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Feb 16th/17th/18th Winter Wx


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Here was my morning forecast FWIW. I dont pretend to be an expert on those tricky ares in SE TN or the various topographic oddities in the TN/NC mountains so take it for what it is worth there.

 

I still could see the band of heavy snow right now looking to be over KY/TN/VA shifting south in model runs today. We shall see. The in-situ wedge that sets-up tomorrow will be very strong so it will be very difficult to see significant warming in the CAD region Tuesday.

post-25-0-43098000-1424006174_thumb.jpg

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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.

Burger, I might be wrong here, but aren't the inputs the model engines use in their algorithms based on climo?
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Looks like the 6z runs trended a hair south and colder. Even the rgem. Hopefully we can shift south on the 12z runs.

 

I was thinking the same thing.

 

It looks the Northern Upstate of SC is going to come down to how much sleet we get before switching to freezing rain... Right now I'm thinking that the first 1/4 inch of liquid will be sleet and then the finally 1/2 inch or so will be freezing rain. Surface temps look to range between 30 and 32 in this area. That, combined with the fact that it looks like the precip might be fairly heavy makes me think we would only see at most 1/4 inch of ice accretion(or less) before the precipitation moves out. 

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Whatever happens it's going to be super cold behind this system, in the middle of the week.  Big 0-5 above 

 

.TUESDAY NIGHT AND WEDNESDAY...MOSTLY CLOUDY. LOWS IN THE LOWER
20S. HIGHS IN THE UPPER 20S. WIND CHILL VALUES AS LOW AS 5 ABOVE.
.WEDNESDAY NIGHT AND THURSDAY...PARTLY CLOUDY. LOWS ZERO TO
5 ABOVE ZERO. H
IGHS IN THE LOWER 20S. WIND CHILL VALUES AS LOW AS
10 BELOW.
.THURSDAY NIGHT AND FRIDAY...PARTLY CLOUDY. LOWS AROUND 10 ABOVE.
HIGHS IN THE MID 20S.
 

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Burger, I might be wrong here, but aren't the inputs the model engines use in their algorithms based on climo?

 

Well obviously it uses the conditions of the climate at the start. What I'm saying is that we know lows don't just slam into giant CAD wedges or that they don't slam into cold fronts and go north of them as an example. So if a model shows that is the model just misreading something? What the model says will happen and what should happen are two different things. That's all I'm saying. At this point it could very well go north of where it should go...but I'm not leaning towards the northernmost solution until we get more in the RAP's range. 

One thing of note, the 9z SREF looked all over the place...would like to see what the individual members show. Something tells me there are a few members showing something further south. 

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TWC has an updated map right now, it looks to have taken last nights runs into account, because KY jackpots with 12-18"! But it still has 3-5" for my area, and the very northern counties of NC, like Person county and west that border VA, is in the 8-12" range! After last nights runs, I would be lucky to see the ground white?

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It'l be interesting to see how much the wave over idaho can carve out of the STJ. I think it's further west than modeled. It would prob' produce a little bit warmer system aloft, but may actually cause more QPF.

 

Yeah, IMO, this could very well continue to trend a little north over the next 24 hr...so, a little warmer aloft...but sfc is still going to be cold

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Looking at the 6z GEFS panels, there is still some variance as to how far north the primary low noses up west of the Apps before it transfers its energy to the coast.  That'll determine how far north the ice/ZR line moves up.  If it happens quicker,  the mid level cold should stay intact a bit more.

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The SREF has a warm bias I believe.

 

 

SREF is an ensemble of high-res models, so unless a lot like 75% were showing something the mean would wash it out.

 

IIf you look at the RDU plume for Tuesday afternoon, there are 4 SREF members with temps at 18z in the 50s, that bring the mean way upt although most are below the mean of 35.

 

i wouldnt trust the SREF too much for surface temp forecasts beyond 24-36 hours and even then know the caveats.

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SREF is an ensemble of high-res models, so unless a lot like 75% were showing something the mean would wash it out.

 

IIf you look at the RDU plume for Tuesday afternoon, there are 4 SREF members with temps at 18z in the 50s, that bring the mean way upt although most are below the mean of 35.

 

i would trust the SREF too much for surface temp forecasts beyond 24-36 hours and even then know the caveats.

 

Just look at hours 54-60 on the 9z....it goes from 30 to 50 to back to 30 again. 

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As many have said this morning, I am also in agreement that a more southern solution will appear with the 12Z runs. Why? Because as we said last week, the overall pattern is the same as it has been for the last several weeks. We've had a good pattern but no cold air. Now we have both. And yes, too, lows never crash into CAD wedges. They should pivot around them to the south. But this is dependent on the strength of the CAD, which I think yesterday's 12Z NAM had gotten right. These northern solutions are of course possible, but they really don't make sense to me. Between overall pattern, CAD, and climo, this is a classic southern stream wave during El Niño. Northern solutions are phasing too much. Look out for the 12Z runs. I'll bet dollars to donuts we shift south...maybe not 100 miles, but at least some more ticks south.

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9z SREF looked better than the 3z to me. Still not cold enough to where we want it but wetter for much of NC.  As I said above it looked to me like there are a good bit of southern solutions in the individual members though I don't have access to that. 

 

The model center here has them!  It's the same variance I just posted about on the GEFS. 

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SREF is an ensemble of high-res models, so unless a lot like 75% were showing something the mean would wash it out.

IIf you look at the RDU plume for Tuesday afternoon, there are 4 SREF members with temps at 18z in the 50s, that bring the mean way upt although most are below the mean of 35.

i wouldnt trust the SREF too much for surface temp forecasts beyond 24-36 hours and even then know the caveats.

Yep. Paying attention to the spread and grouping of the members is very important with the SREF. Overall I don't really like it until we get really close and I don't remember the last time I used it for temps. I like it for Ptype.
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The model center here has them!  It's the same variance I just posted about on the GEFS. 

 

Ha for some reason when I saw you posted I knew you were going to say this. Good to know, I typically use the model center for the GEFS members. You can see on the SREF mean for 9z a qpf max pop right over GSP...so I knew there had to be some members doing something different.

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Just analyzed the 9Z SREF for RDU...

 

The mean snowfall is only about 1 inch but the QPF seems to have increased slightly.. . Seems to confirm what others have said that we will see a little snow at the onset and then a lot of IP or FZRA.  

 

Only time we get slightly above freezing is Tuesday afternoon but then it dips below through Wednesday again.  

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ht made a good point. Often times models will erode cold air too quickly and flood that area with warmth. Therefore you get a surface low pressure following that path. You can see a slight adjustmentioned on the 6z and you will probably see a more subtle shift on the 12z runs. This is not a run of the mill cold air in place. Temps and dew points are very low and the is good confluence in the northeast.

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CAE this morning   :)

 

.SHORT TERM /MONDAY THROUGH TUESDAY/...
MOISTURE WILL BE ON THE INCREASE MONDAY AHEAD OF LOW PRESSURE
APPROACHING FROM THE LOWER MISSISSIPPI RIVER VALLEY. THE
PRECIPITATION CHANCE WILL INCREASE FROM WEST TO EAST DURING THE
AFTERNOON. THE NAM AND GFS INDICATE ENOUGH MOISTURE INCREASE AND
ISENTROPIC LIFT FOR LIKELY PRECIPITATION IN THE WEST WITH CHANCE
IN THE EAST. THE NAM AND GFS FORECAST SOUNDINGS SUPPORT RAIN IN
THE SOUTH...RAIN AND SLEET IN THE CENTRAL SECTION...AND A MIX OF
RAIN...SLEET AND SNOW IN THE NORTH PART. BELIEVE AMOUNTS THROUGH
MONDAY WILL REMAIN LIGHT BECAUSE OF THE VERY DRY AIR INITIALLY IN
PLACE.

THE BULK OF THE PRECIPITATION SHOULD OCCUR MONDAY NIGHT MAINLY
ASSOCIATED WITH A STRONG H85 JET. A SIGNIFICANT WARM NOSE WILL BE
ASSOCIATED WITH THIS FEATURE WITH TEMPERATURES ABOVE FREEZING.
HOWEVER...NEAR THE SURFACE A WEDGE-TYPE PATTERN WILL LIKELY
PERSIST AIDED BY EVAPORATIVE COOLING IN THE DRY AND COLD AIR MASS
INITIALLY IN PLACE. THE GFS AND NAM DISPLAY SURFACE WET BULB
TEMPERATURES ABOVE FREEZING IN THE AUGUSTA AREA...NEAR FREEZING IN
THE COLUMBIA AREA...AND BELOW FREEZING NORTH OF COLUMBIA. THE
GFS...NAM AND SREF MEAN INDICATE SIGNIFICANT QPF WITH AMOUNTS
GENERALLY AROUND AROUND ONE-HALF OF AN INCH. IT IS NOT CLEAR HOW
MUCH OF THIS WILL BE ICE ACCUMULATION. THERE MAY BE CONSIDERABLE
SLEET EARLY AND THE GFS SHOWS SURFACE WET-BULB TEMPERATURES RISING
TO THE MELTING POINT IN THE NORTH PART. THE NAM WAS MORE
PERSISTENT KEEPING WET BULB TEMPERATURES BELOW FREEZING. THE WPC
GUIDANCE HAS TRENDED NORTHWARD WITH HIGHER ICE AMOUNTS. THIS
MORNING/S GUIDANCE HAD ICE ACCUMULATION ONE-TEN TO ONE-QUARTER OF
AN INCH IN THE NORTH PART OF THE FORECAST AREA.

THE MODELS HAVE TRENDED FASTER SHIFTING DEEPER MOISTURE EAST OF
THE FORECAST AREA TUESDAY. THE NAM HAD MOISTURE LINGERING LONGER THAN
THE GFS AND ECMWF. WE LOWERED POPS BASED ON THE MODEL TREND.

THE TEMPERATURE GUIDANCE IS LIKELY MUCH TOO WARM MONDAY BECAUSE OF
A COLD START AND THICKENING CLOUDS. LEANED TOWARD THE COLDER
GUIDANCE MONDAY NIGHT AND TUESDAY FOR FORECAST CONSISTENCY.

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As many have said this morning, I am also in agreement that a more southern solution will appear with the 12Z runs. Why? Because as we said last week, the overall pattern is the same as it has been for the last several weeks. We've had a good pattern but no cold air. Now we have both. And yes, too, lows never crash into CAD wedges. They should pivot around them to the south. But this is dependent on the strength of the CAD, which I think yesterday's 12Z NAM had gotten right. These northern solutions are of course possible, but they really don't make sense to me. Between overall pattern, CAD, and climo, this is a classic southern stream wave during El Niño. Northern solutions are phasing too much. Look out for the 12Z runs. I'll bet dollars to donuts we shift south...maybe not 100 miles, but at least some more ticks south.

Sent from my iPad

 

I agree with everything you said, now where can I sign up for your newsletter. 12z NAM @25 looks a tick south vs. 6z and maybe a hair colder out in front of the storm. Probably not enough to make any big differences though. 

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I agree with everything you said, now where can I sign up for your newsletter. 12z NAM @25 looks a tick south vs. 6z and maybe a hair colder out in front of the storm. Probably not enough to make any big differences though.

Ha thanks man. No newsletters here...just idle thoughts. Now we wait and watch to see if NAM ticks south...even 25-50 miles would be huge at this stage.

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