January 17th-18th Winter Storm Discussion

[MotoWeatherman]

Look at Bham getting hammered by the NAM!

Might get lucky...

 

18z NAM say BHM turns to snow around 1pm.

Date: 24 hour Eta valid 18Z THU 17 JAN 13Station: BHMLatitude:   33.57Longitude: -86.75-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   120                                                                 SFC  990   203   2.2   0.9  91  1.3   1.6 309  13 276.1 276.8 275.3 287.4  4.12  2  950   532  -0.9  -1.0  99  0.1  -1.0 327  25 276.3 276.9 274.8 286.5  3.74  3  900   962  -2.5  -2.6 100  0.0  -2.6 359  29 278.9 279.5 276.0 288.7  3.52  4  850  1416  -0.6  -0.7 100  0.0  -0.7  40  22 285.5 286.2 280.3 297.6  4.29  5  800  1900  -1.1  -1.2  99  0.1  -1.2 102   7 290.0 290.8 282.4 302.6  4.39  6  750  2415  -1.4  -1.4 100  0.0  -1.4  80  15 295.1 295.9 284.8 308.7  4.61  7  700  2963  -4.4  -4.4 100  0.0  -4.4  69  20 297.6 298.3 285.1 309.4  3.93  8  650  3542  -8.8  -8.9  99  0.1  -8.9  91  14 299.0 299.5 284.6 308.0  2.99  9  600  4156 -13.6 -18.0  70  4.3 -14.8 139  16 300.4 300.6 283.5 305.2  1.55

 

4pm...still snow...

Date: 27 hour Eta valid 21Z THU 17 JAN 13Station: BHMLatitude:   33.57Longitude: -86.75-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   137                                                                 SFC  992   203   0.3   0.0  98  0.2   0.2 316  18 274.1 274.7 273.8 284.5  3.86  2  950   547  -1.1  -1.2  99  0.1  -1.2 329  40 276.1 276.7 274.6 286.2  3.68  3  900   977  -2.8  -3.1  97  0.4  -2.9 349  51 278.7 279.2 275.6 288.0  3.37  4  850  1431  -1.9  -2.1  98  0.3  -2.0  14  51 284.2 284.9 279.1 295.1  3.85  5  800  1913  -2.3  -2.5  98  0.2  -2.4  15  51 288.7 289.4 281.4 300.1  3.96  6  750  2425  -3.5  -3.9  97  0.4  -3.7  17  44 292.8 293.5 283.0 304.0  3.82  7  700  2968  -5.8  -6.3  96  0.6  -6.0   7  33 296.1 296.7 283.9 306.3  3.40  8  650  3546  -7.8  -8.7  93  0.9  -8.2   3  31 300.1 300.6 285.1 309.4  3.04  9  600  4166 -10.5 -11.5  92  1.0 -10.9   8  34 304.0 304.5 286.1 312.2  2.64 10  550  4831 -14.7 -16.0  89  1.3 -15.0   2  35 306.7 307.1 286.4 313.1  2.00 11  500  5544 -20.1 -22.1  84  2.0 -20.5 347  40 308.6 308.8 286.4 312.8  1.30 12  450  6315 -26.4 -29.9  73  3.4 -27.0 335  47 310.0 310.1 286.2 312.4  0.71

 

 

7pm...cold core is to the east and precip rates lower so lower levels start to warm...

 

Date: 30 hour Eta valid 0Z FRI 18 JAN 13Station: BHMLatitude:   33.57Longitude: -86.75-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   181                                                                 SFC  997   203   2.6   1.8  95  0.7   2.2 327  15 276.0 276.7 275.5 287.8  4.37  2  950   595   0.8  -0.1  93  0.9   0.4 339  38 278.0 278.7 276.2 289.0  3.99  3  900  1027  -1.4  -2.0  96  0.6  -1.6 358  52 280.1 280.7 276.8 290.3  3.67  4  850  1482  -2.0  -2.7  95  0.7  -2.3  14  55 284.0 284.7 278.8 294.4  3.68  5  800  1964  -2.4  -2.7  98  0.3  -2.6  10  51 288.5 289.2 281.3 299.8  3.91  6  750  2476  -2.5  -3.0  97  0.5  -2.7   6  44 293.8 294.5 283.7 305.8  4.09  7  700  3022  -4.6  -6.8  84  2.2  -5.5   3  43 297.4 298.0 284.3 307.3  3.28  8  650  3602  -7.1 -13.8  59  6.7  -9.3 349  42 300.9 301.3 284.2 307.2  2.02  9  600  4223  -9.6 -20.7  40 11.2 -12.6 328  44 305.1 305.3 284.9 309.

[FallsLake]

Yep been saying that the whole time. THat is why we are not going to get crazy snow totals outside of the mountains. There could be a few hours of moderate to heavy snow, so a good 1 to maybe 4 inches generally seems the best bet.

 

I would say for RDU per the NAM our time frame for snow tomorrow is something 11pm-12zam to 3-4am. With some light snow maybe lingering till 5 or 6am.

That still sounds good to me...Thanks for all your insight!!

[franklin NCwx]

18z NAM says MBY turns to snow between 7pm -10pm.  Not likely to last long nor accumulate much but hey...

 

Date: 33 hour Eta valid 3Z FRI 18 JAN 13Station: 34.59,-83.93Latitude:   34.59Longitude: -83.93-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   167                                                                 SFC  954   549   2.3   1.0  92  1.2   1.7 353  11 279.1 279.9 277.2 291.0  4.32  2  950   582   1.8   0.8  93  1.0   1.4 358  13 279.1 279.8 277.1 290.8  4.27  3  900  1016  -0.4  -0.9  96  0.5  -0.6  14  33 281.1 281.8 277.7 292.2  3.98  4  850  1473  -1.4  -2.7  91  1.2  -2.0  25  50 284.6 285.3 279.1 295.1  3.69  5  800  1955  -1.9  -3.9  86  2.0  -2.7  12  46 289.2 289.8 281.1 299.5  3.58  6  750  2468  -2.1  -3.5  90  1.4  -2.7 358  40 294.3 295.0 283.7 305.9  3.94  7  700  3015  -4.2  -5.1  94  0.9  -4.6 347  31 297.8 298.5 284.9 309.1  3.74  8  650  3596  -7.8  -8.9  92  1.1  -8.2 360  26 300.1 300.7 285.1 309.3  3.00  9  600  4214 -11.3 -12.7  90  1.4 -11.8 351  37 303.1 303.5 285.5 310.6  2.40 10  550  4877 -14.5 -16.1  88  1.6 -15.0 340  46 306.9 307.2 286.5 313.2  1.98 11  500  5593 -19.3 -21.3  84  2.1 -19.8 338  42 309.6 309.8 286.8 314.1  1.39 12  450  6369 -24.5 -27.1  79  2.6 -24.9 339  44 312.5 312.7 287.3 315.6  0.93 13  400  7214 -31.5 -35.3  69  3.8 -32.0 350  43 314.1 314.1 287.3 315.7  0.47

The dynamics will do their dirty work. I will be watching and waiting for the cement truck to dump the paste over the mtns.

[calculus1]

Okay? Hickory had 6" from that event

 

I lived in Lenoir at that time.  Was dead middle of the snow shadow.  Lenoir is really not that far away from Hickory, so a snow shadow could just as easily set up a few miles east of last time.  I'm no forecaster by any means.  I'm still cautiously optimistic about this system, but the snow shadow that has now appeared on multiple models today has occurred for some reason.  The model algorithms are using some kind of input data to produce these results.  It's just a tad unsettling how close that shadow is.  I'm not forecasting any high or low amounts, but it makes one pause and consider.

[phil882]

The SE ridge is going to be a major thorn all winter it seems for NC, I would be surprised if this storm ends up clipping the NE (Boston, NY).

 

 

It certainly could be the death nail for NC if signs continue to push it north.

 

 

Thanks Phil! I was wondering when you would return! If there is a bias toward the ridge, would it be safe to assume that it currently might be modeled too strong and the low takes a track further south than currently modeled?

 

 

Well just because the SE ridge is likely to be modeled stronger doesn't necessary ensure a further north track of the 500 hPa low. There are a lot of other elements that go into the position and intensity of cutoff systems. For starters, the stronger ridge actually probably played a key role in "splitting up" the energy associated with the deep longwave trough that was positioned in the western US the better part of the last week. Instead of the trough swinging eastward in one fell swoop (like you saw at the beginning of the d(prog)/dt animation, we saw the trough break down with part of the energy escaping northward (the weak system that has affected the northeast over the last 18 hours) while the remaining vorticity hanging back, with the eastward progression prevented initially by the stronger than anticipated ridging. 

 

The energy this upper level low will receive is still in the process of cutting off from the longwave pattern, so any unanticipated amplification of the subtropical ridge will likely leave more and more energy behind in the upper level low. Thats a good thing for those wanting a very dynamic system. As many people know a 2-3 contour cutoff low is more significant and can be much more effective at moisture transport since the flow is backing into the higher terrain (ascent is more effective orthogonal to the terrain vs. parallel to the terrain).

[burgertime]

Well just because the SE ridge is likely to be modeled stronger doesn't necessary ensure a further north track of the 500 hPa low. There are a lot of other elements that go into the position and intensity of cutoff systems. For starters, the stronger ridge actually probably played a key role in "splitting up" the energy associated with the deep longwave trough that was positioned in the western US the better part of the last week. Instead of the trough swinging eastward in one fell swoop (like you saw at the beginning of the d(prog)/dt animation, we saw the trough break down with part of the energy escaping northward (the weak system that has affected the northeast over the last 18 hours) while the remaining vorticity hanging back, with the eastward progression prevented initially by the stronger than anticipated ridging. 

 

The energy this upper level low will receive is still in the process of cutting off from the longwave pattern, so any unanticipated amplification of the subtropical ridge will likely leave more and more energy behind in the upper level low. Thats a good thing for those wanting a very dynamic system. As many people know a 2-3 contour cutoff low is more significant and can be much more effective at moisture transport since the flow is backing into the higher terrain (ascent is more effective orthogonal to the terrain vs. parallel to the terrain).

 

Phil you are seriously a board treasure. Thanks for coming around to explain and give some disco! Would love to hear any additional insight you have about it. 

[ncwinterwxman]

IMHO, if you want to see more snow in the Triangle, you should be hoping for a slower solution and not a faster solution so that the deformation band sits over you longer...its not the precip rates that are the issue, its the amount of time that the triangle sits under the deformation band that is the issue...make sense? 

If the precip comes down harder and faster sooner, could it change to snow sooner?

[WilkesboroDude]

WINTER STORM WATCH...RALEIGH...CHARLOTTE...WINSTON SALEM.

[AirNelson39]

I lived in Lenoir at that time. Was dead middle of the snow shadow. Lenoir is really not that far away from Hickory, so a snow shadow could just as easily set up a few miles east of last time. I'm no forecaster by any means. I'm still cautiously optimistic about this system, but the snow shadow that has now appeared on multiple models today has occurred for some reason. The model algorithms are using some kind of input data to produce these results. It's just a tad unsettling how close that shadow is. I'm not forecasting any high or low amounts, but it makes one pause and consider.

Yeah Lenoir and Caldwell county in general got shafted by the storm, I hope for your sake it's not a repeat. It's just hard to see why that shadow keeps showing up. Fingers crossed for y'all down the mtn

[Marion_NC_WX]

I lived in Lenoir at that time.  Was dead middle of the snow shadow.  Lenoir is really not that far away from Hickory, so a snow shadow could just as easily set up a few miles east of last time.  I'm no forecaster by any means.  I'm still cautiously optimistic about this system, but the snow shadow that has now appeared on multiple models today has occurred for some reason.  The model algorithms are using some kind of input data to produce these results.  It's just a tad unsettling how close that shadow is.  I'm not forecasting any high or low amounts, but it makes one pause and consider.

 

 

We got the shaft up here in Marion back in March of 09. However, I think some of that was also due to the fact that the dynamics were a bit south of our area. The optimistic side of me is saying dynamics may do the trick this time around.

[Brick Tamland]

IMHO, if you want to see more snow in the Triangle, you should be hoping for a slower solution and not a faster solution so that the deformation band sits over you longer...its not the precip rates that are the issue, its the amount of time that the triangle sits under the deformation band that is the issue...make sense? 

 

Yes, I thought maybe it could change from rain to snow sooner depending on how heavy the precip was. RAH talked abou snow banding, too. Hope one sits over Wake Forest for a while.

[Thrasher Fan]

via Mr. Spann's twitter:

 

 

[tnweathernut]

WINTER STORM WATCH...RALEIGH...CHARLOTTE...WINSTON SALEM.

Seriously wonder what MRX is up to.  TN guys or mets...................any ideas?  Every model shows accumulating snow.  Are they trying to decide between a watch or an advisory?  It simply doesnt make sense as it's usually out.  Combine that with more marginal areas already going under watches and it just doesn't make sense.

[GreensboroWx]

Sound the alarm!!!  With the NWS on board for snow in the Triad, I would fully expect the TV stations to follow suit.  You'll be hearing a lot about this in the media starting TONIGHT.

 

Right now, I like my position being just NW of GSO. We shall see. 

[GaWx]

 My guess for ATL-AHN northward (but below the mountains), largely based on the 0Z Wed. Euro, is that there will be a rain/snow (possibly also some IP) mix ~3-7 PM Thursday afternoon and possibly a period of almost pure snow (maybe with some IP) ~4-7 PM in heavier precip. Some accumulations of up to ~1" are possible on some elevated surfaces like bushes and maybe even on some grass if it falls at a heavy enough rate. IF tonight's 0Z Euro continues the colder trend, then things could get even more interesting for these areas, especially as regards accumulation potential as well as accumulations on more surfaces.

[BIG FROSTY]

Seriously wonder what MRX is up to.  TN guys or mets...................any ideas?  Every model shows accumulating snow.  Are they trying to decide between a watch or an advisory?  It simply doesnt make sense as it's usually out.  Combine that with more marginal areas already going under watches and it just doesn't make sense.

Same here RNK is always the last to get their update out? For me it may be the snow shadow that keeps showing up? Would not surprise me at all to get dry slotted!!!!

[sctvman]

Good luck to all of our southeast friends. They haven't had a storm like this in a while. While in Charleston we're enjoying upper 70s.

[Stovepipe]

Seriously wonder what MRX is up to.  TN guys or mets...................any ideas?  Every model shows accumulating snow.  Are they trying to decide between a watch or an advisory?  It simply doesnt make sense as it's usually out.  Combine that with more marginal areas already going under watches and it just doesn't make sense.

Yep, it's ridiculous but par for the course for MRX.  WBIR is already calling for 2 to 4 in the valley.

[Brick Tamland]

The National Weather Service has issued a Winter Storm Watch for Durham from 6:00 p.m., Jan 17 until 4:00 a.m., Jan 18.

 

All Counties Affected By This Winter Storm Watch:

  Alamance

  Chatham

  Davidson

  Durham

  Forsyth

  Franklin

  Granville

  Guilford

  Halifax

  Orange

  Person

  Randolph

  Stanly

  Vance

  Wake

  Warren

 

Details:

 

344 PM EST Wed Jan 16 2013

 

...Winter Storm Watch in effect from Thursday evening through late Thursday night...

 

The National Weather Service in Raleigh has issued a Winter Storm Watch...which is in effect from Thursday evening through late Thursday night.

 

* Locations...impacted areas will be along and northwest of a

  line from Albemarle to Raleigh to Louisburg to Roanoke Rapids.

 

* Hazard types...the main precipitation type will be snow...

  although a brief period of mixed snow and sleet is possible.

 

* Snow accumulations...accumulations in the watch area are

  expected to range from one inch to 3 inches... with isolated

  higher totals possible.

 

* Timing...most of the snow is expected to fall between 6 PM

  Thursday and 4 am Friday morning.

 

* Impacts...snow on roads may make driving treacherous...

  especially on bridges and overpasses. In addition... after the

  precipitation ends by late Thursday night and temperatures drop

  below freezing... the wet roads may refreeze in spots...

  especially bridges and overpasses. This black ice could make

  travel dangerous Friday morning.

 

* Winds...winds from the northeast will strengthen Thursday

  afternoon to 15 to 25 mph... gusting up to 25 to 30 mph. These

  winds will continue into the evening before shifting to

  northwest and weakening toward midnight.

 

* Temperatures...readings will fall through the 30s Thursday

  evening... and drop to lows into the upper 20s to lower 30s by

  Friday morning.

 

* Visibilities...visibilities may be reduced to less than one mile in

  snow.

 

Precautionary/preparedness actions...

 

A Winter Storm Watch means there is a potential for significant snow accumulations that may impact travel. People in the watch area should closely monitor the latest forecasts... and remain alert for any further warnings or advisories.

[packbacker]

Sound the alarm!!!  With the NWS on board for snow in the Triad, I would fully expect the TV stations to follow suit.  You'll be hearing a lot about this in the media starting TONIGHT.

 

Right now, I like my position being just NW of GSO. We shall see. 

 

Can we trade?  I agree, you are sitting great, RAH was throwing around ratios 4:1, which with 1" QPF is 4" of snow, really really heavy snow.

[franklin NCwx]

Seriously wonder what MRX is up to.  TN guys or mets...................any ideas?  Every model shows accumulating snow.  Are they trying to decide between a watch or an advisory?  It simply doesnt make sense as it's usually out.  Combine that with more marginal areas already going under watches and it just doesn't make sense.

Don't worry GSP does that a lot for my county in NC. You guys are sitting pretty!

[deltadog03]

 

Thats as far out as the 4KM goes on the current run so far.

[tnweathernut]

just out......speak of conservative (probably a good forecast, but leaves A LOT of room for egg on their face as it would if they issued an advisory.

 

FXUS64 KMRX 162045
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
345 PM EST WED JAN 16 2013

.SHORT TERM THURSDAY AND THURSDAY NIGHT...A LOW PRESSURE SYSTEM
WILL DEVELOP AND MOVE ALONG THE APPALACHIANS ON THURSDAY.  THIS WILL
BRING ANOTHER ROUND OF WIDESPREAD RAIN INTO THE AREA TUESDAY
MORNING. AN ADDITIONAL RAINFALL OF 1 TO 2 INCHES IS POSSIBLE...AND
THIS WILL CONTINUE FLOODING CONCERNS THROUGH THE DAY THURSDAY.  A
FLOOD WATCH REMAINS IN EFFECT THROUGH 00Z FRIDAY.  AIR MASS WILL
COOL QUICKLY THURSDAY AFTERNOON ALLOWING RAIN TO TRANSITION TO
SNOW.  WITH LOW LEVEL MOISTURE DECREASING AS THE COOLER AIR MOVES IN
COMBINED WITH A WARM GROUND...SNOW ACCUMULATIONS ALONG THE
CUMBERLAND PLATEAU AND THE TN VALLEY SHOULD REMAIN BELOW ADVISORY
CRITERIA.  THE TRI-CITIES AREA AND THE LOWER TERRAIN OF SOUTHWEST VA
MAY SEE ACCUMULATIONS HIGH ENOUGH FOR A SNOW ADVISORY...BUT WILL
WAIT FOR LATER MODEL RUNS BEFORE THAT CAN BE DETERMINED.  WITH DEEP
MOISTURE LINGERING OVER THE MOUNTAINS AS THE COLD AIR MOVES
IN...ANTICIPATE BRIEF HEAVY SNOW ACROSS THE EAST TN MOUNTAINS AND
HIGHER ELEVATIONS OF SOUTHWEST VA.  ACCUMULATIONS OF 4 TO 8 INCHES
MAY QUICKLY ACCUMULATE THURSDAY AFTERNOON AND INTO THE EVENING. 
SNOW WILL TAPPER OFF TO FLURRIES AND THEN EXIT THE AREA OVERNIGHT AS
THE LOW PULLS AWAY FROM THE REGION.  A WINTER WATCH WARNING WILL BE
ISSUED FOR THIS AREA.  ADDITIONALLY...AS THE SYSTEM MOVES ACROSS THE
REGION...WINDS WILL INCREASE...ESPECIALLY OVER HIGHER ELEVATION. 
THIS MAY CAUSE SOME DRIFTING OF SNOW AND OCCASIONALLY REDUCE
VISIBILITIES.
 

[phil882]

Phil you are seriously a board treasure. Thanks for coming around to explain and give some disco! Would love to hear any additional insight you have about it. 

 

One other thing that I'd be cautious about is the potential for downsloping in the escarpment just south and east of the highest elevations in the Appalachians  This happens a lot with these marginal setups but any sort of adiabatic warming thanks to strong northwesterly flow off the Appalachians could put a serious damper on both precipitation and snowfall accumulations in areas that typically do very well in CAD setups. 

 

If there was a good analog to the potential outcome of this system, I'd look at the 2009 March 1-3rd southeast snowfall event in the Southeast. CIPS analog guidance  is used quite frequently by the RAH office, and this particular event is actually #3 on all of the analog cases for this event in the 36 hour period. The similarities are pretty remarkable with the exception that its about 2 months later in the season. In terms of expected conditions, the March 1-3rd event had more cold air to work with, but at the same time more solar radiation that was eating away at the cold air source region. However, that particular event also highlights my concerns with descent on the lee side of the mountains, where a local minima in snowfall accumulated resulted.

 

 

Now again I think this event I'm highlighting above had more cold air to work with, but the advantage with this particular system upcoming is that we are still in the middle of winter, so those that do switch over to snow are more likely to get decent accumulations in the absence of a strong sun elevation angle. In heavy wet snow situations such as this, ground temperature is more of an afterthought rather than a primary limiting factor for snowfall accumulation since heavy snowfall rates can easily overcome a warm ground temperature. 

[WilkesboroDude]

WINTER WEATHER ADVISORY ISSUED FOR THE NORTHERN FOOTHILLS...

[bingcrosbyb]

RPM certainly is eye candy given that this thing is just a few hours away. I can't help to think that some will feel some real heartbreak though when the actual event begins.

 

All in all, this could be a win for the NAM. Took the other models (Euro, GFS) to the woodshed if any of this verifies.

[HurricaneTracker]

Only this group can panic AFTER  GSP gets on board. Guys, we are in a money spot here. Unless something goes crazy wrong we're good. So much moisture and the dynamics work in our favor. 

 

GSP official forecast for AVL is only 1-3", per their updated zone forecast.  Personally, given the 18Z run of the NAM, I think this is way too conservative.

 

Still feel 4-6" a good bet for downtown, with 8-12" likely across the Smokies and northward up the spine of the Apps.

[BIG FROSTY]

Just got a alert winter weather adv. 2-5 inches possible... I would have thought WSW but I guess it's because the models keeps showing that shadow? lol

[strongwxnc]

Sure did. Sitting under a flood watch down here in the southern foothills

WINTER WEATHER ADVISORY ISSUED FOR THE NORTHERN FOOTHILLS...

[WilkesboroDude]

Just got a alert winter weather adv. 2-5 inches possible... I would have thought WSW but I guess it's because the models keeps showing that shadow? lol

 

Our criteria may be higher than the Piedmont now after 2010...not sure.