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Potential 1/17-1/18 threat

BullCityWx

By BullCityWx,
in Southeastern States

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Auburn Dawg

Auburn Dawg

Posted
Posted
9 minutes ago, griteater said:

Euro Kuchera...1st image is current run, then previous

2.png

1.png

This is my second post, but couldn't resist... I can confirm the rates in the model in the Auburn, AL (Lee County area). It is snowing very heavily and we already have more than an inch on the grass and elevated surfaces. My house is literally right under the random 4" mark on the latest map above--good news for everyone upstream as these bands are overproducing for sure!

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Rankin5150

Rankin5150

Posted
Posted
37 minutes ago, griteater said:

Nice teardrop closed contour at 500mb on the UKMet....god we have somehow lucked out with these trends the last 2 days...now it's go time

 

1.gif

GRIT, 

You can look at the radar and see the Q-Convergence taking shape. We are in a good spot. A "crossroads" of sorts (albeit a good one!). GAME ON! 

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griteater

griteater

Posted
Posted
5 minutes ago, wncsnow said:

There is turning out to be a major coup for the CMC/RGEM. And a big fail for the NAM/GFS. Euro had the right idea first but went away from it for a bit then Canadian latched on and didnt let go

Agree on the CMC/RGEM with the precip in central and western areas.  From several days ago, I believe the Euro had the best ideas from an early standpoint....I will go back at some point and take a look as I'd like to give some credit where due in the model performance thread...we'll have to see how it all turns out first.

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WarmNose

WarmNose

Posted
Posted
2 minutes ago, Lookout said:

for any upstate folks around, just fyi..snow grains/flurries started here...very little to nothing overhead on radar depending on site. Nice to know precip on radar is actually there and not virga. 

Thanks Lookout. I'm patiently waiting on the first flakes to fly but I really need to get some sleep. Torn 

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Rankin5150

Rankin5150

Posted
Posted

Interesting update from NWS-GSP: 

NEAR TERM /THROUGH TODAY/...
As of 1230 AM EST Wednesday: Still trying to hit the moving
target. Once again, the new model guidance comes in with more precip
than previously thought, continuing the upward trend in snowfall
potential. Have not made any changes to temps, precip prob, or
snow amount with this update. What I find most interesting is how
the models develop the precip across the Piedmont in the pre-dawn
hours and around daybreak. Pay no attention to the precip upstream
moving from Alabama into Georgia, because that`s not what is going
to get us. Instead, the models show the precip blossoming across
the Piedmont, right over the top of us, in the 09Z to 12Z time
frame. Most impressive if it actually happens that way.

Otherwise, as mentioned earlier, 18z guidance came in
stronger/wetter, and 00z NAM trickling in is following that trend,
as did the 21z SREF. NWS Morristown measured a 22:1 SLR at 00z which
is a bit disturbing given the uptick in QPF, but that SLR should
modify as it crosses the mountains with the deeper moisture that
should form as the self- development of the cyclone gets a little
more geared up (nice little baroclinic leaf suggested on 1000-500mb
RH graphics by tomorrow morning). This will help to lift moisture
more into the dendritic growth zone which will moderate the SLRs,
but some mid-level frontogenesis may help to destabilize, which
would also help to lift the moisture.

With the increasing QPFs that have been a trend for the last several
runs now, see no choice but to increase snowfall amounts across the
area. Ended up blending the previous WPC QPF as well as the new 21z
SREF together, and then used the more typical WPC SLRs of 12:1-14:1
to come up with new totals that give me warning criteria across a
good chunk of the Upstate and NC Piedmont Counties. Confidence in
the higher amounts along the I-77 corridor is moderate but generally
went with the mean so at this point in time, the forecast seems
reasonable. Expect a bit of a minimum across the foothills and
adjacent Blue Ridge, and the mountains have a 4" WSW criterion
anyway. This would include all of the CLT metro area and a good
chunk of the GSP area as well.
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burgertime

burgertime

Posted
Posted
On 1/15/2018 at 4:53 PM, griteater said:

Yo Burger, hope you are doing well!  It's a decent analog, was looking at GSP's write-up on it yesterday.  I'd say this one may not be quite as dynamic though.  Check out the 540 contour on the Feb '13 storm, it's down in central Bama, whereas with this week's storm, it is on the NC/VA line.  So, it's not as strong aloft and it's a little more positive tilt.  The NAM and RGEM do show nice precip breaking out as it rolls off the mountains though

Yea this one is def more kind of clipperish. I remember that one was originally looking like a huge phase but that vort kind of rolled off almost like a ULL. Just was the first thing I thought of as. Being out of the game leaves me not so sharp haha. 

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FallsLake

FallsLake

Posted
Posted

Latest from RAH:

.NEAR TERM /TODAY AND TONIGHT/...

As of 235 AM Wednesday...

 

...Winter Storm Warning for most of Central NC through 900 PM

tonight...

...Winter Weather Advisory for the SE Coastal Plain (Wayne and Sampson

through 900 PM...

 

Changes to the forecast...

 

We will have the Winter Storm Warnings and Winter Weather Advisories

run through 900 PM this evening and raise snowfall forecast amounts

in the Warning area to between 3-6 inches.

 

Forecast trends continue to advertise a deepening/stronger and more cut

off mid-level circulation/trough that is forecast to track east across

NC this afternoon and evening. This in turn results in a slower system

which allows more QPF. Partial thicknesses support snow as the main P-

Type over the Piedmont into the Northern Coastal Plain, arriving

between 09z and 12z in the western Piedmont, spreading east into the

Triangle area by mid morning. To the southeast of the Triangle area,

the precipitation is expected to be delayed a few hours, especially

along the Interstate 95 corridor, arriving late morning or early

afternoon. The delayed system down east means that the precipitation is

expected to begin as rain, then transition to snow as the cold air wins

out mid to late afternoon.

 

Current data indicated the arctic front had reached through the

Mountains and extended NE across central VA. Bitterly cold temperatures

behind the front ranged from near zero over TN and in the 20s into

Mountains of NC and over northern VA. Temperatures were mainly in the

30s over central NC, with dew points in the 20s. The partial thicknesses

and wet bulb temperatures were already supportive of snow over most

of the Piedmont, and that is before the arctic air begins to be pulled

into the region after 12z. In addition, a low pressure was developing

along the arctic front over north Georgia. A light southerly flow into

the low pressure has aided in the increase of boundary layer moisture

(dew points in the 30s along the Savannah River in GA/SC and nosing up

into northern SC. This moisture will be transported into the system as

the mid/upper trough sharpens and cuts off through the day and the low

pressure tracks along the front. The strengthening upper feature is

responsible for the introduction of more lift/moisture transport/QPF.

This QPF is expected to be maximized over central NC late morning into

the afternoon with moderate to heavy snow.

 

Snowfall details...

 

As for the snowfall forecasts, it appears that a QPF of 0.30 to 0.50

liquid equivalent is most likely across central NC. This uses a blend

of the models. Using the 10:1 becoming 15-18:1 snow to liquid ratios

would give most of the Winter Storm Warning area between 3-5 inches in

the northwest, 3-6 inches from SW to NE through the center of the

Piedmont into the Northern Coastal Plain, and lesser 1-3 totals in the

SE Coastal Plain (which occurs at the end of the event). The least

totals should be in the Clinton to Goldsboro areas where 1-2 inches is

expected. Snowfall rates of 0.5 to nearly 1 inch an hour will be

possible for 4-6 hours given the latest guidance through the Piedmont

and Northern Coastal Plain.

 

Temperatures, precipitation timing, and P-Type details...

 

Snow is expected to develop over the Triad and Yadkin Valley region by

12z, with the heaviest snow between 12z and 18z, gradually tapering to

flurries mid to late afternoon. Temperatures will fall into the lower

to mid 20s. Snow is expected to spread into the Triangle and western

Sandhills region this morning, with the heaviest snow expected between

10 am and 4 pm. Temperatures will fall into the mid to upper 20s this

afternoon. The snow will likely begin as a period of rain in the

Central and Southern Coastal Plain late morning, then gradually

transition to snow from NW to SE as the cold air works in. Dynamical

cooling associated with heavier precipitation rates will also aid in

the change-over to snow from Fayetteville to Goldsboro mid to late

afternoon. Temperatures in the mid to upper 30s will fall quickly by

mid to late afternoon into the lower 30s in the Advisory Area. The

temperatures will drop quickly today as the arctic air surges in from

the north as the precipitation reaches maximum intensity.

 

Expect the snow to taper off from the west late this afternoon and

evening. Clearing skies will lead to bitterly cold conditions tonight.

Lows 8-18.

 

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Duncana12

Duncana12

Posted
Posted

.NEAR TERM /THROUGH TONIGHT/...

-- Changed Discussion --

As of 330 AM EST Wednesday: Still trying to hit the moving target
early this morning, as once again the new model guidance has
continued on the trend toward more precip. The models now deepen
the upper trof to the point where a low closes off this morning
and moves across the mtns this afternoon, bringing even more
forcing to bear across the Piedmont of the Carolinas in the form
of upper divergence and mid-level frontogenesis. In addition, low
level frontogenesis along the Blue Ridge Escarpment will also come
into play as the cold front hangs up for the next few hours. What
is most interesting is how the guidance shows a blossoming area
of precip developing over the foothills before daybreak and
then expanding eastward over the Piedmont through the morning
hours. Radar imagery suggests this scenario is already underway
as we have seen an increasing trend near the Blue Ridge Escarpment
since about 07Z. The latest WPC guidance and SREF raise the precip
totals even higher than before across parts of the wrn Piedmont
and ern Upstate/metro CLT, to the point where they are solidly
in Warning criteria. We are most confident of reaching warning
criteria east of I-77. Fortunately all this agrees fairly well
with our current warned area. The exception might be Alexander
County NC and the rest of the NC foothills, which we will monitor
for an upgrade depending on how the snow piles up in the next
few hours. Confidence is lagging over the rest of Upstate SC as,
once again, the colder/drier air is having a difficult time being
dislodged from the north, west, and southwest. Some of our precip
will likely be used up bringing the wet bulb temp down low enough
for precip to change to snow. At the same time, the GSP metro
area will probably remain warmer than expected through daybreak,
in the lower 30s, so road conditions might be less likely to
be adversely affected. The warning will NOT be expanded further
across the Upstate or northeast GA as a result. On the back end,
the closing off of the upper low will slow the system down a bit,
so precip chances are tapered off a few hours later into the
afternoon over the eastern zones. This suggests we are ending
the warning for metro CLT too early. It will be extended until
6 pm in part to agree with the other warnings from the RAH and
CAE offices. Temps will be well below normal today. Meanwhile,
over the NC mountains, the wind will pick up and cold advection
will take hold, dropping wind chill down to Advisory criteria
over the higher elevations. Will issue a Wind Chill Advisory that
begins with the expiration of the Winter Weather Advisory, and
that will remain in effect overnight and into Thursday morning. As
for the black ice issue, we will certainly need to address it for
tonight/early Thursday, but prefer to act on that after we get a
feel for how much snow actually falls and after we clear out some
of the Advisories and Warnings. The tonight period should be mostly
clear and cold with fresh snow across parts of the area.

-- End Changed Discussion --
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