UPDATE AND QUESTION: Winter Weather in the Mid-South?

[jkt21787]

Been closely monitoring this midweek system. The models have been wavering back and forth on certain aspects, but keeps a low pressure moving into the Ohio Valley with cold air spilling in behind it.

If the cold air can meet up with the moisture here, which is hard to do in these parts, we could see some wintry weather. The NWS calls for a period of freezing rain then changing to some snow at the end. They havent stated specific amounts yet, but it could be heavy especially northwest of me.

Am really hoping for some winter weather with this system, but still not sure as it is rare for such situations as this to result in significant snow or ice. But time will tell.

[wx247]

As it looks right now... I would say that your chances of a White Christmas are less than your chances of a very icy Christmas. Looks like ice accumulation will be your big event with this system.

[jkt21787]

Yep, thats what I figured. The NWS is already saying winter storm watches could be issued Tomorrow. They really buy into the GFS solution with this one, which spells more ice for me. My BUFKIT showed almost an inch of ice from the 6z run with a couple inches of snow afterward. The 12z ETA which just came shows a lot less potential, but still there. It seems to elongate the low later in the period which may decrease wraparound or cold air advection. I really have no idea though, as Im not an expert on model interpretation.

[wx247]

Yep, thats what I figured. The NWS is already saying winter storm watches could be issued Tomorrow. They really buy into the GFS solution with this one, which spells more ice for me. My BUFKIT showed almost an inch of ice from the 6z run with a couple inches of snow afterward. The 12z ETA which just came shows a lot less potential, but still there. It seems to elongate the low later in the period which may decrease wraparound or cold air advection. I really have no idea though, as Im not an expert on model interpretation.

I am far from an expert either. That is why this place is so much fun!!!

[jkt21787]

Don't worry, cause there are many of us.

Would love to hear Purdue's or any other of these experts view on our situation. The Tv mets here are virtually clueless, calling for all rain with a few snowflurries late. I am relying on the NWS and the models for the forecast.

[PurdueWx80]

This again will be a close call for Memphis, but it does look like the cold air behind the front will undercut warmer air just above the surface - depending on the depth of warm and cold air, you'll have sleet or freezing rain for a period, followed by 1-2" of snow, the way I see it now. I think that definitely warrants a watch for areas that far south. Deformation snow will also fall from north TX through southern and eastern OK and into much of AR and western TN on Wed.

[jkt21787]

Thanks Purdue. Am definitely leaning towards more toward an ice event with this situation with perhaps some snow. Will the deformation snow lead to the 1-2" that you refer to?

Anxious to see the upcoming 12z GFS, with my luck it will be back to a cold rain

It is really hard to see how the TV mets here can see the morning HWO saying potential for a significant winter storm and can forecast all rain. Makes you wonder...

[jkt21787]

Well the 12Z GFS is in (for the time of concern), and it overall looks much the same, just a bit southeast though. Looking at the precip maps, it shows perhaps a little less wintry precip in my area...but that is just my guess.

Any thoughts?

[jkt21787]

Any idea how the 12z models will affect the forecast for my area? Dont see any real changes offhand, but the situation remains very fluid.

[PurdueWx80]

Any idea how the 12z models will affect the forecast for my area? Dont see any real changes offhand, but the situation remains very fluid.

Based on the 12Z GFS 1000-500 thicknesses for Wednesday alone, no snow would fall in western TN. However, looking at low-level thicknesses and temperatures (since the front will be well east of you) tells us that there may be a narrow swatch of sleet and/or freezing rain, followed by a bit of snow. The "forecast" I mentioned earlier was based mostly on the Eta, but either way you dice it, there should be some ice and snow in the Memphis area. Meanwhile, eastern TN may be in for some severe weather and very heavy rain.

[jkt21787]

Okay Purdue, thanks. I'll keep my hopes up!

[jkt21787]

Well, the 12Z models now indicate rain for my area through at least Wednesday afternoon. However, both the ETA and GFS develop another Low near New Orleans and track it northeast. This track seems favorable for snow in the area, but doesn't develop much precip on the NW side.

However, I do have a question. As I said, there isnt much precip indicated in the form of snow or sleet, etc. based on the model maps. But after looking at the MOS data I became confused. Here is the MET and MAV Guidance for Memphis:

KMEM GFS MOS GUIDANCE 12/21/2004 1200 UTC
DT /DEC 21/DEC 22 /DEC 23 /DEC 24
HR 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 06 12
N/X 40 40 19 27 16
TMP 54 56 54 52 50 47 44 40 36 34 31 29 26 23 20 21 23 26 23 21 18
DPT 45 47 46 46 44 42 38 36 35 32 29 24 21 17 13 11 9 8 6 7 4
CLD OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV SC CL FW SC SC BK
WDR 21 19 16 12 11 05 04 03 02 01 01 36 36 35 35 36 36 01 01 01 01
WSP 11 08 07 11 12 12 16 15 13 13 18 20 20 19 15 15 13 12 12 13 12
P06 36 74 100 100 92 93 30 6 8 9 13
P12 100 100 99 11 14
Q06 1 4 5 4 3 4 1 0 0 0 0
Q12 5 4 4 0 0
T06 2/ 1 14/ 1 13/ 4 19/ 2 10/ 0 3/ 1 0/ 2 0/ 3 0/ 1 0/ 4
T12 17/ 1 33/ 4 10/ 1 0/ 7 0/ 1
POZ 0 4 5 4 6 7 15 35 37 40 34 34 39 18 14 4 3 6 3 4 6
POS 0 0 0 0 0 9 18 4 12 22 38 46 41 71 73 85 89 90 82 74 84
TYP R R R R R R R Z Z Z Z Z Z S S S S S S S S
SNW 0 2 0CIG 6 6 6 6 4 4 3 3 3 3 3 4 4 4 6 8 8 8 8 8 8
VIS 7 7 7 7 7 5 5 3 3 5 4 5 7 7 7 7 7 7 7 7 7
OBV N N N N N BR BR BR BR BR BR BR N N N N N N N N N

KMEM ETA MOS GUIDANCE 12/21/2004 1200 UTC
DT /DEC 21/DEC 22 /DEC 23 /DEC 24
HR 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 06 12
N/X 34 34 21 28 18
TMP 57 58 57 56 54 50 46 34 30 28 27 25 25 24 23 23 24 26 25 23 20
DPT 49 50 50 51 47 42 37 30 29 28 25 18 15 14 14 15 16 17 17 15 12
CLD OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV BK OV OV OV SC OV
WDR 20 19 18 16 17 01 03 02 01 02 02 36 01 36 36 01 36 36 01 36 01
WSP 10 09 08 10 08 05 12 15 14 15 15 17 19 14 12 12 12 10 09 08 07
P06 52 62 98 92 70 85 41 13 9 10 12
P12 99 99 90 18 14
Q06 1 1 5 3 1 2 1 0 0 0 0
Q12 5 4 2 0 0
T06 21/ 1 28/ 2 26/ 1 17/ 1 10/ 0 4/ 1 0/ 4 0/ 0 1/ 0999/99
T12 32/ 3 41/ 4 10/ 1 0/ 4 999/99
SNW 0 4 0CIG 5 5 5 6 3 2 3 2 3 3 3 3 3 4 4 8 6 4 8 8 8

As you can see, it indicates between 2 and 4 inches of snow for the area...but based on the actual maps from the 12z data, I just don't see that.

So my question is, does the MOS data overestimate, or could it be a reality?

BTW, the NWS has a Winter Storm Watch in the Jonesboro and Dyersburg area, and mentions at least an advisory further south (hopefully for us! )

[wx247]

It depends on how cold the atmosphere becomes during the precip. I don't see 2-4" for you... more like around 1" or less (more ice I still think!).

[jkt21787]

I have to agree with you there wx247, just based on recent data.

After looking at the forecast soundings from the 12z eta, it definitely shows a freezing rain situation, with a shallow layer of cold air at the surface with warmer air aloft. This needs to be watched closely. The sounding (on BUFKIT) showed about a tenth to two tenths of ice as precip ends around midday.

It shows a second round of precip moving in Wednesday Night, and keeps most of it snow. Using several methods, it shows between 1.3 and 2.9 inches of snow Hmm....

Time will ultimately tell.

[ALhurricane]

Having worked the midnight shift this morning at the NWS, (this is my last one so I forced myself awake), it is going to be a very close call for Memphis.

As I mentioned in the forecast discussion, we are concerned about the possibilities of freezing rain, especially over western Tennessee. From the 00z run, the ETA was only showing a brief ice threat for Memphis before rapidly moving out the moisture. The GFS showed an ice and snow threat. Have only had a chance to briefly look at 12z data and it appears that models are in no more of a consensus than they were early this morning.

A decision will likely be made this afternoon regarding warnings and/or advisories. In reality, the situation for Memphis may not be known until the event begins. Don't you just love winter weather forecasting in the Mid South?

[jkt21787]

Do you think Shelby County will need an advisory?

You wrote this morning's AFD? Very Nice...a good read with lots of info.

[ALhurricane]

It's going to be close. The fact that we're in the 50s now and expect a lot of rain before any changeover will cut down on any ice accumulation. Having said that, looking at the ETA MOS guidance, Memphis would be in trouble as it forecasts them to go below freezing just after 18z. The crazy GFS MOS has us warmer even with a stronger sfc system.

I hate to be a wuss, but I will not commit to anything. That is best left for my coworkers on the dayshift. I will say that if the ETA is correct, we will see advisory conditions.

Also, the new ETA showing much more wrap around moisture after 00z which may give Memphis an inch or so of snow.

[chadtm80]

I hate to be a wuss

lol

Great write up as always al.. Good to see ya around

[jkt21787]

Yep, I was concerned about warm ground temps and rain limiting accumulation, will see how that goes.

Yes, as you said, a look at BUFKIT data on 12z ETA is quite conerning for Memphis, with a period of freezing rain, a short break, then a round of snow from that wraparound.

The GFS is doing so much flip-flopping I don't trust it even at this close range, it jumps between a strong surface low and a weak one, sending it more west or more east.

I guess we will all know soon, AFD should be out in a couple of hours with new forecasr soon after.

Thanks for all the input ALHurricane!

[jkt21787]

Oh, and don't worry about being a wuss because forecasting Memphis weather (especially snow) is virutally impossible, it seems to never go by what is forecast, LOL!