2013 Fall Medium Range Discussion

[donsutherland1]

In this season of the “Fiscal Cliff,” there’s another “cliff” that has some snow geese increasingly anxious. For several days, the models have teased the snow geese, already starving from the non-winter of 2011-12, with possibilities of one or two large snowfalls. Since then, the guidance has evolved in ways that make Scrooge a model of charity. To them, a cliff suddenly looms over which they will tumble into premature spring.

But this is the Holiday Season. There's no reason to despair. The joys of Hanukkah have already brightened an abnormally warm December to date. Christmas lies ahead in what is now a generally colder, but still not severely cold pattern. Gifts, in the form of a series of storms, will be unwrapped as 2012 draws to a close and 2013 begins.

The first will bring moderate to heavy snows across parts of Ohio and Indiana into southern Ontario on December 26-27. The next could bring a stripe of accumulating snow (perhaps moderate to significant) from the northern Mid-Atlantic region into southern New England on December 29-31 (timing still a little uncertain).

In the wake of the latter storm, a full-fledged Arctic outbreak appears increasingly likely, even if the GFS has waffled in Washington-style fashion. Blocking continues and the PNA is likely to go positive. The frigid air that has remained locked safely away across Alaska and parts of northwestern Canada will finally be dislodged. Some of that air will sweep across southern Ontario and southern Quebec and also tumble into the Continental U.S. With snow cover across the Ohio Valley and parts of the East Coast, there will be less moderation than would otherwise be the case. The season's coldest readings to date will occur in many places. Some might see their coldest readings since winter 2010-11.

For now, even as Washington wrestles with the Fiscal Cliff, with perhaps a suboptimal, minimalist outcome the most likely scenario, GFS mirages notwithstanding, there is no cliff that will send the snow geese hurtling into another abnormally early spring. It bears repeating, this is not a replay of winter 2011-12.

Source: Library of Congress

[ezweather]

Don,

Your recent post is awesome. You couldn't have said it any better. While I'm here, I just want to wish everyone Happy Holidays and a Healthy and Happy New Year !!!

[golia1w]

Don,

I always enjoy your well-written insights, but your last several posts have been infused with such wry humor, I have re-read them several times with a smile on my face. You have been a real holiday treat!

[easternsnowman]

I've felt all along this winter will go back and forth with temps. I think early january and early to mid february will be the most wintery periods with late january slightly above normal but reloading to a colder pattern.after. Even above normal temps in late january can bring snow to the northern mid atlantic because it is the coldest time of the year, so we can handle a few above normal in that period.

[Srain]

The medium range guidance has been rather insistent that a New Years Winter Storm is lurking as a deep cutoff 5H cold core low move inland across Baja bringing copious EPAC moisture and cold air across the Southern Rockies/Southern Plains yet again.

[Srain]

The overnight ensembles continue to advertise another potential high impact event for the New Year, +/- a day or two across the Southern Rockies/Southern Plains. This event if modeled correctly would suggest a bit further S track from that of the Christmas Storm with both winter and severe threats once again.

[ezweather]

If you looked at the 12z GFS run, what big storm. Model doesn't show those type of threats. Very flat, but does have a cold look. I'll wait on the ensembles and the Euro later today.

[Srain]

The 12Z Euro is suggesting a rather impressive Winter Storm brewing near the New Year time frame. It appears to have both winter and severe elements involved, if the Euro is correct. The Euro also holds the more southern cut off track across Baja/N Mexico ~vs~ a progressive non event that the GFS has been suggesting. That said the +PNA ridge of high pressure suggested by the ensembles lends a bit of credence to a slowing down or a bit less progressive pattern as the cut off cold core low drops S of California and taps some EPAC moisture. We will see.

[donsutherland1]

Morning thoughts...

1. The PNA remains positive (+0.517). Its stretch of 49 consecutive days < 0 has ended.

2. The AO is currently -0.354. It has been negative for 38 consecutive days (a duration that is consistent with the blocking cases set forth in message #25 back on November 26.

3. The ensemble guidance suggests that the PNA will peak and then slowly head back to neutral levels in the extended range. The AO will very likely go positive, but the EPO will trend toward neutral levels.

All this sets the stage for a period of moderation probably beginning 1/10 +/- a few days (1/5 +/- a few days in the Plains States). This moderation is not likely to mark the end of the winter so to speak. However, a return to cold will likely depend more on the evolution of the PNA and EPO than the AO.

More immediately, the storm that brought more than 10" snow to parts of Arkansas and a foot of snow to parts of Indiana will bring a significant snowfall to portions of northern New England today into tomorrow.

A second storm will likely bring a stripe of accumulating snow (perhaps moderate to significant) from the northern Mid-Atlantic region into southern New England on December 29-31. My thoughts on this storm remain unchanged from those of Message #332, namely that this storm has potential.

Currently, there is disgreement between the GFS and ECMWF/GGEM on the evolution of the weekend storm. Based on how I expected the pattern to evolve and also considering the ensemble guidance, I believe the ECMWF/GGEM will probably be closer to the outcome than the GFS. Therefore, I continue to think that a moderate to possibly significant snowfall form the northern Mid-Atlantic into New England is more likely than little or no snowfall in that area. A lot depends on whether phasing will take place (likely) and the timing (uncertain), but one would think that with its higher resolution the Euro might have somewhat of an edge in handling such events from this timeframe. The caveat is that the Euro hasn't exactly been a rock of consistency, so much uncertainty remains.

Finally, the 12/27 6z GFS notwithstanding, I continue to expect an Arctic outbreak following the weekend storm during the first few days of January. A compromise between the outcome on the 12/27 0z GFS and 12/27 0z ECMWF might be reasonable (perhaps a little closer to the Euro's idea). The season's coldest readings to date should occur in many places. Some locations might see their coldest readings since winter 2010-11.

[uncle W]

Morning thoughts...

1. The PNA remains positive (+0.517). Its stretch of 49 consecutive days < 0 has ended.

2. The AO is currently -0.354. It has been negative for 38 consecutive days (a duration that is consistent with the blocking cases set forth in message #25 back on November 26.

3. The ensemble guidance suggests that the PNA will peak and then slowly head back to neutral levels in the extended range. The AO will very likely go positive, but the EPO will trend toward neutral levels.

All this sets the stage for a period of moderation probably beginning 1/10 +/- a few days (1/5 +/- a few days in the Plains States). This moderation is not likely to mark the end of the winter so to speak. However, a return to cold will likely depend more on the evolution of the PNA and EPO than the AO.

More immediately, the storm that brought more than 10" snow to parts of Arkansas and a foot of snow to parts of Indiana will bring a significant snowfall to portions of northern New England today into tomorrow.

A second storm will likely bring a stripe of accumulating snow (perhaps moderate to significant) from the northern Mid-Atlantic region into southern New England on December 29-31. My thoughts on this storm remain unchanged from those of Message #332, namely that this storm has potential.

Currently, there is disgreement between the GFS and ECMWF/GGEM on the evolution of the weekend storm. Based on how I expected the pattern to evolve and also considering the ensemble guidance, I believe the ECMWF/GGEM will probably be closer to the outcome than the GFS. Therefore, I continue to think that a moderate to possibly significant snowfall form the northern Mid-Atlantic into New England is more likely than little or no snowfall in that area. A lot depends on whether phasing will take place (likely) and the timing (uncertain), but one would think that with its higher resolution the Euro might have somewhat of an edge in handling such events from this timeframe. The caveat is that the Euro hasn't exactly been a rock of consistency, so much uncertainty remains.

Finally, the 12/27 6z GFS notwithstanding, I continue to expect an Arctic outbreak following the weekend storm during the first few days of January. A compromise between the outcome on the 12/27 0z GFS and 12/27 0z ECMWF might be reasonable (perhaps a little closer to the Euro's idea). The season's coldest readings to date should occur in many places. Some locations might see their coldest readings since winter 2010-11.

thanks Don...with the ao forecast to go very positive the second half of January could turn out mild again...If that happens February will make or break this winter in the NYC area...

[Srain]

Don, we in the Southern Rockies/Southern Plains are closely following the New Year Storm potential that the guidance has suggested (namely the European/GEFS) a cut off low solution off the W Coast of Southern California/Baja Region. While the ensembles are a bit more progressive that the operational Euro suggests, the New Year Storm has the potential to be another high impact event. Guidance continues to advertise a Coast Low developing along the NW Gulf bring PW’s into the 2 standard deviation above normal across Texas with a potential severe weather episode developing once again in the warm sector and winter weather further N across the higher ranges of Arizona/New Mexico into the Guadalupe/Davis Mountains of Texas into the Panhandle with an ice storm potential across N Central Texas into Oklahoma.

[Srain]

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

1100 AM EST THU DEC 27 2012

VALID 12Z SUN DEC 30 2012 - 12Z THU JAN 03 2013

...SYNOPSIS...

THE MEDIUM RANGE PERIOD FINDS THE NORTHERN HALF OF THE U.S. ON THE

CHILLY AND DRY SIDE...WITH A LONGWAVE TROUGH AXIS OVER EASTERN

NORTH AMERICA INTO THE WESTERN ATLANTIC...AND NEWLY DEVELOPED MEAN

RIDGING OVER THE PACIFIC NORTHWEST. ENERGY UNDERCUTTING THE RIDGE

WILL SUPPORT THE PLACEMENT OF A CLOSED LOW AFFECTING THE SOUTHWEST

STATES AND SOUTHERN PLAINS...WITH SOME INFLUENCE SPREADING

DOWNSTREAM INTO THE SOUTHEAST BY DAY 6/7.

...MODEL CHOICE...

MODELS ARE TAKING A DEEP CYCLONE FROM OFFSHORE OF NEW ENGLAND UP

INTO FAR EASTERN CANADA ON DAY 3. THE 00Z ECMWF LEANED CLOSER TO

THE COAST...AND WE PREFERRED THE TRACK OF THE GFS/UKMET...BEING

CLOSER TO CONSENSUS AND GIVEN THAT THIS SYSTEM SPINS UP RAPIDLY IN

THE WAKE OF THE PREVIOUS SYSTEM HAVING NUDGED THE BAROCLINIC ZONE

OFFSHORE. THE 00Z GFS AT 981 MB SUNDY MORNING...WAS NOT QUITE DEEP

ENOUGH. ALL THE OPERATIONAL MODELS AND ENSEMBLE MEANS TAKING THIS

LOW DOWN CLOSER TO 970 MB.

BY DAY 4 THE SYSTEM IN THE SOUTHWEST IS OUR FOCUS. THE 00Z GFS

BECAME FAST AND FLAT...AND WE DROP IT BY DAY 4. THE 00Z ECMWF WAS

BETTER UNTIL DAY 6...WHEN ITS PERFORMANCE IS MORE QUESTIONABLE

UPSTREAM IN THE PACIFIC. THE MODELS ARE STRUGGLING WITH SPLIT FLOW

IN THE EASTERN PACIFIC. TELECONNECTIONS BASED ON A PERSISTENT

NEGATIVE ANOMALY OVER NORTHERN QUEBEC WOULD FAVOR A MORE

SUPPRESSED SOUTHERN STORM TRACK THAN IS SEEN IN THE CURRENT

OPERATIONAL MODELS...WHICH ARE TENDING TO PRODUCE

PROGRESSIVE...STRONGER SYSTEMS IN A CONSOLIDATED FLOW STREAM

APPROACHING CALIFORNIA BY DAY 6/7. THUS...WE TURNED TO THE

ENSEMBLE MEANS...WHICH SHOW THIS SUPPRESSED LOOK...AND WE

PREFERRED THE ECMWF ENSEMBLE AND NAEFS...AS THE GEFS SHOWED SOME

OF THE PROGRESSIVE BIAS OF THE GFS.

...IMPACTS...

THE BLOCKY RIDGE/TROUGH COMBINATION OVER THE WEST, COMBINED WITH

THE SUPPRESSED POLAR JET OVER THE EAST SHOULD PRECLUDE WIDESPREAD,

HEAVY PRECIPITATION FOR ALL BUT THE GULF COAST STATES, WHERE WAVES

ALONG THE PRIMARY STORM TRACK SHOULD BE ABLE TO TAP GULF MOISTURE

AS THEY RIPPLE EASTWARD. HOW FAR NORTH THE PRECIPITATION GETS WITH

THESE WAVES IS DEPENDENT UPON WHERE THE CONFLUENCE RESIDES BETWEEN

THE SPLIT STREAMS. THE TELECONNECTIONS ARE DOING A GOOD JOB

DEPICTING THE EXPECTED TEMPERATURE REGIME...WITH BELOW NORMAL

TEMPS IN THE ARCTIC AIR THAT SLIPS THROUGH THE GREAT LAKES. THE

SAME TELECONNECTIONS WOULD SUGGEST LESSER PRECIPITATION CHANCE

INLAND OF THE GULF COAST. THIS IS REFLECTED IN POPS ACROSS THE

TENNESSEE VALLEY, SOUTHERN APPALACHIANS, CAROLINAS, AND MID

ATLANTIC STATES WHICH AT FIRST GLANCE APPEAR HIGH FOR REGIONS

ESSENTIALLY DOMINATED BY CONTINENTAL POLAR AIR. THE BLOCK OVER THE

FAR WEST SHOULD DEFLECT MOST OF THE SIGNIFICANT SHORTWAVES SOUTH

OF THE BORDER. THE GREAT BASIN AND NORTHERN INTERMOUNTAIN REGIONS

WILL CONTINUE TO EXPERIENCE THE CLIMATOLOGICAL TEMPERATURE

INVERSION, WITH COLD NIGHTS NEAR ZERO AND BELOW MANY AREAS.

BURKE/FRACASSO

[easternsnowman]

I think forecasting the ao more than a couple of weeks is a crapshoot. I believe the ao was positive for most of 93-94 winter and we know........

[donsutherland1]

I think forecasting the ao more than a couple of weeks is a crapshoot. I believe the ao was positive for most of 93-94 winter and we know........

Several things:

1. The AO was predominantly negative during winter 1993-94 (60/90 days or 66.7% of the days). There was a 25-day block (12/23 through 1/16), an 18-day period where the AO was positive (1/17 through 2/3), and then another 25-day block (2/4 through 2/28). The severe cold in January briefly gave way to warmer than normal readings during the AO+ regime. Afterward, a cold and snowy pattern (more ice from the Mason-Dixon Line southward) developed in the East.

2. The NAO was positive for almost all of the winter (78/90 days or 86.7% of the days).

3. Given the historical experience with long-duration blocks similar to the current one and the ensemble signal, one probably can have confidence that the AO will likely go positive down the road. Whether such an outcome gives way to another round of sustained blocking remains uncertain at this time.

4. Despite hints of a possible sudden or even major stratospheric warming, there remains a lot of uncertainty. My read on the guidance is that it is mixed. There is no unambiguous signal right now for such an event. Moreover, even as such warmings can trigger the destruction of the polar vortex leading to blocking (top-down response), they can also occur as a result of a prolonged period of blocking (bottom-up response). Should such a warming occur, one would have to watch to see if it begins to translate to the lower levels of the atmosphere.

Having said this, I believe January will probably wind up colder than normal in the Mid-Atlantic region. 1994 is among the past cases coming up, though I don't expect the cold of January 2013 to rival that of January 1994.

[donsutherland1]

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

1100 AM EST THU DEC 27 2012...

A very nice discussion by HPC.

[Isotherm]

I think an important point to make is that US temperatures so far this winter have been negatively correlated to the AO and NAO, which is contrary to the majority of years, and why December ended up being quite a bit warmer than what most of us expected a month ago. Generally a -AO/NAO couplet produces some sustained cold periods in the CONUS and Eastern US, but that has not transpired through the 20th. The last week of December will average below normal in the East, but won't be enough to erase the strong positive temp departures of Dec 1-20.

The H5 height anomaly orientation we saw for Dec 1-20 that produced the CONUS warmth has already reversed, and going forward is likely to be much different than the regime we saw so far. The positive EPO with low heights in the Western Arctic down through AK and NW Canada was largely responsible for the lack of cold air getting into the lower 48. The strongly negative PNA didn't help matters, as there was no mechanism to transport the polar air in Western Canada southwestward due to the troughiness off the West Coast.

Now, the EPO has neutralized and we're seeing major height rises in the regions we've seen low heights so far this winter. Additionally, the PNA is positive, though that pulse is probable to last only a couple weeks before neutralizing again, due to the -PDO regime. The EPO will be an important forecast tool as we progress through the coming weeks. Concerning the AO, statistics strongly favor a renewed period of blocking after our current/upcoming neutralization period. I don't anticipate the AO to remain very positive for a long duration (or reach strongly positive levels).

Most evidence points to the first half of January being cold to very cold in most of the US given the height anomaly flip noted above. The second half of January will probably feature moderation after the PNA relaxes and the AO is not strongly negative. However, I think the build-up of negative departures that we're likely to see the first 10-15 days of January will be more than enough to ensure a cold finish to the month for the East.

[easternsnowman]

Several things:

1. The AO was predominantly negative during winter 1993-94 (60/90 days or 66.7% of the days). There was a 25-day block (12/23 through 1/16), an 18-day period where the AO was positive (1/17 through 2/3), and then another 25-day block (2/4 through 2/28). The severe cold in January briefly gave way to warmer than normal readings during the AO+ regime. Afterward, a cold and snowy pattern (more ice from the Mason-Dixon Line southward) developed in the East.

2. The NAO was positive for almost all of the winter (78/90 days or 86.7% of the days).

3. Given the historical experience with long-duration blocks similar to the current one and the ensemble signal, one probably can have confidence that the AO will likely go positive down the road. Whether such an outcome gives way to another round of sustained blocking remains uncertain at this time.

4. Despite hints of a possible sudden or even major stratospheric warming, there remains a lot of uncertainty. My read on the guidance is that it is mixed. There is no unambiguous signal right now for such an event. Moreover, even as such warmings can trigger the destruction of the polar vortex leading to blocking (top-down response), they can also occur as a result of a prolonged period of blocking (bottom-up response). Should such a warming occur, one would have to watch to see if it begins to translate to the lower levels of the atmosphere.

Having said this, I believe January will probably wind up colder than normal in the Mid-Atlantic region. 1994 is among the past cases coming up, though I don't expect the cold of January 2013 to rival that of January 1994.

Thanks Don for I was'nt sure about whether it was the ao or nao that was positive. I know it's unusual for the majority of the winter to have one to be positive and the other negative. Anyway I agree that January will be colder than average and I believe the cold will reload again toward later in the month.

[The_Global_Warmer]

Several things:

1. The AO was predominantly negative during winter 1993-94 (60/90 days or 66.7% of the days). There was a 25-day block (12/23 through 1/16), an 18-day period where the AO was positive (1/17 through 2/3), and then another 25-day block (2/4 through 2/28). The severe cold in January briefly gave way to warmer than normal readings during the AO+ regime. Afterward, a cold and snowy pattern (more ice from the Mason-Dixon Line southward) developed in the East.

2. The NAO was positive for almost all of the winter (78/90 days or 86.7% of the days).

3. Given the historical experience with long-duration blocks similar to the current one and the ensemble signal, one probably can have confidence that the AO will likely go positive down the road. Whether such an outcome gives way to another round of sustained blocking remains uncertain at this time.

4. Despite hints of a possible sudden or even major stratospheric warming, there remains a lot of uncertainty. My read on the guidance is that it is mixed. There is no unambiguous signal right now for such an event. Moreover, even as such warmings can trigger the destruction of the polar vortex leading to blocking (top-down response), they can also occur as a result of a prolonged period of blocking (bottom-up response). Should such a warming occur, one would have to watch to see if it begins to translate to the lower levels of the atmosphere.

Having said this, I believe January will probably wind up colder than normal in the Mid-Atlantic region. 1994 is among the past cases coming up, though I don't expect the cold of January 2013 to rival that of January 1994.

That was a pretty cold month. 26.8F in STL.

And a nice flip from so far:

[Jebman]

In this season of the “Fiscal Cliff,” there’s another “cliff” that has some snow geese increasingly anxious. For several days, the models have teased the snow geese, already starving from the non-winter of 2011-12, with possibilities of one or two large snowfalls. Since then, the guidance has evolved in ways that make Scrooge a model of charity. To them, a cliff suddenly looms over which they will tumble into premature spring.

But this is the Holiday Season. There's no reason to despair. The joys of Hanukkah have already brightened an abnormally warm December to date. Christmas lies ahead in what is now a generally colder, but still not severely cold pattern. Gifts, in the form of a series of storms, will be unwrapped as 2012 draws to a close and 2013 begins.

The first will bring moderate to heavy snows across parts of Ohio and Indiana into southern Ontario on December 26-27. The next could bring a stripe of accumulating snow (perhaps moderate to significant) from the northern Mid-Atlantic region into southern New England on December 29-31 (timing still a little uncertain).

In the wake of the latter storm, a full-fledged Arctic outbreak appears increasingly likely, even if the GFS has waffled in Washington-style fashion. Blocking continues and the PNA is likely to go positive. The frigid air that has remained locked safely away across Alaska and parts of northwestern Canada will finally be dislodged. Some of that air will sweep across southern Ontario and southern Quebec and also tumble into the Continental U.S. With snow cover across the Ohio Valley and parts of the East Coast, there will be less moderation than would otherwise be the case. The season's coldest readings to date will occur in many places. Some might see their coldest readings since winter 2010-11.

For now, even as Washington wrestles with the Fiscal Cliff, with perhaps a suboptimal, minimalist outcome the most likely scenario, GFS mirages notwithstanding, there is no cliff that will send the snow geese hurtling into another abnormally early spring. It bears repeating, this is not a replay of winter 2011-12.

Source: Library of Congress

Great writeup Don. I don't know why you don't consider blogging. You're a natural at content marketing and metaphors. Ever since the Panda and Penguin updates earlier this year at Google, major businesses have finally realized they need to invest in content marketing and Author Rank. You should blog. You have serious natural talent.

[mrgolf]

Don, merry christmas and happy new year! If a ssw or even mmw event happens, how will we be able to tell that is occuring or will occur besides watching the teleconnection charts? There has been false signals already, which lead to it ultimately not happening. I would like to see a true period of blocking before winter is over. Ive heard it take a few weeks to propagate it to the lower levels if it happens at all. It just seems like its getting colder, but its in and its out a few days later. One more thing don, if an when a ssw or a mmw event occurs, what does it actually do to the overall wx patterns in general? Ive always wondered that. Thanks kevin. Keep up the good work! Ps: if anyone else has an answer or wants to chime in, feel free to do so

[donsutherland1]

Don, merry christmas and happy new year! If a ssw or even mmw event happens, how will we be able to tell that is occuring or will occur besides watching the teleconnection charts? There has been false signals already, which lead to it ultimately not happening. I would like to see a true period of blocking before winter is over. Ive heard it take a few weeks to propagate it to the lower levels if it happens at all. It just seems like its getting colder, but its in and its out a few days later. One more thing don, if an when a ssw or a mmw event occurs, what does it actually do to the overall wx patterns in general? Ive always wondered that. Thanks kevin. Keep up the good work! Ps: if anyone else has an answer or wants to chime in, feel free to do so

You will see it on some of the zonal wind flux and temperature charts:

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

Modeling is still not very accurate when it comes to possible SSW and MMW events.

[donsutherland1]

Brief blizzard update...

One of AmericanWx's Montreal members informed me that Montreal has picked up more than 44 cm (17") snow so far. That breaks record for most snow in a December storm.

[NaoPos]

Brief blizzard update...

One of AmericanWx's Montreal members informed me that Montreal has picked up more than 44 cm (17") snow so far. That breaks record for most snow in a December storm.

Wow, really surprised to hear that. Philly has had a larger dec snow than them? Unreal....

[Srain]

The New Years Eve/New Years Day and beyond forecast remains somewhat muddled this morning with a lot of uncertainty during the mid next week time frame. A trough is diving S this morning as seen on water vapor imagery and this is the feature that some of the guidance had attempted to cut of and develop a closed core low at the base of that trough. The Operational GFS remains progressive and the Op Euro has joined the GFS solution with the first short wave progressing E, but the Euro/GEFS and GGEM Ensembles hold back some upper level energy with embedded short wave disturbances diving S off California and rounding the base of the trough axis that hangs back to the SW over Northern Mexico. A cold front will pass late New Years Eve/New Years Day bringing very chilly air S across the building Central/Northern Plains snow pack into the Southern Rockies/Southern Plains. The fly in the ointment is the next in a series of short waves that rounds the base of the trough near Baja and ripples of upper air disturbances riding along the sub tropical jet over running the shallow cold air next Wednesday into Thursday. The GFS and Canadian suggest enough moisture and over running may create a winter weather episode while the Euro is drier and now just brings freezing temps with perhaps some high clouds across Texas/Louisiana. With the systems and short waves out over the data sparse Pacific, the forecast remains below average and will have to be fine tuned as we get closer to New Years Eve. The various NWS offices across the Southern Rockies/Southern Plains are mentioning the potential for wintry weather next week, but are not forecasting that potential due to the lack of run to run continuity of the model guidance which is understandable with all the uncertainties.

[Ottawa Blizzard]

Wow, really surprised to hear that. Philly has had a larger dec snow than them? Unreal....

No. Montreal saw 45cm of snow in one day, on top of what they already received earlier in the month. It's the greatest one day snowfall in Montreal's recorded weather history, and that's saying something!

[Ottawa Blizzard]

The New Years Eve/New Years Day and beyond forecast remains somewhat muddled this morning with a lot of uncertainty during the mid next week time frame. A trough is diving S this morning as seen on water vapor imagery and this is the feature that some of the guidance had attempted to cut of and develop a closed core low at the base of that trough. The Operational GFS remains progressive and the Op Euro has joined the GFS solution with the first short wave progressing E, but the Euro/GEFS and GGEM Ensembles hold back some upper level energy with embedded short wave disturbances diving S off California and rounding the base of the trough axis that hangs back to the SW over Northern Mexico. A cold front will pass late New Years Eve/New Years Day bringing very chilly air S across the building Central/Northern Plains snow pack into the Southern Rockies/Southern Plains. The fly in the ointment is the next in a series of short waves that rounds the base of the trough near Baja and ripples of upper air disturbances riding along the sub tropical jet over running the shallow cold air next Wednesday into Thursday. The GFS and Canadian suggest enough moisture and over running may create a winter weather episode while the Euro is drier and now just brings freezing temps with perhaps some high clouds across Texas/Louisiana. With the systems and short waves out over the data sparse Pacific, the forecast remains below average and will have to be fine tuned as we get closer to New Years Eve. The various NWS offices across the Southern Rockies/Southern Plains are mentioning the potential for wintry weather next week, but are not forecasting that potential due to the lack of run to run continuity of the model guidance which is understandable with all the uncertainties.

It really doesn't look all that cold for southern Ontario early in the new year, at least according to Environment Canada, with highs in the low to mid twenties. Nothing spectacular. For Toronto, cold would mean highs in the teens, while in Ottawa it would mean highs in the single digets. Severe cold is a high in the single digets for Toronto and highs around zero or below in Ottawa. Nothing like this appears likely early in the new year, at least according to Environment Canada.

[Srain]

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

1047 AM EST FRI DEC 28 2012

VALID 12Z MON DEC 31 2012 - 12Z FRI JAN 04 2013

...SYNOPSIS/IMPACTS...

THE NATION WILL NOT SEE ANY LARGE SCALE CYCLOGENESIS IN DAYS 3-7.

THE POLAR FRONT WILL SPEND MUCH OF THE PERIOD SINKING THROUGH THE

GULF COAST STATES AND INTO THE GULF/FLORIDA. THE ARCTIC FRONT WILL

SPEND MUCH OF THE PERIOD STRETCHED FROM THE MID ATLANTIC TO THE

MIDWEST AND CENTRAL/NORTHERN PLAINS. UPPER LEVEL RIDGING BUILDING

OVER THE NORTHERN ROCKIES WILL SPLIT THE UPPER FLOW

PATTERN...TAKING SYSTEMS AROUND THE WESTERN U.S...AND PROMOTING

FAVORABLE CONDITIONS FOR RADIATIONAL COOLING AT NIGHT...AND FOR

MOUNTAIN/VALLEY EFFECTS TO STRONGLY INFLUENCE DIURNAL

TEMPERATURES. ENERGY UNDERCUTTING THE RIDGE WILL YIELD A COUPLE OF

CLOSED LOWS OVER THE SOUTHWEST U.S...WITH PRECIPITATION EXTENDING

DOWNSTREAM INTO THE SOUTHERN PLAINS/SOUTHEAST. GIVEN THE INITIAL

SUPPLY OF DRY AND COLD AIR...A TRANSITION ZONE TOWARD WINTRY

PRECIPITATION WILL BE LIKELY WITH THE FIRST SYSTEM MONDAY/TUESDAY.

PRECIPITATION AMOUNTS DO NOT APPEAR HEAVY...THOUGH...AS SHORTWAVES

WILL TEND TO SHEAR/DE-AMPLIFY AS THEY HEAD INTO CONFLUENT FLOW

EAST OF THE PLAINS. FINALLY...MODELS CONTINUE TO SUGGEST THAT A

CLOSED LOW WILL REACH A CALIFORNIA BY NEXT THURSDAY OR FRIDAY.

...MODEL CHOICE...

MODEL AGREEMENT WAS GOOD THROUGH EARLY DAY 5. THEN THE GFS

DISPLAYS A TENDENCY TOWARD FLATTER FLOW AND FASTER

PROGRESSION...AS IT HAS DONE CONSISTENTLY THIS WINTER ON THE LARGE

SCALE. KEEPING WITH CONTINUITY...AND WITH THE SUPPORT OF

TELECONNECTIONS BASED ON A NEGATIVE ANOMALY OVER QUEBEC...WE

WEIGHTED THE FORECAST TOWARD THE ECMWF ENSEMBLE MEAN AND TO A

LESSER EXTENT THE NAEFS ENSEMBLE MEAN. FOR THE SMALLER SCALE

DETAILS WE INCLUDED INFLUENCE FROM THE 00Z ECMWF AND 00Z CANADIAN.

WE ARE LESS CONFIDENT IN THE SHORTWAVE DETAILS GIVEN THE LOW

AMPLITUDE OF WAVES IN THIS PATTERN...BUT THE ECMWF AND CANADIAN

ARE CLOSE TO THE ECMWF ENSEMBLE MEAN FOR THE MAJORITY OF THE

TIME...AND THEY FIT OUR EXPECTATION FOR THE TIMING AND LOCATION OF

THE SYSTEM APPROACHING CALIFORNIA ON DAY 6/7.

BURKE/FRACASSO

[Srain]

The trends so far today via the GEFS and the operational Euro and Canadian suggest a stormy New Years Eve/New Years day. There are also growing indications that a cut off low will develop S of the Great Basin by next Tuesday (New Years Day) and continue to bring several upper air disturbance across New Mexico and Texas into Louisiana as a Coastal low develops along the S Texas Coast along a stalled Canadian cold front bringing over running moisture over the shallow very chilly cold air mass at the surface. While it is too soon to know with any certainty, that is the classic recipe for all sorts of winter weather mischief as well as an ice storm threat, should it verify.

[QVectorman]

With the MJO going into phase 1 and the 5-7 day lag for MJO induced waves to traverse the eastern US it would set us up for a wave to arrive in the east between Dec. 18-20 which is progged on the 180hr GFS and Euro moving across the upper Midwest or Great Lakes. The same wave also ushers in relatively "colder" air and plays nicely into the idea I spoke of the other day in my post about the pocket of relatively "colder" air arriving during the Dec. 21-23 time frame based off of GWO analogs for the eastern US.Using that same concept for the GWO I expect another batch of colder air Dec. 27-30. And Following the spike in the 10 and 30 mb temps that peaked back on Dec. 6 seems we should see a good shot of colder air Dec 30-Jan 3.

With the newest GWO numbers today the latest analogs indicate a 15-20F warm up in sfc temps Jan 3-Jan 6 compared to prior days highs across Midwest or NE (the Dec. 31-Jan 3 cold episode) and analogs suggest a stair stepped 15-20F temperature fall behind the warm up 1-2 days after that, meaning another spell of colder air Jan 5-8.

I extended my outlook through Jan 8 on Dec. 14. I still feel comfortable with those dates and with the newest GWO analogs and latest 10 and 30 mb temp forecast it appears the time frame between Jan 8-10 will see a warm up over the east with a short wave moving through the east Jan 10-11 with cooler air dropping in behind it for Jan 10-13 across the MW/GLKS and then pockets of cooler air arriving Jan 15-19 time frame for the east followed by a second reinforcement of cooler air Jan 20-24. My GWO analogs only take me out to Jan 9 so there may be another short wave or two to add to the 2 already expected for the Jan 9-24 time frame. I will update as the newest GWO numbers come out over the next week and half.

I was going to wait until we were upon the first wave of cold air in my date windows but things are slow again in here and the models look like there are in pretty good agreement so I think it's safe to post a analysis and extend the forecast.

First Dec. 27-30 window as mentioned back on Dec. 13...we have the Euro 39h 850's for Dec. 30 with the cold pool of -10 to -12C air covering most of the MW/NE.

After a brief stint of southerly flow on the back side of a hp over Florida 850's warm to 0 to -2C over IN, OH and parts of MI for Dec. 31

Second window Dec. 30-Jan 3 as mentioned back on Dec. 13...signs still pointing to much colder air arriving over the Eastern US...the Euro at 156h 850's for Jan 4 0z---Jan 3 7pm EST with -20 to -22C over WI and N. MI which migrates eastward in the following days.

It appears the Jan 20-24 cold shot should be comparable in magnitude of the upcoming Jan 2-3 airmass. Also latest GWO numbers are currently trending towards an agreement of the Jan 20-24 date. I will have concrete confirmation or rejection of that assumption by Tues.

Extending the outlook Jan 24-26 show up as next pocket of cooler air...although I will say signals are mixed on this window date so I'm not too confident on this time frame producing a cooler airmass for the MW/NE.

Although Jan 26-30 looks very impressive and should out do the Jan 2-3 850mb cold air wrt temps. The newest ECMWF strat. temp forecast shows a ~+48C warming at 10mb from Dec. 29 through Jan. 2 and a ~+42C warming from Jan1 to Jan 2. There is also a wind reversal forecasted to take place Jan 2 at 1mb and 10mb at 60N. This should qualify as a MAJOR SSW since only a +25C temp change is required over a week period for a minor SSW and I believe the wind reversal is extensive enough to qualify also. If not it is still a minor SSW. The EP vector is also forecasted poleward at least at 90N which is a good signal that the SSW will in fact allow arctic air to spill southward. This event should produce the Jan 26-30 window cold pocket...Although I don't have much experiencing timing out SSW events so this may not be the exact window, it may have to be adjusted forward or backwards by a few days.

I will also say that it appears a lot of these dates are back to back and should mention that these forecasted chunks of cooler/colder air are cooler/colder relative to the air in place that they displace. So I don't claim to know the temperature range of the 850mb temps arriving...The concept can only forecast that it will be "colder" than the one that will be in place at the time of it's arrival and are associated with shortwaves so there will be brief time frames of southerly winds ahead of the short waves that will produce WAA ahead of waves and as a result might produce brief minor spikes in 850 temps and sfc temps in transition from time frame to time frame. So for example over a period of days (windows) it could just go from -2C...cool to -5C (window/event 1) then warm to 0C and cool to -4 (window/event 2) where event 2 ends up "cooling" but ends up actually with warmer temps than just a few days prior but cooler compared to just 1 or 2 days prior. This also doesn't elude to AA temps or BA temps just "relative" so even with all the time frames for shortwaves thus...colder airmasses; it doesn't rule out that the resulting cooler temps still produce above average temperatures for daytime highs. When the signals are stronger an estimation of the temp of the air is possible such as the Jan. 2-3 and Jan 20-24 and Jan 26-30 episode. The other time frames are just hiccups in the stat. signal and coincide to minor dips in sfc temperatures relative to previous days' highs but I figure they are worth mentioning.

[donsutherland1]

Great writeup Don. I don't know why you don't consider blogging. You're a natural at content marketing and metaphors. Ever since the Panda and Penguin updates earlier this year at Google, major businesses have finally realized they need to invest in content marketing and Author Rank. You should blog. You have serious natural talent.

Thank you for the very kind words, Jebman.