Christmas Storm VI

[FoothillsNC]

thing to watch today is the Texas wave where it goes and the precip there . The nam has it start dying off rapidly once the line reaches DFW and is really about gone completely on the Texas coast. Right now, its extremely healthy looking, so I'd bet the nam is killing it too quickly

[Wild Weather Monger]

JB morning update FWIW-------

In some way this is similar to a late January 2000 storm that shocked many on the east coast ( see my blog from two days before that, if we have it archived) that lead Congress to get mad because a 10 inch storm hit after a forecast for flurries. That too was an error of where the storm was developing in relation to a perfect upper pattern. Folks upper lows moving from Kentucky to Nantucket and deepening dont normally dump no snow in the mid atlantic states.

Just to show you folks in the east.

But He did say there was alot of light snow deep in the south. He useing the JMA Model

We see the large area of snow, mainly light, north of the pinkish line but snow deep into the southland, a major rare event on Christmas day.

Speaking of the JMA...

[packbacker]

Looking at soundings for RDU, it is too warm at 18z for any snow Saturday afternoon but the profile cools quickly so snow will be supported by 00z Sunday. The issue therafter is saturation is decreasing rapidly as you head into the next several hours and it may switch back over to rain if this were to occur.

This is like rubbing salt in the wound, we always have temp issues. Now I hope it stays dry...a cold and rainy Xmas :-(

[bingcrosbyb]

Speaking of the JMA...

I'll take one order of the JMA. Just checked out JB's latest. Yep, he does think this is similar to January 2000. Still thinking a surprise is in store for those in teh deep south.

[Wild Weather Monger]

thing to watch today is the Texas wave where it goes and the precip there . The nam has it start dying off rapidly once the line reaches DFW and is really about gone completely on the Texas coast. Right now, its extremely healthy looking, so I'd bet the nam is killing it too quickly

Looks to be developing a healthy low level GOM tap.

http://www.ssd.noaa.gov/goes/east/eaus/flash-avn.html

[burgertime]

No its really not. There is only a small window per this run when looking at soundings. It drys out considerably where you need saturation for snow growth so just because there is .25 of QPF does not mean its all snow. It could be a lot of mix early, a dusting in between, then light rain or freezing rain at the end.

We learned this all too well here in CLT with the storm last year in December. People including myself were asking what GSP was smoking when they said that it would be mostly rain here, and low and behold we were stuck with 32.5 and rain and a heavy rain at that.

[eyewall]

I'll take one order of the JMA. Just checked out JB's latest. Yep, he does think this is similar to January 2000. Still thinking a surprise is in store for those in teh deep south.

[NCWeSU]

No its really not. There is only a small window per this run when looking at soundings. It drys out considerably where you need saturation for snow growth so just because there is .25 of QPF does not mean its all snow. It could be a lot of mix early, a dusting in between, then light rain or freezing rain at the end.

Agreed... the 00z GFS was a mostly snow scenario for RDU but it had most of the precip falling as the surface low began to enhance off the coast. This is what we need for the triangle to get significant snow. The 12z NAM has most of the precip associated with the more northerly feature.... Seems to me that the GFS is handling the precip better than the NAM at this time so we'll see what happens at 12z.

[NCSNOW]

just looked at the 12Z NAM simulated reflectivity in Texas. Nowhere near close on the progs as in actuality. Not sure if this means anything but latent heat in convection could alter it from what the NAM is predicting anyway. Theres an awful lot of convection thats is erupting way ahead of the nam it looks like.

With Frosty quoting 2000 and you talking about latent heat possibly throwing amonkey wrench in the NAM. Saw this yesterday in reviewing the post annalysis of the 2000 suprise storm. Just putting it out there, kind of ironic.

Incipient Precipitation and Latent Heat

An area of precipitation developed along a frontal system over southern Alabama and southern Mississippi at around 06Z on January 24, 2000. The area of precipitation expanded and intensified as it moved into the cold airmass north of the front in Georgia by 12Z on January 24. Analysis of surface observations and radar imagery show that this area of precipitation was poorly forecast by the Eta model. Research into this storm indicates that this under forecasted area of precipitation that fell into a cold and somewhat dry airmass across the Deep South had a significant impact in how the models handled the developing storm system.

Based on quasi-geostrophic (QG) theory, height rises (falls) occur above (below) a mid-level latent heating maximum, due to changes in the density of the air above and below. This response also creates a low-level maximum in cyclonic potential vorticity (PV), as low-level static stability is increased. The effects of the induced cyclonic PV max are manifest in wave amplification and enhanced rotation around the PV center. The precipitation across the Deep South induced a PV anomaly that enhanced the easterly flow downstream, creating stronger westward moisture advection over the Carolinas from off the Atlantic (Brennan and Lackmann 2005), thereby extending the heavy snowfall further inland. The inability of the models to accurately predict the precipitation across the Deep South was a major reason that the model forecasts of this storm were so inaccurate.

The combination of increased moisture advection, enhanced dynamics, and a deep subfreezing column of air (see GSO soundings below), created an environment that was primed for intense winter weather.

[WSNC]

http://www.ssd.noaa.gov/goes/east/eaus/flash-wv.html Pretty good look on WV.

[Cold Rain]

There are tons of blackbirds in my neighborhood this morning, so we're good. I was hoping to see this!

I agree though, this is going to come down to a nowcast situation in every way. I think we're in store for some good surprises.

[UpStateCAD]

One thing I hope i have FINALLY learned from this fiasco.............Do Not Trust the Solution ANY Model is showing beyond the 48 to 60 hours range....PERIOD.

The medium range runs are great for recognizing the basic weather pattern for those time frames. Identifying the players that might be on the field at the time, but that's about it. In fact i'm not sure I can remeber one instance of any model calling for a storm even in the 120 hour range that verified relatively closely. The exception to this may be some of the ice storms that are depending on a nice HP in the NE in a fairly simple pattern with moisture coming in from the gulf.

YOu can almost bank on any sort of "good" run in the 5 to 10 day range NOT verifying........and as we have seen this go round that included the ALMIGHTY EURO.

Hoprefully I can watch some flurries in the air tommorow which if you would have told me I would see last week I would have been estatic about.

I continue watching how this plays out because it has been very educational thsnks to our SE mets and more knowledgable posters. I learn a little more with each storm we track whether it verifies or not.

Merry Christmas Guys!! :snowman:

[burgertime]

12z GFS has initialized...let's see where she goes (not that it matters much at this point)

[Cold Rain]

One thing I hope i have FINALLY learned from this fiasco.............Do Not Trust the Solution ANY Model is showing beyond the 48 to 60 hours range....PERIOD.

The medium range runs are great for recognizing the basic weather pattern for those time frames. Identifying the players that might be on the field at the time, but that's about it. In fact i'm not sure I can remeber one instance of any model calling for a storm even in the 120 hour range that verified relatively closely. The exception to this may be some of the ice storms that are depending on a nice HP in the NE in a fairly simple pattern with moisture coming in from the gulf.

YOu can almost bank on any sort of "good" run in the 5 to 10 day range NOT verifying........and as we have seen this go round that included the ALMIGHTY EURO.

Hoprefully I can watch some flurries in the air tommorow which if you would have told me I would see last week I would have been estatic about.

I continue watching how this plays out because it has been very educational thsnks to our SE mets and more knowledgable posters. I learn a little more with each storm we track whether it verifies or not.

Merry Christmas Guys!! :snowman:

Good post! Agree 100%

[burgertime]

Our low is stronger in Tx. @12 then the 6z GFS was.

[crossthread]

KILM AFD Valid @ 9:30am this morning..

Looks like we'll be affected by a "Warn Nose"????? or Warm Air Advection?

Short term /Saturday through Sunday night/...

as of 3 am Friday...low pressure along the western Gulf Coast at the

start of the period will move east along the Gulf Coast and northern

Florida ending up off the southeast coast late Sat night/early sun. 00z

GFS/European model (ecmwf) showing a little more agreement... but still some

significant differences with respect to timing and location. European model (ecmwf)

is a little farther off the coast but is faster and little weaker

than the GFS.

Based on forecast soundings event starts light rain across far

western areas late Christmas day...slowly spreading over the area.

Light precipitation falling into low level dry air will result in

evaporational cooling. Cooling combined with cold advection drops

temperatures close to freezing by midnight inland and a little later

closer to the coast. Majority of the forecast soundings keep an

above freezing layer below 800 or 900 mb...but with colder air aloft

expect precipitation to help mix colder air down. Additionally guidance

always underestimates the dry air in Arctic air masses...even those

that are modifying as is the case Sat. These factors point to a

rain/snow mix changing to all snow as the surface low passes off the

coast late Sat night. So while it looks like snow will fall and some

areas will see an inch plus...most likely inland NC...am not quite

ready to go with a watch.

Confidence remains on the low side and a small shift in the track

will result in more rain than snow...if the low passes closer...or

little to no precipitation falls...low passes farther off the coast and is

weaker...as suggested by the 00z NAM and the last three runs of the

Canadian. Given that the event is Sat night...fourth period...will

hold off raising any headlines with this package.

(My edit, I hope they bust, wrong, or I mean in the right direction OUR way!)

Event should be over Sun morning though light snow flurries/showers

may linger into Sun afternoon. Plenty of moisture aloft sun and

shortwave rotating around base of upper trough just west of the area

should be able to get some precipitation going. Cold advection in

conjunction with cloud cover will keep highs well below climatology. Have

undercut guidance by a good bit but may not be cold enough and some

areas may struggle to get above freezing. Cold advection continues

Sun night...preventing radiational cooling...but cold air mass

combined with highs in the 30s on sun will result in lows in the

upper teens to lower 20s.

Current obs folks..

35.5 °FClear

Windchill:28 °F

Humidity:69%

Dew Point:27 °F

Wind:11.3 mphfrom the NNW

Wind Gust:16.3 mph

Pressure:30.23 in Falling

(My Edit, forcast high of 45 today & 50F tomorrow, as long as We've got NNW winds I cannot see us getting or reaching the mid-40's much less forcast high of 50F tommorrow)..

Here's HOPING everyone see's @ least a 1" or 2", maybe even a trace too 1/1/2 here on the coast, maybe more with Wrap-around moister, as the Low exits. hopfully craws up the coast, or STALLs right off KILM!..

[DopplerWx]

Our low is stronger in Tx. @12 then the 6z GFS was.

Low keeps trending stronger and stronger.

[NEGa]

at this point i am just looking to see if there is any qpf over the interior of the se to give us some light snow tomorrow. trying to decide where to spend christmas eve for the best chance of a wake up snow flake

[burgertime]

@15 it's keep that low in Tx. really strong compared to the 6z run. Also the energy up north isn't as fast and is slightly south west.

[FoothillsNC]

i have to say that this system is still very ripe for a big surprise. I wasn't expecting to see the development with Texas as I'm seeing now, and it appears theres a chance that will become a neutral tilt trough, and if it does, then whoa watch out...if it can get just a wee bit more speed, or even hold its current speed, the RUC has a look to it at 18 hours, which is the closest you'll ever see of "not phasing" but about to. The JMA is possible.

[burgertime]

@21 our low is more NE....also looks like the energy to our north is weaker and getting flattened out?

[burgertime]

Hey Robert, is it just me or does the GFS look really friggin close to something big @24?

[bingcrosbyb]

Oh man. 1013mb LP in the gulf. Here we go. @ 24HR.!

[Wow]

the southern s/w is more NE.. faster.. good grief that northern s/w is so close to just dropping in behind and phasing. It's right there!

[NEGa]

Hey Robert, is it just me or does the GFS look really friggin close to something big @24?

what i wouldnt give for that L and blob of moisture down in louisiana to head ne into n ga and the western carolinas i just hope we dont get the infamous split north/south of n ga and the western carolinas.

[burgertime]

@27 it looks like it's lining up almost perfectly for a phase....can a pro please chime in.

[Wow]

@24.. southern s/w FASTER... northern piece of energy pulling further west behind. i swear this is a phase if i never saw one. s/w is stronger too.. closed contour

[bingcrosbyb]

GFS could be HUGE. @ 24HR, vort is north of 00z/06z. 1013mb in the gulf. Let's go.

[FoothillsNC]

Dude, you're killing me!

:popcorn:Well this is pins and needles for sure for us, but we know we're probably not that lucky here. Anyway at 24, the GFS is on the sw LA coast, stronger, for longer. The trend of that has been with every run, obviously its not going to die as the models keep insisting. At 27 hours, its closed over southern LA and about to go negative tilt it appears. but the northern stream may not be sharp enough, but still, I kind of like that trend for the Coastal Areas to get someing substantial.

[NCSNOW]

Got a shot at 24. Southern wave in front and northern now can come in behind.