*FEBUARY 19th/20th 2012 SNOW THREAT*

BY SATURDAY...A LEFTOVER CUTOFF LOW THAT HAD BEEN RESIDING ACROSS
THE BAJA OF CALIFORNIA WILL HAVE EJECTED EASTWARD ALONG THE GULF
COAST STATES. THIS SYSTEM WILL THEN SWING NORTHEASTWARD ACROSS THE
SOUTHEAST CONUS...AT LEAST BRINGING SOME GLANCING PRECIPITATION TO
EASTERN KENTUCKY SATURDAY NIGHT INTO SUNDAY. THIS IS A FAVORABLE
TRACK FOR SOME SNOW...HOWEVER THERE IS A WIDE ENVELOPE OF SOLUTIONS
RIGHT NOW...SO WILL CONTINUE TO MENTION A MIX OF RAIN AND SNOW AND
NOT PLAY THIS IS UP TOO MUCH UNTIL BETTER MODEL GELLING TAKES PLACE.

UPPER FLOW REMAIN ZONAL FOR FRIDAY WITH SURFACE RIDGING. ANOTHER
NORTHERN STREAM TROUGH WILL MOVE ACROSS THE GREAT LAKES WITH
ASSOCIATED COLD FRONT MOVING INTO THE FORECAST AREA SATURDAY. AT THE
SAME TIME...A SOUTHERN STREAM WAVE MOVING FROM THE NORTHERN
MEXICO/TEXAS WILL PRODUCE CYCLO-GENESIS JUST OFF THE SOUTHEAST TEXAS
COAST SATURDAY. MODELS SHOW THE SURFACE LOW MOVING EAST OR EAST
NORTHEAST ACROSS FAR SOUTHEAST UNITED STATES FOR SATURDAY NIGHT AND
SUNDAY. FAIRLY STRONG SYNOPTIC FORCING WILL MOVE ACROSS THE FORECAST
AREA WITH WIDESPREAD PRECIPITATION. VERTICAL TEMPERATURE PROFILE
WILL BE FAVORABLE FOR A MIXTURE OF RAIN/SNOW OR ALL SNOW. WILL NEED
TO WATCH THE EXACT PATH OF THE SURFACE LOW AND HOW COLD AIR GETS
PULLED INTO THE FORECAST AREA BEFORE THE SYSTEM MOVES IN.

Toot wrote:This is by no means a similar setup to the system that just pissed everybody off yesterday and last night. I heard some people calling that system a southern slider and that was just not the case...there was a more dominant LPS to our N/NW advecting warm air into the state. (NOT A SOUTHERN SLIDER.)

What is being shown by the majority of model guidance is more of a classic setup for snow in middle and east TN and there is quite a bit of support for this. I wouldnt pay a whole lot of attention to smaller scale details right now as all of them will change several times...but its nice to see such a track being depicted by models.

Stovepipe wrote:6z DGEX

It is all about timing as others have stated. Players include the Great Lakes shortwave (GL s/w) and the upstream Pac-NW trough. The latter will influence the all important timing (and perhaps strength) of the system of interest kicking out of Texas. Simple explanation of the 00/06Z GFS differences is just timing. The 00Z was the first GFS run to show a Euro-like solution with our Texas system kicking with/ahead of the GL s/w. Perhaps the 12Z GFS and subsequent runs will go back to the Euro, but one can't just throw out the 06Z as rubbish. This far out it is perfectly acceptable for a human or a computer to be forecasting the Texas system behind the GL s/w which is what the 06Z does. That puts our system in subsidence behind the jet streak associated with the GL s/w. Short wave ridging is another way to put it. The 00Z GFS and Euro have our Texas system coming out with/ahead of the GL s/w which is at least neutral. if slightly ahead that puts our Texas system in ascent ahead of the GL s/w and also gives the system a slight negative tilt. All are fine and good, but not if the 06Z GFS is correct. Remember the GFS had been consistently like the 06Z in prior runs except the 00Z.

I'd wait for the timing issue to work out before even addressing cold air. Maybe when our system is completely onshore today? Of course "better" timing would also generate a little local dynamic cooling with better lift, but not enough to overcome issues in the boundary layer elsewhere. Unfortunately NC may be hosed outside the mountains. Piedmont is not even looking that good with the sfc high back over the Midwest. I don't see a way to deliver cold air east of the Apps. Of course the mountains would do well. Cold air supply may be there for lower elevations of northeast Tennessee, but middle Tenn prolly misses out on best QPF. Looks like another typical Southern forecast (2010 was an exception): When in doubt between rain and snow just go rain.

Totally different story in the mountains, regarding cold air, but even the mountains need the better timing. If the system comes together, timing and interaction with the GL s/w, the mountains will be set.

jmundie wrote:Canadian would make all of us happy. Too bad the Canadian has been terrible in this range this year x

A few quick thoughts on the 12z model data....a lot of this will be shop talk.....keep that in mind.

12z Euro looked oh so close to a bombing phase around 108, but the phase was not terribly strong I think primarily due the orientation of the Great Lakes disturbance.

12z GFS still looks off to me, like the 6z. The entire orientation of the flow pattern at 500mb is different than most other modeling. It might score the coup though...who knows.

12z Canadian is nice for a chunk of NC. Pretty nice phasing, and because of that, a nice pulling sothward of the colder air aloft.

12z UKMET is weaker and farther south.

Here is what to take from this IMO. I see no trend in the modeling. What I see is each time a model is run, you get its latest interpretation of how a very chaotic 500mb pattern will look this weekend. There is no trend north or south....there is just varying positions and strengths of features.

For the upper Southeast to see a nice winter storm, we want some good phasing. Each model has taken turns showing this from time to time. That is needed to pull the colder air necessary for snow southward, and also get the precip rates heavy enough to overcome some marginal low level temps in some places.

Players remain on the field, and I am no more encouraged or discouraged than I was at this point yesterday.

Reb wrote: