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December 15-17, 2022 | Winter Storm


Penn State

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This is when we risk the "big storms come NW" adage burning us.

You can see on the H8 temps from the ECMWF how important is is for the departing system to provide cold for this one. Only when the warmth is "pinched off" can the secondary form along the triple point on the coast.

ecmwf_T850_us_fh75-144.gif.73f182a640d489d7d55674e35cb5676e.gif

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southern Mid-Atlantic on th edge as per usual.

 

Sterling’s Dicussion

 

LONG TERM /WEDNESDAY THROUGH SATURDAY/... H5 ridging will remain overhead locally Wed Am as a 1035 mb + high remains over eastern Quebec. Dry conditions are expected during the day Wednesday, though high clouds will increase through the day. There remains considerable spread and fluctuations between different global guidance on a run to run basis, though the GFS/GEFS have slowly trended toward those of the ECMWF/EPS. Expect fluctuations in model guidance to continue, with the benchmark for model runs and consistency likely starting Sunday afternoon/night as the parent energy associated with this storm becomes better sampled over the Pacific NW. Overall ensemble guidance continues to support an ULL moving through the Ohio Valley Wednesday and Northeast/offshore into the Atlantic by Friday/Saturday. How far south the ULL tracks in the Ohio Valley in turn will influence where/when a coastal low develops in the vicinity of the Mid Atlantic. Uncertainty remains regarding any wintry precipitation. Given the anomalous high pressure north of the region and surface ridge extending down the spine of the Appalachians, wintry precipitation (all types) is possible across the entire area in the late Wednesday to early Friday timeframe with higher chances along and west of the Blue Ridge mountains. Given the forecast 850/925 mb temps, snow, sleet, freezing rain, and rain area all a possibility. There is the potential for travel impacts during this timeframe. As the ULL moves offshore, there is the potential for a period of upslope snow as several vorticity maxes move over the Appalachians. Models hint at 24+ hours of QPF across the mountains starting Friday into Saturday/Saturday night. This will be highly dependent on the aforementioned system and ULL pattern, will continue to monitor. Strong winds are possible areawide on the backside of the low. Temps will be below normal behind the system.

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Really need that confluence and 50/50 to do work here.   Slow the progression/speed of the coastal low so it develops further south and when it’s bombs out it pulls in the cold and wraps the moisture with it.   That’s why blocks are so important.  Helps those at lower latitudes really get into those wound up storms.  Storms that are usually wound up further north.  

Edited by PA road DAWG
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Something to keep an eye on moving forward….

 

the confluence and initial cold press over SE Canada and Maine.  If I recall correctly that’s always undermodeled (goddamn January 2016).  A harder initial press will force the redeveloping coastal low to form further south and east before it eventually lifts and erodes.  Could be the saving grace for some members of this forum.   I know it’s garbage at this range, but the long range 12z NAM showing better confluence than the previous run. 

Edited by PA road DAWG
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1 minute ago, PA road DAWG said:

Something to keep an eye on moving forward….

 

the confluence and initial cold press over SE Canada and Maine.  If I recall correctly that’s always undermodeled (goddamn January 2016).  A harder initial press will force the redeveloping coastal low to form further south and east before it eventually lifts and erodes.  Could be the saving grace for some members of this forum.   I know it’s garbage at this range, but the long range 12z NAM showing better confluence than the previous run. 

This is absolutely right. The one possibility I see being displayed for my hill country area is ice, followed by cold and upslope snow. But at this time, we're nowhere near set in stone. We need today's little bugger out of the way as well. The entire relationship between the primary and coastal low needs to be ironed out. It's very easy to make the case for a warmer or colder solution currently. 

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1 minute ago, MDBlueridge said:

This is absolutely right. The one possibility I see being displayed for my hill country area is ice, followed by cold and upslope snow. But at this time, we're nowhere near set in stone. We need today's little bugger out of the way as well. The entire relationship between the primary and coastal low needs to be ironed out. It's very easy to make the case for a warmer or colder solution currently. 

I’m thinking this too. CAD seems to always be undermodeled for my region in SCPA. I can’t count the times we are supposed to get to 38-40, and the temps just camp out at 30-32. Looks to be quite cold heading into the event in the interior. 

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28 minutes ago, PA road DAWG said:

Something to keep an eye on moving forward….

 

the confluence and initial cold press over SE Canada and Maine.  If I recall correctly that’s always undermodeled (goddamn January 2016).  A harder initial press will force the redeveloping coastal low to form further south and east before it eventually lifts and erodes.  Could be the saving grace for some members of this forum.   I know it’s garbage at this range, but the long range 12z NAM showing better confluence than the previous run. 

Yep, just these minor little trends with a little more press from the north can pay off for more and more of us.

NAM

namconus_z500_vort_eus_fh78_trend.gif

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Cold can't dig it's heels in because the departing ocean storm is so wound up, that a warm front actually comes in from the NE.  A very unusual setup.

 Dynamics could overcome some of this, but we are way too far out to get hung up on details.

gfs_T850_neus_fh60-108.gif.d319772c4cc0bcf13d2cb6b8e75425e8.gif

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