Long Range Discussions 21.0

amugs wrote:

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

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.

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)

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.