today keeps the Northerly feed going throughout the run this morning with further disturbances running South in the flow delivering enhanced wintry showers of sleet and snow at times chiefly but not exclusively over coastal areas in the West, North and East especially in the east towards the middle of next week as winds turn NE for a while.

ECM ECM this morning also shows another week of cold weather across the UK before a moderation in conditions under Atlantic WNW'lies develop by the end of the weekend. Last to see this change will be the SE where cold weather and a NE flow for a time may maintain a risk of wintry showers before the High pressure takes over and backs winds off to the WNW.

ECM 10 DAY MEAN The 10 Day Mean this morning indicates the likelihood of a large Winter anticyclone having dominance across the UK in 10 days time probably over the South with cold, bright weather with frosts at night. The North may see rather less cold Westerly winds at times later.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend continues to slowly grow for High pressure to replace the current cold Northerly flow later next week and beyond. The resting place of such a High is yet to be determined.

MY THOUGHTS The cold Northerly feed of air across the UK between Low pressure to the East and High to the West continues to prove stubborn to shift in this morning's output. All models show the flow maintained through at least the first half of next week tilting towards the NE midweek as High pressure makes it's move towards Northern Britain. This brings NE winds and the coldest weather to the South and East where wintry showers in the SE look likely while many other areas become dry, cold and frosty. Later in the week the general consensus seems to be to migrate the High pressure ridge further South and cut off the cold feed in the South too by then but still with sharp frosts at night. Then as we move into Week 2 things remain far from clear and if cold weather is displaced then it will remain close by to the East and as High pressure is likely to remain over the Atlantic further injections from the North seem quite likely at times so anyone looking for particularly mild conditions will be disappointed by that news. However, snowfall remains very hard to pin down in detail and for many will continue not to be an issue with little or none in shelter. Higher ground and in the East next week could see a shift in emphasis in snow distribution as winds veer NE for a time but the threat of anything for the SW of note seems to have receded from this morning's output. So in summary for many a typical cold wintry spell continues, nothing exceptional with a gradual lightening of winds next week and an increase in severity of frosts looking likely but with compensatory bright sunshine at times and given that it will be February from tomorrow sunshine at least looks stronger in the extending daylight hours.

Issued at 08:00 Saturday January 31st 2015

There is a right split , the control and operational going off in different directions

The more organised band of sleet and snow just diminishes as it pushes further south across the into Tuesday:

It doesn't like England or Wales!   - Notice how it just diminishes as it leaves Scotland and heads south of the border! Argh!! I told Cameron to give Scotland more powers.

So it's either now or never.

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php

Dutch ECM ens

Perhaps we should be looking  for another northerly rather than clinging onto the easterly which doesnt look like holding

Perhaps,but there is far more interest in the now and the very soon.  Tally's maps above show snow for millions in the SE for example.

Edit:

Tomorrow morning will bring a fair bit of snow to parts of the south east

As far as its worth looking (144) GFS 6z op  and we have -10 uppers and coastal convective precipitation modelled.