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Jan 16/17 Event Obs/Disc


mappy

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42 minutes ago, Bob Chill said:

Too early for post mortem of course but this event has been really hard to model. The back and front side ridging putting the squeeze on the trough from above played some havoc with models. MANY timing adjustment at short leads. At first, the constant slowing and amplification of the front looked good but in the end it ended up hurting not just here but right up through the entire 95 corridor. Many areas of the urban corridor north of us who are going to get pretty good precip are going to get rain and non-sticking snow. The amplification is driving the northern wave/low on a nearly  due N trajectory for a time. The onshore flow in front of it really does a number on the surface and mid levels. 

The NC/SVA folks are the only lucky ones. Yea, N CT, MA, and NW of NYC are going to do well but that part always looked pretty good. The corridor isn't going to benefit much from this event pretty much anywhere. Personally, I'm glad the NC folks are doing well. You guys think WE have a lot to complain about...try chasing snow along the NC coastal plain and piedmont for 10 years and get back to us. 

Great write up. In the end it backed too much. Ironically if everything had dug in as one consolidated piece it might have cut like some of those crazy EPS runs that rained. In the end the euro was missing the way this would be a disjointed strung out mess but I can see why it was cutting the low so far west in some cases it was seeing how far back the boundary was going to set up. 

What we needed was either the front to be over us as the wave developed or for there to be no significant wave and have the front just slowly progress east with the southwest flow intact or ironically the trough not to dig as much and the upper low at the tail catch us on its way east. So many ways to win and we found the fail. Lol

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Afternoon disco from LWX re our "event":

.NEAR TERM /THROUGH WEDNESDAY/...
Snow continues to gradually increase in coverage and slowly push
south and east ahead of an approach cold front/upper trough. Forward
progress is slow but steady. Expecting appreciable snow to begin in
the I-81 corridor between noon and 5 PM, and the I-95 corridor
between 8 PM and midnight. Hi-res guidance has been remarkably
consistent on a "snow hole" over much of the Shenandoah Valley in
the lee of the Allegheny highlands, with around an inch expected in
the valley and around inches on the ridges (the Allegheny Front
itself is expected to see 2 to 4 inches).

This relative minima in QPF extends east into northern Virginia and
central Maryland including the Baltimore/DC metros due to a weakness
between better jet forcing to the north and strong PVA with the 500
mb low to the south. Given that the one inch will be falling into
the morning commute Wednesday, an advisory has been issued for the
Interstate 95 corridor/metros. The advisory has also been expanded
to include portions of central Virginia closer to the upper
low/better moisture where 1 to 2 inches is expected. Areas adjacent
to better jet forcing in northern Maryland likely see 1 to 3 inches.

Despite favorable upper level dynamics, low level dry air intrusion
on NW flow begins by daybreak across much of the area, and this is
expected to eat away at the snow from north to south. Snow should
end around midnight across northwestern Maryland, around daybreak
from the northern Baltimore suburbs southwest into the Shenandoah
Valley and by mid-morning elsewhere, though some light snow may
linger across the central VA piedmont until noon as the upper low
moves across. If this drier air moves in quicker than currently
forecast, snow will end sooner and totals will be lower. On the flip
side, if upper level dynamics overcome low level dry air, snow
totals could be a little higher, especially considering the strength
of the upper jet and colder temperatures resulting in higher ratios
toward the end of the event. Overall, a relatively dry and powdery
snow is expected.

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16 minutes ago, NorthArlington101 said:

HRRR finally decided to literally give DCA (basically) nothing. We've hit rock bottom with a couple hours left to build something back.

 

Looking like the EURO honestly. I think areas just south and east of DC could stay in the game in the morning with some stuff from the ULL to our south. That's really our only hope at this point as it appears the front is completely getting dried out before it gets here due to the coastal to our north. We can only hope that the ULL to our south pushes precip a little further north than expected. Still, I doubt we get anything at this point. 

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This event has always been expected to have relatively low rates, and the run-to-run differences in qpf have been largely due to duration.  Most guidance has precip basically shutting off near the corridor by about 12z tomorrow.  But there's still some spread on the RGEM ensemble, with nearly half of the members still snowing in DC at 18z.  If you're looking for a little hope, you can look through some of the members here.

http://meteocentre.com/numerical-weather-prediction/ensemble-forecasting.php?lang=en&map=qc&run=12&mod=cmc_reps&stn=PNMPR&stn_type=postagestamp&display=img&hh=030

Another possible cause for optimism, depending on where you are, is the Swiss HD model.  It got drier again, but it has a strip of about 0.1" qpf running along the corridor.  It actually looks somewhat similar in precip distribution to the FV3 run BTRWx posted earlier. 

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1 hour ago, Bob Chill said:

Euro is pretty much another disaster run for just about 95% of the sub. Northern neck of VA and just south of Emmitsburg PA are the only places that get an inch until you get west of HGR

 

My 1-3" call has about a 1% chance at happening. 

no worries. That was one of the most complex systems we have seen in a long time. We dont do well with complex right?

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11 minutes ago, Mimiof2 said:

I've been under blue in Weather bug for hours here in Sharpsburg with not one flake. Is the air THAT dry that it's not making it to the ground?

I'm looking at Radarscope, and you are living on the edge of the precip. with dews in the low to mid 20s, anything really light in nature won't reach the ground. 

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2 minutes ago, Ji said:

no worries. That was one of the most complex systems we have seen in a long time. We dont do well with complex right?

That's a complicated question with a complicated answer. Instead of posting a thousand keystrokes that nobody cares about...nope, we don't do complicated well unless we do. Which happens sometimes. Usually when we're not looking. 

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12 minutes ago, Bob Chill said:

That's a complicated question with a complicated answer. Instead of posting a thousand keystrokes that nobody cares about...nope, we don't do complicated well unless we do. Which happens sometimes. Usually when we're not looking. 

Absolutely....complicated that goes in our favor is almost always one of those SURPRISE things.

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17 minutes ago, 87storms said:

almost looks like NC is getting nam'd on this run.  warning level snow down there by raleigh (though with temps currently in the 40s, you gotta wonder).   not much change so far from 12z i don't think.  

Warning level snow for my oldest in Greensboro, NC - 2-4 inches - so good for them...

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3 minutes ago, North Balti Zen said:

Warning level snow for my oldest in Greensboro, NC - 2-4 inches - so good for them...

spent camps and a year of college down there so i have a bit of a soft spot for that area, so i don't mind seeing them steal our snow for a change.  we still have about 2 months to make up the deficit.

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37 minutes ago, Bob Chill said:

That's a complicated question with a complicated answer. Instead of posting a thousand keystrokes that nobody cares about...nope, we don't do complicated well unless we do. Which happens sometimes. Usually when we're not looking. 

My expectations with the NAM dropped from 2.0 inches 24 hrs. ago to .2 inch.  That is fine, there will be other opportunities before April 15.

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