3 PM Thursday - Posted by Dave Longley - Sorry I haven't poasted in a couple days.  Needless to say the weather will get exciting again by the weekend. 

As for today, clouds are here, and snow is getting ready to cross the NY/PA line.  Hey, it's snowing in DC!  They had to shovel in Asheville, NC.  The bulk of this moisture appears headed just to our east, with just some light snow around most of CNY.  Could pick up an inch or two tonight.  The one exception that Jim Teske and I were noticing this morning is over Oneida and Herkimer counties where 4 to 6 inches of snow are possible.  The latest NAM runs have been consistent in showing that accumulation.  The RPM model ( a version of the WRF) did have 4 to 6 in those areas north and east of here.  Dave Eichorn will have the latest tonight at 5 and again at 11.

Any precipitation will be winding down tomorrow morning, with some breaks of sun possible in the afternoon.  We had been carrying highs near 40, but some of the new data in shows the boundary layer temps a bit cooler, so mid 30s seem a bit more reasonable.  While temperatures tomorrow afternoon will be cold enough for lake effect, the winds will be pretty southwesterly, so most of that will be well to our north.

Saturday will be our day of change.  The true arctic cold front is forecast to arrive during the day.  Along that front should be an area of low pressure, that will help to keep winds pretty southwestly through at least the first half of the day. 

Snow should increase Saturday afternoon as the arctic front starts to move through.  Once that thing goes through and the winds settle down we'll be able to sink our teeth into the lake effect. 

Here's some of my initial thoughts.  Once the wind shear settles down Saturday night, we should get a healthy band going east of Lake Ontario.  One thing that's complicating things for me right now is the NAM.  The system lifting up the east coast today is going to lay down a front across Florida.  A new storm is forecast to develop in the Gulf of Mexico later tomorrow and then move north along the coast.  This is all the surface reflection of the digging jet stream.   The NAM seems to be the most excited with this and if this solution is correct, winds may be a bit more northwesterly come Sunday morning, and this could bring the heavy lake snows briefly down into the SYR area.  For the sake of discussion and sanity, let's assume this happens.  One sidenote, this could bring more in the way of accumulating snow Saturday, so we need to keep an eye on this.

So, the storm zips on through later Saturday, band sets up off the lake and swings south close to SYR sunrise Sunday.  There could be thunder.  Looks like about a 6 hour period of heavy snow through northern Cayuga, southern Oswego, northern Onondaga and Madison counties Sunday morning.  Throw in the wind and cold---it could be kind of rough in those heavier lake snows the first part of Sunday. 

Sunday afternoon, the boundary layer winds will start to back, or become more westerly, and the lake snows will start to shift north.  The instability is forecast to diminish through the afternoon, but if we have a strong band, that won't matter.  There should be some heavy snow for areas north of Syracuse Sunday afternoon and night.  The good news (if you're not into crazy snow totals) is that the band does right now (84 hours from the event) look like it will be moving a bit and the air will be drying out Sunday night.  High pressure building in Monday will attempt to weaken the lake snows.

There are the initial thoughts.  We'll certainly be fine-tuning through the next few days, and trying to update as much as possible.  If the science above is a little overwhelming, your takeaway from this should be the potential is high for heavy lake effect snow southeast of Lake Ontario from later Saturday evening through Sunday night.  Given the strength of the cold push and the significant lake water to air temperature difference, when it does snow, it should snow hard in the localized bands of lake effect.  Again, outside of the lake snows, it'll be downright cold Sunday with highs in the teens.

-Dave