Rain and Flurries: Weekend Storm Discussion

[Crockett]

How often does West Tennessee see winter wx while the Cumberland Plateau doesn't? I can remember a couple of occasions . . . one of them being last year. But I'd venture a guess that it hasn't happened often over the last 20 years. But that seems to be the scenario setting up here.

In my uneducated opinion, we need the track of the low to slide southeast just a skosh to start feeling confident about a rain-to-snow changeover on this end of the state occurring while there is still some moisture to work with.

You guys who are watching the models: I'm a little skeptical simply because this happens by a northern ULL merging with a southern ULL and blowing up into a major system. Given the drought we're in and how much trouble we've had getting winter weather systems in here, I'm a little skeptical; thinking maybe the models are jumping to conclusions a bit. Does anyone else feel the same way?

[Thundersnow]

Oh, I may be watching the models.  But, I'm definitely skeptical.  

...especially after the February 2006 fiasco when Memphis was getting buried, and Nashville was fully expected to get 6+ inches... before that stinkin' warm nose came up from the south and spoiled it.     

[Ron_Jarrell]

Crockett, the models don't really "jump to conclusions". They simply run calculations. Sometimes they're wrong and don't get a good feel for a particular system especially with timing issues. The GFS is trying to phase that s/w and leave enough moisture behind the front to provide us with frozen precip. I'm skeptical on that one thing alone. For a sharply demarcated front, it is almost always very cold dry air behind it (that's why it's demarcated in the first place - very cold air).

We'll have to see... stay tuned.

BTW, I can't stand Nancy Van Camp. I loathe "weather readers" that don't know the first thing about what they're saying.

[Ron_Jarrell]

Wow. I just pulled the txt data file for the GFS and it's pretty impressive bringing in the cold with this system. Takes us to 19'F as precip ends with a full 1.5" precip after changeover. Beautiful setup, but the Low tracks very near us bottoming out at 983mb.

BTW, just saw Henry Margusity's call map for this weekend. Very interesting. He always calls these superstorms, but at least he's got us painted in for some snow - 1-3"

[Ron_Jarrell]

18z NAM coming out now, out to 24.

[Reneezelle]

What about James Spann calling for us to have 6 inches???

[joemomma]

This afternoon's NOAA has the hill updated to 60% for Saturday as a changeover, then snow showers on saturday eve.  Hmmm...

[Ron_Jarrell]

I don't listen to James Spann.

[Reneezelle]

Yeah I thought the whole James Spann thing has always sounded kinda wack-o. But what do I know.


    So as of now is it gonna be clean easy snow or nasty icy mess? Cuz I have about three  hundred people to entertain Saturday.

[Ron_Jarrell]

Reneezelle - Are you talking about the 12Z GFS he posted?

My opinion from what the models are saying right now is that we'll see some snow, but not much accumulation. The ground is way too warm until we get into the upper 20s 2mTemp. At that point, it looks like a dusting to 1". Nowhere near 6" unless something changes drastically.

[Ron_Jarrell]

Nashville AFD:

LONG TERM...
HI PRES FRI. SURFACE WAVE FORMS OVERS S TX LATE FRI AND MOVES NE
TO NEAR ANB BY 18Z SAT. THIS IS CONSISTENT WITH PREVIOUS 2 RUNS
AND IS EVEN A LITTLE COLDER. ECMWF MODEL MEANWHILE IS FURTHER N
AND W WITH SYSTEM. GFS TRACK WOULD MEAN MORE SNOW AND SOONER...AND
WILL TEMPER FORECAST TOWARD THIS FOR NOW. OF COURSE PLATEAU HAS
BEST CHANCE FOR MEASURABLE SNOW...ESPECIALLY SAT NITE.

[Ron_Jarrell]

Memphis AFD:

THE PERIOD BEGINS ACTIVE. MODELS IN AGREEMENT WITH ANOTHER
SHORTWAVE MOVING OUT OF THE SOUTHWEST. THIS TIME THE UPPER LOW IS
MUCH FARTHER SOUTH WITH THE SURFACE LOW TRACKING ALONG THE GULF THEN
ALONG THE EASTERN SEABOARD. MODELS DIFFER IN THE THERMAL PROFILE
WHICH MAKES THIS A POTENTIALLY TRICKY FORECAST FOR FRIDAY NIGHT AND
SATURDAY. GFS IS COLDER THAN ALL MODELS DUE TO POLAR HIGH BUILDING
SOUTHWARD FASTER DURING THE DAY ON FRIDAY BEFORE WARM AIR ADVECTION
FROM THE APPROACHING STORM BEGINS. CANADIAN AND ECMWF ARE LESS
AGGRESSIVE WITH THE COLD AIR AT FIRST...ALTHOUGH ALL MODELS DRAW
ENOUGH COLD AIR IN BY SATURDAY EVENING TO MIX WITH OR TURN
PRECIPITATION TO ALL SNOW FOR MUCH OF THE WESTERN 2/3RDS OF THE
FORECAST AREA.

ALTHOUGH SYSTEM STILL 96 HOURS OUT THERE IS A FAIRLY HIGH CONFIDENCE
THAT PRECIPITATION WILL OCCUR...SO WILL GO LIKELY POPS...HOWEVER THE
PRECIPITATION TYPE IS STILL TOO UNCERTAIN. FOR NOW WILL KEEP A
MIXTURE FOR THE NORTHEASTERN PORTION AND CHANGEOVER TO A MIXTURE
SATURDAY LATE AFTERNOON OR EVENING IN THE CENTRAL THIRD AND STILL ALL
RAIN OVER THE SOUTHEAST. HAVE LEANED TOWARD THE ECMWF AT THIS TIME
WHICH IS A WARMER THERMAL PROFILE. THE LATEST NAM AND CANADIAN
MODELS SUPPORT THIS AT THIS TIME

[Snowman]

Ron, I know several of them are saying that because the ground is relatively dry due to the drought, that the ground will cool rather quickly. What is your thinking about this? I had never heard that before.

[Ron_Jarrell]

The ground cools more quickly when it is dry since the moisture in the soil holds in heat. This is especially true in diurnal heating/cooling cycles.

Our ground is not dry though. We have had a good amount of rain recently and before we have yet to see the rain that will be coming this week. We also will see rain before any changeover happens, so I don't think the dry ground can be cited for this storm.

[Ron_Jarrell]

18z GFS coming out now...