1/15-1/18 Storm System

[Eric]

FWIW, Davis Nolan shows rain and in the 40s on Saturday with snow showers on the back side on Sunday and a high of 37.
By the way, I have a trip to Gatlinburg planned this weekend.  So, I'll be most curious how that area is affected by this.

Almost verbatim as Neese, but without the snow showers.

[SnowSeek]

WCYB here in East Tn is giving 37/28 forecast for next sunday, if conditions are that cold it could get very interesting for that storm system....

they also show snow/ice/rain...

[SnowSeek]

For the monster lows coming out of the gulf, what is the best path for them to take for cold air?  I have seen them create their own cold and warm air before.  It seems like my history with these storms shows that when the low tracks directly upward it brings warm air vs tracking a sharp west to east like from the Flordia pan handle through GA then through the middle of the carolinas, we seem to get teh cold air.  A matter of fact, the last big Low we had the week before christmas it took that sharp angle that allowed for east tn to get walloped with 6-10 inches of snow.  Is that a correct assumption?

[jmundie]

For the monster lows coming out of the gulf, what is the best path for them to take for cold air?  I have seen them create their own cold and warm air before.  It seems like my history with these storms shows that when the low tracks directly upward it brings warm air vs tracking a sharp west to east like from the Flordia pan handle through GA then through the middle of the carolinas, we seem to get teh cold air.  A matter of fact, the last big Low we had the week before christmas it took that sharp angle that allowed for east tn to get walloped with 6-10 inches of snow.  Is that a correct assumption?

The path doesn't have much to do with the cold air source. It just needs to be in a position that gives Nashville at the very least a northeasterly flow.

But this "storm" that we're tracking now is two lows, a surface low and an upper level low, that at this point in the models are phasing (basically connecting to one another) which allows the low to deepen (achieve lower pressure and more strength) leading to more precipitation, as well as a cold core underneath the upper level low that can produce snow even when areas to the north of said low are above freezing.

With this system, based on current model trends, we'll be facing a zonal flow, which is a flat jet stream in the west, leading to mild air from the pacific flooding the country, causing tranquil mild weather for most. We are forecast to still have a negative NAO (north atlantic oscillation) and models are also forecasting a positive PNA. The PNA has something to do with the amount of ridging in the jet stream in the west, so its possible that the models are underestimating the size of the ridge in the western half of the CONUS, which will lead to , if not a trough in the east, at least a less warm scenario. With a strong phased low coming out of the gulf, that creates its own cold air, we can still get snow, but a better chance is if the northern stream gets involved, making it easier for an arctic air mass to involve itself in the storm.

So, all that to say, there's not a specific track that's going to pull in more cold air. As always, we're dealing with possibilities based on somewhat flawed data. Just keep checking the models, watching trends, and if you really want to start to learn how everything interacts, start comparing gfs runs at the same time periods and look for the differences, say for the 0z and the 12z, and try to put together how the small changes can result in larger changes down the line.

[jmundie]

wow.

0z run was terrible. no phasing going on. Just look at the difference between Sunday's 12z and the current 0z runs
12z


0z


Will check out the ensembles tomorrow morning. We've had four significantly different solutions for this storm 4 runs of the gfs in a row. The fact that all the models caught onto something means a strong storm will be around in that timeframe, but a lot depends on when or if the phase occurs (I think it will) and whether or not the northern stream is involved (big if there).

[Eric]

6z GFS shows a whopper of a storm in the gulf, but our old friend Mr. Suppression keeps in down there.  If that run verifies, the majority of the rain stays along and south of I-20, with temps well supportive of liquid precip....no doubt about that, even in our neck of the woods.  I'm gonna wait until the 12z to write this one off, but it's definitely not promising.

[mempho]

6z GFS shows a whopper of a storm in the gulf, but our old friend Mr. Suppression keeps in down there.  If that run verifies, the majority of the rain stays along and south of I-20, with temps well supportive of liquid precip....no doubt about that, even in our neck of the woods.  I'm gonna wait until the 12z to write this one off, but it's definitely not promising.

We've used up most of the cold air.  At this point, the track seems virtually irrelevant.  There's only two ways to get what we want with this storm and one of the appears to be extremely unlikely (that being a cold high centered in the vicinity of the great lakes) and the second also appears less than 20% likely (that being a system that brings down it's own cold air as a source).

In short, I'm not exicted about it at all.  It may be time to put these thoughts to rest for at least 10 days or so and check back as we move towards the very end of January and early February.  This period, after a pattern reload, will be our last chance for a major storm with widespread and prolonged snowcover. 

On the bright side, I have confidence that the blocking will reassert itself and give us another period staying within the deep freeze, so let's just hope we catch a storm on the front end of the next pattern change back to cold. 

[Eric]

Just ran the loop for the 12z GFS, and she says one thing...........................NEXT! 

[Curt]

Put a nail in the coffin for this thread! Should hopefully see another winter thread in early Feb. 

[ams30721us]

Where is the upper level low supposed to track? I have been away a few days but just got back to work and read the GSP discussion about it and it sounds interesting whereever it does go

[ams30721us]

hmmmm nevermind looks like Nashville NWS answered that for me...

IN THE EXT FCST...UPPER LOW TO DEVELOP JUST EAST OF BAJA ON
THURSDAY. THIS SYSTEM WILL TRACK OUR WAY AND PERHAPS EVEN MOVE
ACROSS TN BY NEXT WEEKEND. SYSTEM IS STRONG BUT NOT VERY DEEP.
THUS...VERBATIM...THERMAL PROFILE LEANS TOWARD AN ALL RAIN EVENT.
HOWEVER...MODELS ARE USUALLY TOO WARM WHEN WITHIN THE UPPER LOW`S
PATH. LOOKING AT MEX NUMBERS...WE WILL BE DOWN TO NEAR FREEZING SAT
NT. THUS...I WILL INCLUDE A CHANCE OF RAIN FOR SATURDAY AND SUNDAY...WITH
A POSSIBLE RAIN/SNOW MIX FOR SAT NT.

[Eric]

hmmmm nevermind looks like Nashville NWS answered that for me...

IN THE EXT FCST...UPPER LOW TO DEVELOP JUST EAST OF BAJA ON
THURSDAY. THIS SYSTEM WILL TRACK OUR WAY AND PERHAPS EVEN MOVE
ACROSS TN BY NEXT WEEKEND. SYSTEM IS STRONG BUT NOT VERY DEEP.
THUS...VERBATIM...THERMAL PROFILE LEANS TOWARD AN ALL RAIN EVENT.
HOWEVER...MODELS ARE USUALLY TOO WARM WHEN WITHIN THE UPPER LOW`S
PATH. LOOKING AT MEX NUMBERS...WE WILL BE DOWN TO NEAR FREEZING SAT
NT. THUS...I WILL INCLUDE A CHANCE OF RAIN FOR SATURDAY AND SUNDAY...WITH
A POSSIBLE RAIN/SNOW MIX FOR SAT NT.

That's very interesting.....

[FunnySnowBunny]

it's ALIVE!!!!

[jmundie]

That's what I've been trying to say. The  upper low is gonna bring some snow to the deep south. How manytimes has it been in the 40s in Nashville and Jackson ms gets a snowstorm from an ull? It happens every couple years it seems.

If we are directly under the ull, I say we will see some snow... Accumulations are another issue, and I can understand being conservative this far out (ulls are notoriously hard to forecast) but if the thing deepens more than currently proggex, and that strong high holds in te northeast thing could certainly get interesting for a Dallas to nashville to dc axis

[ams30721us]

HPC PM Discussion:

AND SHOULD LEAD EXPLOSIVE CONVECTIVE
DEVELOPMENT WITHIN THE GULF OF MEXICO IN 4-5 DAYS TIME WHICH
SHOULD DEEPEN THE SURFACE LOW.  IN SOME RESPECTS...THIS IS SIMILAR
TO THE FLOW PATTERN AROUND NOVEMBER 8-9 2009...BUT WITH STRONGER
DYNAMICS ALOFT AND NO TROPICAL CYCLONE INVOLVED.  THE GFS IS A
FAST OUTLIER WITH THIS SYSTEM.  SINCE ITS QUICK SOLUTION IS NOT
SUPPORTED BY THE 00Z MULTI-MODEL ENSEMBLE MEMBERS...DISCOUNTED ITS
SOLUTION.  IF THE GUIDANCE IS SOMEHOW A LITTLE TOO WEAK WITH THIS
SYSTEM...MEASURABLE FROZEN PRECIPITATION WOULD BE POSSIBLE ACROSS
SOUTHERN/CENTRAL TEXAS AS 850 HPA TEMPERATURES ARE BARELY ABOVE
FREEZING WITHIN ITS EXPECTED COMMA HEAD.  ONCE THE SYSTEM LIFTS
OUT ALONG THE GULF COAST/DEEPENS NEAR AND OFFSHORE THE EAST
COAST...PRECIPITATION COULD START AND END AS FROZEN ACROSS THE
MID-ATLANTIC/NEW ENGLAND STATES THIS WEEKEND INTO EARLY NEXT WEEK.
 STAY TUNED.