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Feb 16th/17th/18th Winter Wx


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With that said, do you think the timing of the Euro will ultimately cave to the America suite or vise versa?

 

I think we are beginning to get into the period where the short and medium range models begin to outperform long range models such as the Euro & GFS (that being said they still are useful...) so I think it's best to use a blend.

 

Honestly I don't know enough, nor have enough time to follow the models like I would like to in order to comment on expected trend between the Euro & GFS, other than to say I think we are in for significant change before models settle on a solution probably sometime tomorrow (12 or 0Z).

 

I think the NAM an UKMET (from the sounds of it) do the best at modeling temperature profiles and therefore precipitation types.

 

My best guess on the track at this point (not too confident given recent model trends) is for the storm to follow the southern edge of the cold air which seems to be central GA to northern SC then up towards the Outer Banks of NC and North-Northeast from there.

 

Edit: Upon checking out the 3Z SREF model it seems that a further northward trend seems possible though the control run did follow my thoughts here)

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.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...

AS OF 240 PM...AS CYCLOGENESIS DEVELOPS OVER THE ARKLATEX REGION IN

RESPONSE TO CENTRAL CONUS HEIGHT FALLS LATE SUNDAY...A BAND OF

FRONTOGENESIS WILL BECOME ESTABLISHED ACROSS THE SOUTHEAST SUNDAY

NIGHT. THERE REMAINS DISCREPANCY AMONG THE OPERATIONAL MODELS

REGARDING THE TIMING OF THIS PRECIP INTO THE WESTERN CAROLINAS ON

MONDAY...WITH THE NAM REMAINING AS THE MOST AGGRESSIVE MODEL IN

DEVELOPING PRECIP OVER THE SOUTHWEST NC MTNS BY 12Z MONDAY.

INTERESTINGLY...THE NAM HAS A GREAT DEAL OF SUPPORT FROM THE

SREF...AS MOST ENSEMBLE MEMBERS PRODUCE MEASURABLE PRECIP ACROSS FAR

SOUTHWEST NC BY 12Z. WITH THAT IN MIND...POPS WERE INCREASED TO

LIKELY IN THOSE AREAS BY THAT TIME. HOWEVER...POPS WILL DROP OFF

CONSIDERABLY SOUTH AND EAST FROM THERE TOWARD THE PIEDMONT...IF FOR

NO OTHER REASON THAT IT WILL TAKE LONGER FOR THE VERY DRY NEAR-

SURFACE AIR MASS TO SATURATE OVER THE LOWER ELEVATIONS. POPS WILL

INCREASE THROUGHOUT MONDAY...WITH LIKELY POPS RESERVED FOR THE

WESTERN UPSTATE/NORTHEAST GA AND SOUTHWEST NC. THERE IS LITTLE DOUBT

THAT WHEREVER PRECIPITATION FALLS ACROSS THE FORECAST AREA ON

MONDAY...THE P-TYPE WILL BE SNOW...THE ONLY QUESTION BEING QPF/

ACCUMS.

CONFIDENCE IS RATHER HIGH THAT 3-6 INCHES WILL FALL ACROSS THE

SOUTHWEST NC MTNS BY THE END OF MONDAY...BUT QPF IS MORE UNCERTAIN

SOUTHEAST OF THERE...BUT BASED UPON A CONSENSUS NAM/GFS FORECAST

THROUGH THAT TIME...THE WESTERN UPSTATE AND NORTHEAST GA COULD SEE

SIGNIFICANT ACCUMS BY THE END OF THE DAY. CONFIDENCE IS HIGH ENOUGH

TO ISSUE A WINTER STORM WATCH ON THIS SHIFT FOR OUR FAR WESTERN

AREAS...FROM ROUGHLY CARNESVILLE TO CLAYTON GA...TO SYLVA TO

WAYNESVILLE...TO MARS HILL IN NC.

 

 

 

 

The quoted area above was from Greer's afternoon discussion on Saturday. Their morning AFD, which should be out fairly soon, should be epic... :facepalm:

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Big snow for GSO from hr 39-42.  Nice.  CAD is doing its job.  The snow/ice line runs from N of GSP to RDU.  It is warming and we'll all go over to ice eventually, though.  Looks icy in upstate SC.

 

Yea, the run ended up better than I expected. 850s below freezing through 45 at least for Asheville through your area.

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Looks like Raleigh gets 1-2 inches of snow before turning over to ice according to 6Z NAM... Shows one heck of a temperature inversion. If cold air damning is just a bit stronger perhaps we can force the warm nose (temps above freezing aloft) higher in the atmosphere and therefore cooling off the column of air enough to allow snow to last longer..

06_NAM_042_35.6,-78.8_skewt_ML.gif

 

06_NAM_045_35.6,-78.8_skewt_ML.gif

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From Greer Just Now:

 

 

 

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 430 AM...SHORT RANGE MODELS FEATURING SIGNIFICANT LLVL
THICKNESS WARMING THROUGH THE PERIOD. A BLEND OF THE 0Z ECMWF AND 0Z
GFS WILL BE USED THROUGH THE PERIOD. BOTH SOLUTIONS INDICATE THAT
THE CENTER OF THE LOW WILL TRACK GENERALLY ALONG THE I-20 CORRIDOR.
IN ADDITION...A WELL DEVELOPED SFC RIDGE WILL REMAIN ACROSS THE
FOOTHILLS AND PIEDMONT AS THE LOW APPROACHES ON MON. THIS PATTERN
WILL SUPPORT SIGNIFICANT ISENTROPIC LIFT THROUGH THE DAYLIGHT HOURS
ON MONDAY. THE THICK CLOUD COVER...ENE WINDS...AND PRECIP SHOULD
KEEP HIGHS LIMITED TO THE U20S ACROSS THE MTNS TO AROUND FREEZING
EAST...MID 30S ACROSS THE LAKELANDS. BASED ON THE FORECAST
SOUNDINGS...PRECIP SHOULD BEGIN AS SN ACROSS THE NC ZONES...A MIX OF
SN/IP/RA ACROSS THE UPPER SAVANNAH RIVER VALLEY THROUGH MON
AFTERNOON.

MON EVENING AND NIGHT...WINTER WEATHER PRECIP WILL PEAK ACROSS THE
FORECAST AREA...WILL TIME CATE POPS. PARTIAL THICKNESSES AND TOP
DOWN APPROACHES INDICATE THAT PRECIP WILL GRADUALLY FAVOR FZRA SOUTH
OF THE MTN THROUGH PIEDMONT I-40 CORRIDOR...WITH SN NORTH. CAA WILL
INCREASE DURING THE PRE DAWN HOURS TUESDAY...RESULTING IN A MIX OVER
TO SN FROM WEST TO EAST. DURING THE MORNING DAYLIGHT HOURS
TUESDAY...DEEP MOISTURE AND FORCING WILL LIFT NORTH AND EAST OF THE
REGION...RESULTING IN STEADILY DECREASING POPS. THIS P-TYPE TREND
AND COVERAGE IS SUPPORTED BY THE SREF PLUMES.

I WILL BLEND WPC AND SREF QPF THROUGH THE PERIOD. USING CONSENSUS
QPF VALUES...SNOWFALL IS FORECAST TO RANGE FROM 6 TO 8 INCHES ACROSS
THE TN BORDER COUNTIES TO 4 TO 6 ACROSS THE I-40 CORRIDOR...AREAS
CLOSER TO THE NC/SC LINE MAY SEE AROUND AN INCH. FREEZING RAIN
TOTALS GENERALLY RANGE AROUND A QUARTER TO .3 INCHES SOUTH OF THE
NC/SC LINE AND EXTREME WESTERN NC MTNS. AREAS WITHIN THE UPPER
SAVANNAH RIVER VALLEY WILL BE EXPOSED TO THE WARMEST TEMPS THE
LONGEST....RESULTING IN THE LIGHTEST AMOUNTS OF WINTER PRECIP. GIVEN
THE FORECAST...WE WILL HIGHLIGHT THE CWA WITH A WINTER STORM WATCH
FROM MON THROUGH NOON TUES.

TUESDAY...CONDITIONS WILL DRY...WITH LIGHT NWFS CONTINUING ALONG THE
TN LINE. TEMPERATURES ARE FORECAST TO REACH INTO THE 30S ACROSS THE
REGION...WITH MOST AREAS ABOVE FREEZING. HOWEVER...ANOTHER ROUND OF
STRONG CAA WILL OCCUR TUESDAY NIGHT. LIGHT NWFS WILL PERSIST THROUGH
THE OVERNIGHT HOURS. MIN TEMPS SHOULD FALL INTO THE TEENS ACROSS THE
MTNS TO LOW 20S EAST.

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GFS is not as keen with heavier precip and is much warmer than the other models. Has 850s at va/nc border but 2m temps way down into nc. Looks like a significant ice storm on the GFS for most of nc. It seems kind of out to lunch compared to all the other models as the majority have moved northward including the recent 6z nam and rgem.

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6z GFS says that CLT-RDU-ORF is going to be the snow sleet battle line. I think it is safe to say that 20-30miles on either side of this axis will switch to sleet at some point, just a matter of when.

 

EDIT: assuming we can begin to halt the North trend

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The good news is cold antecedent conditions will promote good accumulations of snow on the front end. I expect a general 2-4" of snow followed by sleet and I'm happy to take that.

I agree the way this winter has been I'll gladly take my 1-2" of snow and an ice storm on top. It's going to be so cold the rest of the week the cement that looks to fall I'll be around a lot longer than usual.

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Models trended north and west last night in a very big way, which will change the dominate precipitation type for many people. The 12z model suite will be crucial in determining if the runs last night were a fluke, or if the storm will track up the Appalachian Mountains.

 

I have also noticed a subtle but important difference is the jet streaks just 48 hours out. As you may have noticed, the GFS has nearly double the QPF as the NAM in western NC, and this is due to the placement of the jet streak at 250 mb. On the GFS, western NC is under the left exit region of the jet, a spot of good upper level divergence. On the NAM, western NC is in the right exit region, a spot of good upper level convergence. By the time the jet slides to our east on the NAM, the moisture has pushed out.

 

Regardless, the track of the storm is now in question, once again, after last nights runs. Now we wait for the 12z runs to see what they show. Regardless, I will be issuing my first accumulation map for this system after the 12z runs. I expect to issue the map early this afternoon.

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Seems the SREF has come in a little colder (going off what was discussed last night). Just my interpretation, RDU would get > .25 liquid eq. snow and another .5 or so of ice. I think, not good at looking at these maps. Still it looks like a significant storm for many.

 

24 hour total precip at hour 63 (but > .25 would have fallen before these totals): 

http://mag.ncep.noaa.gov/Image.php?image=data%2Fsref%2F03%2Fsref_namer_063_precip_p24.gif&model=sref&area=namer&storm=&cycle=03&param=precip_p24&fhr=063&group=Model+Guidance&imageSize=&ps=model&use_mins=no&preselected_formatted_cycle_date=20150215+03+UTC&scrollx=0&scrolly=0

 

2m temps as precip at hour 48:

 

http://mag.ncep.noaa.gov/Image.php?fhr=048ℑ=data%2Fsref%2F03%2Fsref_namer_048_2m_temp.gif&model=sref&area=namer&param=2m_temp&group=Model+Guidance&preselected_formatted_cycle_date=20150215+03+UTC&imageSize=&ps=model

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Models trended north and west last night in a very big way, which will change the dominate precipitation type for many people. The 12z model suite will be crucial in determining if the runs last night were a fluke, or if the storm will track up the Appalachian Mountains.

 

I have also noticed a subtle but important difference is the jet streaks just 48 hours out. As you may have noticed, the GFS has nearly double the QPF as the NAM in western NC, and this is due to the placement of the jet streak at 250 mb. On the GFS, western NC is under the left exit region of the jet, a spot of good upper level divergence. On the NAM, western NC is in the right exit region, a spot of good upper level convergence. By the time the jet slides to our east on the NAM, the moisture has pushed out.

 

Regardless, the track of the storm is now in question, once again, after last nights runs. Now we wait for the 12z runs to see what they show. Regardless, I will be issuing my first accumulation map for this system after the 12z runs. I expect to issue the map early this afternoon.

sounds good.  is there a chance this could trend better, maybe a little south ticking hopefully ?

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Models trended north and west last night in a very big way, which will change the dominate precipitation type for many people. The 12z model suite will be crucial in determining if the runs last night were a fluke, or if the storm will track up the Appalachian Mountains.

 

 

 

I 100% agree. Today is going to be very important for the runs. It's concerning the RGEM made a north trend at 6z. Right now NAM, RGEM and SREF should be followed the most closely. One thing I'm not sure I'm sold on and haven't been sold on since this storm threat was real are the temp profiles shown on the models. Even the RGEM has a low tracking in one of the worst positions for the piedmont and we still end up with IP. This is a solidly cold airmass, so can the low track that far north and can it be underestimating the cold at lower levels? One thing for sure this is going to be a storm of strong defined lines of who gets snow, IP, ZR and just rain. Your usual winter storm in the south is always a game of miles...just a few miles in one direction you can find all the snow you want while you're left out with a bunch of mixing issues. 

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Looking at the EPS from 0z this morning compared to 0z 24 hours ago, not a lot has changed with the 50/50, it's a hair further NE.   But the PV over Hudson Bay is stronger and a tick further south and thus causes the trough to be a little sharper and heights to rise a little in the east.  The big difference is the northern stream energy is digging further south and is stronger.  This is where having the west coast ridge a little further east would have helped immensely, just little changes here and there, nothing drastic, but all adds up to non-snowy event for a lot of NC.  I still think western NC, triad and points west may do OK with snow but non-elevation will mix with sleet.  Unless we see this storm get stronger and stronger....

 

The blocking over the top was stronger, the west coast ridge was stronger and the weak ridging into Greenland was stronger, yet this event is going north.  Head scratching winter, that's for sure.

 

 

post-2311-0-19016600-1424005203_thumb.pn

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It's interesting the RAP is close to carving out the STJ cutoff w/ the lead wave. That lead pj wave continues to trend stronger/west on the models. It wouldn't surprise me if we see things trend higher QPF wise and quicker today on the models as this trend continues. I see this storm as a classic overrunning setup. If you sit back and look at the current setup overall with the 50/50 low, large pacific ridge and pj/stj waves, miller a hybrid or b, this is as classic as it gets. Right now I'm thinking a solid front end thump of snow followed by ice. Wouldn't surprise me to see QPF totals ramped up near an inch today in spots.

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The blocking over the top was stronger, the west coast ridge was stronger and the weak ridging into Greenland was stronger, yet this event is going north.  Head scratching winter, that's for sure.

 

Never forsake climo. I'm not sold on this event playing out how models trended yesterday. One thing of note from the epic blizzard in Boston a few weeks ago was the whole NYC debacle. It seemed to me that climo supported NYC not getting slammed...but pretty much every model was going against climo and giving NYC huge snows (except the GFS). At the end of the day climo won out and that storm did what it climo dictated it should do. Models could be write but when overall climo screams for something and models are going against it I wouldn't take any of those models too seriously until the event really starts unfolding which is going to be tomorrow morning. 

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