WidreMann told us it was gonna snow thread

[DopplerWx]

models seem to be converging on a solution, widespread .25" from midlands of sc up to central/eastern nc.  with the trends we have seen and the wv imagery and rap runs there's no doubt points west of raleigh are not far off from seeing some decent snowfall.

[CaryWx]

Per RAH WWA will be issued...

[CaryWx]

AS OF 245 PM FRIDAY...

...A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR CENTRAL AND EASTERN
PORTION OF NORTH CAROLINA FOR SATURDAY AFTERNOON AND EVENING...

THE STRONG DEEP LAYER FORCING ASSOCIATED WITH THE AMPLIFYING MID/
UPPER LEVEL WAVE DIGGING INTO THE DEEP SOUTH AND SOUTHEAST US
WILL SUPPORT STRONG CYCLOGENESIS ALONG THE LOW-LEVEL FRONTAL ZONE
OFF THE NORTH CAROLINA COAST.

WITH THE EXCEPTION OF THE NAM AND WRF/ARW...THE MAJORITY OF THE 12Z
GUIDANCE CONTINUES TO TREND WETTER ACROSS CENTRAL NC(GFS IS
CONSIDERED TO BE AN OUTLIER)WITH SREF MEAN LIQUID EQUIVALENT OF ONE
TO TWO TENTHS IN THE WEST...TO THREE TO FOUR TENTHS IN THE
EAST...FALLING BETWEEN 18Z SATURDAY TO 06Z SUNDAY. THE HIGHER QPF
AMOUNTS HAS ALSO RESULTED IN COOLER TEMPERATURES...WITH THE SFC
WET-BULB ADVANCING MORE RAPIDLY TO THE SOUTHEAST THROUGH THE
AFTERNOON AND EVENING.

LIGHT RAIN IS EXPECTED TO DEVELOP OVER THE CAROLINAS DURING THE MID
TO LAYER MORNING HOURS. A WEST TO EAST CHANGE OVER TO SNOW THROUGH
THE AFTERNOON AND INTO THE EARLY EVENING IS THEN EXPECTED AS THE
ENTIRE COLUMN UNDERGOES COOLING...IN THE LOW-LEVELS BY THE 30 TO
35KT NORTHERLY LOW-LEVEL FLOW WRAPPING AROUND THE DEEPENING LOW AND
ALOFT AS THE COLD UPPER TROUGH MOVES OVER THE AREA AND AIDED BY
STRONG DYNAMIC COOLING WITHIN WHAT COULD POTENTIALLY BE A MODERATE
TO HEAVY MESOSCALE PRECIP BAND PIVOTING ACROSS EASTERN AND POSSIBLY
CENTRAL PORTIONS OF CENTRAL NC LATE FRIDAY AFTERNOON/EVENING WITH
MODELS SHOWING STRONGLY SLOPED FRONTOGENETICAL LIFT.

IT IS IN THESE AREAS THAT WILL STAND TO RECEIVE ACCUMULATING
SNOWFALL ACCUMULATIONS OF 1 TO 2 INCHES...WITH THE HIGHEST AMOUNTS
ACROSS THE NORTHERN COASTAL PLAIN COUNTIES...ROUGHLY NORTH OF US 64
AND EAST OF INTERSTATE 95...WITH IT NOT ENTIRELY IMPOSSIBLE THAT
A NARROW BAND OF LOCALLY HIGHER/NEAR WARNING CRITERIA SNOW AMOUNTS
(~3 INCHES)IS POSSIBLE WITHIN THE AFOREMENTIONED MESOSCALE PRECIP
BAND. WEST OF THE TRIANGLE...WITH THE DEEPER MOISTURE IN THE
EAST...QPF WILL BE A LIMIT SIGNIFICANT SNOW ACCUMULATION..WITH
GENERALLY LESS THAN AN INCH EXPECTED.

GIVEN SUCH A DYNAMIC AND VIGOROUS SYSTEM...IT WILL BE IMPERATIVE TO
PAY VERY CLOSE ATTENTION TO UPSTREAM PRECIPITATION OVER THE DEEP
SOUTH SATURDAY MORNING...AND HOW WELL MODEL GUIDANCE IS VERIFYING
W/REGARD TO QPF. ADDITIONALLY...A SHIFT IN THE TRACK OF THE COASTAL
LOW WILL SIGNIFICANTLY ALTER EXPECTED SNOWFALL AMOUNTS ACCORDINGLY.
AND FINALLY...INITIALLY WARM SOIL TEMPERATURES(CURRENTLY IN THE MID
TO UPPER 40S) AND ABOVE FREEZING BOUNDARY LAYER TEMPS WILL DETER ANY
SNOW ACCUMULATION PARTICULARLY PRIOR TO 21Z...WITH SNOW MORE READILY
ACCUMULATING THEREAFTER AS SOIL TEMPS DROP INTO THE LOWER 40S VIA
STRONG LOW-LEVEL COLD AIR ADVECTION FROM THE NORTH.

HIGHS SATURDAY WILL DEPEND ON THE ONSET OF PRECIP...WITH DAYTIME
HIGHS OCCURRING BY OR BEFORE 18Z. HIGHS IN THE UPPER 30 NW TO MID
40S SOUTHEAST. STRONG SW-NE CLEARING WILL SPREAD OVER THE AREA
BETWEEN 06 TO 12Z SUNDAY MORNING...ALLOWING FOR COLD MORNING LOWS IN
THE LOWER TO MID 20S WITH ANY WET ROADS BECOMING ICY...MAKING FOR
DANGEROUS TRAVELING CONDITIONS SUNDAY MORNING.

 

[lilj4425]

None for central SC?

The snow map posted is only for the area with GSP which doesn't include Columbia.

[cmh90]

What kind of totals can I expect in Beaufort County North Carolina? I've been keeping up with this thread as best as I could since the beginning and I just can't figure it out on my own. Anyone mind helping a simpleton?

[burgertime]

Everyone let's keep the my back yard posts to a minimum. 

[Bozart]

Don't worry about the NAM.  It hasn't had a good QPF forecast since December.  Last Friday it suggested we would get 1.2" of rain that night, while the GFS had us less than .4".  Actual amount was .38".  And we all know how the NAM was way off with the upper level low system back in January (while the GFS essentially nailed it).

 

Until the NAM can prove it can be accurate again within 24 hours, I'm not putting much stock in it.

 

Notice GSP's discussion didn't talk about the NAM at all.  And for good reason.

If the NAM were showing a non-event, that would be more troubling. That's not a problem, though.

[scgirl]

De-lurking to post this statement I got on my phone from Simple Weather Alerts

 

... A WINTRY MIX OF RAIN AND SNOW POSSIBLE SATURDAY...

A VIGOROUS UPPER-LEVEL DISTURBANCE CURRENTLY IN THE GREAT PLAINS WILL SWEEP ACROSS THE REGION ON SATURDAY. THIS DISTURBANCE HAS STRONG DYNAMICS ASSOCIATED WITH IT ALONG WITH VERY COLD AIR ALOFT. ALTHOUGH MOISTURE APPEARS TO BE LIMITED WITH THIS SYSTEM... DUE TO THE STRONG UPPER-LEVEL DYNAMICS... THERE IS A POSSIBILITY OF RAIN MIXING WITH SNOW ACROSS MUCH OF THE AREA.

THE BEST POSSIBILITY OF PRECIPITATION APPEARS TO BE FROM MID- MORNING THROUGH THE AFTERNOON HOURS ON SATURDAY. PRECIPITATION SHOULD BEGIN AS RAIN... THEN MIX WITH SOME SNOW BY MID-DAY ... BEFORE CHANGING TO ALL SNOW DURING THE AFTERNOON BEFORE ENDING SATURDAY EVENING. AT THIS TIME... NO SNOW ACCUMULATION IS EXPECTED ON ROADS DUE TO RELATIVELY WARM SURFACE TEMPERATURES. BRIDGES AND OVERPASSES SHOULD STAY FREE OF SNOW ACCUMULATION AS WELL. THE THREAT OF PRECIPITATION WILL END BY EARLY SATURDAY EVENING AS THE DISTURBANCE MOVES OFF TO THE EAST.

I'm in the midlands area of SC

[ncwinterwxman]

An inch or two probably...check back again this evening and tomorrow am

What kind of totals can I expect in Beaufort County North Carolina? I've been keeping up with this thread as best as I could since the beginning and I just can't figure it out on my own. Anyone mind helping a simpleton?

[cmh90]

An inch or two probably...check back again this evening and tomorrow am

 

 

Thanks for the reply.

 

I'm going to check back as often as possible and I'll post reports if we get any accumulation.

[DopplerWx]

how much of an issue will temps be?  nam precip totals were good but snowfall was .5" or less for the most part for many areas.

[Jon]

Someone on twitter shared this link with me. Interactive map & graphs for SREF for those interested you can click on a point or put in LAT/LON...

 

SREF snow for RDU, newest run actually went down 1":

http://www.spc.noaa.gov/exper/sref/fplumes/index2.php?YMD=20130215&RT=15&PRM=Total-SNO&SID=RDU&INC=ALL&NNC=&max=&min=&mZOOM=7&mLAT=35.42906773122139&mLON=-77.728687890625&mTYP=roadmap

[griteater]

I have 'analyzed' this storm for Charlotte (CLT) and Raleigh (RDU).

 

For Charlotte (at CLT), I've got a mix of rain and snow in the morning, and either a rain/snow mix or transitioning to all snow into early afternoon.  Precip will overall be on the light side.  Trace to a light dusting for Charlotte (GSP going with 'around an inch' of snow for CLT)

 

For Raleigh (at RDU), I've got a mix of rain and snow in the morning, transitioning to all snow in the afternoon.  Light to moderate precip, but snow amounts limited to a Trace to 1 inch (RAH going with something similar for RDU it looks like).

 

With respect to temperatures, the low level cold air advection is moving in from the NW & NNW.  The mountains will likely play some level of hindrance to the speed in which the cold air moves in east of the mountains.  This is different from cold air damning where the cold air is moving in unimpeded from the N / NE.  For temperatures I used a combination of GFS/GFS MOS/NAM/NAM MOS...reviewing both temps aloft and surface wet-bulb temps.

[Lowpressure]

griteater- sounds well thought out and reasonable. Good work.

[Cold Rain]

I have 'analyzed' this storm for Charlotte (CLT) and Raleigh (RDU).

For Charlotte (at CLT), I've got a mix of rain and snow in the morning, and either a rain/snow mix or transitioning to all snow into early afternoon. Precip will overall be on the light side. Trace to a light dusting for Charlotte (GSP going with 'around an inch' of snow for CLT)

For Raleigh (at RDU), I've got a mix of rain and snow in the morning, transitioning to all snow in the afternoon. Light to moderate precip, but snow amounts limited to a Trace to 1 inch (RAH going with something similar for RDU it looks like).

With respect to temperatures, the low level cold air advection is moving in from the NW & NNW. The mountains will likely play some level of hindrance to the speed in which the cold air moves in east of the mountains. This is different from cold air damning where the cold air is moving in unimpeded from the N / NE. For temperatures I used a combination of GFS/GFS MOS/NAM/NAM MOS...reviewing both temps aloft and surface wet-bulb temps.

That's a good forecast, I think. It's really hard to envision how we'd do better than an inch or so around here. We'd need a much more intense solution than is being shown by any of the models at this point. So unless nowcasting reveals a surprise, I think a dusting to an inch is good. At least we'll hopefully get to see some snow falling.

[griteater]

griteater- sounds well thought out and reasonable. Good work.

 

Appreciate it, one other point is that with respect to precip, the one thing you would like to see in this type of setup is higher vorticity values at the base of the 500mb trough as it swings through....and obviously, have the trough swing through at a slower pace.

[griteater]

That's a good forecast, I think. It's really hard to envision how we'd do better than an inch or so around here. We'd need a much more intense solution than is being shown by any of the models at this point. So unless nowcasting reveals a surprise, I think a dusting to an inch is good. At least we'll hopefully get to see some snow falling.

 

Thanks, and good luck

[airmarci]

RAH Office just put out Winter Weather Advisories for areas east of the Triangle 

 

[GaWx]

Predicting Raleigh snowfall limits for this sysem using climo:

 

0.5-2" is probably a pretty reasonable prediction at RDU as of now. It could, of course, end up being less than 1". Could it be more? I suppose but I highly doubt this can end up as a major (5"+) based on the climo of no Gulf low and KATL expecting next to no measurable liquid. I'm bringing this up because I thought I saw some posts referencing a model or models that may suggest close to 0.50" liquid/ 5" snow there. I looked back at the 15 major S/IP at RDU since 1974:

 

1) This low isn't progged to be much of anything in the GOM. 14 of the 15 were Gulf/Gulf coast surface lows at some point. I found only one that was never centered along the Gulf coast or further south: the one that produced the 2/16-17/1987  5.0" snow.  Still, that low picked up a lot of gulf moisture as it traversed the inland SE US (KATL got 0.52" of rain). 

 

2) 14 of the 15 produced 0.30+" of liquid equivalent at KATL. Only one produced less: 0.08"at KATL regarding the 2/5-6/1984 RDU 6.9" snow. That one still that had some weak Gulf aspect to it.

 

3) So, with the weekend system not progged to be a Gulf/Gulf coast low per se/not progged to do much til it is off the SE coast and with KATL progged to get hardly any precip. (quite possibly not measurable), climo says this has only a very remote chance of producing 5"+ of snow at RDU. I'd say 2-3" on the high end and 1/2-2" as the most likely interval. I'd say that any model that is spitting out 5"+ of snow at RDU is very likely out to lunch.

[Brick Tamland]

That's a good forecast, I think. It's really hard to envision how we'd do better than an inch or so around here. We'd need a much more intense solution than is being shown by any of the models at this point. So unless nowcasting reveals a surprise, I think a dusting to an inch is good. At least we'll hopefully get to see some snow falling.

 

That's it? Seems really low based on the models and how excited people have been over them today.

[nchighcountrywx]

For folks out in the Piedmont and Down East:

Official NWS RDU Briefing on storm

http://www.erh.noaa.gov/rah/news/content/2013Feb15_2PM_Briefing.pdf

[rduwx]

Predicting Raleigh snowfall limits for this sysem using climo:

 

0.5-2" is probably a pretty reasonable prediction at RDU as of now. It could, of course, end up being less than 1". Could it be more? I suppose but I highly doubt this can end up as a major (5"+) based on the climo of no Gulf low and KATL expecting next to no measurable liquid. I'm bringing this up because I thought I saw some posts referencing a model or models that may suggest close to 0.50" liquid/ 5" snow there. I looked back at the 15 major S/IP at RDU since 1974:

 

1) This low isn't progged to be much of anything in the GOM. 14 of the 15 were Gulf/Gulf coast surface lows at some point. I found only one that was never centered along the Gulf coast or further south: the one that produced the 2/16-17/1987  5.0" snow.  Still, that low picked up a lot of gulf moisture as it traversed the inland SE US (KATL got 0.52" of rain). 

 

2) 14 of the 15 produced 0.30+" of liquid equivalent at KATL. Only one produced less: 0.08"at KATL regarding the 2/5-6/1984 RDU 6.9" snow. That one still that had some weak Gulf aspect to it.

 

3) So, with the weekend system not progged to be a Gulf/Gulf coast low per se/not progged to do much til it is off the SE coast and with KATL progged to get hardly any precip. (quite possibly not measurable), climo says this has only a very remote chance of producing 5"+ of snow at RDU. I'd say 2-3" on the high end and 1/2-2" as the most likely interval. I'd say that any model that is spitting out 5"+ of snow at RDU is very likely out to lunch.

Great job Larry! I agree w/ you w/ the 1" to 2" call. I said yesterday that I'd be happy w/ and inch and will be doing cartwheels if we get 2 inches.

[SnowDeac]

So we are now throwing out the GFS? I'm confused..

[Brick Tamland]

I am confused, too. People all day have been saying the trend was better, the models have been wetter, this was a great run. And now people are saying just a dusting to an inch when the models show 4 to 5. It just seemed from the disussion that it was a bigger deal than that.

[eyewall]

I am left out of RAH's advisories by a county. All I need is to eek out 0.3" to match last winter's total LOL.

[beanskip]

I think people are wisely factoring in the marginal boundary layer we will be dealing with. We just kind of ignored that no the non-event in January. Not going to do that this time. Even the juicy 12z GFS, which gave Shelby almost .5 of qpf, had a temp of 34 at the height of the storm. While the GFS clown map put out 3-5 inches, there is no way that is going to happen coming off a 60-degree day in late February.

I am confused, too. People all day have been saying the trend was better, the models have been wetter, this was a great run. And now people are saying just a dusting to an inch when the models show 4 to 5. It just seemed from the disussion that it was a bigger deal than that.

[metalicwx366]

So we are now throwing out the GFS? I'm confused..

It seems like any model that isnt showing snow for NC is being thrown out.

[rduwx]

I've only seen 1 model run that has had the elevated totals that others are mentioning here and that was the 12z gfs. The 6z gfs, 6z nam, 12z nam, 12z euro, or 18z nam didn't show 4 to 5 inches. You can't just go w/ what the highest model is showing. We need to be realistic and that means looking at all the models. At this point I think 1 to 2 inches is a good forecast for the RDU area.

[Jon]

So we are now throwing out the GFS? I'm confused..

 

 

I am confused, too. People all day have been saying the trend was better, the models have been wetter, this was a great run. And now people are saying just a dusting to an inch when the models show 4 to 5. It just seemed from the disussion that it was a bigger deal than that.

Other close range models aren't showing what the GFS is showing for the most part. SREF is down to 2" from around 4" earlier I believe. NAM doesn't matter because it hasn't been right as of late so even if it trends wetter, who cares.

 

Even if 0.5 liquid fell as the GFS is pointing out, with the onset being rain and the borderline temps in most areas until the evening, accumulation totals will be low. So you take the snow maps with a grain of salt, when in reality some of that snowfall is probably a mix and will melt. So generally people forecast low totals for events like these, despite some high events on *some* models.

[SnowNiner]

So we are now throwing out the GFS? I'm confused..

 

I think most are throwing out the 12Z snowmap yes (maybe not the QPF, I don't know).  I think the accumulations "projected" to fall are being forecasted to be cut by falling on warm soils in over freezing surface temps.