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Rainshadow

Come For The First Probable Snow Of The Season On Nov 12th, Stay For The Likely Record Breaking Barney II Cold On Nov 13th.

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Snow or not, the air mass behind the Monday/Tuesday cold frontal passage will be mighty cold.   Mind you normal high temperatures during this period are in the mid to upper 50s.  The normal low temperature for Philadelphia on November 13th is 40F.

These are the possible daily records that might fall at Philly.  November 13th looks like the best chance for a record at this point.  It is still about timing and how cold is cold, but the 12th and 14th as is probably not.

November 12th: record low temp of 26F (would have to be at 1159 pm based on current timing)

November 13th  record low temp of 24F, record low maximum temp 35F.

November 14th record low temp of 19F, record low maximum temp 35F.

The GFS has "warmed" the last couple of runs, but as an fyi, the earliest 32F or lower max temp day of the season is November 16, 1933.

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2 hours ago, Rainshadow said:

Snow or not, the air mass behind the Monday/Tuesday cold frontal passage will be mighty cold.   Mind you normal high temperatures during this period are in the mid to upper 50s.  The normal low temperature for Philadelphia on November 13th is 40F.

These are the possible daily records that might fall at Philly.  November 13th looks like the best chance for a record at this point.  It is still about timing and how cold is cold, but the 12th and 14th as is probably not.

November 12th: record low temp of 26F (would have to be at 1159 pm based on current timing)

November 13th  record low temp of 24F, record low maximum temp 35F.

November 14th record low temp of 19F, record low maximum temp 35F.

The GFS has "warmed" the last couple of runs, but as an fyi, the earliest 32F or lower max temp day of the season is November 16, 1933.

Here in Western Chesco - WXSIM has a high of 30.0 and a low of 23.0 on the 13th - of note earliest 32F or lower max temp day was November 11, 1987 at 30.0

Nov 12th record low high elevation is 24.0 (1995) and all-time 15.0 (1926) record low max 36.0 (1995) all-time

Nov 13th record low high elevation is 20.0 (1996) and all-time 17.0 (1920) record low max 37.0 (1995) and all-time 35.0 (1911)

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06 gfs with a flatter wave and a bit more back-end, an inch or so on the grass in the burbs perhaps. Euro has a few tenths.

CONUS2_GFS0P5_SFC_ACCUM-SNOW_90HR.gif

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No changes to Wednesday.  Models a little more bullish on rain changing to snow before ending on Tuesday.  Wouldn't hurt.  Since this air mass is so cold and the thermal trof is predicted to pass thru during the day on Wednesday.  Wednesday night temperatures in urban areas might just flatline after the evening.  They did this morning.

The Freeze Box Award for Wednesday still goes to the ICON be the coldest again. EC predicted high is 34F.

icon_T2m_neus_37.png.78d43e7f3bed654fd9bc2ba1d0b8a9b2.png

 

gem_T2m_neus_20.png

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EPS members with measurable occurring at PHL have been ranging between 25 to 30 lately.  06z OP GFS 500mb trof is closer to neutal tilt, other models remain more pos tilt.  Anyway looks like a race of which arrives first precipitation ending or enough cold air for it to snow.  This looks like the more northwest of the coastal plain one lives, the better the chances of not only seeing snow, but measuring.

ecmwf-ensemble-avg-ma-total_snow_10to1-3689600.png.d8dfd0dc108504c45511a31034375e59.png

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On 11/8/2019 at 1:09 PM, chescopawxman said:

Here in Western Chesco - WXSIM has a high of 30.0 and a low of 23.0 on the 13th - of note earliest 32F or lower max temp day was November 11, 1987 at 30.0

Nov 12th record low high elevation is 24.0 (1995) and all-time 15.0 (1926) record low max 36.0 (1995) all-time

Nov 13th record low high elevation is 20.0 (1996) and all-time 17.0 (1920) record low max 37.0 (1995) and all-time 35.0 (1911)

I remember the 1987 cold outbreak.   I was removing leaf springs on a Dodge pickup.   Surprised we hit 30 that day.   My recollection was mid 20s with a brutal wind chill.

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euro still showing some skiffs of snow for the nw burbs. Also, modelling starting to pick up on a little clipper system with some WAA later Thursday could add some more mode flakes. 

ecmwf-deterministic-ma-total_snow_10to1-3668000.png

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NAM & GFS snow maps look slightly better for city. Could the city break and inch? I gotta wonder how much can accumulate after rain in November

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45 minutes ago, Heisenberg said:

NAM & GFS snow maps look slightly better for city. Could the city break and inch? I gotta wonder how much can accumulate after rain in November

No, those maps are counting every flake as sticking which it won’t. I’d be shocked if the city records more than .2

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We drop 20° in 3 hours with enough energy trailing the front to keep precip going.  There's a 1-3 hour window, depending on location/elevation, where precip rates should make for a wintry scene on non-paved surfaces.  Given we flirt with 60° Monday, ground temps will be warm and roadways should overcome the short burst of snow, although the first snow often makes Philly drivers look like deep South drivers.  It's a late AM early PM snow and the sun will work its magic too.  Hopefully enough sticks around to enhance the enjoyment Wednesday of Barney II: Arctic Assassin, playing in theaters for 2 days only.

download (1).png

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2 hours ago, susqushawn said:

We drop 20° in 3 hours with enough energy trailing the front to keep precip going.  There's a 1-3 hour window, depending on location/elevation, where precip rates should make for a wintry scene on non-paved surfaces.  Given we flirt with 60° Monday, ground temps will be warm and roadways should overcome the short burst of snow, although the first snow often makes Philly drivers look like deep South drivers.  It's a late AM early PM snow and the sun will work its magic too.  Hopefully enough sticks around to enhance the enjoyment Wednesday of Barney II: Arctic Assassin, playing in theaters for 2 days only.

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Here is my first foot in the mouth moment of the season.  Models overpredict precipitation amounts with positive tilt flow. The last event out of 36 evaluated forecasts, 35 were too wet, one was perfect (GFS the "winner").  You are right the ground is going to be warm leading into this.  We are starting a period of 48 consecutive hours of above freezing temperatures and to think that every flake will stick, well we know better.  Now stepping this back halfway.  Yes the timing is not bad (well November sun angles stink anyway, but I guess every little bit hurts) north and west, even if the amounts are overdone, the intensity is not the worst and there is a predicted jet streak or correct entrance region quadrant with this one.  My thought would be this is going to be more than a 33% of predicted qpf event.  Plus you guyz north and west seem to manage stickage in spite of some hostile conditions.  So I think you N & W guys will measure, I think Philly and VAY are likely to measure, I am not sure closer to the coast.

gfs_uv250_us_12.png.dfee6062f6e27f67b410dd49fbde92a6.png

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No changes in any of the OP models about rain changing to snow before ending.   All of the SREF (oh you arw(s)) and GEFS members have measurable at PHL while the EPS has been pretty steady with 25 to 35 members (out of 51) showing measurable at PHL.  Wednesday remains the cold day.  I am not sure about the MOS guidance min temps for the suburbs on Wednesday morning.   We get into the schemes of model biases, like the GFS thinks the city of PHL extends out beyond the city limits for 30 miles in all sirections and the Euro doesn't know the city of PHL is there.  But at this point it looks like the wind will persist thru the night and that should lessen the differential between suburbs and city.  Now Mark DeLisi gave me the 15kt NAM BL rule for decoupling and we are at 14kt at 6z.  So Wednesday morning could be one of those mornings where locations which first decouple (Parsley's old house) will get in the teens while other places that don't (Paul) will struggle to get there.   The other random element is we get a snowier day on Wednesday and it makes it through any afternoon sun.  For VAY, I am going over. 

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BTW ICON is the coldest global model for predicted 2M temps. (NAM is about the same, a couple more teens out Paul's and LNS's way).

icon-all-pennsylvania-t2m_f-3635600.png.13d07dc9c439a9d49c2c541680b73f1b.png

 Now Wednesday night could be even colder for the suburbs as it will be a light wind night.  Right now models are predicting cloudiness to increase as the night progresses.  Here I would think MOS forecasts (only GFS at this point) have a shot at coming closer. 

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Models hanging on to weak 2nd wave.  Trade-off between temps (NW) and qpf (SE) for local "jackpot".

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I'd be shocked if anyone gets more than a half inch of snow out of this. This looks more and more like rain over to some festive flakes before ending. Any area that can get a burst of snow could get some minor accum

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1 hour ago, tombo82685 said:

I'd be shocked if anyone gets more than a half inch of snow out of this. This looks more and more like rain over to some festive flakes before ending. Any area that can get a burst of snow could get some minor accum

What?  No love for the ARW SREF members?  :rolleyes:

1111111.JPG.b8871ef50315d78440497274ccae0e2b.JPG

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60.7F for the high today and now looking at sloppy coating of snow. I love the fall!! 

More in line with this discussion, looks like we get a quick change over to "mood flakes" just for fun according to most of the models that I would believe, at least to a point...

 

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1 hour ago, tombo82685 said:

I'd be shocked if anyone gets more than a half inch of snow out of this. This looks more and more like rain over to some festive flakes before ending. Any area that can get a burst of snow could get some minor accum

 

Mood Flakes

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Modelling has really slashed qpf amounts over the last 12 hrs. Wonder if there really is a widespread changeover to some snow. Or do we just get a lucy pulls the football out

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On 11/9/2019 at 2:15 PM, iceman56 said:

I remember the 1987 cold outbreak.   I was removing leaf springs on a Dodge pickup.   Surprised we hit 30 that day.   My recollection was mid 20s with a brutal wind chill.

I believe you're thinking of 11/21/1987,  easily the coldest NOV day I've experienced in this area, midnight highs in the low 30's, arctic front blew thru around 6:00-7:00am with squalls that covered the ground,  in the northern burbs morning temps fell thru the 20's to the upper teens by early afternoon accompanied by winds gusting 40-45 mph.

11/11/1987 was the infamous Veterans Day surprise snowstorm for the DC area. After DC got crushed with 11.5" & thunder they issued WSW's for 6-10" in Philly however the heavy stuff died before it got here & naturally redeveloped for SNE & nailed Boston.

https://www.c-span.org/video/?661-1/vietnam-memorial-rededication

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1 hour ago, tombo82685 said:

Modelling has really slashed qpf amounts over the last 12 hrs. Wonder if there really is a widespread changeover to some snow. Or do we just get a lucy pulls the football out

Very anemic indeed.  Must be a rain shadow off the ChesCo mountains

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41 minutes ago, colonel_kurtz said:

I believe you're thinking of 11/21/1987,  easily the coldest NOV day I've experienced in this area, midnight highs in the low 30's, arctic front blew thru around 6:00-7:00am with squalls that covered the ground,  in the northern burbs morning temps fell thru the 20's to the upper teens by early afternoon accompanied by winds gusting 40-45 mph.

11/11/1987 was the infamous Veterans Day surprise snowstorm for the DC area. After DC got crushed with 11.5" & thunder they issued WSW's for 6-10" in Philly however the heavy stuff died before it got here & naturally redeveloped for SNE & nailed Boston.

https://www.c-span.org/video/?661-1/vietnam-memorial-rededication

You're right, I stand corrected.

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11 minutes ago, iceman56 said:

You're right, I stand corrected.

I remember 6" or so of snow on the ground Thanksgiving around that year...I was a young pup so details are fuzzy 

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