Feb. 18-20, 2012 Disco/Analysis

[NCMET]

If you HAD to give a forecast for this weekend for NC, what would you say?

Bulk of the moisture moves through central NC (from I77-95 roughly) between 102-114 hrs, at 102 2mT maybe into the upper 30's for GSO / areas just N & W of CLT, @ 108, most of NC is in the 30's, although any <32F at the surface is confined to the NW mountains. Comparing to 0z, about the same @ 850 valid Sun 1pm, 0C isotherm runs from south of Richmond to around Mooresville, slightly colder than 0z along 77 in NC, but more WAA into the Coastal Plain. I do like that ~1000mb coming off the SC coast just north of CHS at 102hrs though, still kind of strung out, but better defined and stronger compared to 0z. @ 114 looks like 988 a couple hundred miles east of HAT. Summation, it cooled slightly from 0z, certainly stronger, but still no dice...

[WeatherNC]

It did look close once the low moved just off shore....at this point who knows, but Allan has the right of it; best bet is to go with the Euro right now.

I should have clarified, the bulk of the backside moisture moves through between 102 & 108, front end stuff well before that. I was mainly referring to what would have a chance for changeover/banding stuff, which this run shows a healthy band moving across central and eastern NC between 102 -114 hrs as the low wraps up offshore. Not a comma head like the GGEM showed yesterday, but definitely deform type stuff.

[WeatherNC]

If you HAD to give a forecast for this weekend for NC, what would you say?

Easy, when in doubt just go with RN...

Damn, that is a hard question... Pros, including the on air mets and WFO's have an obligation to the public to present accurate information based on all available data, and up until this point I see no indication that this will be more than a nuisance type event for our state, specifically the northern 1/3, maybe flirting with advisory criteria for the VA boarder counties if the 12z Euro verifies, but even that is a stretch. All the information I have seen up until this point says RN, if enough variability was in the setup for something different we would at-least see hints of that in the ensembles and they have been pretty consistent over the last 48-72 in showing any chance for sig winter wx likely resides from central VA north. As everyone else though, I have no flipping clue, I mean imagine having to make a forecast for the NE on this one, nearly impossible to do with any certainty today.

Raleighwx' NC snowstorm climo page is a great tool. If you look at the mean heights prior to, during, and after hickory/rdu major 6"+ snows, this one is not even close. That is a very strong signal that despite some more waffling which is inevitable given so much energy in play, a shift large enough to bring a sig winter storm here is nearly impossible, approaching zero. I am always hesitant though with northern energy originating in NW Canada & interacting with the southern stream. Kind of like a wild card until that stuff comes into the northern Plains, as we saw with the 12/26 storm last winter. Granted, totally different setup, retrograding greenland block crashing into the central part of the country, but two pieces of energy, initially modeled to hookup, guidance lost it between 6-3 days out, only to find out with the high res meso models within 48, that there would be a phase, but with a backside parcel that nothing even saw coming as the original northern stream energy missed.

These extreme solutions we see 10 days out usually never verify, but when almost everything picks up on something as we saw last Fri/Sat, then all breaks loose in the mid-term, don't be surprised to see it trend back towards that original solution, albeit not as extreme.

[Thrasher Fan]

So everything I am reading/seeing is that for NGa this will be all rain unless cold air can magically find it way much further south correct?

[Marion_NC_WX]

So everything I am reading/seeing is that for NGa this will be all rain unless cold air can magically find it way much further south correct?

Yep...

We would need 2 things to happen in order for anybody outside of the mountains to get snow.

1. Keep a slower and closed off southern stream system much like the 12z NAM.

2. Need a strong 50/50 low in Canada to re-appear. Yesterday's model runs began to process of eliminating it. Today's models, especially the GFS has no indication at all of northern stream assistance.

[strongwxnc]

Good post Dan. Let's go NAM !

Yep...

We would need 2 things to happen in order for anybody outside of the mountains to get snow.

1. Keep a slower and closed off southern stream system much like the 12z NAM.

2. Need a strong 50/50 low in Canada to re-appear. Yesterday's model runs began to process of eliminating it. Today's models, especially the GFS has no indication at all of northern stream assistance.

[superjames1992]

So the CMC slid this thing out to sea and barely got any precip north of the NC/VA border?

Meanwhile, the GFS takes the storm inland and gives us tons of rain, slamming PA/NY with a huge snowstorm.

Geez...

One thing I am concerned about is boundary layer temperatures. I am fearful of getting a nice track, but with no cold air to work with, with sub-zero (centigrade) temperatures at 850 mb while we sit sizzling in the 40s at the surface.

[NCMET]

Haha...wasn't trying to pin you down...I was just curious as to your thoughts as you haven't posted many thoughts on here lately :-) I haven't either because I really haven't had time. If I had to make a forecast for NC, I would pretty much say exactly the same thing you did. Thanks for your input.

Easy, when in doubt just go with RN...

Damn, that is a hard question... Pros, including the on air mets and WFO's have an obligation to the public to present accurate information based on all available data, and up until this point I see no indication that this will be more than a nuisance type event for our state, specifically the northern 1/3, maybe flirting with advisory criteria for the VA boarder counties if the 12z Euro verifies, but even that is a stretch. All the information I have seen up until this point says RN, if enough variability was in the setup for something different we would at-least see hints of that in the ensembles and they have been pretty consistent over the last 48-72 in showing any chance for sig winter wx likely resides from central VA north. As everyone else though, I have no flipping clue, I mean imagine having to make a forecast for the NE on this one, nearly impossible to do with any certainty today.

Raleighwx' NC snowstorm climo page is a great tool. If you look at the mean heights prior to, during, and after hickory/rdu major 6"+ snows, this one is not even close. That is a very strong signal that despite some more waffling which is inevitable given so much energy in play, a shift large enough to bring a sig winter storm here is nearly impossible, approaching zero. I am always hesitant though with northern energy originating in NW Canada & interacting with the southern stream. Kind of like a wild card until that stuff comes into the northern Plains, as we saw with the 12/26 storm last winter. Granted, totally different setup, retrograding greenland block crashing into the central part of the country, but two pieces of energy, initially modeled to hookup, guidance lost it between 6-3 days out, only to find out with the high res meso models within 48, that there would be a phase, but with a backside parcel that nothing even saw coming as the original northern stream energy missed.

These extreme solutions we see 10 days out usually never verify, but when almost everything picks up on something as we saw last Fri/Sat, then all breaks loose in the mid-term, don't be surprised to see it trend back towards that original solution, albeit not as extreme.

[dalejr88]

Any word on the Euro ensembles.

[WeatherNC]

Haha...wasn't trying to pin you down...I was just curious as to your thoughts as you haven't posted many thoughts on here lately :-) I haven't either because I really haven't had time. If I had to make a forecast for NC, I would pretty much say exactly the same thing you did. Thanks for your input.

No problem

Adding insult to injury, 12z euro ens are likely amped, mean has a 1000mb low parked over HAT @ 102hrs, 0z mean was in the 1008mb range and offshore same time. H5 is deeper, 546dm heights clipping the VA boarder counties in NC, 0z mean had the 546 isohypse in MD

[tarheelwx]

So the CMC slid this thing out to sea and barely got any precip north of the NC/VA border?

Meanwhile, the GFS takes the storm inland and gives us tons of rain, slamming PA/NY with a huge snowstorm.

Geez...

One thing I am concerned about is boundary layer temperatures. I am fearful of getting a nice track, but with no cold air to work with, with sub-zero (centigrade) temperatures at 850 mb while we sit sizzling in the 40s at the surface.

I suspect that if the lp goes to the east, even with no cold air, we'll likely fully saturate the atmosphere, reach web bulb, and be upper 30's at best. Only think worse than 38 and rain is 33 and rain.

TW

[WeatherNC]

From am19psu in the Philly thread, either a all or nothing ensemble, two distinct camps, EC hit or OTS from what I read, op kind of in the middle...

Spread of the 552dam at 96 on the 12z is Morgantown, WV to Augusta, GA. At 108 in the 0z, it was Green Bay to New Orleans. Either way, questions still outnumber answers.

[bingcrosbyb]

I don't think any of us give much weight to the 18z NAM, but it's digging the vort a little further south through Mexico @ 54HR.

[burgertime]

FWIW 18z NAM is keeping it's slowed down approach to our energy out west. Not as strong as the 12z NAM but stronger than the 12z GFS...also looks close to a big phase out to hour 66.

[burgertime]

I don't think any of us give much weight to the 18z NAM, but it's digging the vort a little further south through Mexico @ 54HR.

Yep also further south.

[burgertime]

No one wants to see hour 84 of the NAM it aint pretty...

[beanskip]

^{18z NAM totally caves -- weakens the southern s/w; weakens the 50/50 low -- surface low taking inland track -- no cold air. We are done.}

[burgertime]

^{18z NAM totally caves -- weakens the southern s/w; weakens the 50/50 low -- surface low taking inland track -- no cold air. We are done.}

Watch the GFS now come out with something totally opposite of the NAM.

[Southern Track]

^{18z NAM totally caves -- weakens the southern s/w; weakens the 50/50 low -- surface low taking inland track -- no cold air. We are done.}

Yep, I guess bring on Spring and severe season.

[jmundie]

The NAM is dropping the second disturbance from the pacific in faster and stronger than the gfs, which is causing the northern stream to rush through, the vort doesn't phase, but its close.

I think it may be time for those east of the mountains to hang it up. Track is looking increasingly inland. Southern arkansas to wv, then up the east coast, however, should take notice.

[WeatherNC]

Maybe the best long range disco ever from MHX, had to do a double take and make sure I was not under the RAH WFO... HWO hoisted for +RN, wind and coastal flooding.

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...

AS OF 315 PM WED...MAIN AREA OF INTEREST IN THE LONG TERM

CONTINUES TO BE THE STRONG COASTAL STORM THIS COMING WEEKEND.

FOR THUR NIGHT...SHORTWAVE TROUGH AND TRAILING COLD FRONT EXITS THE

AREA BRINGING WITH IT THE RAIN. THE RAIN WILL END OVER INLAND AREAS

DURING THE MID EVENING HOURS...AND EXIT THE OUTER BANKS AND OFFSHORE

WATERS SOMETIME JUST AFTER MIDNIGHT. CLOUDS WILL SCATTER SHORTLY

AFTER AND TEMPS WILL FALL INTO THE LOWER 40S. WEAK CYCLOGENESIS WILL

OCCUR OVER THE COASTAL WATERS WHICH WILL PRODUCE A NORTHERLY BREEZE

PREVENTING TEMPS FROM BOTTOMING OUT AS LOW AS THEY COULD. H85 WINDS

WILL REMAIN WESTERLY ALLOWING FOR A DOWNSLOPING COMPONENT ON FRIDAY

WITH MAX TEMPS SLIGHTLY ABOVE AVERAGE DESPITE THE FRONTAL PASSAGE.

CIRRUS WILL STREAM IN AND THICKEN BEGINNING FRIDAY NIGHT AHEAD OF

THE WEEKEND STORM...THOUGH TEMPS WILL STILL MANAGE TO DROP INTO THE

MID 30S AS WINDS REMAIN LIGHT TO CALM.

CONFIDENCE HAS INCREASED FURTHER FOR THE COASTAL STORM AND NOREASTER

EXPECTED TO HAVE AN IMPACT ON E NC BEGINNING AS EARLY AS SAT

AFTERNOON. THE ECMWF HAS BEEN THE MODEL OF CHOICE WITH THIS

SYSTEM...AS IT HAS SHOWN VERY GOOD RUN-TO-RUN CONSISTENCY OVER THE

LAST TWO DAYS. SOUTHWESTERN CONUS CLOSED LOW WILL EJECT EASTWARD

THROUGH THE DEEP SOUTH DURING THE DAY SAT...WHILE AT THE SAME TIME

NORTHERN STREAM ENERGY PUSHES EAST THROGUH THE MID ATLANTIC REGION.

APPROACHING JET ENERGY ASSOCIATED WITH SOUTHERN TIER LOW WILL LINK

WITH DEPARTING JET MAX OVER THE MID ATLANTIC TO SPUR CYCLOGENESIS

OVER THE SE COASTAL WATERS. LATEST ECMWF IS MOST IMPRESSIVE WITH

THIS SYSTEM...SPURRING BOMBOGENESIS EAST OF CAPE HATTERAS. THIS

SCENARIO IF IT PLAYS OUT WILL PRODUCE NEAR STORM FORCE WINDS OVER

PORTIONS OF THE COASTAL WATERS AND DEFINITE COASTAL FLOODING FOR E

NC. AT THE VERY LEAST...GALES WILL OCCUR WITH MINOR COASTAL

FLOODING. RAIN WILL BEGIN TO SPREAD INTO THE AREA SAT AFTERNOON...AS

SIGNIFICANT ISENTROPIC LIFT OCCURS WITH DEVELOPING COASTAL TROUGH

JUST ON COOL SIDE OF THE H85 BAROCLINIC ZONE. THERMAL GRADIENT WILL

TIGHTEN FURTHER SAT EVENING...WITH PERIODS OF HEAVY RAIN DEVELOPING

WITH STRENGTHENING FGEN. SOMEWHAT OF A BREAK IN THE HEAVY RAIN MAY

OCCUR SOMETIME SUNDAY AS GULF COAST SFC MOVES EAST OVER THE COASTAL

WATERS. THE SYSTEM AS STATED ABOVE WILL UNDERGO DEEPENING THROUGH

SUNDAY...REACHING ITS PEAK INTENSITY SUNDAY NIGHT...WITH ANOTHER

AREA OF HEAVY RAIN POSSIBLE LATE SUNDAY AS VORTICITY ADVECTION AND

Q VECTOR CONVERGENCE INTENSIFY. INDICATIONS ARE THAT AS MUCH AS 2

INCHES OF RAIN OR MORE IS POSSIBLE WITH THIS SCENARIO...WHICH WOULD

BRING MUCH RELIEF TO RAIN STARVED EASTERN NC. P-TYPE LOOKS TO REMAIN

RAIN THROUGHOUT THE EVENT...THOUGH A PERIOD OF NON SIGNIFICANT SNOW

SHOWERS MAY AFFECT THE OBX AS COLD AIR WRAPS AROUND COINCIDENT WITH

UPPER TROUGH EARLY MON MORNING. VERY WINDY CONDITIONS WILL ACCOMPANY

THE DEEPENING LOW SUNDAY EVENING...WITH WIND ADVISORY CONDITIONS

EXPECTED ACROSS COASTAL LOCALES. RESIDENTS ARE URGED TO MONITOR THIS

APPROACHING STORM OVER THE NEXT SEVERAL DAYS AS IMPACT DETAILS ARE

WORKED OUT.

RAIN ABATES SOMETIME LATE SUNDAY NIGHT AS THE LOW PULLS EAST...

THOUGH WINDY CONDITIONS WILL CONTINUE AS THE LOW DEEPENS AND HIGH

PRES APPROACHES...PRODUCING STRONG NORTHERLY WINDS. MOSTLY SUNNY

SKIES EXPECTED FOR MON THROUGH TUE AS HIGH BUILDS IN. NEXT STORM

SYSTEM COULD AFFECT THE AREA AS EARLY AS LATE TUE NEXT WEEK.

[WilkesboroDude]

^{18z NAM totally caves -- weakens the southern s/w; weakens the 50/50 low -- surface low taking inland track -- no cold air. We are done.}

Does it matter?

I thought the EURO was the choice model for this upcoming system anyway...

[griteater]

^{18z NAM totally caves -- weakens the southern s/w; weakens the 50/50 low -- surface low taking inland track -- no cold air. We are done.}

Yep, massive cave job, particularly with its handling over the great lakes and 50/50 low.....not surprised though

[NavarreDon]

GSP afternoon long term....Sounds like the fat lady is clearing her throat for all but the higher mnts.

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...

AS OF 240 PM WEDNESDAY...A SOUTHERN STREAM SHORT WAVE WILL CROSS THE

REGION DURING THE DAY ON SUNDAY. THE GFS HAS CONSISTENTLY BEEN

FASTER WITH THE SHORT WAVE AND FARTHER NORTH WITH THE SFC LOW. IN

FACT...IT CONSOLIDATES THE NRN AND SRN STREAMS...BRINGING A POTENT

NOR/EASTER UP THE MID-ATLANTIC COAST LATE SUNDAY. THIS WOULD ALSO

IMPLY A POSSIBLE SEVERE THREAT OVER OUR AREA AS A 996 MB SFC LOW

MOVES NEAR CHARLOTTE.

THE ECMWF IS FARTHER SOUTH...SLOWER AND NOT AS PHASED WITH THE

SYSTEM...AND THE CANADIAN IS SLOWER YET. HPC HAS GONE WITH A

SOLUTION QUITE CLOSE TO THE ECMWF. THIS TAKES THE SFC LOW SOUTH OF

THE REGION ON SUNDAY...THOUGH NOT QUITE AS FAR SOUTH AS PREVIOUS

RUNS. WE/LL HAVE A BETTER HANDLE ON P-TYPE TMRW AS THE EVENT

WILL BE WITHIN THE DOMAIN OF THE SHORT TERM MODELS. HOWEVER...IT

APPEARS THAT PCPN WILL BE ALL RAIN OUT ACROSS THE FOOTHILLS AND

PIEDMONT. THE ECMWF THICKNESSES IMPLY THAT SOME OF THE HIGHER NC

MOUNTAIN ELEVATIONS COULD SEE ACCUMULATING SNOWFALL...OR A WINTRY

MIX...SAT NIGHT AND SUNDAY. AND THAT/S ABOUT AS MUCH DETAIL AS CAN

BE GIVEN AT THIS POINT.

[Dunkman]

It reads like whoever did the discussion at GSP today prefers the GFS solution but is deferring to the HPC and thus the ECMWF. Or maybe I'm just reading too much into it....

[burgertime]

It reads like whoever did the discussion at GSP today prefers the GFS solution but is deferring to the HPC and thus the ECMWF. Or maybe I'm just reading too much into it....

No I think they are just pointing out the madness going on with models. They are taking the safe road and choosing the Euro for now until they can be sure. Smart bet.

[beanskip]

Yes, it does.

Does it matter?

I thought the EURO was the choice model for this upcoming system anyway...

[GaWx]

Does it matter?

I thought the EURO was the choice model for this upcoming system anyway...

It shouldn't because the late NAM (along with the DGEX) is typically pure caca. However, in this case I think it may have been perceived to be more favorable for NC snow chances in the 12Z run. I'm not sure.

[Cold Rain]

I think what we're going to see play out over the next 48 hours or so is the northern stream energy come in stronger, which would result in a stronger 50/50 and a stronger push of cold air and potentially more cold being drawn into the system, depending on phasing.

In the end, it'll probably still be a marginal event for those outside the mountains. But I think it'll still be close enough to keep our interest piqued.

[Carvers Gap]

18z NAM is an Apps runner it appears. Just one of the many possible solutions. It is my opinion that this storm will be pretty strong. It's an absolute shame more cold is not depicted on the models. Wish the high in the plains was a bit stronger. Maybe the one hope we all have is for the storm to really bomb out - unlikely but w/in the realm possibility. Nina is playing havoc with this system.