Friday Night/Saturday Morning Freezing Rain Threat

[FallsLake]

RAH (long) discussion; basically they don't think it will amount to much, but concede at the end there is a chance this could over perform:

NEAR TERM /TODAY and TONIGHT/... Updated to include additional
forecast discussion at bottom of the near term.
As of 445 AM Friday...

Advisory for any icing not anticipated for tonight at this time.

Confidence in some very light freezing rain/mist overnight (a
nuisance event) remains low in the NW and north-central Piedmont,
mainly NW of Raleigh. Elsewhere, confidence is higher that it will
be a non-event as any precipitation will be very light and the
temperatures marginal for icing concerns.

Of course, any icing -no matter how patchy in the wrong location can
lead to driving issues. This is the only thing that makes this
expected very light possibly freezing rain/mist event potentially
hazardous.

First things first, Increasing and thickening cloudiness today as
the cold surface high moves overhead this morning, then shifts off
the Mid-Atlantic coast this afternoon. Models show a lingering then
redeveloping ridge axis SW from the center of the surface high
pressure back inland over the Piedmont Damming Region of VA/NC/SC by
this evening and overnight, with the development of a coastal trough
just offshore of the Carolina`s late today and tonight. The latter
feature may very well play an important role in limiting QPF and POP
inland, deep in the developing stable dome. Highs today have warmed
a few degrees from yesterday`s guidance, now most statistical
guidance indicates 36-38 Triad, 38-40 Triangle, 40-42 at FAY/GSB.
Obviously, these readings are above freezing which will also play a
role in tonight`s light precipitation event.

For tonight, the GFS/NAM forecast only trace to 0.05 liquid
equivalent amounts between 00Z/12Z with only a trace to 0.01 in the
first 6 hours (ending at 06Z) around midnight. The EC forecasts are
about the same with timing and amounts, but focus the QPF more along
the developing coastal trough later tonight and early Saturday.
There is a small pocket of 0.03 to 0.07 amounts are forecast for the
NE Piedmont, with lesser totals to the west. The SREF averages still
indicate around a few hundredths of QPF, and due to the very dry
boundary and near surface layer that has to moisten up, this QPF is
mainly after 06Z. And that is very critical when partial thicknesses
are considered.

What we do know is that all models agree in that the parent high
will shift offshore today, leaving residual very dry (dew points
around zero initially) and chilly (highs in the 30s most areas
today).
A strong WAA pattern with increasing S-SW flow to 40-50kt indicated
later this evening and overnight from a top the dry boundary layer
to H7 will aid in shallow lift. However, must of this lift is
forecast to quickly shift north of our region later tonight. This
leaves the window of time of any potential for precipitation to be
mainly between 06Z-12Z. Again the first few hours will go into
simply moistening the boundary layer.

As for the critical temperatures and P-Type, this will be a real
battle just to simply get any icing, even in the climatological
favored NW and N Piedmont per the forecast partial thicknesses/ and
applied Universal Nomogram/ very low QPF (less than 0.10 expected).

Using all the above, the most likely forecast critical thicknesses
using a blend of the latest models indicates enough warming even at
1000/850 (from the 1290s through the critical 1315-1320M range) in
all areas south and east of a line extending from Stanly County NE
to Chatham/Durham to Warren County around 06Z/tonight. This combined
with very strong warming aloft with 1560-1570M mid level thickness
forecasts (too warm aloft for anything than rain) all areas by 06Z.
These forecast thicknesses using the Nomogram implies any very light
freezing rain would occur based on enough moistening and evaporative
cooling to "wet bulb" temperatures down to freezing or below. This
process, most likely will not be able to complete itself given the
very dry antecedent air by 06z.

In the most critical time for any icing, between around 06Z through
12Z, dramatic rises continue to be forecast by the models for the
partials, even in the lowest 1000/850 layer. Most areas, even
Winston-Salem and Roxboro are forecast to be in the 1330M+ range by
12Z, with mid level warming into the 1570s, and the distinct warm
nose topping 12 to 15 degrees C aloft. This strongly suggests that
any light freezing rain would most likely occur between 06Z-10Z or
so, and confined to the Triad to Roxboro and Henderson, as far south
as possibly N Durham. However, given the warming aloft and the very
marginal road temps (likely 33+), it appears that any icing problems
would be confined to bridges and overpasses, and most likely in
areas that are typically the coldest low-lying areas away from solar
energy from the previous day.

The most likely forecast tonight, a chance of light rain south and
east of Raleigh, a chance of mixed light freezing rain/rain NW and N
Piedmont, mainly late this evening and overnight. Any light icing
should be limited to normally colder spots including possibly
bridges and overpasses from the Triad to Roxboro. Icing is not
expected elsewhere. Lows 28-32 NW and N Piedmont late this evening,
rising to 32+ by daybreak. Lows 30-35 elsewhere early in the
evening, rising into the mid 30s by 12z/Saturday.
QPF of 0.05 on average, with only Trace ice possible in the
aforementioned areas. Again, a trace of ice in the wrong location
can be a serious weather hazard, so be extra cautious tonight, NW of
Raleigh, just in case. Temps rise well above 32 by 13Z/Sat.

What could go wrong? The precipitation turns out to be slightly more than
currently forecast, I.E. enough precipitation falls to allow for
evaporative cooling of the surface temperatures very close to the
wet bulbs. Since the air mass is so dry and cold initially,
the partial thicknesses, universal nomogram, and the wet bulb
32 degree placement all point to the amount of light precipitation
to be the most critical issue with this potential
icing forecast.

If around 0.10 can be realized during the critical time frame before 12z/Sat.,
the above thinking would put the Interstate 40/85 corridor into a potential
advisory for light icing. However, the current probability of this worst
case scenario is only about 25-30 percent in that region.

&&

 

[weatherlover]

Where will the moisture come from for tonight's "event"?  Radar looks dry as a bone all across the south this morning

[mackerel_sky]

10 minutes ago, weatherlover said:

Where will the moisture come from for tonight's "event"?  Radar looks dry as a bone all across the south this morning

What little there is will just pop up from moist up glide as return flow starts ahead of the system/front

[strongwxnc]

High thin clouds have made it to the southern foothills.


Sent from my iPhone using Tapatalk

[strongwxnc]

High thin clouds have made it to the southern foothills.


Sent from my iPhone using Tapatalk

[SteveVa]

Cloudy and 28, there are even some virga around. wasn't it supposed to be mostly sunny today?

[No snow for you]

29 here at KGMU with a light cloud cover. Expected high today is 40 with a low of 33. Oops. Also DP is 2

[weatherlover]

if we get any moisture at all tonight it's going to be an ice skating rink in the morning.  Sitting at 29 here in the piedmont

[Brick Tamland]

Looks like the temp forecast is going to bust today for most folks. 30 here with a high of 33 in the forecast. Not sure it will make a difference, though, because it looks like lack of precip is what will keep this from being a big deal. 

[FallsLake]

Freezing rain advisory for central NC. Can't post image or advisory, on phone. 

[FallsLake]

Here's the advisory:

Freezing Rain Advisory

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE RALEIGH NC
138 PM EST FRI DEC 16 2016

...LIGHT FREEZING RAIN WILL RESULT IN DANGEROUS TRAVEL CONDITIONS
ACROSS CENTRAL NC TONIGHT THROUGH EARLY SATURDAY ...

.MOISTURE OVERSPREADING ANTECEDENT COLD AIR WILL RESULT IN LIGHT
FREEZING RAIN OVERSPREADING CENTRAL NC TONIGHT.

NCZ007>011-021>028-038>043-073>077-083-084-170900-
/O.NEW.KRAH.ZR.Y.0001.161217T0000Z-161217T1400Z/
PERSON-GRANVILLE-VANCE-WARREN-HALIFAX-FORSYTH-GUILFORD-ALAMANCE-
ORANGE-DURHAM-FRANKLIN-NASH-EDGECOMBE-DAVIDSON-RANDOLPH-CHATHAM-
WAKE-JOHNSTON-WILSON-STANLY-MONTGOMERY-MOORE-LEE-HARNETT-ANSON-
RICHMOND-
INCLUDING THE CITIES OF...BUSHY FORK...CONCORD...ROXBORO...SURL...
OXFORD...BUTNER...CREEDMOOR...DABNEY...HENDERSON...NORLINA...
WISE...AFTON...WARRENTON...LAKE GASTON...ROANOKE RAPIDS...
PFAFFTOWN...STANLEYVILLE...WINSTON-SALEM...GREENSBORO...
LAKE TOWNSEND...HIGH POINT...BURLINGTON...GRAHAM...CHAPEL HILL...
CARRBORO...BETHESDA...DURHAM...RESEARCH TRIANGLE...PILOT...
INGLESIDE...LOUISBURG...FRANKLINTON...NASHVILLE...AVENTON...
RED OAK...SHARPSBURG...SPRING HOPE...ROCKY MOUNT...LEXINGTON...
THOMASVILLE...ASHEBORO...ULAH...ARCHDALE...TRINITY...HASTY...
SILER CITY...BYNUM...MONCURE...PITTSBORO...RALEIGH...CARY...
SMITHFIELD...CLAYTON...FLOWERS...SELMA...BENSON...
COATS CROSSROADS...NEW HOPE...WILSON...ALBEMARLE...PLYLER...
TROY...BISCOE...MOUNT GILEAD...PEKIN...BADIN LAKE...ELDORADO...
SOUTHERN PINES...PINEHURST...ABERDEEN...EAGLE SPRINGS...
SEVEN LAKES...CUMNOCK...GUM SPRINGS...SANFORD...TRAMWAY...DUNN...
ANDERSON CREEK...TIMBERLAKE...DUNCAN...ERWIN...ANGIER...
LILLINGTON...WADESBORO...POLKTON...ROCKINGHAM...HAMLET...
EAST ROCKINGHAM
138 PM EST FRI DEC 16 2016

...FREEZING RAIN ADVISORY IN EFFECT FROM 7 PM THIS EVENING TO
9 AM EST SATURDAY...

THE NATIONAL WEATHER SERVICE IN RALEIGH HAS ISSUED A FREEZING
RAIN ADVISORY...WHICH IS IN EFFECT FROM 7 PM THIS EVENING TO 9 AM
EST SATURDAY.

* LOCATIONS...MUCH OF CENTRAL NC, NORTH AND WEST OF A LINE
  EXTENDING FROM HAMLET TO DUNN TO TARBORO.

* HAZARD AND TIMING...LIGHT FREEZING RAIN IS EXPECTED TO SPREAD
  ACROSS THE AREA LATE THIS EVENING WITH A SE TO NW CHANGE-OVER TO
  RAIN OVERNIGHT.

* ACCUMULATIONS...ICE ACCRUAL WILL RANGE FROM A TRACE TO SEVERAL
  HUNDREDTHS OF AN INCH, AND MAINLY CONFINED TO ELEVATED SURFACES.

* IMPACTS...ICING MAY CREATE SLIPPERY ROAD CONDITIONS ESPECIALLY
  ON BRIDGES AND OVERPASSES AND SIDEWALKS.


* TEMPERATURES...IN THE UPPER 20S TO LOWER 30S.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FREEZING RAIN ADVISORY MEANS THAT PERIODS OF FREEZING RAIN OR
FREEZING DRIZZLE WILL RESULT IN HAZARDOUS TRAVEL CONDITIONS. BE
PREPARED FOR SLIPPERY ROADS. DRIVERS ARE URGED TO SLOW DOWN...
LEAVE PLENTY OF FOLLOWING DISTANCE....AND TO EXERCISE EXTREME
CAUTION AT INTERSECTIONS AND ON HIGHWAY ONRAMPS AND OFFRAMPS
WHERE ACCIDENTS ARE MORE LIKELY TO OCCUR.

&&

$$

[FallsLake]

Here's the current warnings and advisories across the US:

 

[burrel2]

Well, no surprise here but the 18z 4k NAM just took a huge jump colder. It now keeps the I-85 region of SC below freezing until 10am tomorrow morning. It also has this area bottoming out in the 29/30 range where prior runs were bottoming out in the 31 range.

Precipitation still doesn't look impressive with maybe .01 to at most .10 of liquid falling during that time frame. I think area's around and just to the west of Raleigh have a chance of seeing >.10 of liquid.

[mackerel_sky]

ZR advisory!

[drfranklin]

11 minutes ago, mackerel_sky said:

ZR advisory!

Nothing "south" of I-85 - guarantee it!

See Kendra Kent's latest blog post - rain after 5am and into the balmy 50's tomorrow.

[burrel2]

4 minutes ago, drfranklin said:

Nothing south of I-85 - guarantee it!

See Kendra Kent's latest blog post - rain after 5am and into the balmy 50's tomorrow.

That's one of the worst forecasts I've ever seen.

1. The mountains will go above freezing before the upstate.

2. I'll never analyze another weather model again if the upstate is in the 50's tomorrow afternoon.

[drfranklin]

12 minutes ago, burrel2 said:

That's one of the worst forecasts I've ever seen.

1. The mountains will go above freezing before the upstate.

2. I'll never analyze another weather model again if the upstate is in the 50's tomorrow afternoon.

someone needs to leave a comment on her blog post - not sure if she will even read it

[BlueRidgeFolklore]

12 minutes ago, burrel2 said:

That's one of the worst forecasts I've ever seen.

1. The mountains will go above freezing before the upstate.

 

The French Broad River valley and the areas along the escarpment will trap cold air longer than the upstate will, especially as the cold begins to retreat NE away from the upstate. You are correct about the higher elevations and inversion. 

[mackerel_sky]

22 minutes ago, drfranklin said:

someone needs to leave a comment on her blog post - not sure if she will even read it

She does read them, she's replied back to my comments before

[LithiaWx]

The warm push from the SE is intense.  Went from 26 this morning to almost 50 now here in west Atlanta. 

[strongwxnc]

Current obs.
Dew points in greenish



Sent from my iPhone using Tapatalk

[NEGa]

1 hour ago, burrel2 said:

Well, no surprise here but the 18z 4k NAM just took a huge jump colder. It now keeps the I-85 region of SC below freezing until 10am tomorrow morning. It also has this area bottoming out in the 29/30 range where prior runs were bottoming out in the 31 range.

Precipitation still doesn't look impressive with maybe .01 to at most .10 of liquid falling during that time frame. I think area's around and just to the west of Raleigh have a chance of seeing >.10 of liquid.

this cad appears to be a pretty decent one and gradually got "cooler" as we approached the event. the real issue is lack of precip.  with such low dewpoints and little qpf looks like we are going to just barely miss what could have been a nice little winter wx event    we need to get another one of these cads in here with .25 or so of moisture then it would get really interesting lol. 

[franklin NCwx]

When they refer to the mtn they're talking about Asheville and Hendersonville.  The areas west of Asheville don't exist to them.

[VanillaDream]

The warm push from the SE is intense.  Went from 26 this morning to almost 50 now here in west Atlanta. 

Yeah I was in Lithia Springs earlier and it was 51 there. Got back home up near holly springs and it's currently 36.8 with gusty east winds. The wedge is an amazing thing for sure!


Sent from my iPhone using Tapatalk

[BIG FROSTY]

26/4 WHERE is the moisture when you need it?????????????????????????????????????  

[mackerel_sky]

25 minutes ago, BIG FROSTY said:

26/4 WHERE is the moisture when you need it?????????????????????????????????????  

JB's bathtub!! 

[LithiaWx]

1 hour ago, VanillaDream said:

Yeah I was in Lithia Springs earlier and it was 51 there. Got back home up near holly springs and it's currently 36.8 with gusty east winds. The wedge is an amazing thing for sure!


Sent from my iPhone using Tapatalk

I am right in the edge of the cad.  Temp is dropping again but I knew when I moved from Cobb county to Lithia I would get even less cad. The cutoff line is amazingly sharp. 

[burrel2]

Some light returns are starting to show up on the Columbia, SC radar. Looks like they might be reaching the ground as you can see the returns right next to the radar site where the beam is close to the ground.

[FallsLake]

22 minutes ago, burrel2 said:

Some light returns are starting to show up on the Columbia, SC radar. Looks like they might be reaching the ground as you can see the returns right next to the radar site where the beam is close to the ground.

I see that. Could start getting interesting soon.

[jburns]

4 hours ago, burrel2 said:

That's one of the worst forecasts I've ever seen.

1. The mountains will go above freezing before the upstate.

2. I'll never analyze another weather model again if the upstate is in the 50's tomorrow afternoon.

 

Be careful. They have 47 way up here in Greensboro tomorrow. 47 is also forecast to be the low tomorrow night before a 62 on Sunday. This will be a strong push of warm air with the wind speeds to get the job done quickly.  What will your next hobby be?