March 12th-13th ULL Discussion

[SN_Lover]

12 minutes ago, BIG FROSTY said:

Allan's latest Map!!

 

Don't think that this is how it will go down....

[calculus1]

1 hour ago, wncsnow said:

New EURO much farther south with snow all the way to CLT

 

13 minutes ago, BIG FROSTY said:

Allan's latest Map!!

 

So, the latest Euro model and Huffman's first-call prediction both go against the dry slot being advertised by the NAM and GFS.  I do so hope they are both correct.  What do they see that our US models are not seeing?

[calculus1]

Here is the Euro a little further out:

[Solak]

RAH

The NAM and GFS differ significantly in the 900-800mb layer where 
the GFS depicts a deep isothermal layer where as the NAM maintains a 
prominent warm nose until late mid-afternoon when it becomes deeply 
isothermal. The NAM, historically, as done a better job with the 
existence/strength of the warm nose compared to the GFS, so will 
give some sway to the NAM. With this in mind, expect the rain/sleet 
to become a wintry mix of rain/snow/sleet to occur with the 
deformation band that will accompany the passage of the mid-upper 
level low to our south Monday afternoon. During times of heavier 
precip rates, expect more snow/sleet, and during times of lighter 
precip rates, mostly rain/sleet. Per some of the CAM presentations, 
some of the heavier precip rates will occur during the afternoon 
hours primarily along and north of I-85. This region will stand the 
highest threat to see a minor accumulation of snow-sleet on grassy 
surfaces, and mainly slush on the roadways. Currently think an inch 
to approaching two inches of snow/sleet possible in swath from the 
INT/GSO area east-ne to Roxboro and the northern reaches of 
Granville County. Considering the strong dynamics/forcing in the 
deformation band, an isolated amount of 3-4 inches definitely 
possible. With this package, plan to issue a winter weather advisory 
for the far northern Piedmont Monday-early Monday evening.
 
For areas in the western Piedmont in vicinity of highway 64, a half 
inch or less of snow/sleet expected. In the Triangle vicinity and 
areas east-ne, the transition to sleet/snow mixture will not occur 
until mid-late afternoon. Expect the bulk of this mixture to melt on 
impact, though where heavier precip rates occur, a quick half inch 
or so may accumulate but then melt once the rates lighten up.  As 
the system exits the region Monday evening, the column should become 
cold enough to support mostly light snow for locations east and 
northeast of Raleigh with a light dusting possible, primarily north 
of Rocky Mount-Wilson.

[NCSNOW]

35 minutes ago, calculus1 said:

 

 

So, the latest Euro model and Huffman's first-call prediction both go against the dry slot being advertised by the NAM and GFS.  I do so hope they are both correct.  What do they see that our US models are not seeing?

Reality is what they see. Whole reason MA guys kept hanging on buying into the gfs and its northern outlier solution.

[calculus1]

4 minutes ago, NCSNOW said:

Reality is what they see. Whole reason MA guys kept hanging on buying into the gfs and its northern outlier solution.

No mention at all of the ECMWF in GSP's afternoon disco.  Hmmm...

Quote

.NEAR TERM /THROUGH MONDAY/...
As of 315 PM EDT: A vigorous shortwave over Missouri will dive SE
and close off into a compact upper low as it swings thru the TN
Valley and to the Carolinas tonight thru Monday. Meanwhile, at the
sfc, a weak low was analyzed over central TN with a secondary low
now showing up south of Cape Hatteras. This second low will quickly
become the primary low, as the upper wave approaches, deepening into
a typical coastal storm. As this happens, a hybrid cold air damming
wedge will hold on thru tonight, keeping temps nearly steady, if not
falling slightly thru the night. The 12z models have come in warmer
with the low-level thicknesses atop the wedge and delay the
dynamical cooling as the coastal low spins up. So this makes for a
challenging forecast with respect to timing the expected wintry
precip in the NC mountains late tonight thru Monday. Blending the
12z NAM and GFS, thicknesses stay too warm for anything but rain
until about 12z Monday. The exceptions may be along the eastern
slopes of the northern mountains, if the barrier jet from the CAD
can advect some sub-freezing temps in from the north. For now,
expect only very isolated freezing rain in the northern mountains
with a few hundredths of an inch of ice possible. Otherwise,
increasing light rain is expected with near steady temps in the
upper 30s to mid 40s. QPF should be generally around half an inch.

On Monday, guidance is in good agreement on a deformation zone
pivoting over the NC Piedmont between 12-18z as part of the
deepening coastal low. Strong mid-LVL frontogenesis is expected and
the dynamical cooling may bring temps down such that a changeover of
snow or wintry mix of sleet/snow/rain may occur in the most intense
part of the band. These areas may see a quick 1-2" of snow on grassy
surfaces, but ground temps should be too warm to cause much problems
on the roads. This combined with low confidence on exactly where the
band may set up precludes me from issuing any advisory at this time.
Using the Bourgouin technique to get precip type with a blend of the
GFS and NAM results in a changeover across the NW piedmont around
14z, possibly getting as far south as northern Mecklenburg and
Cabarrus by 16z (noon). Again, any snow accums should be mainly on
grassy and elevated sfcs and should be light. Otherwise, precip
should start tapering off, except along the TN border, as NW upslope
flow ramps up and keeps snow shower activity going thru the day.
This is when I think snow levels will finally start falling and
accums begin for the areas in our Winter Storm Warning and Advisory
areas. With all that said, I don`t plan to make any changes to the
going headlines, despite the later onset of snow and storm total snow
amts being lowered to mainly 1-3" above 3500 ft. Temps will be
tricky with cooling temps in the high terrain, near steady or only
slight warming across the I-77 corridor, and the most warming across
the Upstate and NE GA.

 

[FallsLake]

18z NAM is a crush job for RDU. Of course it's 10:1 ratios but it has ~9" at hour 30 with snow still coming down:

https://www.tropicaltidbits.com/analysis/models/?model=namconus&region=seus&pkg=asnow&runtime=2018031118&fh=31

 

Cut that by 2/3 and we could see some 3-4" totals

[FallsLake]

LOL,,,then over a foot for the folks just east of RDU:

https://www.tropicaltidbits.com/analysis/models/?model=namconus&region=seus&pkg=asnow&runtime=2018031118&fh=31

 

[SouthCentralWake]

18z NAM...sheesh

[Cold Rain]

13 minutes ago, FallsLake said:

LOL,,,then over a foot for the folks just east of RDU:

https://www.tropicaltidbits.com/analysis/models/?model=namconus&region=seus&pkg=asnow&runtime=2018031118&fh=31

 

Could not possibly draw it up any better if you were wanting worse timing.

[tramadoc]

18z NAM is a crush job for RDU. Of course it's 10:1 ratios but it has ~9" at hour 30 with snow still coming down:
https://www.tropicaltidbits.com/analysis/models/?model=namconus&region=seus&pkg=asnow&runtime=2018031118&fh=31
 
Cut that by 2/3 and we could see some 3-4" totals

Use the 3K. Better resolution.

[tramadoc]

Could not possibly draw it up any better if you were wanting worse timing.

12K isn't as good as the 3K

[FallsLake]

3K still has some high totals but they're in bands and spots across NC and VA. ^^You're right, it's probably showing a more realistic type outcome; and of course we still need to drop the totals (because of lower ratios):

https://www.tropicaltidbits.com/analysis/models/?model=nam3km&region=seus&pkg=asnow&runtime=2018031118&fh=38

 

[BIG FROSTY]

Well, I see that business is picking up in here, did somebody get Nam'd 

[tramadoc]

3K still has some high totals but they're in bands and spots across NC and VA. ^^You're right, it's probably showing a more realistic type outcome; and of course we still need to drop the totals (because of lower ratios):
https://www.tropicaltidbits.com/analysis/models/?model=nam3km&region=seus&pkg=asnow&runtime=2018031118&fh=38
 

I'm highly skeptical of anything east of RDU other than a few token flakes mixed in with a cold pissy rain.

[tramadoc]

I do have to say that this from AKQ does intrigue me.

[FallsLake]

1 minute ago, tramadoc said:

13 minutes ago, FallsLake said:

3K still has some high totals but they're in bands and spots across NC and VA. ^^You're right, it's probably showing a more realistic type outcome; and of course we still need to drop the totals (because of lower ratios):
https://www.tropicaltidbits.com/analysis/models/?model=nam3km&region=seus&pkg=asnow&runtime=2018031118&fh=38
 

I'm highly skeptical of anything east of RDU other than a few token flakes mixed in with a cold pissy rain.

The storm is going to be winding up off the coast. it will be pulling cold air down as the storm intensifies. I know it's the classic cold chasing precip, but sometimes it works out. In this particular case I think eastern folks have a shot. Then dealing with timing (..CR), the change over would occur later in the day/evening for eastern areas. But, who knows... 

[tramadoc]

The storm is going to be winding up off the coast. it will be pulling cold air down as the storm intensifies. I know it's the classic cold chasing precip, but sometimes it works out. In this particular case I think eastern folks have a shot. Then dealing with timing (..CR), the change over would occur later in the day/evening for eastern areas. But, who knows... 

AKQ has us with rain until 11pm, mix from 11pm to 2am, then snow from 2am until it winds up. I guess we will see.

[cbmclean]

28 minutes ago, tramadoc said:

40 minutes ago, FallsLake said:

3K still has some high totals but they're in bands and spots across NC and VA. ^^You're right, it's probably showing a more realistic type outcome; and of course we still need to drop the totals (because of lower ratios):
https://www.tropicaltidbits.com/analysis/models/?model=nam3km&region=seus&pkg=asnow&runtime=2018031118&fh=38
 

I'm highly skeptical of anything east of RDU other than a few token flakes mixed in with a cold pissy rain.

I agree.  Luckily for me, I am one of the few people in the world who likes cold rain.  Of course I prefer snow, but I'll take cold rain over 70's (until we get to April).

[SN_Lover]

You got DP in the teen's with a classic CAD setup and models want to keep DP's in carolina's in the 40's?? I'm sorry, I call BS. 

 

[SN_Lover]

Summetime for GA and SC folks....

 

[tramadoc]

I agree.  Luckily for me, I am one of the few people in the world who likes cold rain.  Of course I prefer snow, but I'll take cold rain over 70's (until we get to April).

Nope. Cold is for snow. I like 70's.

[SN_Lover]

Winter weather advisories now includes Durham. 

[PackGrad05]

14 minutes ago, SN_Lover said:

Winter weather advisories now includes Durham. 

Yeah since this afternoon.   

I think they need to be expanded east.  

[Buddy1987]

Guys loving the look of that ULL to our west. Thing is juiced up and is moving slowly. Someone is gonna see some solid rates late tonight and tomorrow. I keep saying it but I got a feeling with this thing that it overperforms for areas in its way. 

[kvegas-wx]

Buddy, ease up on your snowmaggedon forecasts.  If you get what you think you might get your tree damage is gonna be severe.  You get 4+ inches of concrete dropped on budding trees and you can kiss your power goodbye for a few days.   Although I could stand for these bradford pears in my yard to explode.  It would make the decision to cut them down much easier!

Is a WSW based on accums that have a duration and can be measured?  What if it snows 3-4" but it snows an inch, melts an inch, and so on?  Curious if RAH would issue a WSW even if they expected melting to occur throughout the event?

[tarheelwx]

Kvegas,

They're easing into the WSW.  If the 00z suite comes in like the 18z suite, it'll happen.  One thing they should consider, several models show very heavy frozen precip for 2-3 hours.  If this happens when they let the kids out, it could make driving very hazardous.  Sure it will melt, but snow falling at 1-2" per hour will easily overwhelm snow melting at 1/2" per hour.  I suspect it is coming either later tonight or in the morning.  Same happened for us with the December storm. 

TW

[Wow]

ULL snows can be unpredictable and very quick hitters with a heavy, wet snow.  It'll accumulate quickly and will melt just as fast once it pulls out.

[cbmclean]

53 minutes ago, tramadoc said:

1 hour ago, cbmclean said:

I agree.  Luckily for me, I am one of the few people in the world who likes cold rain.  Of course I prefer snow, but I'll take cold rain over 70's (until we get to April).

Nope. Cold is for snow. I like 70's.

To each their own.  Based on the euro metograms posted for DCA by the folks on the MA thread, I would say this is the last hurrah for coolish weather for a while

[Buddy1987]

26 minutes ago, kvegas-wx said:

Buddy, ease up on your snowmaggedon forecasts.  If you get what you think you might get your tree damage is gonna be severe.  You get 4+ inches of concrete dropped on budding trees and you can kiss your power goodbye for a few days.   Although I could stand for these bradford pears in my yard to explode.  It would make the decision to cut them down much easier!

Is a WSW based on accums that have a duration and can be measured?  What if it snows 3-4" but it snows an inch, melts an inch, and so on?  Curious if RAH would issue a WSW even if they expected melting to occur throughout the event?

I guess I’m speaking more of my area in general. I’ve seen time and time again what these ULL can do and how they almost always create havoc when they slide under you in a perfect position. Lolll good thing for me is I live in a newly developed neighborhood, so trees are at a minimum and everything is run underground. I did see Wow’s post and I agree with him. I hope some of you folks can cash in and have a little surprise.