How Well Do The Appalachian Mountains Block Cold Air?

[PalmTreeDude]

How well do the Appalachian mountains block cold air? Are they simply not tall enough to block as much cold air as the Rockies on the West Coast (areas that share the same latitude as me on the West Coast and that are as far from the ocean as me are zone 9a/9b for the most part)? From this tempature map (I am currently just Southwest of Richmond) it seems like they do a good job. Although this is never something I really paid attention too (much). 

Edited January 30, 2019 by PalmTreeDude

[Jimbean]

I'm going to guess probably not much.  It is also hard to tell how much cold air is being blocked versus how much does the coastal plain benefit from the coastal influence. 

[GottmitAlex]

Yup, I doubt they block the cold as well as the Rockies do out west....

 

[Sabal_Louisiana]

The Rockies is what really screws the East but protects the West Coast. If America was largely flat like Australia you'd have a much more uniform climate across the continent. We'd still be unprotected from arctic air invading from Canada but it probably wouldnt be as amplified and mild Pacific air would spread east with more ease.

I think the Appalachians help a little - during a typical cold wave, Nashville is noticeably colder than Raleigh and Ohio much colder than eastern PA and NJ but this may have more to do with geographical position.

The Appalachians do have some effect in "resisting" or impeding cold air movement.

In a phenom called cold air damming, the Appalachians might make the cold worse on the Atlantic coastal plain and Piedmont by preventing cold air from spreading out - allowing it to "slide" southward from New England down as far south as Georgia - so if it prevents cold air from spreading west I would think it also impedes cold air coming from the west.

Perhaps some expert can tell us more.

[Josue Diaz]

The highest peak in the Appalachian range is 6,683 high. Laughable by west coast standards (Sierra Nevada, Cascade Range, Rocky Mountains, etc). Mt Whitney is 14,508 feet and surrounded by countless peaks just shy of that altitude. 

This is a picture from Alta Peak (11,200'). The range in the background is the great western divide. Most of those peaks are well over 13000 in elevation. Beyond the divide is the Kern River Canyon (at roughly 7000' in elevation) and beyond that is the crest of the Sierra Nevada Mountain Range - most of which is over 13,000 in elevation and includes many peaks over 14,000 - Whitney being the tallest. Beyond that crest lie the interior deserts. When the deserts have their monsoon season, rarely does anything come across this range. Same goes for weather patterns originating in the Pacific. Moisture is pushed upward (eastward) and it condenses into clouds which fall on the western slopes of these mountains. The deserts receive virtually none of it. 

 

Edited January 31, 2019 by Josue Diaz

[cm05]

5 hours ago, Josue Diaz said:

The highest peak in the Appalachian range is 6,683 high. Laughable by west coast standards (Sierra Nevada, Cascade Range, Rocky Mountains, etc). Mt Whitney is 14,508 feet and surrounded by countless peaks just shy of that altitude. 

This is a picture from Alta Peak (11,200'). The range in the background is the great western divide. Most of those peaks are well over 13000 in elevation. Beyond the divide is the Kern River Canyon (at roughly 7000' in elevation) and beyond that is the crest of the Sierra Nevada Mountain Range - most of which is over 13,000 in elevation and includes many peaks over 14,000 - Whitney being the tallest. Beyond that crest lie the interior deserts. When the deserts have their monsoon season, rarely does anything come across this range. Same goes for weather patterns originating in the Pacific. Moisture is pushed upward (eastward) and it condenses into clouds which fall on the western slopes of these mountains. The deserts receive virtually none of it. 

 

While it’s true that the Appalachians aren’t as high as the Rockies, their prominence (height measured from base to peak) isn’t significantly different in many cases. The west itself is generally higher in elevation than the east, so the Rockies get sort of a boost in height.

Nice pic btw.

[mdsonofthesouth]

With the top peaks sitting at 6600ft, the rest sitting well bellow that and all the weather it doesn't seem to prevent I'm going with the Atlantic regulating the coast. Just so happens that Appalachia parallels the coast.

[cm05]

The Appalachians do indeed help moderate our temperatures, though not as much as the Atlantic. Similar story on the west coast with the Rockies and the Pacific.

The main difference being that air/weather/etc. blows from west to east, so the west coast gets most of its weather from the Pacific, whereas we on the east coast get most of ours from North America.

The opposite may be true during the summer however, the east coast becomes an extension of the tropical Atlantic while much of the west coast experiences warm/hot dry continental air.

[GottmitAlex]

Could another factor be where the sun sets as well?

Could west coast afternoon/evening sun help warm things up more than  east coast morning/afternoon?

 

 

[Josue Diaz]

8 hours ago, cm05 said:

While it’s true that the Appalachians aren’t as high as the Rockies, their prominence (height measured from base to peak) isn’t significantly different in many cases. The west itself is generally higher in elevation than the east, so the Rockies get sort of a boost in height.

Nice pic btw.

IDK, Mt Whitney and surrounding peaks have a prominence of over 10,000 feet on the eastern side. The entire crest of the Sierra Nevada looks like a fistful of daggers jutting into the sky when you look at them from highway 395. 

By contrast, only 2 peaks in the east coast have a prominence above 6000. Only 3 over 4000' and the rest just over 2000 and 3000'. My guess is the Appalachian range doesn't stop major weather patterns from blowing over them.

 

[RJ]

Cold air sinks. So yes for the the Appalachians aren't as high. But Living in the SE I often watch the cold air get diverted off towards Atlanta and then spill down into Alabama. Sure it still gets to us, but it seems to be delayed. Long duration cold events eventually effect us. Not very often to we stay below 32 during the day. There are MANY peaks above 6k ft along the Appalachian chain. Here is a list of 50+

 

https://en.wikipedia.org/wiki/Southern_Sixers#List_of_Southern_Sixers

 

 

[NC_Palms]

The Appalachians do a better job with blocking the cold than what we give them credit for. I just wish they were slightly higher so my climate can be more in connected with other regions around the world at 35ºN. But unfortunately, the Appalachians seem to be slowly eroding away

[RJ]

32 minutes ago, NC_Palms said:

The Appalachians do a better job with blocking the cold than what we give them credit for. I just wish they were slightly higher so my climate can be more in connected with other regions around the world at 35ºN. But unfortunately, the Appalachians seem to be slowly eroding away

I agree, I think Texas, considering how far south it can be gets much more of a roller coaster ride then we do in the SE. 

 

 

[AnTonY]

10 hours ago, RJ said:

I agree, I think Texas, considering how far south it can be gets much more of a roller coaster ride then we do in the SE. 

 

 

Even if this were true (and it isn't necessarily so), the Appalachians wouldn't be a reason for the difference. 

Edited February 2, 2019 by AnTonY

[AnTonY]

The Appalachians are still pretty N-S oriented, so they only temporarily protect from the cold. Because while the cold airmasses can get stalled from the NW, they can still come around through Eastern Canada, then slip down via the eastern spine. Hence "cold air damming."

The exaggerated SW-NE temperature difference you see tends to be a given with certain patterns (i.e. positive tilt troughs, strong SE ridge, etc), so the disparity would still exist regardless of whether or not the Appalachians are present.

Edited February 2, 2019 by AnTonY

[Lard Greystoke]

A factor not mentioned is the Gulf of Mexico.  Weather is typically more severe just east of the Rockies where Canadian air predominates.  As you head east Gulf air becomes more of a factor.  The Appalachians seem to protect the East Coast during tornado season.  The Appalachians also probably screen the Midwest from the influence, good or ill, of the Atlantic.

[AnTonY]

1 hour ago, Lard Greystoke said:

A factor not mentioned is the Gulf of Mexico.  Weather is typically more severe just east of the Rockies where Canadian air predominates.  As you head east Gulf air becomes more of a factor.  The Appalachians seem to protect the East Coast during tornado season.  The Appalachians also probably screen the Midwest from the influence, good or ill, of the Atlantic.

It's also because the Appalachians aren't tall enough. The air flowing over them doesn't get as cool and dry as it does over the Rockies. As a result, the area East of the Appalachians gets no combination of steep lapse rates + warm moist air that are key to those Central US tornado outbreaks.

[Nj Palms]

They do prevent some cold air, but since the storm systems come off the pacific in the west is what keeps it warm there. The appalachians can also dam cold air along the coastal plain with NE winds.

[Nj Palms]

Here's a quick drawing showing what usually happens in Polar Vortexes. The Apps moderate temps a little bit keeping us from getting extreme temps such as the Midwest. If the wind is coming off the Atlantic that would moderate temps even more. In the west the Rockies     Are tall enough to block the Cold blasts. Since lows usually move west to east  the warm air from the pacific settles into the west. Just a short explanation detailed info can be found online.

[AnTonY]

Temps may be debatable, but the same can't be said for precipitation. Areas east of the Appalachians seem to have a stronger winter-dry pattern, with more sunshine, compared to soggier conditions farther west. Just compare Jax with Mobile to see what I mean.

Edited February 5, 2019 by AnTonY

[AnTonY]

@Nj Palms

I came back to this thread, and have come to a realization based on the map that you posted. And that is, the Appalachians would only protect NC, maybe parts of SC -  everywhere else US South (even Florida!) is completely exposed and fair game to the full sweep of a Canadian Arctic airmass, depending on the jet stream pattern.

[RedRabbit]

It’s interesting how the Appalachian mountains do have some effect on the east coast weather. It’s not just blocking cold, there’s a rain shadow effect too where portions of SC for example are pretty dry while a few spots in NC can get 100” of precipitation annually. 

[Nj Palms]

3 hours ago, AnTonY said:

@Nj Palms

I came back to this thread, and have come to a realization based on the map that you posted. And that is, the Appalachians would only protect NC, maybe parts of SC -  everywhere else US South (even Florida!) is completely exposed and fair game to the full sweep of a Canadian Arctic airmass, depending on the jet stream pattern.

Yeah. The Appalachians do protect a bit while areas like Alabama and Mississippi are more prone to colder temps than areas at the same longitude east of the mountains. 

[AnTonY]

@Nj Palms

That's definitely true. Although it's often quite hard to tell at times, due to how Appalachian CAD events end up minimizing the temperature differentials.

[Nj Palms]

14 minutes ago, AnTonY said:

@Nj Palms

That's definitely true. Although it's often quite hard to tell at times, due to how Appalachian CAD events end up minimizing the temperature differentials.

They do both jobs of filtering in cold air and keeping a bit out. CAD should be evident and easy to see around Monday as a wintry system approaches.

[AnTonY]

@Nj Palms

What I meant with "hard to tell" were with regards to winter minimums and lows when looking at first glance - basically, you look at the map, and see that Eastern NC is still, more or less, a similar hardiness zone compared to some areas farther west like Tennessee and Arkansas.

I think the CAD events, and that cooling that can result from wintry precipitation ends up minimizing what could have otherwise been a much more obvious contrast with respect to winter minimums on the west vs east sides.

[Nj Palms]

On 1/22/2021 at 6:09 PM, AnTonY said:

@Nj Palms

What I meant with "hard to tell" were with regards to winter minimums and lows when looking at first glance - basically, you look at the map, and see that Eastern NC is still, more or less, a similar hardiness zone compared to some areas farther west like Tennessee and Arkansas.

I think the CAD events, and that cooling that can result from wintry precipitation ends up minimizing what could have otherwise been a much more obvious contrast with respect to winter minimums on the west vs east sides.

Spot on.

[Cevven]

On 1/22/2021 at 6:09 PM, AnTonY said:

@Nj Palms

What I meant with "hard to tell" were with regards to winter minimums and lows when looking at first glance - basically, you look at the map, and see that Eastern NC is still, more or less, a similar hardiness zone compared to some areas farther west like Tennessee and Arkansas.

Sorry, but I have to correct you on this. Most of TN is 7a and most of NC is 7b/8a based on the 2010 USDA Hardiness Zone map.  All of Eastern NC (Coastal Plain region) is a solid 8a (with 8b and zone 9 microclimates in parts of the Outer Banks). Northern Arkansas is mostly zone 7a/b., the 8a section of AR is not north of the 35N parallel in NC. The hardiness zones between NC and those states you mentioned are not RADICALLY different but the difference is def noticeable. 

Edited March 9, 2021 by Cevven