December 8-10, 2018 Winter Storm

SnowDawg · December 6, 2018

Yeah means look really good, unchanged for the most part. A lot less making it to the upper mid Atlantic and then higher totals pushing a little further east in NC. Just wish we could see the EPS maps in Kuchera to see how much support the OP has for the quicker erosion of the upper level cold, and ensuing sleet fest, despite the stronger initial push.

burgertime · December 6, 2018

1 hour ago, griteater said:

I mean, that's what you would normally think, but the upper air pattern has been trending to suppress the storm a little. We'll see if that holds...but regardless, there is usually a late tick north

Yea looking at the models I feel the same...Given the high pressure cutting across the lakes and the confluence in the northeast I have a hard time buying that low tracks much north.

JoshM · December 6, 2018

27 minutes ago, burgertime said:

Yea looking at the models I feel the same...Given the high pressure cutting across the lakes and the confluence in the northeast I have a hard time buying that low tracks much north.

NAM is a doozy, too bad its hour 84

wxduncan · December 6, 2018

Latest from GSP:

Quote

.SHORT TERM /FRIDAY NIGHT THROUGH MONDAY/... As of 355 AM EST Thursday: High confidence that a nearly ideal synoptic set up for widespread and significant winter weather will commence across the forecast area this weekend and possibly continue into early next week. The highest in significant winter weather is placed across the mountains foothills and NC Piedmont along and north of I-40 where snow is expected to be the dominant precipitation type, although periods of sleet and freezing rain are also likely, especially outside of the mountains. Moderate confidence for significant winter weather exists in the SC/NC Piedmont along and north of I-85 and south of I-40 mainly east of I- 25. South of I-85 is not out of the woods with periods of moderate to heavy ice and/or snow possible, but rain is expected to mix in most often here, likely limiting ice/snow accumulations and related impacts. The expected overall synoptic setup has not really changed much for several days, although model guidance has fairly uniformly tracked track of the winter storm a bit further south and therefore leading to snow and mixed precip types becoming more likely a bit further south. A key to the upcoming winter storm is that cold air will be locked in place across the region as confluence aloft ahead of the system maintains a 1030+ mb W-E elongated sfc high pressure system to our north with cold air damming (CAD) persisting through most of the event. Good model consensus shows sfc low pressure riding along the fringe of the strong high, initially along the Gulf Coast Saturday before riding along or just off the Southeast Coastline while intensifying Sunday. This setup will bring light to moderate precip overspreading much of the sometime Saturday afternoon or evening before becoming heavy at times overnight into Sunday. The latest NAM indicates very dry air courtesy of the CAD possibly delaying precip onset, especially across NC foothills, Piedmont and northern mountains. A strong low level jet of 40+ kt is expected to push through the region Sunday bring breezy conditions to many location and gusty winds to the mountains above 3K or 4K feet where wind gusts in excess of 40 mph are likely. This combined with period of heavy snow may support at least brief blizzard conditions, especially across east facing mountains. The strong low level jet will also support an elevated (700-800mb), but now somewhat cooler warm nose which will likely increase the icing threat which model guidance and climatology would suggest would change somewhere between the I-85 and I-40 corridors, lasting at least 3-6 hours. The timing of the change over is likely sometime late Sunday night though early evening and would like be limited across the mountains, although sleet and freezing rain may mix in at times during this period, especially south of I-40. The CAD will likely gradually dissipate late Sunday into Monday but be replaced by cold air filtering in behind the storm. Any ice should be large over during this time with snow the predominate type area-wide, except during the afternoon when rain may mix in at times outside of the mountains mainly into the Upstate of SC and northeast GA. A deformation zone with banding precip is possible during this time, but there is still some uncertainly where exactly sets up and how much precipitation we may see. The bottom line is the additional snow is possible just about anywhere during this time. Melted snow/ice or liquid precip storm total amounts continue to be around 2 inches across most of the forecast area with local amounts approaching 3 inches possible south of I-85 and across higher east facing mountains due to upslope enhancement. Early estimates continue to place snow amounts between 10 and 20 inches across the mountains, foothills Piedmont northwest of I-85. Local 20+ amounts are possible across higher east facing mountain and foothill locations. Dangerous freezing rain and sleet accumulations in excess of one half an inch continue to be possible with the high totals and therefore impacts between I-85 and I-40 outside of the mountains. Although latest model trends suggest areas closer to I-85 might have the most cause for concern. the bottom line is that a potentially very dangerous winter storm looms for much of the forecast area this weekend. And as the day shift yesterday put it, this could be a once-in-a-generation event for areas that experience mostly snow and ice. Now is the time to prepare. Finish preparations by Friday as if this storm speeds up Saturday may be too late, especially for the Upstate of SC into northeast GA.

wxduncan · December 6, 2018

Never seen GSP put those kind of totals out before getting real around here!

ajr · December 6, 2018

From RAH this morning:

Quote


P-type: As mentioned above, a lot of uncertainty still remains with
respect to wintry precipitation, as any small change/difference in
timing, temperature, thermal profile, etc. will impact the p-type.
As past events would suggest, a purely snow event is not likely as
there is usually a mix of wintry p-types. Expect precipitation to
start as rain across the far south and southwest, though chances are
looking decent for a mix of rain/snow across the northwest half of
central NC when precipitation moves in overnight. A mix of p-types,
especially over the northwest half of central NC, is likely
overnight as temperatures fall, while the southeast could remain
rain for the duration. Expect several p-type changes throughout the
event, especially along and north of US-1, with snow, sleet and
freezing rain all possibilities. Regardless of p-type, liquid
equivalents could range from one to two inches. Will hold of on
getting too cute with any snow amounts at this time given the degree
of uncertainty and how the varying p-types would impact
accumulations.

Overall reads as more bullish compared to prior ("It's too early for specific amounts, but an inch or two is not out of the question in the Triad region, with a non-zero chance of greater amounts.") - I'm not sure what it means to be "too cute with any snow amounts" though.

ajr · December 6, 2018

Look at GEFS plumes for KRDU for the most recent 00z run and a day prior, huge increase in the probability of snow (vs rain):

12/5 00z:

12/6 00z:

franklin NCwx · December 6, 2018

Lol... nam might be the driest model.

Blue_Ridge_Escarpment · December 6, 2018

Just now, franklin NCwx said:

Lol... nam might be the driest model.

I read somewhere recently that it underwent an update and has actually had a slightly drier bias since. Not sure as I don’t have studies to back it up.

ajr · December 6, 2018

Just FYI Cobb method via Bufkit thinks we're mostly rain/snow mix and only gives about 2" of snow to RDU: http://www.meteor.iastate.edu/~ckarsten/cobb/cobb.php?model=gfs&site=krdu

lilj4425 · December 6, 2018

4 hours ago, burgertime said:

Look where the red dot is

Is that Mack’s house? It’s right near mine also. Lol.

Blue_Ridge_Escarpment · December 6, 2018

1 minute ago, lilj4425 said:

Is that Mack’s house? It’s right near mine also. Lol.

That map actually is not too far off from what a now banned user created yesterday.

burgertime · December 6, 2018

6z still looks good though our temps still hang in the balance verbatim.

Blue_Ridge_Escarpment · December 6, 2018

Through 36, FV3 is virtually identical to its 0Z run.

NavarreDon · December 6, 2018

I realize we're all big boys & girls with the capability to find it own our own but the ST disco from GSP is well......simply stunning! It needs to be posted for posterity. Even a mention of the B word!

.SHORT TERM /FRIDAY NIGHT THROUGH MONDAY/...
As of 355 AM EST Thursday: High confidence that a nearly ideal
synoptic set up for widespread and significant winter weather will
commence across the forecast area this weekend and possibly continue
into early next week. The highest in significant winter weather is
placed across the mountains foothills and NC Piedmont along and
north of I-40 where snow is expected to be the dominant
precipitation type, although periods of sleet and freezing rain are
also likely, especially outside of the mountains. Moderate
confidence for significant winter weather exists in the SC/NC
Piedmont along and north of I-85 and south of I-40 mainly east of I-
25. South of I-85 is not out of the woods with periods of moderate
to heavy ice and/or snow possible, but rain is expected to mix in
most often here, likely limiting ice/snow accumulations and related
impacts.

The expected overall synoptic setup has not really changed much for
several days, although model guidance has fairly uniformly tracked
track of the winter storm a bit further south and therefore leading
to snow and mixed precip types becoming more likely a bit further
south. A key to the upcoming winter storm is that cold air will be
locked in place across the region as confluence aloft ahead of the
system maintains a 1030+ mb W-E elongated sfc high pressure system
to our north with cold air damming (CAD) persisting through most of
the event. Good model consensus shows sfc low pressure riding along
the fringe of the strong high, initially along the Gulf Coast
Saturday before riding along or just off the Southeast Coastline
while intensifying Sunday. This setup will bring light to moderate
precip overspreading much of the sometime Saturday afternoon or
evening before becoming heavy at times overnight into Sunday. The
latest NAM indicates very dry air courtesy of the CAD possibly
delaying precip onset, especially across NC foothills, Piedmont and
northern mountains. A strong low level jet of 40+ kt is expected to
push through the region Sunday bring breezy conditions to many
location and gusty winds to the mountains above 3K or 4K feet where
wind gusts in excess of 40 mph are likely. This combined with period
of heavy snow may support at least brief blizzard conditions,
especially across east facing mountains. The strong low level jet
will also support an elevated (700-800mb), but now somewhat cooler
warm nose which will likely increase the icing threat which model
guidance and climatology would suggest would change somewhere
between the I-85 and I-40 corridors, lasting at least 3-6 hours. The
timing of the change over is likely sometime late Sunday night
though early evening and would like be limited across the mountains,
although sleet and freezing rain may mix in at times during this
period, especially south of I-40.

The CAD will likely gradually dissipate late Sunday into Monday but be
replaced by cold air filtering in behind the storm. Any ice should be
large over during this time with snow the predominate type area-wide,
except during the afternoon when rain may mix in at times outside of
the mountains mainly into the Upstate of SC and northeast GA. A
deformation zone with banding precip is possible during this time,
but there is still some uncertainly where exactly sets up and how
much precipitation we may see. The bottom line is the additional
snow is possible just about anywhere during this time.

Melted snow/ice or liquid precip storm total amounts continue to be
around 2 inches across most of the forecast area with local amounts
approaching 3 inches possible south of I-85 and across higher east
facing mountains due to upslope enhancement. Early estimates
continue to place snow amounts between 10 and 20 inches across the
mountains, foothills Piedmont northwest of I-85. Local 20+ amounts
are possible across higher east facing mountain and foothill
locations. Dangerous freezing rain and sleet accumulations in excess
of one half an inch continue to be possible with the high totals and
therefore impacts between I-85 and I-40 outside of the mountains.
Although latest model trends suggest areas closer to I-85 might have
the most cause for concern.

the bottom line is that a potentially very dangerous winter storm
looms for much of the forecast area this weekend. And as the day
shift yesterday put it, this could be a once-in-a-generation event
for areas that experience mostly snow and ice. Now is the time to
prepare. Finish preparations by Friday as if this storm speeds up
Saturday may be too late, especially for the Upstate of SC into
northeast GA.

BornAgain13 · December 6, 2018

From what I see, the latest trends have a sharp cutoff on the N & NW side of this storm. Starting to look more and more southern VA is near the fringed line. Will this be more expansive than what the models are Depicting?

sarcean · December 6, 2018

RAH is still almost refusing to acknowledge the possibility of significant snow

Wintry precipitation is still likely this weekend and confidence in said occurrence is high, however the exact timing, amounts and p-types are still uncertain due to continued model differences and
thus low confidence. Best chances for wintry precipitation are still
along and north of the US-1 corridor.

Overview: A pair of upper level lows/troughs will develop on Saturday, one off the Southern Rockies/Desert Southwest and the other over the Northern High Plains/SW Canada. The former will shift eastward then east-northeastward through the ARKLATEX and into the TN Valley while the latter will dive south-southeastward, deepening
over the Plains/Midwest. The southern stream low will become absorbed into the stronger northern stream low over the MS/TN Valley Monday/Monday night as it continues its southward dive toward the
Gulf. Expect strong moisture advection into the Gulf Coast states and Southeast US ahead of the system Saturday and Sunday. Cold, high pressure will dominate at the surface over the Great Lakes region, ridging into western/central NC through the period in a CAD setup.
Meanwhile, a surface low will develop along the Gulf Coast on Saturday in response to the upper level system. The surface low is
expected to move along the Gulf Coast, through the panhandle of FL and northeast along the Carolina coast, while the wedge remains in place over northwestern portions of the area. As a result, there will be a very strong pressure gradient from west to east across NC on Sunday/Sunday night. Even the slightest shift in track, timing, temperature, etc. will result in significant impacts to the
forecast.

Timing: The latest medium-range models suggest precipitation will likely move into central NC very slowly from the south-southwest late Saturday or Saturday night. The ECMWF continues to be a tad
slower than the GFS, though the timing has come into significantly better agreement from 24 hours ago.

P-type: As mentioned above, a lot of uncertainty still remains with respect to wintry precipitation, as any small change/difference in timing, temperature, thermal profile, etc. will impact the p-type. As past events would suggest, a purely snow event is not likely as there is usually a mix of wintry p-types. Expect precipitation to
start as rain across the far south and southwest, though chances are looking decent for a mix of rain/snow across the northwest half of
central NC when precipitation moves in overnight. A mix of p-types, especially over the northwest half of central NC, is likely overnight as temperatures fall, while the southeast could remain
rain for the duration. Expect several p-type changes throughout the
event, especially along and north of US-1, with snow, sleet and freezing rain all possibilities. Regardless of p-type, liquid equivalents could range from one to two inches. Will hold of on getting too cute with any snow amounts at this time given the degree of uncertainty and how the varying p-types would impact accumulations.

Temperatures: Highs on Sunday expected to top out in the low to mid 40s while Sunday will be much colder in the NW, with highs topping out around freezing while the SE should reach into mid 40s again.
Lows both Saturday and Sunday nights will be similar, upper 20s to
mid 30s Saturday night and low 30s to around 40 degrees Sundayb night. Monday highs in the upper 30s to mid 40s expected at this time. -KC

Monday night through Wednesday: Medium range model guidance in
general agreement depicting a deep upper level low traversing the SE U.S., initiating yet another deepening sfc wave just offshore of SC/southern NC. The string dynamics associated with the upper level low and the potential for the sfc wave to sling moisture back into central NC. The models have trended a little farther south with the system and attendant precipitation. Thus, expect a chance of rain or rain/snow mixed primarily focused across the southern counties Monday night. If the system drifts just a little farther north, could see a threat for snow across the northern counties with some light accumulation possible. Min temperatures generally in the 20s to the lower 30s.

The upper level system and associated coastal low will sweep quickly eastward and offshore Tuesday with improving weather conditions into mid week. If there is any residual snow/ice pack across the Piedmont, could see temperatures Tuesday night drop into the teens. Away from the snow/ice pack, expect overnight lows in the 20s. Afternoon highs will remain well below normal with high temperatures in the 40s expected, closer to 50 across the far south southeast by
mid week. -WSS

Amos83 · December 6, 2018

Woke up and read the Disco out of GSP, all I can say is that I'm officially hyped bow. Can't remember the last time they used such strong wording this far out. Those guys are some of the best Mets in the country

mclean02 · December 6, 2018

1 minute ago, sarcean said:

RAH is still almost refusing to acknowledge the possibility of significant snow


Wintry precipitation is still likely this weekend and confidence in
said occurrence is high, however the exact timing, amounts and p-
types are still uncertain due to continued model differences and
thus low confidence. Best chances for wintry precipitation are still
along and north of the US-1 corridor.

Overview: A pair of upper level lows/troughs will develop  on
Saturday, one off the Southern Rockies/Desert Southwest and the
other over the Northern High Plains/SW Canada. The former will shift
eastward then east-northeastward through the ARKLATEX and into the
TN Valley while the latter will dive south-southeastward, deepening
over the Plains/Midwest. The southern stream low will become
absorbed into the stronger northern stream low over the MS/TN Valley
Monday/Monday night as it continues its southward dive toward the
Gulf. Expect strong moisture advection into the Gulf Coast states
and Southeast US ahead of the system Saturday and Sunday. Cold, high
pressure will dominate at the surface over the Great Lakes region,
ridging into western/central NC through the period in a CAD setup.
Meanwhile, a surface low will develop along the Gulf Coast on
Saturday in response to the upper level system. The surface low is
expected to move along the Gulf Coast, through the panhandle of FL
and northeast along the Carolina coast, while the wedge remains in
place over northwestern portions of the area. As a result, there
will be a very strong pressure gradient from west to east across NC
on Sunday/Sunday night. Even the slightest shift in track, timing,
temperature, etc. will result in significant impacts to the
forecast.

Timing: The latest medium-range models suggest precipitation will
likely move into central NC very slowly from the south-southwest
late Saturday or Saturday night. The ECMWF continues to be a tad
slower than the GFS, though the timing has come into significantly
better agreement from 24 hours ago.

P-type: As mentioned above, a lot of uncertainty still remains with
respect to wintry precipitation, as any small change/difference in
timing, temperature, thermal profile, etc. will impact the p-type.
As past events would suggest, a purely snow event is not likely as
there is usually a mix of wintry p-types. Expect precipitation to
start as rain across the far south and southwest, though chances are
looking decent for a mix of rain/snow across the northwest half of
central NC when precipitation moves in overnight. A mix of p-types,
especially over the northwest half of central NC, is likely
overnight as temperatures fall, while the southeast could remain
rain for the duration. Expect several p-type changes throughout the
event, especially along and north of US-1, with snow, sleet and
freezing rain all possibilities. Regardless of p-type, liquid
equivalents could range from one to two inches. Will hold of on
getting too cute with any snow amounts at this time given the degree
of uncertainty and how the varying p-types would impact
accumulations.

Temperatures: Highs on Sunday expected to top out in the low to mid
40s while Sunday will be much colder in the NW, with highs topping
out around freezing while the SE should reach into mid 40s again.
Lows both Saturday and Sunday nights will be similar, upper 20s to
mid 30s Saturday night and low 30s to around 40 degrees Sunday
night. Monday highs in the upper 30s to mid 40s expected at this
time. -KC

Monday night through Wednesday: Medium range model guidance in
general agreement depicting a deep upper level low traversing the SE
U.S., initiating yet another deepening sfc wave just offshore of
SC/southern NC. The string dynamics associated with the upper level
low and the potential for the sfc wave to sling moisture back into
central NC. The models have trended a little farther south with the
system and attendant precipitation. Thus, expect a chance of rain or
rain/snow mixed primarily focused across the southern counties
Monday night. If the system drifts just a little farther north,
could see a threat for snow across the northern counties with some
light accumulation possible. Min temperatures generally in the 20s
to the lower 30s.

The upper level system and associated coastal low will sweep quickly
eastward and offshore Tuesday with improving weather conditions into
mid week. If there is any residual snow/ice pack across the
Piedmont, could see temperatures Tuesday night drop into the teens.
Away from the snow/ice pack, expect overnight lows in the 20s.
Afternoon highs will remain well below normal with high temperatures
in the 40s expected, closer to 50 across the far south-southeast by
mid week. -WSS

Yeah I hope they are wrong but normally when they are meh or have low confidence about a storm they are right quite a bit. I hope that changes today !

BornAgain13 · December 6, 2018

06z GEFS looks like it increased in Northern NC and Southern VA

BornAgain13 · December 6, 2018

0z Run

06z Run

Orangeburgwx · December 6, 2018

4 minutes ago, BornAgain13 said:

0z Run

06z Run

Increased further south

sarcean · December 6, 2018

7 minutes ago, mclean02 said:

Yeah I hope they are wrong but normally when they are meh or have low confidence about a storm they are right quite a bit. I hope that changes today !

It's basically RAH vs every model at this point. They will have to cave if these models keep it up (atleast for the Triad) today or tomorrow or they risk it being too late too sound an alarm.

I understand they don't want their torecacts to busts but I don't remember a winter storm ever getting this general model concensus for this many days straight

Orangeburgwx · December 6, 2018

I want to fight somebody at the CAE office... They are still using that bull**** wording from Tuesday

wxdawg10 · December 6, 2018

18 minutes ago, sarcean said: