12/17/18 Disco/Obs - Rain/Wind Event

[87storms]

I’m surprised at some of the meager rainfall reports. Feels like it’s been pouring for f’ing HOURS.

I think 2” is in play across the region. Now we just need this when there’s an arctic high building in from Ontario and Quebec.

[pazzo83]

1.7" here in Tenleytown - pouring.

[87storms]

1.7" hear in Tenleytown - pouring.

Flood warnings just got issued in Moco. Haven’t seen that too often this year.

[Terpeast]

Just drove from Tysons to Ashburn, pouring. 1.2” here. Awful

[mattie g]

1 hour ago, SnowLover22 said:

 No need to imagine, the way thermodynamics work, it wouldn’t be that QPF if it were snow.

It is why you can get 3 inches of rain per hour but not 30 inches of snow per hour. It doesn’t work like that.

But it’s not at all unheard of for us to get 2-3” of QPF during a big southern stream storm in a Nino.

I get that warmer air can hold more moisture, but that doesn’t mean we can’t pick up copious precip during cold storms given the right conditions.

And please…I’m all ears to hear why I might be mistaken!

[pazzo83]

1 minute ago, mattie g said:

But it’s not at all unheard of for us to get 2-3” of QPF during a big southern stream storm in a Nino.

I get that warmer air can hold more moisture, but that doesn’t mean we can’t pick up copious precip during cold storms given the right conditions.

And please…I’m all ears to hear why I might be mistaken!

some place in SC got 13" of rain - absolutely insane for a non-tropical system.

[mattie g]

Also…power flickered four times here in Burke about 20-30 minutes ago. Thought we were cooked come the second time. Fingers crossed it holds out!

[pazzo83]

looks like some back-filling coming in from the south - wonder if these are more squally so will have some winds with them.

[Jebman]

That rain shield is amazing! It's so BIG! I have snapped dozens of snapshots! There are HUMONGOUS GLOBS of solid yellow and even some RED up in there!

I am so damned JEALOUS over all of your rain, it's not even funny.

[Stormpc]

7 minutes ago, pazzo83 said:

some place in SC got 13" of rain - absolutely insane for a non-tropical system.

They are saying 15" plus now. With a dew point in the mid-60s down here there's some tropical characteristics for sure

[Jebman]

11 minutes ago, Stormpc said:

They are saying 15" plus now. With a dew point in the mid-60s down here there's some tropical characteristics for sure

Wow they got to enjoy mid 60s dewpoints! Plus incredible torrential rains! I would have been out on one hell of an E-P-I-C jebwalk, right in the low water areas, just savoring the water levels rising all around me! Kind of like taking an epic jebwalk in the Bay of Fundy as the tide is coming in! Or the Holy Island Causeway in England as the tide is coming in! Man I am truly crrazy about rising waters!

South Carolina is such a wonderful place to live, and it gets such incredible weather!

Oh by the way folks.

7,000th Post.

[Kay]

lwx 9:19 pm AFD/obs

ETA forgot to add 1.7" here so far

.NEAR TERM /THROUGH MONDAY NIGHT/...

989 mb low pressure center is located not too far from Cape
Fear NC. Latest NAM has the best initialization in terms of
position and magnitude, the GFS is not too far off, while Euro
is more than 100 miles off with its position. So far, up to 1.32
inches of rain have fallen at Leonardtown MD (St. Mary`s
County) with up to 0.6 inch per hour rainfall rates being
observed at several locations. Rain will continue to pivot
north and west of the low pressure center overnight. Southern
MD will see a brief lull in intensity in the next couple hours,
but another batch of moderate/heavy rain currently over
northeastern NC will move in overnight. Latest guidance continue
to indicate areas east of I-95, particularly southern MD will
see the heaviest rain. Risk of flooding rainfall will continue
overnight until the rain begins to exit around daybreak Monday.

Wind Advisories were issued earlier for the potential for 40kt
gust with the initial surge of winds behind exiting low
pressure. Strongest winds are likely between 12Z-18Z before they
start diminishing during the mid-late afternoon.

[mappy]

1.46” so far and pouring. Was under some oranges for a bit earlier. 

[pazzo83]

Dews are in the 60s along the eastern shore with gusts of 60+ mph.  I mean...

[wxmeddler]

Wait for the PIVOT..

[pazzo83]

2" here.

[Mrs.J]

1.91” here so far. Will push over the 2” mark soon though. 

[SnowLover22]

51 minutes ago, mattie g said:

But it’s not at all unheard of for us to get 2-3” of QPF during a big southern stream storm in a Nino.

I get that warmer air can hold more moisture, but that doesn’t mean we can’t pick up copious precip during cold storms given the right conditions.

And please…I’m all ears to hear why I might be mistaken!

You’re right that you can, my point is it is harder. The answer is a bit complicated.

 

Part of the answer is in the physical process of rain and snow formation and how fast they fall.

 

Rain forms through liquid droplets coalescing in the atmosphere creating larger and heavier droplets that can fall quicker under the force of gravity

 

Snowflakes form when water vapor turns directly into ice crystals. 
 

Snowflakes form at a slower rate than rain droplets and obviously the structure is different with air pockets within the snow flake causing them to be lighter than rain drops.

Thus,
 

Rain can physically fall at a faster rate than snow and rain forms at a faster rate.

 

This explains it better.

 

https://geo.libretexts.org/Bookshelves/Geography_(Physical)/The_Physical_Environment_(Ritter)/07%3A_Atmospheric_Moisture/7.04%3A_Clouds_and_Precipitation/7.4.03%3A_Precipitation_Process

Bergeron Process vs Warm-Rain Process 

Now assuming that one is dealing with the Bergeron Process for areas that get rain and areas that get snow, rain will still fall at a faster rate due to structure differences between a snow flake vs rain drop.

[Steve25]

I'm just so thankful my sump pump is working! Have been having issues with it. Kind of had to improvise to get it functional because I wasn't able to buy a new one before the storm. It's been chugging along really well!

[pazzo83]

just pouring here - man.  we are making a late run to close our annual precip deficit lol

[stormtracker]

3 hours ago, Eskimo Joe said:

If the radar is to be believed, this thing is out of here by midnight or early tomorrow?

Why do you always do this?  You will be insufferable come game time.

[stormtracker]

Anyway, pouring here, with heavier returns incoming from the south.

[stormtracker]

21 minutes ago, pazzo83 said:

2" here.

We're gonna make a run at 3 dude

[pazzo83]

Just now, stormtracker said:

We're gonna make a run at 3 dude

easily.

[Mrs.J]

Over 2” here 2.07” to be exact. My station will dump data at midnight but will keep an event total. 

[pazzo83]

Just now, Mrs.J said:

Over 2” here 2.07” to be exact. My station will dump data at midnight but will keep an event total. 

what do you have?  I have one of the Ambient Weather models.

[pazzo83]

it's even above freezing on the top of Mount Washington right now.

https://mountwashington.org/weather/mount-washington-weather/

[midatlanticweather]

A little over an inch for Purcellville. Breezy and my Christmas lights have taken a hit. One strand so far, but that is over 1000 lights. 

[nj2va]

Heavy rain, local PWS are all over the place but seems to be about 2”.  

[SnowtoRain]

1.69"