December 22-24, 2022 | Winter Storm

[1816]

21 minutes ago, Chris2333 said:

I had another gif lined up with a curse in it but didn’t know if anybody had baby ears so this will do for now lol 

[JDClapper]

WPC update just prior to 12z .. woof

[clm]

30 minutes ago, Chris2333 said:

I had another gif lined up with a curse in it but didn’t know if anybody had baby ears so this will do for now lol 

Actually its funnier with that gif if you know the background of forking shirt balls.

Edited December 16, 2022 by clm

[clm]

GFS at odds with its sibling.

 

 

[1816]

Just now, clm said:

GFS at odds with its sibling.

 

 

If the next ecmfw starts to look more like the last gfs then the internet is going to melt down. 

[JDClapper]

12 minutes ago, 1816 said:

If the next ecmfw starts to look more like the last gfs then the internet is going to melt down. 

Since we have a GLC and a coastal already, Euro needs to pump out a slider.

[clm]

2 minutes ago, JDClapper said:

Since we have a GLC and a coastal already, Euro needs to pump out a slider.

[1816]

2 minutes ago, clm said:

Reminds me - time for lunch

[TLChip]

A week yet… last runs snuff me out of the big stuff, but like the signal. Let’s keep the GLC out of here please. 

[1816]

24 minutes ago, 1816 said:

If the next ecmfw starts to look more like the last gfs then the internet is going to melt down. 

Narrator: it doesn't. 

[telejunkie]

Through hr102, liking Euro a lot more than Canadian

[Sentinel]

Given the synoptic set up, something big will happen here; of this I am nearly convinced. 

The Confluence being shown precludes a cutter. The West based NAO precludes an OTS, as long as the PNA continues to cooperate. 

While this may be a bit of inland runner threat, I really do not see it given all the other variables, even though the PNA looks to really sharpen and the system is exploding. Delmarva region -of course- is in a much more questionable area. 

Lots to go with this system, howver, given the synoptic picture, someone is getting burried, potentially the NE I95 corridor (which is how I would lean at this point). 

[telejunkie]

Differences at h5 over the east coast speak volumes at hr120

[JDClapper]

😐

[telejunkie]

6 minutes ago, JDClapper said:

😐

yeah...we're going to need help by that lead wave in order for the main wave to not tilt too soon...

[Southern Maine Snow]

That cuts so much on Euro can it even be called a GLC? It would have to hop on a plane to become a coastal 

[Wally Ho]

The Euro cut one big time, lads.

[Penn State]

12z Operational Guidance Roundup.. Hours 132-204 

GFS 

ECMWF 

GDPS 

[Penn State]

12z 500mb Comparison Roundup..

[Penn State]

WPC (Day 6 and 7) 

[Penn State]

12z Ensemble Roundup..

GEFS 

EPS

CMCE 

[Penn State]

12z Ensemble Comparison (Hour 168) 

[Poco]

Wpc extended latest disco 

Extended Forecast Discussion NWS Weather Prediction Center College Park MD

218 PM EST Fri Dec 16 2022 Valid 12Z Mon Dec 19 2022 - 12Z Fri Dec 23 2022

***Bitterly cold temperatures likely to settle over the northern Plains for much of next week, spreading south and east after Wednesday***

***Potential for a significant winter storm over the East late in the week***

 

..Synoptic Overview... Expect a significant pattern change to evolve across much of the continental U.S. next week as a pronounced upper trough digs into the eastern half of the nation, accompanied by an impressive arctic airmass settling southward across the Plains and then advecting eastward, with widespread subzero temperatures likely for the north-central states. This is mainly in response to a building West Coast upper ridge (+PNA pattern) and a negative arctic oscillation (-AO pattern) that allows arctic airmasses to drop southward from Canada. Most guidance suggests that the amplifying trough may support strong surface development after midweek, producing areas of heavy rain and/or snow along with strong wind. Details of this evolution will depend on the relative emphasis of features in the northern and southern streams and how/when they may interact. ...Guidance/Predictability Assessment... Over the past several days the guidance has had difficulty in resolving important details for flow across areas from northwestern North America and the northeastern Pacific through southern Canada and the lower 48. This originates from the typically low predictability for flow downstream from a closed upper high such as the one expected northwest of Alaska by the start of the medium range period. Even in the new 12Z guidance, there is pronounced spread for leading energy tracking across southern Canada and the northern tier U.S. (GFS/GEFS deepest/southward with the southern Canada upper low and most amplified with the trough to its south) and then the shape of upstream flow. UKMET runs thus far have been the most amplified with broad troughing that passes through the West, but now the 12Z CMC/ECMWF have adjusted away from consensus toward more western-central U.S. trough amplification Wednesday-Thursday as well (just a little east of the UKMET). Latest GFS runs are somewhat between established consensus and the western extremes. These differences lead into the significant spread for where potentially deep low pressure may develop/consolidate late in the week. GFS runs dig the strongest bundle of northern stream energy well into the Southeast by early Friday, leading to farther south/later development (and more Mid-Atlantic snow threat). In contrast, the new 12Z CMC/ECMWF evolution leads to a deep upper low over the Michigan/Ohio/Indiana region and a strong Midwest/Great Lakes surface low. This would produce the greatest snow threat much farther west while sweeping a strong cold front (with more liquid precipitation) over the East. Other alternatives include prior ECMWF runs that emphasized a leading coastal wave that merged with the approaching Great Lakes system. Meanwhile, ECens/CMCens means have been quite consistent in positioning an upper low over the eastern Great Lakes as of early Friday. A lagged average of operational ECMWF runs has tracked the upper low just a bit south of those means. GEFS means have been waffling more, at times keeping the upper low farther north though this is partially just due to being about 12 hours slower with overall development.Even among the preferred more consistent ECMWF/ECens/CMCens cluster (adding the 00Z CMC operational as well), there is meaningful spread for whether the main surface low takes a coastal or more inland track--related to the uncertainty of relative emphasis of the system reaching the Great Lakes and potential leading wave near the East Coast. A blend emphasizing that past couple ECMWF runs, the 00Z ECMWF mean, and 00Z CMC best accounted for the most stable guidance available through the 06Z cycle. new 12Z runs suggest that the "most likely" scenario could well change, depending on how the remainder of the 12Z ensemble suite turns out.

 

...Weather/Hazard Highlights... The main weather story that will make weather headlines next week will be the massive expanse of frigid temperatures from Montana/Northern Plains to the Midwest and then farther south and east by next Thursday-Friday. A couple of reinforcing cold fronts will usher in the coldest air of the season by a considerable margin with the expectation of widespread subzero readings for overnight lows from the Northern Rockies to the central/northern Plains and the Upper Midwest, with some lows approaching -30 degrees across portions of Montana and North Dakota. Although the frigid airmass will modify as it reaches the Ohio Valley and Mid-South, it will still be quite cold with widespread 0s and 10s for overnight lows by the end of the week, and this very cold weather is expected to have some staying power as the Climate Prediction Center outlook indicates high probabilities of below average temperatures persisting over much of the eastern half of the country for the week beyond next Friday. As cold as it will likely be, it will be difficult to challenge daily record lows/cold highs due to this event overlapping with portions of the historic 1983 and 1989 cold waves. At the very least portions of the East may end up seeing the coldest temperatures for any December since 2017. As for the potential storm affecting the eastern U.S. late next week, the most common theme in the current guidance is that the strong upper trough amplification and potentially deep upper low would produce a vigorous surface system and a broad area of strong winds. Beyond that, a potential storm track anywhere between the Great Lakes and East Coast make it very difficult to outline where the heaviest snow is most likely. The composite of ensemble-based guidance and models before arrival of the 12Z runs highlighted the central Appalachians/northern Mid-Atlantic into New England as having the highest probability of significant snowfall, corresponding to a near-coastal surface low track. However if trends end up going somewhat farther westward, then the greatest snow threat could shift as far back as the Midwest with more liquid precipitation farther east along a strong cold front. Continue to monitor forecasts for updated information as guidance hopefully better resolves this development in coming runs. Elsewhere, a shortwave tracking near the Gulf Coast along with an associated frontal wave over the northern Gulf of Mexico could produce a period of enhanced rainfall across portions of southern Texas and Louisiana on Monday, and then into Florida on Tuesday. The Northwest should see multiple episodes of rain and higher elevation snow with highest totals over favored terrain. Confidence is moderate at best for day-to-day details regarding amounts and coverage given the dependence on exact shape of the upper flow over the region. The gradual warming trend over the West as upper ridging builds toward the coast should lead to slowly rising snow levels with time. Rausch/Hamrick

[Sentinel]

Just now, Poco said:

Wpc extended latest disco 

Extended Forecast Discussion NWS Weather Prediction Center College Park MD

218 PM EST Fri Dec 16 2022 Valid 12Z Mon Dec 19 2022 - 12Z Fri Dec 23 2022

***Bitterly cold temperatures likely to settle over the northern Plains for much of next week, spreading south and east after Wednesday***

***Potential for a significant winter storm over the East late in the week***

 

..Synoptic Overview... Expect a significant pattern change to evolve across much of the continental U.S. next week as a pronounced upper trough digs into the eastern half of the nation, accompanied by an impressive arctic airmass settling southward across the Plains and then advecting eastward, with widespread subzero temperatures likely for the north-central states. This is mainly in response to a building West Coast upper ridge (+PNA pattern) and a negative arctic oscillation (-AO pattern) that allows arctic airmasses to drop southward from Canada. Most guidance suggests that the amplifying trough may support strong surface development after midweek, producing areas of heavy rain and/or snow along with strong wind. Details of this evolution will depend on the relative emphasis of features in the northern and southern streams and how/when they may interact. ...Guidance/Predictability Assessment... Over the past several days the guidance has had difficulty in resolving important details for flow across areas from northwestern North America and the northeastern Pacific through southern Canada and the lower 48. This originates from the typically low predictability for flow downstream from a closed upper high such as the one expected northwest of Alaska by the start of the medium range period. Even in the new 12Z guidance, there is pronounced spread for leading energy tracking across southern Canada and the northern tier U.S. (GFS/GEFS deepest/southward with the southern Canada upper low and most amplified with the trough to its south) and then the shape of upstream flow. UKMET runs thus far have been the most amplified with broad troughing that passes through the West, but now the 12Z CMC/ECMWF have adjusted away from consensus toward more western-central U.S. trough amplification Wednesday-Thursday as well (just a little east of the UKMET). Latest GFS runs are somewhat between established consensus and the western extremes. These differences lead into the significant spread for where potentially deep low pressure may develop/consolidate late in the week. GFS runs dig the strongest bundle of northern stream energy well into the Southeast by early Friday, leading to farther south/later development (and more Mid-Atlantic snow threat). In contrast, the new 12Z CMC/ECMWF evolution leads to a deep upper low over the Michigan/Ohio/Indiana region and a strong Midwest/Great Lakes surface low. This would produce the greatest snow threat much farther west while sweeping a strong cold front (with more liquid precipitation) over the East. Other alternatives include prior ECMWF runs that emphasized a leading coastal wave that merged with the approaching Great Lakes system. Meanwhile, ECens/CMCens means have been quite consistent in positioning an upper low over the eastern Great Lakes as of early Friday. A lagged average of operational ECMWF runs has tracked the upper low just a bit south of those means. GEFS means have been waffling more, at times keeping the upper low farther north though this is partially just due to being about 12 hours slower with overall development.Even among the preferred more consistent ECMWF/ECens/CMCens cluster (adding the 00Z CMC operational as well), there is meaningful spread for whether the main surface low takes a coastal or more inland track--related to the uncertainty of relative emphasis of the system reaching the Great Lakes and potential leading wave near the East Coast. A blend emphasizing that past couple ECMWF runs, the 00Z ECMWF mean, and 00Z CMC best accounted for the most stable guidance available through the 06Z cycle. new 12Z runs suggest that the "most likely" scenario could well change, depending on how the remainder of the 12Z ensemble suite turns out.

 

...Weather/Hazard Highlights... The main weather story that will make weather headlines next week will be the massive expanse of frigid temperatures from Montana/Northern Plains to the Midwest and then farther south and east by next Thursday-Friday. A couple of reinforcing cold fronts will usher in the coldest air of the season by a considerable margin with the expectation of widespread subzero readings for overnight lows from the Northern Rockies to the central/northern Plains and the Upper Midwest, with some lows approaching -30 degrees across portions of Montana and North Dakota. Although the frigid airmass will modify as it reaches the Ohio Valley and Mid-South, it will still be quite cold with widespread 0s and 10s for overnight lows by the end of the week, and this very cold weather is expected to have some staying power as the Climate Prediction Center outlook indicates high probabilities of below average temperatures persisting over much of the eastern half of the country for the week beyond next Friday. As cold as it will likely be, it will be difficult to challenge daily record lows/cold highs due to this event overlapping with portions of the historic 1983 and 1989 cold waves. At the very least portions of the East may end up seeing the coldest temperatures for any December since 2017. As for the potential storm affecting the eastern U.S. late next week, the most common theme in the current guidance is that the strong upper trough amplification and potentially deep upper low would produce a vigorous surface system and a broad area of strong winds. Beyond that, a potential storm track anywhere between the Great Lakes and East Coast make it very difficult to outline where the heaviest snow is most likely. The composite of ensemble-based guidance and models before arrival of the 12Z runs highlighted the central Appalachians/northern Mid-Atlantic into New England as having the highest probability of significant snowfall, corresponding to a near-coastal surface low track. However if trends end up going somewhat farther westward, then the greatest snow threat could shift as far back as the Midwest with more liquid precipitation farther east along a strong cold front. Continue to monitor forecasts for updated information as guidance hopefully better resolves this development in coming runs. Elsewhere, a shortwave tracking near the Gulf Coast along with an associated frontal wave over the northern Gulf of Mexico could produce a period of enhanced rainfall across portions of southern Texas and Louisiana on Monday, and then into Florida on Tuesday. The Northwest should see multiple episodes of rain and higher elevation snow with highest totals over favored terrain. Confidence is moderate at best for day-to-day details regarding amounts and coverage given the dependence on exact shape of the upper flow over the region. The gradual warming trend over the West as upper ridging builds toward the coast should lead to slowly rising snow levels with time. Rausch/Hamrick

Great Writeup, as usual.  

Basically.. a S/W over no mans land Alaska/Canada is wreaking havoc with the models. 

If the S/W shears out, then we get no separation and essentially a zonal flow leading to a cutter. It does not push further South and therefore the PNA does not shift and the AO is allowed to be essentially forced out of the way. 

If the S/W remains vigorous, that energy pushes South into the lower 48, sharpening the PNA and allowing the AO to flex and force itself further South, thus a coastal solution. 

I still tend to favor the secondary solutions for reasoning outlined before. That withstanding, we will have a much better idea in about 36 hours (once that S/W is better sampled). 

[Iceresistance]

My current Local TV Met currently suggests light snow on December 22nd and Christmas Eve (December 24th)

But the 12z ICON for December 22nd has other ideas, with a snowstorm in Oklahoma and Missouri in Below Zero Temperatures!