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January 3-4, 2015 Storm Obs/Nowcast


Baroclinic Zone

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Wow, NWS (and everybody else) really busted the temp forecast, at least for me.. they've already dropped my forecast high from 55 (no prob getting rid of the snow/ice!) to 45 (ugh, shoveling cement) .. I wouldn't be surprised if I don't hit 40 :(

 

Time to get out and start digging.. 32.3/31.5

 

I'm with Will on that and I don't think the story is told in total ... still have many hours prior to cold fropa, and this "tuck" sort of pattern behind that meso-beta scaled low out E of Cape Ann merely delays...for the time being.  

 

Temps could still spike as that cfront nears, the gradient steepens just a little, and warm conveyor winds pick up a bit. 

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Yeah. I understood it was a long shot, but the scenario for it looked ok at the time

Thanks anyways

 

Here ...I've just quickly drafted out charts to demo what is observed in the runs... The chart on the left below, is the 00z (12 hour) NAM position of features and so forth off the 12z run.  The chart on the right is the 06z position of features ...same run.

 

post-904-0-10221500-1420390059_thumb.jpg

 

At the time yesterday this was denoted as "weak sauce" ...meaning the signal was there, but vague and not deterministic.   This morning ... perhaps a little spicier is the crock pot, but I would still not get to giddy.  The taste is still fairly bland. 

 

Anyway, you can clearly see a "lag-back" blossoming of the precipitation as the cold front has already cleared the coast.  Moreover, there are about 10 to 12dm of thickness advection, and with that many isobars crossing normal to the isopleths, that means that CAA is for real. 

 

Here is the 500mb and it clearly shows at 1am (06z) ... jet streak passing west of the baroclinic axis (roughtly the position of the cold front), and it is culpable in what is exciting the growth of precipitation back west, as restoring mass is veered winds back up the frontal slope.  

 

post-904-0-98876300-1420390369_thumb.jpg

 

Will's right tho - the boundary layer is too warm in eastern sections (as modeled). If that can somehow correct colder for whatever reason, that would be how to get some of that lag action to become snow. Otherwise, it's more cold rain.  I would say, however, getting out to ORH Hills may be able to get an inch out of this.  

 

The NAM FRH grid clearly shows a new .31" at Logan, indicative of the ANA.  ALB is .04" ... so quick and dirty differential has Amherst to Fitchburg in around .2" and hilly country there is going to be already poking above. 

 

Any other guidance and/or NAM being full of shister, notwithstanding...

 

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BOS NAM.

 

The farthest right couplet is the 800mb temperature = 0C

The middle couplet is the 900mb temperature = +1C

The middle-left ... is the 980mb temperature = +7C

The 31 is the QPF in bucket up through 1am (06z).  

 

There is very little/0 accumulated after this time, but ... envision west of Boston, out in Metro and ORH County, there could be more of a 040099 grouping for the thermal depth, which is +4, 0C and -1C respectively, and that is large aggregate snow if that is the case.  It's kind of how to use the FRH grid to fashion events.  

 

18031925011 -7210 042522 4307 01 00

 

and we're not talking much .. almost pettiness, but ...seeing as people live and die by their next breath of snow chances, we'll leave no oxygen on detected.

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