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Jan 4th Coastal Obs/Disc


mappy

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Just now, mitchnick said:

What makes no sense is that below is the radar reflectivity at 2am off the 3k Nam. One problem.  That's what radar looks like right now at 9:18.

 

nam3km_ref_uv10m_neus_7.png

The straight line west edge also suggests they ran out of time/data and Darryl just went in and fixed it with a pencil.

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3 minutes ago, mitchnick said:

What makes no sense is that below is the radar reflectivity at 2am off the 3k Nam. One problem.  That's what radar looks like right now at 9:18.

 

nam3km_ref_uv10m_neus_7.png

Yeah, the NAM 1 hr from now looks like we're not even gonna get virga until tomorrow

namconus_ref_frzn_us_1.thumb.png.c12ff64e774b185f80a3eb8e66054d3c.png

Pretty sure there's no reason to panic. NAM isn't up to par with the radar

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15 minutes ago, Bob Chill said:

Nam did the one thing I was nervous about...outer edge dies as the coastal wraps up. Could be right but who knows. 

It sure could be right. I have seen this happen right before my eyes on radar returns up my way during rapidly developing coastals. It seems more prevalent with Miller B's though.

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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
912 PM EST Wed Jan 3 2018

.SYNOPSIS...
Rapidly strengthening low pressure will pass east of the region
tonight into Thursday. Arctic high pressure rebuilds Thursday
night into the weekend. High pressure will move off the coast
early next week as another storm system approaches from the
west.

&&

.NEAR TERM /THROUGH THURSDAY/...

Update...
Going forecast generally on track, so will leave previous
discussion below for those interested. Low pressure (996 mb)
southeast of Cape Hatteras as of 9 pm. Radar returns noted
across the southeastern half of the KLWX radar scope, but
dewpoint depressions still 20-25 degrees, so at worst a flurry
is possible as the lower levels saturate. Latest guidance in
agreement that will take place over the next 2 to 4 hours.
Made a couple tweaks to better reflect that timing in the PoPs
(it was already in our onset graphic), but ultimately it doesnt
change the snowfall accumulation forecast.

The other place where forecast could go astray is predawn/toward
sunrise, which is when snowfall should be at its heaviest.
Subtle differences in QPF or snow-to-liquid ratios (SLR) might
result in adjustments of an inch or two. At this time, it looks
like the best frontogenetical forcing will be over the eastern
shore. If that were to shift west, then an enhanced band of
accumulation would set up, which would require a Warning. While
there are some superensemble members that do support this, the
synoptic forcing elements do not. The next 6 hours will be
telling.
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2 minutes ago, Maestrobjwa said:

Was something like this also responsible for the Dec 2010 storm of misery? Lol

No. Very different. Let's not get off track. The premise is when a coastal low rapidly deepens it can pull best dynamics closer to the center at the expense of the edges. The euro is the most accurate global at short range with qpf and it was much drier than everything else in our area. That can't be ignored even when meso's show much bigger totals. 

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Just now, Eskimo Joe said:

Some heavier echoes along the Rt. 50 corridor up through Fells Point in the last 2 frames of LWX radar.

I'm under that heavier echo and still virga right now. I was staring at the street light for about 5 minutes to see if I could spot any flakes. 

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Just now, Ltrain said:

I'm under that heavier echo and still virga right now. I was staring at the street light for about 5 minutes to see if I could spot any flakes. 

There's still a decent bit of dry air to overcome...00z IAD sounding tells the story:  http://www.spc.noaa.gov/exper/soundings/18010400_OBS/ 

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