February 2nd: Light Snow Event

Good Morning,

After slight moderate on Thursday we're expected to turn cold again on Friday. Check out this cut-off ridge NW of Alaska on the 500mb anomaly map. The result of that ridge will be arctic air ushering into the central and eastern U.S.



An arctic front is expected to pass through the area on Friday. Precipitation, likely in the form of snow, is expected to develop along and ahead of this frontal passage. The GFS depicts a weaker system while other guidance, such as the NAM and Hi-RES NAM, show a stronger front bringing more in the way of snow.

GFS Friday morning:



NAM Friday morning:





Eastern NJ, NYC, and LI stand the best chance to see the most snow while those N&W are likely to see very little from this front. Snow enhancement is shown as the front nears the Atlantic.

Timing would be late Thursday through 11am Friday. It could start as rain or a mix along the coast then switch to snow in the overnight hours. My initial thoughts are 1-3" for eastern areas and a C-2" for places N&W of Newark, NJ.

12z may be signaling the change Id hope for starting with the NAM. Lets see the rest

sroc4 wrote:12z may be signaling the change Id hope for starting with the NAM.  Lets see the rest

It seems like the 12z NAM backed off, no?

aiannone wrote:

sroc4 wrote:12z may be signaling the change Id hope for starting with the NAM.  Lets see the rest

It seems like the 12z NAM backed off, no?

Wait, i did the new forbidden practice. I looked at the QPF lol. Now i did what i should be doing and looked at 500mb, and I see what you mean. The southern piece got out just barely ahead of the northern piece. But just a tad late

18z NAM a little more juiced with the front

Upton DISCO
Temperatures aloft remain above freezing through the day
Thursday, then lower below freezing during Thursday night.
Temperature profiles suggest initial rain/showers Thursday
evening, but quickly changing to snow as the colder air moves
in. Bufkit temperature profiles show a marginal pattern with
either rain or snow possible...we favor the transition to the
colder solution Thursday night.

QPF along/ahead of the front ranges from 0.10 to 0.30 inches
depending on the model. Some of this will fall as rain, but the
residual moisture would support an inch or two of snow.

0z NAM

SREF:

Alex what the hell is going on outside right now. The wind is absolutely HOWLING from the south. The gusts are shaking my house!

syosnow94 wrote:Alex what the hell is going on outside right now.  The wind is absolutely HOWLING from the south.  The gusts are shaking my house!

Gusty southerly flow out of the south ahead of the front tmw. Wasn't expecting it to get this gusty. Temp is going up with the flow though haha

aiannone wrote:SREF:

That is 2-4" easily on its and 3" plus fir that dark green. Ocean enhancement? Don't know but no LP forming on the front as I see it.
One thingnisnfirnsure, the cold press is there and if this holds we may have a flash freeze come Friday morning which would make the morning rush a mess especially in the burbs N&W. Snow would of courae hold in over LI.
See what the mseos have come tomorrow

GFS:

aiannone wrote:GFS:

Much warmer look. With this southerly flow and temps getting into,at least the mid 40s tomorrow I can’t see snow

syosnow94 wrote:

aiannone wrote:GFS:

Much warmer look.  With this southerly flow and temps getting into,at least the mid 40s tomorrow I can’t see snow

That’s what you said about the last storm and.....

0Z EURO doesn't show much in the way of snow for Thursday night into Friday morning.

The Euro has been by far the worst model this winter

NWS hugging warmer guidance as well.  Says rain snow mix with minor accumulation less than 1” for this entire forum area.

Temps went up overnight. Snow melting. Not good signs. NWS lowered qpf amounts and raised temperatures for both threats.

NWS model huggers. Remember that. Th y said snow showers for my area for Monday into Tuesday. I had 8” IMBY.

sroc4 wrote:NWS model huggers. Remember that. Th y said snow showers for my area for Monday into Tuesday. I had 8” IMBY.

I know Scott. That’s why I’m on here. I trust you guys but the temps going up and the south winds are not a good sign IMO

syosnow94 wrote:

sroc4 wrote:NWS model huggers. Remember that. Th y said snow showers for my area for Monday into Tuesday. I had 8” IMBY.

I know Scott.  That’s why I’m on here.  I trust you guys but the temps going up and the south winds are not a good sign IMO

We may get a quick burst of snow after the cold air pushes through capable of putting down 1-2" pretty fast.  My argument:  On pretty much all models there is very potent 500mb energy trailing behind the main frontal boundary.  Here is the RGEM showing my idea. When you look at the 500mb map up close and compare to the surface you'll notice the heaviest axis of precip, seen in the greens, is in response to the leading line of vorticity.  However; lagging behind is a much more potent streak of vorticity that swings through the area AFTER the temp profiles crash to the coast.  I would argue that there should be enhancement to the upward motion further N&W, in between the leading vort maxx and the second stronger vort max, compared to what the current surface maps show(only light gray precip).  The problem I suppose with this theory is that overall everything moving pretty fast so maybe not, but again there should be strong PVA out ahead of that second more potent Vort max enhancing lift; therefore, precip.  I'm not talking about going from expecting snow showers to a 4-8" surprise(easy now) like we just saw, but a quick 1-2" 1-3" wouldn't surprise me, esp over eastern sections.  






Here are the NAM and EURO.  Same thing.  There "should" be enhancement to precip in the area I have circled in response to the trailing vorticity. The energy just looks too strong to me. 

Scott I remember a situation like this a few years ago. The date escapes me now but we had a bit of light rain between midnight and 5 am. Then the front came through and temps CRASHED. With the front was a 2 hour period of heavy snow. The NWS described it coming in like a wall of white. From nothing to 2-4” in under 2 hours. Everyone was driving to work during rush hour from 6-8 am as it happened.

12z NAM THUMPS!

Alex if the 12z NAM verifies verbatim we’d all be 2-4” easy.

Big if though

syosnow94 wrote:Alex if the 12z NAM verifies verbatim we’d all be 2-4” easy.  

Big if though

Yupp, i strongly dislike changeover events (wet ground, NW winds cause downsloping and erode the precip, etc), however this event has strong jet energy moving over our area which could mitigate those factors (NAM is showing this), so we will really have to nowcast. But regardless, a flash freeze will occur. Ground will not dry by the time the cold air crashes in obviously.