Long Range Discussions 21.0

amugs wrote:

cannot see what you tried to post here mugs, image is blank.

Not that it means a lot at 7 days out but 18z GFS has the Fri/Sat storm slipping way to the south in NC/VA.

Looking likely for a 1-3" event NW of I-95 for Monday.  The reason I don't include the coastal plain in this is the southerly winds that come in strong as the precip is getting ready to move in.  What may offset that somewhat is a cold antecedent surface.  I do think C-1" on coastal plain off the immediate shoreline in NJ is possible especially on the colder surfaces.  The 540 thickness line remains below the area so mid-levels will be cold.

Winds around 2000' ASL right out of the south will warm up the coastal plain.



Dew points

Is there a quick explanation as to how dew point affects the onset of snowfall?

Is the dewpoint temp a better indicator than surface temp as far as low levels go?

What's the max dew point temp for snow? 32* F?

Any help with these questions would be greatly appreciated. I did try to look it up...too much meteorlogical-ese in what I found though. lol

SENJsnowman wrote:Is there a quick explanation as to how dew point affects the onset of snowfall?

Is the dewpoint temp a better indicator than surface temp as far as low levels go?

What's the max dew point temp for snow? 32* F?

Any help with these questions would be greatly appreciated. I did try to look it up...too much meteorlogical-ese in what I found though. lol

SNEJ the dew point is the temperature at which the air is totally saturated.  The process of wet bulbing is the saturation of the atmosphere which caused evaporation cooling and hence drops the surface temperature.  The surface temp really cannot go below the dew point until the atmosphere dries up.

The dewpoint above 32 means surface temps are going to be above freezing.  You can certainly have dew points above 32 and it still snows because the mid-levels are cold.  But the surface will be above freezing.  Hope that helps.

Just to add to this many times you will hear the term great overrunning surface. This means you have low dewpoints even the though the surface temperature may close to freezing and people get skeptical of it being cold enough. Once the saturation takes place the surface temp will fall and the dew point will rise and they will meet in the middle.

heehaw453 wrote:Looking likely for a 1-3" event NW of I-95 for Monday.  The reason I don't include the coastal plain in this is the southerly winds that come in strong as the precip is getting ready to move in.  What may offset that somewhat is a cold antecedent surface.  I do think C-1" on coastal plain off the immediate shoreline in NJ is possible especially on the colder surfaces.  The 540 thickness line remains below the area so mid-levels will be cold.

Winds around 2000' ASL right out of the south will warm up the coastal plain.



Dew points

what about the coastal areas just north of NYC or the long Island sound edge of Westchester? I'm also very close to Hudson dunno if that makes a difference.

3K NAM ticked colder - accumulations in midday with Sun angle at play and marginal temps as Hee pointed out. Colder surfaces at the Fall line and elevations will see accumulations. 50 hours out so we'll see how this trends.

heehaw453 wrote:

SENJsnowman wrote:Is there a quick explanation as to how dew point affects the onset of snowfall?

Is the dewpoint temp a better indicator than surface temp as far as low levels go?

What's the max dew point temp for snow? 32* F?

Any help with these questions would be greatly appreciated. I did try to look it up...too much meteorlogical-ese in what I found though. lol

SNEJ the dew point is the temperature at which the air is totally saturated.  The process of wet bulbing is the saturation of the atmosphere which caused evaporation cooling and hence drops the surface temperature.  The surface temp really cannot go below the dew point until the atmosphere dries up.

The dewpoint above 32 means surface temps are going to be above freezing.  You can certainly have dew points above 32 and it still snows because the mid-levels are cold.  But the surface will be above freezing.  Hope that helps.

Just to add to this many times you will hear the term great overrunning surface.  This means you have low dewpoints even the though the surface temperature may close to freezing and people get skeptical of it being cold enough.  Once the saturation takes place the surface temp will fall and the dew point will rise and they will meet in the middle.

Thanks heehaw...i think this is what I needed, but working all day so can't really chew it up till later.

12Z NAM snow map for Monday

Euro is aggressive for the snow. Really shows a good thump for several hours for NW of I-95.  It's been trending consistently colder as has most all guidance.

12Z Euro


12Z GFSv16 (New GFS)

CPcantmeasuresnow wrote:12Z NAM snow map for Monday

NAM is getting into range soon, but definitely trending colder.

heehaw453 wrote:Euro is aggressive for the snow. Really shows a good thump for several hours for NW of I-95.  It's been trending consistently colder as has most all guidance.

12Z Euro


12Z GFSv16 (New GFS)

I'll take that 2.6 right now being this isn't great for coast if new gfs is right I'm all in.

RGEM pushing that snowline further SE.  It's been consistent with further south progression of that.

18Z GFSv16

The snowline continues to push SE on these model runs and wetter. Pushing 2" into NYC metro with more western burbs.

3K NAM shows yet a certain solution as does 18Z EURO




National Blend of Models


18z EURO



Still thinking Fall line storm and white rain at the coast. Accumylatuons since it starts late Monday morning will be in elevations and interior areas of NW NJ

Yeah, this storm seems like a minimal threat at best, moving on...

Monday is a 2-4" threat for NW of I-95.
I-95 C-2" probably on colder surfaces.
I don't see much accumulation for coastal plain (points SE of I-95).

NWS has me for 1 to 2 inches tomorrow, rain mix taken out, all snow.

Accuweather mobile app has my area little or no accumulation for tomorrow.  NWS being conservative too.  I'm going to take the over on little to no accumulation for tomorrow.  

Based on this map below I'm almost certain Morristown NJ sees more than c-1" on this.  Never want to be too confident though, but the guidance overwhelming says otherwise.

12Z NAM a decent hit for NEPA and NWNJ 3-5 through there, a couple inches through most of HV and NWCT, not much below those areas.

12Z HRR, pretty widespread 3 inch distribution through EPA, NNJ, HV and NWCT. I'd be pretty happy with this.

heehaw453 wrote:Accuweather mobile app has my area little or no accumulation for tomorrow.  NWS being conservative too.  I'm going to take the over on little to no accumulation for tomorrow.  

Based on this map below I'm almost certain Morristown NJ sees more than c-1" on this.  Never want to be too confident though, but the guidance overwhelming says otherwise.

Thoughts on how much Morristown might see? That’s where I work and I have to go in the office tomorrow.

sabamfa wrote:

heehaw453 wrote:Accuweather mobile app has my area little or no accumulation for tomorrow.  NWS being conservative too.  I'm going to take the over on little to no accumulation for tomorrow.  

Based on this map below I'm almost certain Morristown NJ sees more than c-1" on this.  Never want to be too confident though, but the guidance overwhelming says otherwise.

Thoughts on how much Morristown might see? That’s where I work and I have to go in the office tomorrow.

I'm thinking 3 or 4 inches in Morristown. Certainly not a blockbuster, but certainly not a just a coating.

CPcantmeasuresnow wrote:12Z HRR, pretty widespread 3 inch distribution through EPA, NNJ, HV and NWCT. I'd be pretty happy with this.

Yes. Models have been consistent with showing this kind of distribution for at least 24-36 hours now. NAM is getting into range and it's been ticking up amounts.

Nice thump tomorrow on GFSv16.  I think CPK will get accumulation tomorrow too.  Maybe enough to crack 40" for the season?

I think Next Friday/Saturday 2/26-2/27 needs to be monitored too. Models aren't screaming anything but there is going to be a baroclinic zone near by. It won't take much for a wave to ride it and produce something. Are we on the good side of the zone and is there a strong enough wave?

Looking at the long range, looks like spring is right around the corner. Even if things line up just right and we get lucky with a storm, it won't hang around long.

Correct me if I'm wrong.