Dec 10 Morning Crusher (obs/nowcasting)

[Bob Chill]

 

 The mansion brings back some great sledding party memories. For a while the nanny state prohibited sledding but it's back now. A relative is getting married there 2014.

 

yea, back in the 80's when it snowed a lot we used to go there at night under a bright moon and have great parties. 55 gallon drum fireplaces and drink lots of um.....soda.... Even when the cops came they rarely harassed anybody unless they deserved it. Same thing with the Strathmore hill before they built the arts center. Oh how times have changed. Having too much fun is apparently very frowned upon now. 

[wxmeddler]

Lesson I learned from this storm is that QPF is not everything. Temp profiles, saturation and UVV's are equally important. I got as much precip (or even less) than Fredrick or Caroll did today but I beat them by 2 inches or more due to the colder air at onset.

Edit:

I had 0.39 liquid, so basically 10:1 ratios.

Perfect example. I got .35" but ended up getting 5.1" (14:1) and I'm only 20 mi N of you.

[Bob Chill]

Lesson I learned from this storm is that QPF is not everything. Temp profiles, saturation and UVV's are equally important. I got as much precip (or even less) than Fredrick or Caroll did today but I beat them by 2 inches or more due to the colder air at onset.

 

I learned something too. In DC, only predict how much will fall once the storm is over. Better yet, don't even predict a storm. Just go partly cloudy and slightly warmer than you think and you win every time. 

[Ian]

Lesson I learned from this storm is that QPF is not everything. Temp profiles, saturation and UVV's are equally important. I got as much precip (or even less) than Fredrick or Caroll did today but I beat them by 2 inches or more due to the colder air at onset.

Edit:

Perfect example. I got .35" but ended up getting 5.1" (14:1) and I'm only 20 mi N of you.

We could have had better ratios if we got prolonged banding but this is why I didn't get the talk before the storm. It's like figuring how much to embellish your imaginary snow. Hours of non accumulating or accumulating and melting snow not quite as fun to talk about I guess.

[Avdave]

Good to know. I thought once my 17 yr old Beagle finally goes I might get a husky. I know we (wife) would want him in the house.

Yeah they can adapt to either way, though when they are young til about age 6-7 then they start to slow down. Otherwise make sure you have a 6 foot tall fence cuz they like to run and run and run when they are young and are amazing escape artists.

 

Back to wx, just outside to let them out and wow the wind has picked up. It is cold out there, though it is only 32* feels a lot colder

[nw baltimore wx]

Temps are dropping quick. Scraped up the last of the 2" here and the remains were freezing up as soon as the sun dipped out.

[feloniousq]

Yea the melting is going to make the black ice worse.  I walked out to shovel and get the mail and whatever wasn't snow was an ice rink.  Some folks are going to struggle on the roads in the morning.

[PhineasC]

Ahh, finally. Everything that was dripping is either dry or frozen now. Smells like snow out there. Let's stay below freezing until the end of March, OK?

[snowfan]

Had to pick up the little one from the in laws, so I figured I'd take the camera along.

 

Gundpowder (or is the Little Gundpowder??) from the Steel Bridge on Sparks Rd in Monkton

 

And a few other randoms from the area

 

 

 

 

 

[Avdave]

Nice pics Snowfan

 

I drove past Ji's house this morning and caught him doing this

 

 

[ravensrule]

Nice pics Snowfan

 

I drove past Ji's house this morning and caught him doing this

 

 

photo(75).JPG

I knew from his posts that Ji was young but I did not realize he was that young.

[NeedaSnowday]

Nice pics Snowfan

 

I drove past Ji's house this morning and caught him doing this

 

 

photo(75).JPG

Bazinga!

[KAOS]

Finally took the time to measure the snow that accumulated on my sidewalk.....

 

 

 

 

 

 

 

 

 

 

 

Yes.....I am bitter.

[phil882]

I know this is not anything new for those that have followed the event today, but precipitation rates matter increasingly more as both the depth and thickness of the warm nose increases. Today's biggest problem in the metro area seems to stem from the following issues today:

 

1) Precipitation rates ramped up slowly... aka started light and gradually became heavier over a 2-3 hour period. Thus a significant amount of liquid precipitation was spent just trying to get the surface cold enough for snow accumulation.

2) Much of the precipitation started out as sleet... which is less effective at saturating the column in comparison to rain or snow. 

2) Surface temperatures and low-level temperatures started above freezing. 

4) Most of the forcing for mesoscale banding was off to the north and east (further west in MD and WV).

5) The heaviest precipitation occured during the day. While the solar elevation is low this time of the year, absorption of the solar radiation is more substantial in metro areas with a lot of concrete, dark surfaces (low albedo)

 

Going into this event, I think most knew this would be only a moderate event (.3 to .5" total liquid precipi over a 6 hour period). However, the fact that temperatures started out from 35-39 degrees meant that the first half of precipitation would essentially be used up to reach an isothermal profile in the low-levels. That combined with the ground surface in the city receiving at least some solar insolation made it even more difficult to get the snowfall ratios you expect in 30-32 degree temperatures. Once the ground is fully covered though, albedo changes and solar insolation are not nearly as much of an issue. 

[ravensrule]

I know this is not anything new for those that have followed the event today, but precipitation rates matter increasingly more as both the depth and thickness of the warm nose increases. Today's biggest problem in the metro area seems to stem from the following issues today:

 

1) Precipitation rates ramped up slowly... aka started light and gradually became heavier over a 2-3 hour period. Thus a significant amount of liquid precipitation was spent just trying to get the surface cold enough for snow accumulation.

2) Much of the precipitation started out as sleet... which is less effective at saturating the column in comparison to rain or snow. 

2) Surface temperatures and low-level temperatures started above freezing. 

4) Most of the forcing for mesoscale banding was off to the north and east (further west in MD and WV).

5) The heaviest precipitation occured during the day. While the solar elevation is low this time of the year, absorption of the solar radiation is more substantial in metro areas with a lot of concrete, dark surfaces (low albedo)

 

Going into this event, I think most knew this would be only a moderate event (.3 to .5" total liquid precipi over a 6 hour period). However, the fact that temperatures started out from 35-39 degrees mean that the first half of precipitation would essentially be used up to reach an isothermal profile in the low-levels. That combined with the ground surface in the city receiving at least some solar insolation make it even more difficult to get the snowfall ratios you expect in 30-32 degree temperatures. Once the ground is fully covered though, albedo changes and solar insolation is not nearly as much of an issue.

Phil thanks for the info, we would love to see you around here more often.

[EastCoast NPZ]

I know this is not anything new for those that have followed the event today, but precipitation rates matter increasingly more as both the depth and thickness of the warm nose increases. Today's biggest problem in the metro area seems to stem from the following issues today:

 

1) Precipitation rates ramped up slowly... aka started light and gradually became heavier over a 2-3 hour period. Thus a significant amount of liquid precipitation was spent just trying to get the surface cold enough for snow accumulation.

2) Much of the precipitation started out as sleet... which is less effective at saturating the column in comparison to rain or snow. 

2) Surface temperatures and low-level temperatures started above freezing. 

4) Most of the forcing for mesoscale banding was off to the north and east (further west in MD and WV).

5) The heaviest precipitation occured during the day. While the solar elevation is low this time of the year, absorption of the solar radiation is more substantial in metro areas with a lot of concrete, dark surfaces (low albedo)

 

Going into this event, I think most knew this would be only a moderate event (.3 to .5" total liquid precipi over a 6 hour period). However, the fact that temperatures started out from 35-39 degrees mean that the first half of precipitation would essentially be used up to reach an isothermal profile in the low-levels. That combined with the ground surface in the city receiving at least some solar insolation make it even more difficult to get the snowfall ratios you expect in 30-32 degree temperatures. Once the ground is fully covered though, albedo changes and solar insolation is not nearly as much of an issue. 

 

Great explanation, thanks.  Interestingly, out here the snow went from 0 to 60 almost instantly.  Wonder why the onset was so much different than in DC?  Also, any ideas as to why the models busted so badly on temps?  Why were they seeing so much colder air than ultimately was available?

[EastCoast NPZ]

Beautiful pics, Snowfan.

[Ian]

What's DT had to say about his forecast?

[Bob Chill]

What's DT had to say about his forecast?

 

Brashly humble for the most part. He needs to be linked up to Tony Pann. THAT guy is MONEY

 

"I WILL HAVE BUSTED HORRIBLY Y IN THE CHARLOTTESVILLE AREA... NO Excuses even through the event is still going on and it MAY end as snow...in that area I will be 100% totally wrong 

Mind you all other forecasts will be as well... but my concern is MY forecast. TOTAL BUST.

The upper air sounding say it SHOULD be at least snowing there but toi have 32 / 33 degrees and all rain ... hard to figure out'

[phil882]

Phil thanks for the info, we would love to see you around here more often.

 

 

Great explanation, thanks.  Interestingly, out here the snow went from 0 to 60 almost instantly.  Wonder why the onset was so much different than in DC?  Also, any ideas as to why the models busted so badly on temps?  Why were they seeing so much colder air than ultimately was available?

 

You guys are too nice... to EastCoastNPZ, you were far enough west that you got under that initial mesoscale band that was well forecasted by the HRRR. Instead of the atmosphere slowly moistening up (like what happened in KDCA) the better forcing resulted in much higher rates earlier on which prevented any major mixing issues early on. Additionally you have elevation on your side, which helps with both temperatures (less of a warm layer before reaching the surface) and overall precipitation rates early on (less unsaturated air for precipitation to drop into).

 

4 hr HRRR Forecast valid at 11z Today

 

 

Verification (click here for the loop):

 

 

The color scale is not quite the same but you get the impression. That mesoscale band was far enough west that it received the best dynamical forcing from the strong 250 hPa jet streak located further to the NW. 

[WinterWxLuvr]

You guys are too nice... to EastCoastNPZ, you were far enough west that you got under that initial mesoscale band that was well forecasted by the HRRR. Instead of the atmosphere slowly moistening up (like what happened in KDCA) the better forcing resulted in much higher rates earlier on which prevented any major mixing issues early on. Additionally you have elevation on your side, which helps with both temperatures (less of a warm layer before reaching the surface) and overall precipitation rates early on (less unsaturated air for precipitation to drop into).

4 hr HRRR Forecast valid at 11z Today

Verification (click here for the loop):

The color scale is not quite the same but you get the impression. That mesoscale band was far enough west that it received the best dynamical forcing from the strong 250 hPa jet streak located further to the NW.

The banding you refer to was something to see. I can't remember now down to the minute but we had four inches in well under two hours. It was dark so you don't get the feel for the rates like you do in daylight but it was impressive.

[HighStakes]

Highstakes...yes indeed that early band put down 2 inches in about 1.5 hr. ..If that. I'm sure that cooled the column well and this area overachieved once again. Hopefully Balt/dc can get a good rake soon.

I hope all those who have missed out can cash in too. People can talk climo and climate change and all that stuff as much as they want but I think the DC snow drought has just been plain dumb bad luck. This is clearly not the same as the last two winters. There is much more very cold air close by to tap. It will be simply unexplainable if DC doesn't break 10 inches this season. I will certainly be rooting for those guys.

[EastCoast NPZ]

You guys are too nice... to EastCoastNPZ, you were far enough west that you got under that initial mesoscale band that was well forecasted by the HRRR. Instead of the atmosphere slowly moistening up (like what happened in KDCA) the better forcing resulted in much higher rates earlier on which prevented any major mixing issues early on. Additionally you have elevation on your side, which helps with both temperatures (less of a warm layer before reaching the surface) and overall precipitation rates early on (less unsaturated air for precipitation to drop into).

 

4 hr HRRR Forecast valid at 11z Today

 

 

Verification (click here for the loop):

 

 

The color scale is not quite the same but you get the impression. That mesoscale band was far enough west that it received the best dynamical forcing from the strong 250 hPa jet streak located further to the NW. 

Thanks for the explanation.  Indeed, that HRRR forecast was money.

[Ian]

The best thing about the HRRR and RAP is they show something different every hour. You're bound to get one run that nails it.

[WinterWxLuvr]

The best thing about the HRRR and RAP is they show something different every hour. You're bound to get one run that nails it.

The RAP is a hard one to figure for me. Sometimes it seems to be perfect and then other times it seems awful.

[Ian]

The RAP is a hard one to figure for me. Sometimes it seems to be perfect and then other times it seems awful.

seems to be the case with mesoscale models in general.  see the NAM. they do have their use but they can be wildly varied run to run. not sure i'd assign any great victory to the hrrr here but i didn't watch it all night or anything.  there was plenty of guidance/climo knowledge pointing to the area that got the most snow today getting the most snow.  our issue around here wasn't so much mixing which was very short lived in the grand scheme as much as lack of consistent rates and temps too warm.  if temps were like 4 colder we probably would have doubled our total as it was today. partly where we got duped was just assuming that some sort of megaband was going to roll east. though the very beginning of the storm also had that weird dc gap where it was snowing all around us but not here for a while. 

[stormtracker]

I miss the NGM

[stormtracker]

and the MRF

[WinterWxLuvr]

seems to be the case with mesoscale models in general. see the NAM. they do have their use but they can be wildly varied run to run. not sure i'd assign any great victory to the hrrr here but i didn't watch it all night or anything. there was plenty of guidance/climo knowledge pointing to the area that got the most snow today getting the most snow. our issue around here wasn't so much mixing which was very short lived in the grand scheme as much as lack of consistent rates and temps too warm. if temps were like 4 colder we probably would have doubled our total as it was today. partly where we got duped was just assuming that some sort of megaband was going to roll east. though the very beginning of the storm also had that weird dc gap where it was snowing all around us but not here for a while.

I did watch the RAP from about 7-11 last night. It looked great for me but bad for DC which is why I didn't mention it. So last night it was great but other times not so much. One thing I have noticed is that when it suddenly changes drastically it's usually on to something. Usually that's been something bad.

[Ian]

I did watch the RAP from about 7-11 last night. It looked great for me but bad for DC which is why I didn't mention it. So last night it was great but other times not so much. One thing I have noticed is that when it suddenly changes drastically it's usually on to something. Usually that's been something bad.

How much snow did you get both days?