Christmas Storm

[snowlover91]

Hour 60, looking good! (if this image is too large I can remove it)

[beanskip]

DT's EE rule!!!

wow... very much so

[UpStateCAD]

in the weather world, you can never really say never. Each and every year we get systems that many folks say there's no way it can head into the Lakes or northeast, or Midatlantic for various reasons, yet they most of the time have done just that. I cant count the number of times NC thought it was a lock at 5 days out, only to hit DC and NYC. Theres always the chance this shears out , which wouldn't be good for anybody, then bombs off new england I suppose. I like our chances though right now. The NAM has the trough just east of LAX at 60 hours. Just comparing how it is to the Euro. So far, so good.

thanks Robert. I hope we can finally all get one. If this happens this weekend......and Christmas to boot. I promise not to poor mouth the SC winters EVER AGAIN....lol

[WeatherNC]

RAH Update Long Term (underlined part is the only thing I don't understand)

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE RALEIGH NC

326 PM EST MON DEC 20 2010

.LONG TERM /FRIDAY THROUGH MONDAY/...

AS OF 300 PM MONDAY...

FRIDAY THROUGH SATURDAY NIGHT...MEDIUM RANGE GUIDANCE STILL IN A BIT

OF DISARRAY FOR THE PERIOD FRIDAY NIGHT INTO SATURDAY NIGHT...MAINLY

IN HOW THEY DEVELOP A SURFACE LOW OVER THE SE U.S. THOUGH THE ECMWF

IS MUCH SLOWER...IT IS CONSISTENT WITH ITS PREVIOUS RUN OF EJECTING

PACIFIC TROUGH EAST INTO THE SOUTH CENTRAL U.S. WHERE IT PHASES WITH

NORTHERN STREAM ENERGY FRIDAY NIGHT INTO EARLY SATURDAY. THIS LEADS

TO A SURFACE LOW OVER THE NORTHERN GULF COAST LIFTING NE SATURDAY

NIGHT INTO EARLY SUNDAY ALONG THE SE U.S. COAST. THE ECMWF SUGGEST

PRECIP ARRIVAL NOT UNTIL SATURDAY AFTERNOON. MEANWHILE THE GEM/GFS

HAVE TRENDED SOUTHWARD FROM THEIR PREVIOUS RUNS. THE GEM SOUTHWARD

SHIFT APPEARS TO BE CAUSED BY AN UPPER LEVEL LOW THAT DEVELOPS OVER

THE GREAT LAKES WHILE THE SOUTHWARD SHIFT IN THE GFS APPEARS TO BE

LINKED TO A SECONDARY VORT MAXIMUM DIVING SE ON THE BACK SIDE OF THE

TROUGH OVER THE GREAT LAKES. BOTH THE GEM/GFS BRING PRECIP INTO

CENTRAL NC AROUND MIDNIGHT CHRISTMAS EVE WITH POTENTIAL FOR

WIDESPREAD PRECIP CHRISTMAS MORNING. PARTIAL THICKNESSES SUGGEST

MAINLY LIQUID AT ONSET THOUGH AS THE SURFACE LOW LIFTS NE ALONG THE

COAST...POTENTIAL FOR PRECIP TO BECOME SOME WINTRY TYPE.

DUE TO TIMING ISSUES AND HOW MODELS EVOLVE THE SURFACE LOW...AM

LEARY ABOUT MAKING WHOLESALE CHANGES TO THE EXTENDED AT THIS TIME.

FOR NOW WILL LOWER MAX TEMPS SATURDAY SEVERAL DEGREES FROM PREVIOUS

FORECAST. WILL MAINTAIN SOLID CHANCE POPS ACROSS THE REGION SATURDAY

WITH MAIN PRECIP TYPE LIQUID FOR NOW. SINCE THIS SYSTEM APPEARS TO

RESEMBLE A "MILLER A" SCENARIO...WOULD EXPECT TO SEE NARROW

TRANSITION PRECIP CORRIDOR. SINCE COLD AIR (OR A SOURCE OF COLD AIR)

APPEARS TO BE LACKING...KEEPING PRECIP LIQUID AT THIS TIME APPEARS

TO BE BEST ROUTE AT THIS TIME.

SUNDAY INTO MONDAY...COLD AND DRY CONDITIONS EXPECTED AS ARCTIC HIGH

OVER THE NORTH CENTRAL U.S. BUILDS SOUTH INTO THE DEEP SOUTH. THIS

WILL PLACE CENTRAL NC IN THE 850MB THERMAL TROUGH THROUGH THE PERIOD

WITH MAX TEMPS 10-15 DEGREES BELOW NORMAL.

Conservative as expected and prudent at this range, but they do throw a bone to us common folk...

.CLIMATE...

AS OF 1230 PM SUNDAY...

TAKING A LOOK BACK AT CHRISTMASES PAST... HERE ARE SOME DECEMBER

25TH SNOWFALL AND SNOW DEPTH STATISTICS FOR THE RALEIGH AND

GREENSBORO AREAS. THIS INFORMATION IS FOR THE AIRPORT LOCATIONS...

HOWEVER IT ALSO APPLIES FOR OTHER OBSERVATION SITES IN THE RALEIGH

AREA (STATISTICS DATE BACK TO 1887) AND GREENSBORO AREA (STATISTICS

DATE BACK TO 1903).

AT GSO (PIEDMONT TRIAD INTL AIRPORT) (RECORDS KEPT SINCE 1928):

SNOW HAS FALLEN ON CHRISTMAS DAY ON THREE OCCASIONS... THE LAST

HAVING OCCURRED IN 1947 (2.8 INCHES). MEASURABLE SNOW WAS REPORTED

ON THE GROUND AT 7 AM CHRISTMAS MORNING ON SEVEN OCCASIONS. THE MOST

RECENT OCCURRENCE WAS IN 1966 (2 INCHES ON THE GROUND)... ALTHOUGH

HIGHER TOTALS WERE REPORTED IN 1947 (3 INCHES) AND 1930 (4 INCHES).

AT RDU INTERNATIONAL AIRPORT (RECORDS KEPT SINCE 1944):

SNOW HAS FALLEN ON CHRISTMAS DAY ON JUST ONE DAY... 0.4 INCHES IN

1947. MEASURABLE SNOW WAS REPORTED ON THE GROUND AT 7 AM CHRISTMAS

MORNING ON JUST ONE OCCASION... 1 INCH IN 1966.

[FoothillsNC]

Your vortex is stronger on the NAM (like Euro). I'm beginning to think sheared out is a bigger concern than too far north with this baby.

its strong on all the models, and seems like each run just gets stronger. NC, north stays in the deep freeze all week i believe now. West of the Apps gets a little warmer, but only the southern Plains is the real warm spot. I hope that thing moves or relaxes a little, just in time. But the longer its in place, the better (and later and further south) any phaser would be. That very well could be right over Georgia/Ala/or Tenn, maybe even NC.

At 69 hour, just south of the 4 corners, standing neutral tilt and very healthy looking. Nice PnA ridge in western Canada. All systems go. Just a gorgeous setup so far.

[eyewall]

RAH

FRIDAY THROUGH SATURDAY NIGHT...MEDIUM RANGE GUIDANCE STILL IN A BIT

OF DISARRAY FOR THE PERIOD FRIDAY NIGHT INTO SATURDAY NIGHT...MAINLY

IN HOW THEY DEVELOP A SURFACE LOW OVER THE SE U.S. THOUGH THE ECMWF

IS MUCH SLOWER...IT IS CONSISTENT WITH ITS PREVIOUS RUN OF EJECTING

PACIFIC TROUGH EAST INTO THE SOUTH CENTRAL U.S. WHERE IT PHASES WITH

NORTHERN STREAM ENERGY FRIDAY NIGHT INTO EARLY SATURDAY. THIS LEADS

TO A SURFACE LOW OVER THE NORTHERN GULF COAST LIFTING NE SATURDAY

NIGHT INTO EARLY SUNDAY ALONG THE SE U.S. COAST. THE ECMWF SUGGEST

PRECIP ARRIVAL NOT UNTIL SATURDAY AFTERNOON. MEANWHILE THE GEM/GFS

HAVE TRENDED SOUTHWARD FROM THEIR PREVIOUS RUNS. THE GEM SOUTHWARD

SHIFT APPEARS TO BE CAUSED BY AN UPPER LEVEL LOW THAT DEVELOPS OVER

THE GREAT LAKES WHILE THE SOUTHWARD SHIFT IN THE GFS APPEARS TO BE

LINKED TO A SECONDARY VORT MAXIMUM DIVING SE ON THE BACK SIDE OF THE

TROUGH OVER THE GREAT LAKES. BOTH THE GEM/GFS BRING PRECIP INTO

CENTRAL NC AROUND MIDNIGHT CHRISTMAS EVE WITH POTENTIAL FOR

WIDESPREAD PRECIP CHRISTMAS MORNING. PARTIAL THICKNESSES SUGGEST

MAINLY LIQUID AT ONSET THOUGH AS THE SURFACE LOW LIFTS NE ALONG THE

COAST...POTENTIAL FOR PRECIP TO BECOME SOME WINTRY TYPE.

DUE TO TIMING ISSUES AND HOW MODELS EVOLVE THE SURFACE LOW...AM

LEARY ABOUT MAKING WHOLESALE CHANGES TO THE EXTENDED AT THIS TIME.

FOR NOW WILL LOWER MAX TEMPS SATURDAY SEVERAL DEGREES FROM PREVIOUS

FORECAST. WILL MAINTAIN SOLID CHANCE POPS ACROSS THE REGION SATURDAY

WITH MAIN PRECIP TYPE LIQUID FOR NOW. SINCE THIS SYSTEM APPEARS TO

RESEMBLE A "MILLER A" SCENARIO...WOULD EXPECT TO SEE NARROW

TRANSITION PRECIP CORRIDOR. SINCE COLD AIR (OR A SOURCE OF COLD AIR)

APPEARS TO BE LACKING...KEEPING PRECIP LIQUID AT THIS TIME APPEARS

TO BE BEST ROUTE AT THIS TIME.

SUNDAY INTO MONDAY...COLD AND DRY CONDITIONS EXPECTED AS ARCTIC HIGH

OVER THE NORTH CENTRAL U.S. BUILDS SOUTH INTO THE DEEP SOUTH. THIS

WILL PLACE CENTRAL NC IN THE 850MB THERMAL TROUGH THROUGH THE PERIOD

WITH MAX TEMPS 10-15 DEGREES BELOW NORMAL.-- End Changed Discussion --

[Wow]

Not in love with the Euro ensemble mean- faster and farther north, it has a weak surface low over central GA Xmas at 12Z. Still would be OK for NC, GA and SC not so much. As stated before, a long way to go, let's not wish forecast.

would that not indicate divergent solutions? Do you have access to individual panels?

[beanskip]

Significantly colder out ahead of the low at 60-66 hours -- -9 line makes it into extreme NW NC mountains!

[tnweathernut]

Speaking of DT - he says on his blog there are similarities between this and the big Jan of 96 snow. Good to have mets in other regions with their ears perking up for potential snow in the south/southeast

[Wow]

its strong on all the models, and seems like each run just gets stronger. NC, north stays in the deep freeze all week i believe now. West of the Apps gets a little warmer, but only the southern Plains is the real warm spot. I hope that thing moves or relaxes a little, just in time. But the longer its in place, the better (and later and further south) any phaser would be. That very well could be right over Georgia/Ala/or Tenn, maybe even NC.

At 69 hour, just south of the 4 corners, standing neutral tilt and very healthy looking. Nice PnA ridge in western Canada. All systems go. Just a gorgeous setup so far.

As the s/w trends slower, the impact of the PV will be less and thus the probability of shearing lessens. NAM looks to be slower compared to 12z.

[griteater]

Significantly colder out ahead of the low at 60-66 hours -- -9 line makes it into extreme NW NC mountains!

This has been the most encouraging thing about the model trends to me - colder air

[beanskip]

Yeah, 0C line on the 12z NAM at 78 hours barely dipped into S.C. and only covered the NE 1/3 of Tenn.

Now's it straddles the Ga./SC line and cover the NE 2/3 of Tenn.

This has been the most encouraging thing about the model trends to me - colder air

[FoothillsNC]

As the s/w trends slower, the impact of the PV will be less and thus the probability of shearing lessens. NAM looks to be slower compared to 12z.

Did you see how strong this shortwave is? I'm extremely impressed for a non-Nino year. It also has a 850 low developing in southeast Colorado and moves it into Southwest kansas ast 78 hours. Now the run is done, has almost a bowling ball uppr low. so far, not much gulf tappage, but who ever winds up under that low or closest to the dynamics on the north shield is going to be loving life. NC stays in the deep freeze the whole run. Sub zero.

[Snow haven]

Yeah, 0C line on the 12z NAM at 78 hours barely dipped into S.C. and only covered the NE 1/3 of Tenn.

Now's it straddles the Ga./SC line and cover the NE 2/3 of Tenn.

Yea im not to worried about this storm im suppose to be above freezing according to the forecast im suppose to be 37 degrees. its been like that for the past few days.

[FoothillsNC]

I wonder if southern California has mudslide watches out. Looks likea lot of rain coming for the Southwest and the deserts.

[Rob]

For once I am not too bummed about sitting in this location. Nashville looks to have a excellent chance on this should the trends hold true. Foothill if this was to Close off , how would that affect the overall ULL track. I assume it would slow down and let the Northern stream ahead a bit and not really pick it up as high in Lat.?

[Wow]

Did you see how strong this shortwave is? I'm extremely impressed for a non-Nino year. It also has a 850 low developing in southeast Colorado and moves it into Southwest kansas ast 78 hours. Now the run is done, has almost a bowling ball uppr low. so far, not much gulf tappage, but who ever winds up under that low or closest to the dynamics on the north shield is going to be loving life. NC stays in the deep freeze the whole run. Sub zero.

Indeed, quite potent. Once the low pops in the gulf, then we begin the precip begin to breakout like mad all over the SE. Setting up for excellent divergence ahead of the wave there.

[eyewall]

I wonder if southern California has mudslide watches out. Looks likea lot of rain coming for the Southwest and the deserts.

Yeah they have been highlighting it in their issuances especially in the LA burn areas (debris flows and mud slides).

[HKY18]

yeah i think areas north of LA where closing in on 8 inches at 12:30 est so im sure there at 8 by now if not 9

[DopplerWx]

If the models continue to look this good through weds/thurs we will be on cloud nine. It is crazy to think that northern SC and NC wont have to worry about temps, or precip. Heres to a historic snowstorm.

[HurricaneTracker]

DT's EE rule!!!

Remind me again, what is that rule?

[beanskip]

Ahhhh, so glad you asked.

The EE rule is that when the Euro and the ETA are in agreement, you can take that solution to the bank.

Of course, EE doesn't work anymore because the ETA became the NAM, but you get the point.

Remind me again, what is that rule?

[rduwx]

Remind me again, what is that rule?

Back when we had the eta model, DT's theory was if the the Eta and Euro showed the same it was a lock.

[FoothillsNC]

the NAM looks pretty reasonable. If you get a chance, look at the 5H loop of it. Nice the way it rotates east like a surfer riding a wave from the main Pacific low, and it starts to turn southeast. In the next few frames the moisture should suddenly explode in the region I have circled. Thats when the system is dropping southeast/east, taps the gulf and has the core of the jet max on its southeast side so excellent lifting process. You can see it starting in southeast Kansas. Even with out a true Gulf tap for Ok, and southern Kansas, with the dynamics and how loaded this feature is going to be, I think some major snow is going to shut down a a lot of those 2 states. Oklahoma starts off warm, but will change arond this time. The 850 low is already impressive as well and should strengthen, ( i think)

[Carvers Gap]

I'd call this playing your cards close to the vest...I don't want to be too critical because this is a very good weather office here in Morristown.

000

FXUS64 KMRX 202041

AFDMRX

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE MORRISTOWN TN

319 PM EST MON DEC 20 2010

.SHORT TERM (TONIGHT AND TUESDAY)...FRONT ENTERING THE AREA TONIGHT

AND TUESDAY. DEEPEST MOISTURE HOLDS OFF UNTIL LATE TONIGHT...SO WILL

KEEP A DRY FORECAST DURING THE EVENING HOURS. SOUNDINGS INDICATE

FREEZING RAIN AND SNOW POSSIBLE LATE TONIGHT AND INTO TUESDAY

MORNING ACROSS MAINLY THE NORTHERN PORTIONS OF THE CWA. ONLY VERY

LIGHT PRECIPITATION IS EXPECTED TONIGHT AND TUESDAY MORNING...SO

WILL NOT ISSUE AN ADVISORY. WILL KEEP HIGH CHANCE POPS GOING FOR

TUESDAY...BUT PRECIPITATION SHOULD BE ALL LIQUID BY THE AFTERNOON

HOURS. WITH CLOUDS INCREASING TONIGHT...STAYED ABOVE GUIDANCE

NUMBERS FOR TONIGHT. STAYED NEAR GUIDANCE FOR TEMPERATURES TOMORROW.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)...TUESDAY NIGHT STARTS

ON THE TAIL END OF A COLD FRONT WITH WEAK NORTHWEST FLOW AND LIMITED

MOISTURE BY THE TIME WEDNESDAY FINISHES UP. SHORT UPPER RIDGE AND

SURFACE HIGH SETTLE IN FOR THURSDAY FOR A BREAK IN THE PRECIP. SOME

DISAGREEMENT AMONG MODELS AND SURROUNDING OFFICES AS TO TIMING OF

FOLLOWING SYSTEM FOR FRIDAY. WENT WITH GFS WHICH HOLDS SYSTEM BACK

AND INTENSIFIES THIS SYSTEM WITH FAIRLY TIGHT PRESSURE GRADIENTS AND

DEEPENING SURFACE LOW. HAVE OPTED TO USE CHANCE WORDING IN

FRIDAY-EARLY SUNDAY WITH DECREASE FROM WEST ON SUNDAY AS LOWS

POTENTIALLY DEEPENS AND SLOWS. PLUS...THIS IS MONDAY AND FRIDAY,

SATURDAY, AND SUNDAY ARE A LONG WAY OFF. THERE IS AN OUTSIDE CHANCE

FOR A BRIEFLY WHITE CHRISTMAS IN THE MORNING BEFORE IT WARMS UP

ENOUGH TO TURN TO RAIN. WE`LL KEEP AN EYE ON THIS.

THE SURFACE RAPIDLY DEEPENS AND BOMBS OUT IN THE GFS AND HEADS UP

THE EAST COAST ON SUNDAY AND MONDAY WITH SOME LINGER RH BEHIND IN

THE NORTHWEST FLOW OF THE ASSOCIATED UPPER TROUGH. POPS RAPIDLY DROP

OFF THEN.

TEMPS WERE A LITTLE DIFFICULT TO PIN DOWN. STARTED WITH GFS TEMPS

AND THEN ADJUSTED FOR CLOUDS AND PRECIP. MOSTLY JUST MASSAGES TO

PREVIOUS TEMPS.

ONE THING TO WATCH AND WILL PASS THIS ON TO SUBSEQUENT SHIFTS IS THE

CHANCE FOR INCREASING WINDS AS THE SURFACE LOW DEEPENS MID-LATE

WEEK.

&&

[Wow]

Remind me again, what is that rule?

RULE #7 DOUBLE EE RULE

When the 60 - 84 Hour ETA matches the ECMWF day 3-4 at surface and 500 MB that is a pretty good winning hand. Take it to the bank.

[strongwxnc]

Skip,

I think you have talked about the EE rule a few times in the past two days.

It will be named the Skip rule if this system wins out!

Ahhhh, so glad you asked.

The EE rule is that when the Euro and the ETA are in agreement, you can take that solution to the bank.

Of course, EE doesn't work anymore because the ETA became the NAM, but you get the point.

Links those Rules John

RULE #7 DOUBLE EE RULE

When the 60 - 84 Hour ETA matches the ECMWF day 3-4 at surface and 500 MB that is a pretty good winning hand. Take it to the bank.

[Snow haven]

Back when we had the eta model, DT's theory was if the the Eta and Euro showed the same it was a lock.

So does the NAM and Euro show agreement?

[griteater]

We definitely want the vort max tracking through Texas per the CMC and Euro and NOT through Oklahoma per the GFS and NAM. That's just one state north, but that means everything for keeping it cold enough.

[UpStateCAD]

RULE #7 DOUBLE EE RULE

When the 60 - 84 Hour ETA matches the ECMWF day 3-4 at surface and 500 MB that is a pretty good winning hand. Take it to the bank.

So .....if by this time tomorrow the NAM and the Euro say "WOOF" then it's milk and bread time?

Yeah Baby!!