Will it? Won't it? Nowcasting snow risk Monday and Tuesday

[Laurence Hill]

 Mcconnor8 Love it, many thanks.

[chapmanslade]

 Midlands Ice Age Dew Point Calculator 

Dew Point Calculator

WWW.DPCALC.ORG

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Dew Point Calculator is a web resource created by the Image Permanence Institute to help express and visualize the relationship between temperature, relative humidity and dew point.

 

Looks spot on to me

[Notty]

The LP out west is changing shape:

https://www.xcweather.co.uk/m/GB/Map/Pressure

[Severe Siberian icy blast]

 Notty that split already and the one behind looks more organised

[Mcconnor8]

 Severe Siberian icy blast Looks like we are honing in on the Arpege/Arome/Harmonie/ECM solution, very poor from the UKV as it still doesn't show that even now!

[HarvSlugger]

Ukv is awful just compare it to the radar right now, not even close! I've always said ukv underestimates precipitation no matter the time of year...

[Battleground Snow]

 Mcconnor8

I'm not sure why they didn't put a warning further south, surely it's better to not need it rather than not warn people travelling.

No doubt they will throw one overnight when No1 will see it

[Mcconnor8]

GFS moves to ECM with low further South and split.

[feb1991blizzard]

At 1300 it was 5c dew point 3c according to bbc weather

[sheikhy]

Gfs 12z picks up the slightly more elongated low for tonight!!!

[Mcconnor8]

GFS now showing the precip across the Midlands tomorrow morning that the UKV refuses to acknowledge.

[Midlands Ice Age]

45 minutes ago, danm said:

That cannot be correct surely. 

 

Danm ..

 I didn't believe it was correct either when i wrote it as my DP's are always below other peoples around here.

That is why I said that both TurnedOutNice and my dewpoints were incorrect....

However as is reported above in the article referred to by chapmanslade above..

I have checked it out and it looks OK..

Simple approximation

[edit] |(from GOOGLE...)

There is also a very simple approximation that allows conversion between the dew point, temperature, and relative humidity. This approach is accurate to within about ±1 °C as long as the relative humidity is above 50%:

Td≈T−(100−RH)/5;

RH≈100−5(T−Td);

So in my calculation T is 5.1c and Rel humidity is 53 and you get around -4C as the DP

also supported  by this graph (which doesn't get below zero). 

 

I realise that it gets less accurate below 50%

So what to make of it?.

MIA

[Harsh Climate]

 Mcconnor8

Has rain on the back edge  Strange chart from the GFS that

[Dennis]

2 rounds possible tuesday

 

[Mapantz]

 Midlands Ice Age

I suspect your RH sensor is broken MIA.

I had a look around your area at various PWS's, and they're all around 80% - 90%

When relative humidity sensors are crocked, they usually read much lower.

[CoventryWeather]

The lows elongating and splitting slowly now. Current pressure chart.

[Mcconnor8]

 Harsh Climate Think it's because the precip isn't heavy enough to create enough evaporative cooling to turn it to snow? 

GFS 12z showing snow across the South tomorrow afternoon, doubt it would settle though.

[Harsh Climate]

Doesn't matter what the gfs is showing regarding precipitation tonight. The radar is all that matters now. 

Heavy precipitation way further north than originally predicted, I think as far north as Harrogate could do well tonight now

 

 Mcconnor8  Nah I just think it's a dud chart. The back edge of the system should have snow down to low levels as it clears

[Mcconnor8]

 Harsh Climate I think it means it will still be snow for the Midlands but the Northern extent is also greater, so just more snow overall.

[Lukesluckybunch]

2 minutes ago, Mcconnor8 said:

showing snow across the South tomorrow afternoon, doubt it would settle though.

Surely it would depend on the uppers like always,perhaps falling as snow but I doubt that the ground would be cold enough for any settling

[CoventryWeather]

 Harsh Climate correct, think it could be more widespread than first thought..

Next few hours are going to be interesting..

[Ali1977]

Certainly looking good to me

 

As is the Arôme - upgrades for central southern England 

Edited November 18 by Ali1977

[phil b]

Right in from work now let the fun begin.

Temp has dropped 0.5C to 3.9C while the Dew point has stayed the same at 2.7C as the humidity has risen with rain setting in.

[Mcconnor8]

Obviously not worth much but GFS snow depth 6z vs 12z.

[GokouD]

 Mcconnor8 If it comes in further north would it not cut off the cold air coming down, so it's not cold enough for the midlands? At least for the overnight precipitation, maybe on the back edge tomorrow would be better.