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Winter Storm 1/6 - 1/8, 2017


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KMHX just upgraded to Warning for parts of their forcast area




...WINTER STORM WARNING IN EFFECT FROM 10 PM FRIDAY TO 1 AM EST
SUNDAY...

THE NATIONAL WEATHER SERVICE IN NEWPORT/MOREHEAD CITY HAS ISSUED
A WINTER STORM WARNING FOR SNOW, SLEET AND POSSIBLY FREEZING RAIN
...WHICH IS IN EFFECT FROM 10 PM FRIDAY TO 1 AM EST SUNDAY. THE
WINTER STORM WATCH IS NO LONGER IN EFFECT.

* LOCATIONS...GREENE, PITT, MARTIN, WASHINGTON, AND TYRRELL
  COUNTIES.

* HAZARD TYPES...RAIN FRIDAY EVENING WILL CHANGE OVER TO SNOW AND
  SLEET AFTER MIDNIGHT THEN CONTINUE INTO SATURDAY AFTERNOON. SOME
  FREEZING RAIN WILL BE POSSIBLE LATE FRIDAY NIGHT INTO SATURDAY
  MORNING.

* ACCUMULATIONS...SNOW AND SLEET ACCUMULATION OF 3 TO 5
  INCHES...ALONG WITH A MINOR ACCRETION OF ICE.

* TIMING...THE HEAVIEST PRECIPITATION WILL OCCUR FROM MIDNIGHT
  FRIDAY NIGHT THROUGH EARLY SATURDAY AFTERNOON.

* IMPACTS...THE HEAVY SNOW AND SLEET WILL CREATE SNOW COVERED
  ROADS AND PRODUCE SCATTERED POWER OUTAGES.

* TEMPERATURES...DROPPING INTO THE UPPER 20S FRIDAY NIGHT AND
  LIKELY REMAINING AT OR BELOW FREEZING SATURDAY.
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excerpt from KRAH warning

 LOCATIONS...MOST OF CENTRAL NORTH CAROLINA, INCLUDING ALL OF THE
  PIEDMONT, NORTHERN COASTAL PLAIN, AND THE NORTHERN PORTIONS OF
  THE SANDHILLS.

* HAZARD TYPES...SNOW... OR A MIXTURE OF SNOW AND SLEET

* ACCUMULATIONS...SNOW ACCUMULATION OF 3 TO 5 INCHES WITH LOCALLY
  HIGHER AMOUNTS OF 5 TO 7 INCHES EXPECTED FROM THE CENTRAL
  PIEDMONT TO THE NORTHERN COASTAL PLAIN.

* TIMING...PRECIPITATION IS EXPECTED TO BEGIN AS A WINTRY MIX LATE
  FRIDAY AFTERNOON AND EVENING, TRANSITIONING TO ALL SNOW WEST OF
  HIGHWAY 1, AND A MIX OF SNOW AND SLEET SOUTH AND EAST OF THE
  TRIANGLE FRIDAY NIGHT. THE HEAVIEST PRECIPITATION WILL OCCUR
  BETWEEN MIDNIGHT AND NOON SATURDAY.
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1 minute ago, SN_Lover said:

with a 40mb gradient between the high and the low and the low being under the right rear quadrant of the jet, it's possible. 

 

Yeah once the low is in the Atlantic and the comma cloud begins to form....sure, but I don't think the storm will be dynamic enough for snow rates of 2+ inches an hour while the low is still passing under/over Georgia. FFC is talking convective banding that drops " a few inches" in an hour. A little too much.

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RAH AFD:

...Winter storm warning in effect for much of central NC from Friday
evening through Saturday evening...

Models are still showing a good chance for winter weather
beginning on Friday night through Saturday as a low pressure
system develops along the southeast coast and interacts with an
arctic airmass moving into the area from the central CONUS. The
latest model trends have come more in line with climatology for a
winter event for central NC in that the models have trended warmer
across the southern tier of the forecast area and the main axis of
heaviest snow has been displaced north and westward along the
US-64 corridor from Chatham county through the Triangle and
through Rocky Mount. Points south and east of this line will have
more of a mix of precipitation types introduced which will cut
down on snowfall totals but will increase the sleet and freezing
rain potential. So counter-intuitively this area could see a
reduction in snowfall totals but an increase in potential impacts
due to very poor travel conditions as a result of the possible
freezing rain.

Most likely scenario: At this point the most likely scenario is for
a heavier band of snow between I-85 and US 64 corridors, including
the Triangle with most likely amounts in this area are between 5-7
inches with locally higher totals possible. The cutoff line for snow
to the north of this corridor may be very rapid due to lack of
moisture so VA border so confidence in snowfall totals in the Triad
at this time are very low but 3-5 inches is a first guess.

To the south of US-64 expect an increasing amount of wintry mix into
the precipitation equation will erode snowfall totals. Do not want
the shift the forecast too much because the track of the low is
uncertain but expect 3-5 inches immediately south of 64 with more of
a 2-4 inch range through much of the sandhills and lower I-95
corridor with potentially less than that along the southern tier
counties. These areas will be more susceptible to a prolonged period
of rain/sleet/snow mix with potentially freezing rain both at the
onset and the end of the event. This could result in some small ice
accretions.

Bust potential: The most likely bust potential is across the south
were significant warming in the low levels could extend the period
of liquid rain and sleet and severely cut down any snowfall
accumulations.

On the other side of the coin, there is bust potential on the high
side through the Triad area and along the VA border counties where
if enough moisture makes it back into that area, it will certainly
be cold enough to support higher snowfall totals than the 3-5 inches
currently expected.

P-Type progression and timing: North of 64, the event will start
off on Friday afternoon as rain in most locations with the
exception of the Triad which could be cold enough aloft to support
a rain/snow mix. Depending on the track of the low we could see a
changeover to snow across the north with sleet/snow mix across the
US 64 corridor late Friday evening or during the overnight hours.
This should change to all snow by Saturday morning and continue
through the end of the event.

The southern tier could be much more complicated as the event should
begin as rain on Friday afternoon and could continue as rain well
into the overnight hours Friday before a period of freezing rain
early Saturday morning will proceed a changeover to snow or
snow/sleet mix near daybreak which will continue into the early
afternoon before potentially ending with another brief period of
freezing drizzle as the precipitation exits the area to the east.
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1 minute ago, LovingGulfLows said:

 

Yeah once the low is in the Atlantic and the comma cloud begins to form....sure, but I don't think the storm will be dynamic enough for snow rates of 2+ inches an hour while the low is still passing under/over Georgia. FFC is talking convective banding that drops " a few inches" in an hour. A little too much.

Why not? The models have been hinting at the narrow band of heavier accumulations for a while now.

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10 minutes ago, Queencitywx said:

For those in the metro, looks like if you draw a line from CLT to Concord Regional, if you're North and west, you're okay. 

I'm in the snow. Woo hoo! :) I doubt this thing becomes that amped and warm, so close to the coast.  If it were going to, I don't think the NAM would lead the way, IMO. 

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18 minutes ago, Brick Tamland said:

No denying the NAM looks bad for the Triangle. Looks way too warm. Crazy seeing the Euro and GFS still have a major snow storm here this close to go time and the NAM looks like mostly rain here. Not sure what to think.

Still pretty good. eastern wake county maybe mixed with sleet/rain for a couple hours. Temps are 32.5-33 with cold layer Beneath warm layer  deeper  than warm nose so likely sleet.

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25 minutes ago, Snow Miser said:

12Z GFS keeps the heavier precip around much longer for our area. If the 18Z NAM were to verify most of the heavy stuff looks like it's gone before 850s really drop to a safe level. Definitely going to be very sharp cutoffs in the ATL/Athens area. I'd hate to be any further east of Athens with the warm nose.

well truth be told i think the models are over playing it a little bit as far as temps go at the surface in the upper savannah river valley considering low wetbulb zero heights, heavy precip, and time of day. The fact most falls at night will help quite a bit vs the day time in terms of helping to bring colder air to the surface. The warm surface temps  is the primary reason why the model is "seeing rain" and not sleet or snow..if it is just 2 degrees cooler they probably would be showing something else in their output.

that said, the nam has a more prominent warm nose than the gfs centered above 850mb.. around 750 to 800mb south of a line from rome to gainesville to toccoa into friday evening.....which means there could actually be more heavy sleet than initially expected if it's profile is correct.

As you can see here..this is atlanta's profile from the 18z nam valid 06z friday. Note the ELW around 750 mb

SFC  987   273  -0.8  -3.5  82  2.7  -1.9 319  10 273.4 273.9 272.1 281.5  2.98
  2  950   572  -3.8  -4.8  93  1.0  -4.2 329  16 273.3 273.8 271.7 281.0  2.80
  3  900   999  -3.0  -3.3  98  0.3  -3.1  45  14 278.4 278.9 275.4 287.6  3.32
  4  850  1452  -3.0  -3.2  98  0.2  -3.1 101   3 283.0 283.6 278.2 293.0  3.54
  5  800  1933  -1.2  -1.4  98  0.2  -1.3 230  24 289.9 290.7 282.3 302.4  4.32
  6  750  2453   2.0   1.8  99  0.2   1.9 233  49 298.8 299.8 287.4 316.0  5.82
  7  700  3009  -0.3  -0.4  99  0.1  -0.4 236  58 302.1 303.1 288.1 318.1  5.30
  8  650  3598  -4.1  -4.4  98  0.3  -4.3 240  67 304.3 305.1 287.9 317.3  4.23
  9  600  4225  -7.5  -8.4  93  0.9  -7.9 238  74 307.4 308.1 288.1 318.0  3.38
 10  550  4897 -12.4 -14.0  88  1.6 -12.9 236  80 309.4 309.8 287.8 316.9  2.35
 11  500  5617 -17.4 -20.6  76  3.2 -18.3 233  85 311.8 312.1 287.6 316.7  1.48
 12  450  6398 -23.1 -29.0  59  5.9 -24.2 234  91 314.2 314.4 287.7 316.9  0.78

 Considering the potentially convective and heavy nature of the precipitation, i believe there is the potential for more dynamical cooling than what is being shown...which could in fact destroy that very narrow warm nose. I'm actually a but surprised the models aren't showing more of it to be honest......as i've seen less impressive precip rates/lift produce more cooling in the face of  strong waa in other situations. But it's something that is hard to pin down and even harder to count on. 

 

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2 minutes ago, RaleighWx said:

Still pretty good. eastern wake county maybe mixed with sleet/rain for a couple hours. Temps are 32.5-33 with cold layer Beneath warm layer  deeper  than warm nose so likely sleet.

Sounds like RAH thinks I'll be all snow, but not sure how much. This one really does seem up in the air. You have the NAM looking like it'll be more and more rain here, and everything else pointing to a big snow storm. 

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1 minute ago, Lookout said:

well truth be told i think the models are over playing it a little bit as far as temps go at the surface in the upper savannah river valley considering low wetbulb zero heights, heavy precip, and time of day. The fact most falls at night will help quite a bit vs the day time in terms of helping to bring colder air to the surface. The warm surface temps  is the primary reason why the model is "seeing rain" and not sleet or snow..if it is just 2 degrees cooler they probably would be showing something else in their output.

that said, the nam has a more prominent warm nose than the gfs centered above 850mb.. around 750 to 800mb on a line from rome to gainesville to toccoa into friday evening.....which means there could actually be more heavy sleet than initially expected if it's profile is correct.

As you can see here..this is atlanta's profile from the 18z nam valid 06z friday. Note the ELW around 750 mb


SFC  987   273  -0.8  -3.5  82  2.7  -1.9 319  10 273.4 273.9 272.1 281.5  2.98
  2  950   572  -3.8  -4.8  93  1.0  -4.2 329  16 273.3 273.8 271.7 281.0  2.80
  3  900   999  -3.0  -3.3  98  0.3  -3.1  45  14 278.4 278.9 275.4 287.6  3.32
  4  850  1452  -3.0  -3.2  98  0.2  -3.1 101   3 283.0 283.6 278.2 293.0  3.54
  5  800  1933  -1.2  -1.4  98  0.2  -1.3 230  24 289.9 290.7 282.3 302.4  4.32
  6  750  2453   2.0   1.8  99  0.2   1.9 233  49 298.8 299.8 287.4 316.0  5.82
  7  700  3009  -0.3  -0.4  99  0.1  -0.4 236  58 302.1 303.1 288.1 318.1  5.30
  8  650  3598  -4.1  -4.4  98  0.3  -4.3 240  67 304.3 305.1 287.9 317.3  4.23
  9  600  4225  -7.5  -8.4  93  0.9  -7.9 238  74 307.4 308.1 288.1 318.0  3.38
 10  550  4897 -12.4 -14.0  88  1.6 -12.9 236  80 309.4 309.8 287.8 316.9  2.35
 11  500  5617 -17.4 -20.6  76  3.2 -18.3 233  85 311.8 312.1 287.6 316.7  1.48
 12  450  6398 -23.1 -29.0  59  5.9 -24.2 234  91 314.2 314.4 287.7 316.9  0.78

 Considering the potentially convective and heavy nature of the precipitation, i really believe there is the potential for more dynamical cooling than what is being shown...which could in fact destroy that very narrow warm nose. I'm actually a but surprised the models aren't showing more of it to be honest......as i've seen less impressive precip rates/lift produce more cooling in the face of  strong waa in other situations. But it's something that is hard to pin down and even harder to count on. 

 

Do you think would apply for Athens also?

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Regarding the Euro Ens Mean....h5 showed a similar move as the Op to have less stream separation...and while it has more snow than the Op back thru Atlanta, it had less than it's previous run.  The footprint of the snow on the mean was tighter.  Bottom line, less stream separation is a riskier play and not the direction we want to go in.  NE NC seems to get hit regardless, so probably fine there, but more risky as you go back SW   

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