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Snow/Sleet Storm Va/Maryland March 1-2, 2019


Wxmidatlantic

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Interesting system to say the least. The great mystery is, how long will it last.

 

A general 2-4 inches of snow/sleet. A band of moderate to heavy snow and a band of heavy sleet. Anomalies: 1-2" sleet, 6" snow.

 

This morning thunderstorms rolling in Alabama. NW quadrant extends further than prog. Snow/ZR- MO/Ill.

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A Navy Chief said, "Never change your forecast. That way you can only be wrong once."

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The ECMWF keeps moving the QPF max northward towards the mason dixon line. It did that with the last storm too, and it busted. Hopefully the same holds true this go around.

 

If there’s precip falling, I always go bullish w/ in-situ CAD. We’ll see..precipitation is key to everything. As it usually is in these situations.

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What’s with all the temperature variability in such a well mixed atmosphere? I think some of these sensors might be overexposed or poorly sited..makes no sense otherwise.

 

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Light rain/snow mix, 36.9/20 here as of 12:20AM.

 

Edit: Sleetfest.

 

Edit #2: It’s a sleet tsunami! Coating the ground like snow.

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Finally some flakes mixing in. Band that will flip us over is moving in from the west.

 

Down to 34.2/26..would like to make it to 30*F.

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Well, it took the entirety of the first wave of precip, but we finished as all snow. Have a 1/2” glacier on the ground right now.

 

Waiting for wave-2. Hopefully the airmass doesn’t rebound too much in the meantime. Currently 32.4/29..running out of room to wetbulb.

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Didn’t even reach an inch here..too much sleet. Temp did drop to 31.5*F last night with the second wave, which was colder than the 33*F NWS point-&-click forecast.

 

Ended up with a 2/3” sheet of ice. Currently 35.1*F as of 420pm, which is a tad bit cooler than modeled, as usual w/ in-situ CAD. But still plenty warm..probably too warm for a wintry scenario tonight barring unforeseen dynamic cooling from heavy precip after sundown.

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Hmm..I’ll believe that when I see it. Would need some legit dynamic cooling since thermals aloft are relatively toasty right now. We do have E/NE flow present in the boundary layer across the region, which isn’t really going to warm the profile after sundown, but it feels like a situation where we’re just one degree too warm (down here) up to 900mb.

Maybe you guys in Baltimore can pull it off. The higher terrain along/west of the BR will probably score some legitimate sleet/zr totals. But my area doesn’t do well when the inversion is already present *and* we’re well above freezing with warm thermals aloft.

Holding CAD isn’t the issue here (we’re great at that, stuck in this low-elevation river gorge) It’s advecting cooler air in here that’s hard.

Yea. Jury is still out. Its so close 1 degree. Precip rates will decide..phase change from solid to liquid cools the atmosphere. Low confidence.
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A Navy Chief said, "Never change your forecast. That way you can only be wrong once."

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Yea. Jury is still out. Its so close 1 degree. Precip rates will decide..phase change from solid to liquid cools the atmosphere. Low confidence.

Yeah, though 925mb temps are colder than 850mb temps right now (warm nose), so there will be freezing and latent heat release in the upper portion of the inversion..so snow is very unlikely. In very heavy precip, maybe sleet instead of rain/ZR but this will be very tough because outside of the heavy bands, any ZR will warm the surface too.

 

So we have to rely on the loss of insolation and full scale dynamic cooling, and avoid any unfavorable latent heat balance in the latent heat machine.

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Though, as the precipitation is moving in here, my temperature has dropped from 35.1 to 34.7, and the dewpoint is down from 30.9 to 30.2.

 

Still feels like it might be one degree too warm, but we’ll see I guess.

 

8m8QebA.jpg

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Yeah, ~ 1 degree too warm through 900mb locally.

 

I’m at 33.6/31.5 as of 620pm. Near miss here, though there is some bright banding showing up to the W/NW, where the profile is cooler.

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