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nj2va

Feb 18/19 Disco/Obs

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1 minute ago, Bob Chill said:

Def could have been 2015. Makes sense coming in a week after the VDay supersquall. We tracked fails all season up until that arctic front. The storm was so unconventional we didnt take it as serious as we usually do iirc

Yup, the high at IAD was 15F and 19F on the 2 days leading up to the event (2/19/15 and 2/20/15). Superb airmass that the models just didn’t have a good handle for and hence our great positive bust here in the suburbs. 

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6 minutes ago, blueberryfaygo said:

   The GFS gives the Baltimore-dc corridor 5 inches in the 6 hours leading up to the change over.. if you can believe that it stays all snow up to or around 18Z, then this would be a legit event.  Should be fun to watch... Although we are not seeing the big totals from last couple of days.. this quick hitter warning criteria type event should be very impactful and fun to watch!

 

image.thumb.png.fef38326d0828f906b8fff2be5475d27.png

Dude.. SLEET.

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Interesting tidbits from Mount Holly AFD-

The ultimate evolution of the first southern-stream perturbation will be what is responsible for our winter weather late tonight and Thursday. A strong anticyclonic upper-level jet streak will combine with midlevel differential cyclonic vorticity advection to aid in intensifying surface low pressure from the northern Gulf of Mexico tonight to the Mid-Atlantic coast Thursday afternoon. Intense warm advection atop a low-level baroclinic zone will aid in widespread precipitation to the north and northeast of the developing low. Meanwhile, a strong surface high will remain in southeast Canada, providing cold onshore flow for the northern Mid-Atlantic preceding the storm. Models are, as usual, too moist with the predecessor boundary-layer environment, with dew points a good 6-10+ degrees lower than model consensus today. This will be important in two ways. First, it is likely that low-level saturation requirements will delay precipitation onset in our CWA, with snow not likely to get going in earnest until near or just after daybreak. Second, models are likely too warm at the surface, especially during the main "thump" of precipitation during the morning hours. Sided with colder guidance here.

With models trending slightly northward with the warm-nose influence on precipitation type on Thursday, our inclination was to be a little less aggressive than consensus in this regard. No question that the strength of warm advection will be intense, likely leading to a veritable sleet storm in a good chunk of the area as the event unfolds during the day. However, there has been a tendency for higher-res guidance to be a little too aggressive in shunting the warm nose to the north this season. Of course, there has also been a tendency for northwest shifts in the snow/sleet/freezing rain geographical distributions within 24 hours of the event (playing out once again with today`s guidance). It will be quite interesting to see how the 00z solutions play out, as run-to-run variability has been diminishing confidence in the forecast for this event considerably.

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4 minutes ago, Bob Chill said:

Def could have been 2015. Makes sense coming in a week after the VDay supersquall. We tracked fails all season up until that arctic front. The storm was so unconventional we didnt take it as serious as we usually do iirc

mid February 2015 featured a very cold stretch of  record breaking temperatures for our region.. hands down the coldest stretch we have ever seen

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My first and only call for my area is 3-4" of snow and a bunch of sleet. Once it shuts off I'm thinking 5" total of frozen stuff. Sleet will pummel and compact for sure. My plan is to measure snow at the beginning of the flip, clear the table, then measure sleet. Roads will be the worst they've been since Jan 16. Jan 19 was 11" in my yard but iirc the roads were fine. Not to mention snow distribution was all over the place so road impacts varied by the mile. Tomorrow will be a different story. 

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34.6/17. Gotta get the bottoms to drop out now the sun is down and before clouds roll in

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2 minutes ago, CAPE said:

Dude.. SLEET.

The sounding at 18Z for Baltimore county says that it is just about ready to sleet.. that tells me that the 850s hold on until just about then (per the model)

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11 minutes ago, blueberryfaygo said:

   The GFS gives the Baltimore-dc corridor 5 inches in the 6 hours leading up to the change over.. if you can believe that it stays all snow up to or around 18Z, then this would be a legit event.  Should be fun to watch... Although we are not seeing the big totals from last couple of days.. this quick hitter warning criteria type event should be very impactful and fun to watch!

 

image.thumb.png.fef38326d0828f906b8fff2be5475d27.png

Oh that 5-inch mark....can we do it? Or will we be trolled again with another 4 or 4.5" result? Lol

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Just now, blueberryfaygo said:

The sounding at 18Z for Baltimore county says that it is just about ready to sleet.. that tells me that the 850s hold on until just about then (per the model)

Ok, as long as you realize the TT "snow" maps are shit.

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This sounding says Baltimore is snow for the hours leading up to 18Z.. but of course.. it really cant predict that level of detail

Just now, CAPE said:

Ok, as long as you realize the TT "snow" maps are shit.

image.thumb.png.c1e1a9e900e8f1ee8aa091c60a43128f.png

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Just now, blueberryfaygo said:

The sounding at 18Z for Baltimore county says that it is just about ready to sleet.. that tells me that the 850s hold on until just about then (per the model)

Sleet warm layer is higher up. Typically between 700-800mbs. 850s going above 0c often happens after the flip has already happened. Used to piss me off too because I used to use 850 0c line for judging when I would flip and it always happened sooner. 

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15 minutes ago, Bob Chill said:

It was a single storm iirc and was on the tail of a snow heater in that wild progressive pattern. None of us really drilled down on it leading in. We were kinda burned out from other storms and this one had literally no high pressure to our north. All return flow from the arctic high sliding off the coast. 99.9% of those storms would be a mix and mess everywhere at best. It was such a legit airmass we capitalized when we really shouldnt have. Thats as much as this old guy can remember 

You did better than me. That was a busy tracking month, with a big storm smack in the middle.

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20 minutes ago, gymengineer said:

I think he’s referring to the 2/21/2015 event? The 2/2014 2-parter was a coastal storm. 

Ahh makes sense. Thanks

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Agree with the 3 to 6 inch calls (I-95) with best snow axis MRB to 50s ABE ... slight uncertainty remains about part two which depends on any development of low pressure currently in the central GOM south of Houma LA at about 27.5 N, oil rig obs indicate a juicy warm sector has developed (75/73 south wind to 30 mph) and this is supposedly heading for landfall near Pensacola or Mobile Bay then tracking through southern GA and up the Carolina coast. However, almost all guidance does nothing more than drag along an ill-defined trailing wave to the first low that forms in resonance with the inland snowfall energy, and eventually most models just ripple all the energy forward into that leading wave for explosive development south of NS Canada by Friday (late). If that were to prove inaccurate and this Gulf low maintains a stronger and more intact center and develops a circulation, then it could increase your snow and decrease the otherwise apparently inevitable sleet producing longer duration portion of the event. Let's say later models show a 1004 mb center deepening to 996 mb (which is probably only now on a few perturbations in the ensemble) then it would distort the thermals enough to keep the column colder and might turn into a heavier snowfall. That's the only route I see to anything heavier than about 6" and my forecast range is 3-6" for the three airports, 6-8" Frederick and 8-12" max in the MRB to MDT zone. 

A different evolution of the Gulf low could add several more inches to that but as I say no guidance supports this, although it has to be said that the weak feature now on the map is managing to produce quite a good circulation at the moment in the central to western GOM. Probably what would be needed is more digging of the upper trough to energize this low further, it has all the thermal gradients a low could possibly use. 

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HRRR throwing out a very rate dependent look. Pretty much says anyone DC south will start as sleet and flip between as rates improve/diminish. Some hilarious weenie panels in the run regardless. Really seems to have trouble with the 1hr snowfall rate when sleet is thrown in the mix.

1613656800-xw9gYXWCq64.png

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Just now, nw baltimore wx said:

 

Cool.  I'm good.

1900365092_ScreenShot2021-02-17at5_36_18PM.png.0da3c2ada7b60b9af10e70223b7e09e1.png

Chill says maybe not.. IDK.. if we hold on to snow for a 6-8 hours we are gonna win pretty big up here.  

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3 minutes ago, blueberryfaygo said:

Chill says maybe not.. IDK.. if we hold on to snow for a 6-8 hours we are gonna win pretty big up here.  

It’s going to sleet like a mofo here tomorrow, but as long as the roads are trashed, I don’t care. 

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