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December Forecast Discussion


Wow

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These models are still clueless on this storm. I think the margin of error is still well to the SE of where they are taking the SLP. In general, with blocking and a strong 500mb low in the NF region, redevelopment is the most likely situation. IE) a low from Louisiana to the TN Valley and then redevelopment off of Hatteras. The HP sitting up there in the great lakes region is normally ideal for CAD.

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These models are still clueless on this storm. I think the margin of error is still well to the SE of where they are taking the SLP. In general, with blocking and a strong 500mb low in the NF region, redevelopment is the most likely situation. IE) a low from Louisiana to the TN Valley and then redevelopment off of Hatteras. The HP sitting up there in the great lakes region is normally ideal for CAD.

This can be worked on from here. This was the first time true CAD showed up and the high stuck around. I agree that this could easily adjust S and E given that setup on the 18z run.

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If it played out like the 18z GFS... all the damming regions would be in for some freezing rain. We have had several events like this before where the wedge locked in and we recieved significant wintery precip from the baroclinic leaf that streaks way out ahead of the actual system. That band of precip almost always over performs for a localized region.

If it played out as depicted by the GFS, some people would get a crippling ice-storm long before the actual front approaches and turns what’s left with the main band over to rain.

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anything for the mtns.

Prob some initial sleet/snow to rain. Looks like hickory is .15 then to rain w/ temps around 34, up near martinsville they prob get .4 or .5 of freezing rain before rising above zero. But keep in mind, this is 7 days out. If that HP is seriously 1040+ sitting up there over top the great lakes, this would trend significantly cold. But it's hard to trust any solution at this point. But as I've said for several weeks, the indices support something occurring around this timeframe.

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NWS Blacksburg...before the 18z GFS came in.

Details of the initial weaker wave still have plenty of

questions...but with overall zonal pattern at that time...trends now

seen for faster solutions are preferred. Have begun leaning this way

with slight chance probability of precipitation arriving later Monday but may even need to

speed this up more. Right now have highest chance probability of precipitation later Monday

night given remaining uncertainty in 00z ensembles...but 12z GFS and

European model (ecmwf) both suggest light precipitation will push through quickly by early

Monday evening. Best to keep probability of precipitation low at this point given

uncertainty in timing. If the timing is either early Monday

morning...or even into Monday night...surface temperatures could be cold enough

for some lighit freezing rain in spots...and across far north high

elevations may even see light snow or rain/snow mix. Most of this

should be rain though...and amounts light enough so that anything

frozen that might fall would have little impact. Have undercut

guidance on high temperatures though give light precipitation and very weak

damming as this wave passes over.

While current guidance does indicate a short break between this and

next digging and more potent system...given uncertainty in all this

timing...have left low chance probability of precipitation up for the time being...with next

overrunning precipitation possibly arriving by Tuesday night...but with slower

solution more likely think this may hold off until web morning. Have

introduced likely probability of precipitation by ties night and Wednesday given this stronger

system with much better chances for widespread precipitation. More classic

damming pattern likely to set up in advance of this with surface high

over New England...but not especially strong or very cold/dry air

initially. Still...despite strong warm advection by later

Wednesday...surface wet bulbs could be low enough for some freezing rain

or mix...and again much may depend on exact timing. Have undercut

guidance on Wednesday for highs given likelihood of some kind of damming.

Best chance for any wintry precipitation would be across northern portion

of area...but this whole system is still a long way off and strength

and timing of all aspects could change quite a bit. Certainly the

next important system to keep an eye on.

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Prob some initial sleet/snow to rain. Looks like hickory is .15 then to rain w/ temps around 34, up near martinsville they prob get .4 or .5 of freezing rain before rising above zero. But keep in mind, this is 7 days out. If that HP is seriously 1040+ sitting up there over top the great lakes, this would trend significantly cold. But it's hard to trust any solution at this point. But as I've said for several weeks, the indices support something occurring around this timeframe.

I think it should be noted how hard it is for models to model cold air damming events. granted they have gotten better, but it's still not good. I agree the synoptic setup should for now only be followed. Do you see a way the high pressure can move east? That would be ideal for a CAD event.

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From your quote it looked like you were saying rain verbatim in the CAD area.

I should have been more specific. Went back and looked at Burger's map, good deal of people in the prime CAD region, we will need cooler trends still for the majority here. Otherwise, they or even we might predominately be looking at a cold rain.

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Strong CAD signature -- even at 850 -- on this run. 0C line stays in Virginia through 165.

Cad signatures are almost always underestimated at the longer ranges. This has the possibility of becoming something much bigger. I am actually becoming a little interested and I think things will come into focus much better once this short-term midwest storm gets out of the way. As so many have pointed out already, this one bears watching if you live in the damming areas.

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No more blizzard talk in the special weather statements...

Statement as of 9:03 AM CST on December 19, 2012

... Hazardous winter weather still possible across parts of

Oklahoma and North Texas early next week...

The overall forecast in regards to winter weather potential

around Christmas has changed somewhat since yesterday. The most

recent computer models are less aggressive with the system set to

impact the southern and Central Plains from Monday through

Wednesday of next week... yielding less confidence in a major

winter storm for Oklahoma and North Texas. However... there are

still indications that some wintry precipitation will be possible

from late Christmas eve through December 26th. As of now... the

most likely timing of any winter weather will be from early

Christmas morning through the day after Christmas. Exact

precipitation type and accumulations remain unclear. It takes very

little wintry precipitation to cause travel problems... especially

if any ice accumulations occur. If you plan to travel the week of

Christmas... monitor the weather situation closely... and be

prepared for weather related travel delays.

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