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December 16th event

RaleighWx

By RaleighWx,
in Southeastern States

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FoothillsNC

FoothillsNC

Posted
Posted

this event is similar to a few we had around 2004 or 2003, where from a distance the models trended colder, and should have done so based on the pattern. The key here is the GFS has a new strong s/w rounding through the Lakes at 60 to 72 hours, which feeds the main vortex over new England, wasn't there before. I don't know yet if thats right, but we've seen the new shortwaves come into the picture a lot last season when we weren't wanting one, in this case we DO want it, because it helps maintain the stationary Vortex, keeping the low level and upper level cold, and furthern south and west. All in all, like Raleigh said, its classic overrunning, its pretty light now, but these things can trend much wetter. I still don't see a strong high up there to keep the low levels cold, but synoptics argue the cold east of the Apps remains in place with the vortex where it is (good confluence). Stil time to watch if the models shift something, for example take too much moisture to our nw into Kentucky, like they were doing, but again the vortex may save us east of the Apps. Not that I want ice, but something interesting for a change to happen here would be nice. Could start as snow, but hard to say where that transistion would be, probably go to sleet quickly around upper SC and the southern border of NC, then to ZR. Still not a lot of qpf printed but some accumulations would def. be possible. I also think the slight speeding up is likely, there could be a stretch of precip all the way from Ok to NC by midnight Wed. night.

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Jon

Jon

Posted
Posted

Definitely looking like a classic light overrunning wintry precipitation event for NC. If you think this should be merged with the general SE thread, feel free.

http://www.examiner....ble-on-thursday

Good stuff, as always...I'd like to see a surprise fromt his event for sure. Something other than rain, even though we do need it.

this event is similar to a few we had around 2004 or 2003, where from a distance the models trended colder, and should have done so based on the pattern. The key here is the GFS has a new strong s/w rounding through the Lakes at 60 to 72 hours, which feeds the main vortex over new England, wasn't there before. I don't know yet if thats right, but we've seen the new shortwaves come into the picture a lot last season when we weren't wanting one, in this case we DO want it, because it helps maintain the stationary Vortex, keeping the low level and upper level cold, and furthern south and west. All in all, like Raleigh said, its classic overrunning, its pretty light now, but these things can trend much wetter. I still don't see a strong high up there to keep the low levels cold, but synoptics argue the cold east of the Apps remains in place with the vortex where it is (good confluence). Stil time to watch if the models shift something, for example take too much moisture to our nw into Kentucky, like they were doing, but again the vortex may save us east of the Apps. Not that I want ice, but something interesting for a change to happen here would be nice. Could start as snow, but hard to say where that transistion would be, probably go to sleet quickly around upper SC and the southern border of NC, then to ZR. Still not a lot of qpf printed but some accumulations would def. be possible. I also think the slight speeding up is likely, there could be a stretch of precip all the way from Ok to NC by midnight Wed. night.

Any qpf is good qpf by me, thanks for your thoughts!

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Marion_NC_WX

Marion_NC_WX

Posted
Posted

Just took a quick look at the numerical guidance from the 12z GFS...it seems to be putting out about .35 QPF starting overnight Wednesday into Thursday with the temps below critical levels at 850, haven't looked at the detail but it could be supportive for snow. Then another .11 afterwards with 1 degree (850's), which BTW the temps never get above 30 on Thursday.

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weatherlover

weatherlover

Posted
Posted

Just took a quick look at the numerical guidance from the 12z GFS...it seems to be putting out about .35 QPF starting overnight Wednesday into Thursday with the temps below critical levels at 850, haven't looked at the detail but it could be supportive for snow. Then another .11 afterwards with 1 degree (850's), which BTW the temps never get above 30 on Thursday.

Sure hope that scenario pans out.. We are due for a nice little winter event before Christmas!! Especially since Atlanta is white right now!

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Marion_NC_WX

Marion_NC_WX

Posted
Posted

After further detail on model soundings, that .35 overnight Wednesday looks like a mainly snow profile. Only problem is that 0.7 that pops up at 800mb. It's back down below zero at 850 and about -3 near the surface. I think it could overcome that one obstacle.

BTW, just for clarification I'm using my closest location which is KMRN. I'll make sure and note specifically when making reference to another location.

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FoothillsNC

FoothillsNC

Posted
Posted

I think the new 12Z euro is still having trouble , it continues to get colder, like the GSF but then suddenly jumps temps, even though it keeps delaying that jump. By 96 hour, GSP and AVL are in middle 30's. I very much doubt that with that strong Vortex stil in place, even with the lack of a suraface high. It is having a terrible handle of the evaparative cooling aspect. The GFS by contrast is handling much better I think, with upper 20's in the western Carolinas Thurs AM.

the Euro does generate a pretty decent swath of snow to ice though esp in NC. It also keeps northern NC subfreezing the whole event at the surface, and there is quite a tight gradient Thursday on Temps in NC., from north to south, not your usual CAD wedging necessarily.

By late Friday and Saturday, it has an amazing snowstorm sweeping out of the Deep South and up the coast. GA and the Carolinas get hit hard with a classic Gulf snowstorm.

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WXinCanton

WXinCanton

Posted
Posted

I think the new 12Z euro is still having trouble , it continues to get colder, like the GSF but then suddenly jumps temps, even though it keeps delaying that jump. By 96 hour, GSP and AVL are in middle 30's. I very much doubt that with that strong Vortex stil in place, even with the lack of a suraface high. It is having a terrible handle of the evaparative cooling aspect. The GFS by contrast is handling much better I think, with upper 20's in the western Carolinas Thurs AM.

the Euro does generate a pretty decent swath of snow to ice though esp in NC. It also keeps northern NC subfreezing the whole event at the surface, and there is quite a tight gradient Thursday on Temps in NC., from north to south, not your usual CAD wedging necessarily.

By late Friday and Saturday, it has an amazing snowstorm sweeping out of the Deep South and up the coast. GA and the Carolinas get hit hard with a classic Gulf snowstorm.

This Friday? Interesting

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Carvers Gap

Carvers Gap

Posted
Posted

Definitely a quick retreat of cold air on Thursday on the 12z Euro. Even the west slopes of the Apps might see something on the front end, especially if it stays on the track it is and arrives at night. Freezing rain in NE TN is unusual. And yes, that storm is in a great spot for next weekend on the Euro for someone in the SE to get slammed. The Canadian has it as well. I posted a pic of its 132 hr frame on the Dec 14th thread. I'm keeping level about this one. That low that just went through Minnesota was at one point closer to this area on the models. Didn't Sutherland's thread talk about how rare a strong SE low was during blocking found in strong La Nina's. If that storm happened, it would be rare air indeed.

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NCSNOW

NCSNOW

Posted
Posted

I think the new 12Z euro is still having trouble , it continues to get colder, like the GSF but then suddenly jumps temps, even though it keeps delaying that jump. By 96 hour, GSP and AVL are in middle 30's. I very much doubt that with that strong Vortex stil in place, even with the lack of a suraface high. It is having a terrible handle of the evaparative cooling aspect. The GFS by contrast is handling much better I think, with upper 20's in the western Carolinas Thurs AM.

the Euro does generate a pretty decent swath of snow to ice though esp in NC. It also keeps northern NC subfreezing the whole event at the surface, and there is quite a tight gradient Thursday on Temps in NC., from north to south, not your usual CAD wedging necessarily.

By late Friday and Saturday, it has an amazing snowstorm sweeping out of the Deep South and up the coast. GA and the Carolinas get hit hard with a classic Gulf snowstorm.

Best of all, this is within 5-6 days and not 200+ hours out. I'm loving how this December 2010 is unfolding. Not only do we have a legit shot at the coldest on record, but if things materialize as modeled this week, it would be our snowiest. Putting the cart before the horse, but amazing potential in wake of expecting the worst winter imagianable just a few weeks ago with all the pre-season forecast.

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rduwx

rduwx

Posted
Posted

For those that haven't been reading the 12z euro thread on the main page, this is what Allan had to say about the 12z euro run.

"Lead system is snow to ice in the Triangle with the 2nd system a heavy snow event. I will take it.

This lines up with the majority of the 00z ECMWF Ensemble members, (As far as evolution, timing, and placement of low) "

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Marion_NC_WX

Marion_NC_WX

Posted
Posted

Very interesting wording in the HPC's afternoon extended discussion...

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

225 PM EST SUN DEC 12 2010

VALID 12Z WED DEC 15 2010 - 12Z SUN DEC 19 2010

THE BASIC SURFACE ISOBARIC PATTERNS AND METEOROLOGICAL REASONING

WERE LEFT UNCHANGED IN OUR FINAL EDITION.

THE MODELS ARE SHOWING AN UNUSUALLY ANOMALOUS UPPER HIGH

RETROGRADING FROM GREENLAND TO CENTRAL CANADA DURING THE MEDIUM

RANGE PERIOD. FAIRLY DEEP MEAN TROFS OFF EACH COAST THIS PERIOD

WILL BE BOOKENDS TO A VERY FLAT MEAN RIDGE OVER THE ROCKIES. THE

NEW SET OF 00Z/12 ENSEMBLE SPAGHETTI PLOTS SUPPORTED THE REASONING

OF THE PRELIMS. AN UPPER CYCLONE OVER THE GULF OF ALASKA SLOWLY

PIVOTS TOWARD THE PACIFIC NORTHWEST WHILE ASSOCIATED SHORTWAVE

TROUGHS ON ITS S SIDE MOVE ACROSS CA/THE GRT BASIN/THE ROCKIES.

GUIDANCE SHOWS CONSIDERABLE SPREAD DEVELOPING WITH THESE SHORTWAVE

FEATURES THU AND BEYOND IN THEIR TREK ACROSS THE LOWER 48 STATES.

BELOW NORMAL TEMPS WILL PREVAIL MOST PLACES OVER THE ERN HALF OF

THE CONUS WHILE MILDER AIR OVER THE WRN STATES STRUGGLES TO

PENETRATE THE COLD PATTERN OVER THE EAST. THE MAIN THRUST OF

MILDER AIR MAY BRING PRECIP TO THE SERN CONUS THU OR FRI. THE

PACIFIC NW WILL SEE FREQUENT INTERVALS OF PCPN IN ONSHORE FLOW

WITH HEAVY PCPN EXPECTED AS FAR S AS THE NRN HALF OF CA BY FRI DAY

5. FARTHER E...LAKE EFFECT SN WILL BE THE MAIN WEATHER STORY UNTIL

THU...WHEN AN ILL-DEFINED YET SIGNIFICANT AREA OF PCPN DEVELOPS S

OF THE OH RIVER IN CONNECTION WITH WHATEVER WAVES MIGHT BE

CROSSING THAT REGION.

12Z MODELS: THE MAIN PROBLEM CONTINUES TO BE RESOLVING THE PACIFIC

SHORTWAVES CROSSING THE CONUS UNDERNEATH THE RETROGRADING CANADIAN

BLOCK THU DAY 4 AND BEYOND. THE 12Z/12 GFS IS FAIRLY CONSISTENT

WITH ITS OWN 00Z/12 CONTINUITY IN MOVING A NRN STREAM UPPER

LOW/SHORTWAVE ACROSS THE NERN QUARTER OF THE NATION DAYS 3-5 AND

DOWNPLAYING THE SRN STREAM. ON THE OTHER HAND...THE NEW

CANADIAN/UKMET SUGGEST OTHERWISE...COMING UP WITH A FORECAST QUITE

AT ODDS WITH THAT OF THE GFS. THE UKMET AND CANADIAN BOTH ROUGHLY

FOLLOW OUR PRELIM ECMWF/ECENS MEAN CONTINUITY THU/FRI...YET STILL

DIFFER SIGNIFICANTLY FROM EACH OTHER THOSE DAYS. THE UKMET GIVE A

BETTER FIT TO OUR CONTINUITY DAY 4 WHILE THE CANADIAN GIVES A

BETTER FIT DAY 5. THE UKMET APPEARS TO TRACK A WAVE TOO FAR NE FRI

DAY 5 GIVEN THE MEAN DEEP TROF OFF THE E COAST. THE NEW 12Z ECMWF

SUPPORTS THE FLATTER CANADIAN SOLUTION. THESE MODEL DIFFERENCES

LEAD INTO THE UNCERTAIN TIME FRAME NEXT WEEKEND OFF THE SE COAST

OF THE CONUS. AM NOT TERRIBLY CONFIDENT OF ANY SOLUTION NOW. THE

NEW 12Z ECMWF HAS ITS MAIN ERN CONUS SHORTWAVE ENERGY SLOWER DAYS

5-6 THAN THE CANADIAN...SLOW ENOUGH TO LEAD INTO THE CHANCY

CYCLOGENESIS OFF THE SE COAST NEXT WEEKEND DESCRIBED BELOW.

00Z/12 ENSEMBLE 500MB SPAGHETTI PLOTS HIGHLIGHTED AN AREA OF

POSSIBLE CYCLOGENESIS OFF THE SE COAST OF THE CONUS LATER SAT 6

AND BEYOND. IT WAS MOSTLY ECMWF ENSEMBLE MEMBERS THAT WERE

SUPPORTING CYCLOGENESIS OFF THE SE COAST NEXT SAT OR SUN. THE

06Z/12 GFS RUN SEEMED TO BE PICKING UP ON THIS POSSIBILITY FOR

NEXT SAT/SUN....BUT THE NEW GFS RUN HAS GONE BACK FLAT. RECENT

RUNS OF THE ECMWF HAD EARLIER SHOWN A CHANCE FOR CYCLOGENESIS NEXT

WEEKEND OF THE SE COAST BUT THE MOST RECENT RUN HAD BACKED OFF

FROM IT. NOW THE 12Z/12 RUN OF THE ECMWF IS BACK ON

BOARD...DEVELOPING A MAJOR SNOWSTORM NEXT WEEKEND FROM INTERIOR NC

TO NEW ENG. IF CORRECT...IT COULD LAY DOWN A HEAVY BLANKET OF SNOW

IN THE SAME AREAS AS THE BIG SYS LAST YEAR...ALMOST TO THE DATE! A

WHITE CHRISTMAS FOR THAT AREA 6 DAYS LATER WOULD BE HIGHLY FAVORED

IN THE PERSISTENT COLD PATTERN.

FLOOD

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Carvers Gap

Carvers Gap

Posted
Posted

Morristown, TN, - NWS Afternoon Discussion:

....WEDNESDAY PATTERN BECOMES MORE ZONAL AS TROUGH

EXITS THE NE STATES. A DEVELOPING SYSTEM ACROSS THE SOUTHERN PLAINS

WILL BRING MOISTURE BACK OVER THE COLD AIRMASS WEDNESDAY AFTERNOON

AND NIGHT BRINGING A MIXTURE OF PRECIPITATION TYPES WITH FREEZING

RAIN POSSIBLE ACROSS THE SOUTHERN HALF OF THE FORECAST AREA.

NORTHERN SECTIONS WILL LIKELY SEE SNOW AND SLEET WEDNESDAY NIGHT

CHANGING TO FREEZING RAIN AND RAIN THURSDAY. HIGHS WEDNESDAY SHOULD

REACH THE MID 30S TO NEAR 40 SOUTH AND MID 20S TO LOWER 30S NORTH.

WEDNESDAY NIGHT TEMPERATURES WILL BE STEADY OR SLOWLY RISE. THURSDAY

SHOULD BE SEVERAL DEGREES WARMER IN THE UPPER 30S TO UPPER 40S. AS

LOW PRESSURE SHIFTS EAST WITH THURSDAY SYSTEM AND TROUGH DEVELOPS

AGAIN ACROSS THE EAST THE RAIN SHOULD CHANGE BACK TO SNOW ACROSS

NORTHERN SECTIONS THURSDAY NIGHT OR FRIDAY. PRECIPITATION ENDS WITH

COLDER TEMPERATURES FOR THE WEEKEND. BUT TEMPERATURES WILL BE WARMER

THAN BEHIND THIS EARLY WEEK COLD BLAST.

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rduwx

rduwx

Posted
Posted

I'm guessing light snow/flurries then dry while somewhere in SE NC actually gets something interesting. Next!

OK, I'll bite...What are you talking about? Does this mean you think Thursday might be some flurries then next weekends possibilities is nothing interesting?

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FallsLake

FallsLake

Posted
Posted

Man, this week sure looks interesting. And I'm loving the talk of a white Christmas here! This is going to be a fun couple of weeks for sure!

Brick I'm with you man!! If we can get just one of these two systems (Thursday or Sunday) to give us some more winter weather it will make this pre-Christmas a year to remember.

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SBUWX23

SBUWX23

Posted
Posted

Kinda surprised no one has mentioned how far north the 18z GFS ensembles are. Almost all of them are north of the OP, most would imply a much reduced frozen/freezing precip threat.

Hoping they are wrong.

Are you sure your looking at todays 18z ensembles? I do not see them yet..

EDITL Ok I see the 18z mean and the mean is a bit further north.

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