September 30th-? MidAtl/NE Cool Spell, Reality: Short Range(0-4 Days Out) Forecasts Options

[WEATHERFREAK]

With the PNA forecasted to go positive and the AO/NAO forecasted to go negative by the first week of October, it appears likely a cool down will hopefully greet the Eastern 2/3s of the nation. This should weaken and drive the Bermuda ridge eastward. Giving a taste of Fall even to the Sunshine State.

Discuss...

This post has been edited by WEATHERFREAK: Sep 23 2011, 02:19 PM

[NYCSuburbs]

Interesting signals showing up for this one... the models seem to be split with two main solutions, one of them where the cold never really makes it into the region and instead remains stuck in Canada, with temperatures staying above average with a few occasional cool spells. The other scenario, currently supported by most models but is subject to change considering the time range, is where a stronger cool air mass drops into the NE, bringing the coldest air mass since last week. With this scenario, the pattern in Canada also seems to be more favorable for sustained near-below average temperatures in the NE US.

The first possible round of cold air for next weekend (10/1), however, would have to depend on the storm that picks up the ULL and on the ULL's position, which is quite tricky to forecast almost a week out. At this time, I'm not going with any solid forecast of above or below average temperatures, but the potential is there for colder than average temperatures for the start of October. Should this potential fail to verify, near to above average temperatures will continue.

[jdrenken]

With the PNA forecasted to go positive and the AO/NAO forecasted to go negative by the first week of October, it appears likely a cool down will hopefully greet the Eastern 2/3s of the nation. This should weaken and drive the Bermuda ridge eastward. Giving a taste of Fall even to the Sunshine State.

Discuss...

Be careful in picking and choosing the ENS members. For instance, the majority of ENS members have a +NAO showing up in the CPC site.


I've discussed this multiple times regarding the vast differences between the CPC and ESRL. Look at the PNA forecast as you alluded to.


A -PNA implies that there is a trough over the Rockies and ridge in the Central part of the nation. We know that's far from correct with higher anomalies over the Rockies. Something else is how the models are showing a +PNA, yet the CPC is showing a -PNA.


The ESRL shows this difference nicely. Even the NCEP side shows a +PNA.

[albanyweather]

I had been keeping an eye on this as well. 12z suite now all agree on the cold. GFS, Euro below. The GGEM looks to be following but does not go that far out. We could see out first frost. Still far out, but let the model hugging commence

[Removed_Member_NYsnowlover_*]

I had been keeping an eye on this as well. 12z suite now all agree on the cold. GFS, Euro below. The GGEM looks to be following but does not go that far out. We could see out first frost. Still far out, but let the model hugging commence

When could we start the first thread for "NE snow" !!!

[Undertakerson]

Interesting time period in the early days. State College mentions something I posted earlier - the persistance of the Omega Block is now in Global Op run concert.

THE 12Z ECMWF HAS COMPLETELY
CHANGED COURSE FROM ITS PREVIOUS 00Z RUN AND NOW AGREES /AT LEAST
IN PRINCIPLE/ WITH THE GFS/GEFS BY FAVORING ANOTHER ERN TROUGH BY
THE START OF OCT.-- End Changed Discussion --

http://forecast.weather.gov/product.php?si...p;highlight=off

Ok - so they don't say Omega Block but take a look at what HPC disco says.

VALID 12Z MON SEP 26 2011 - 12Z FRI SEP 30 2011

THE MODELS AND ENSEMBLE MEANS CONTINUE TO DEPICT A SIMILAR LARGER
SCALE PATTERN EVOLUTION FROM THE PACIFIC INTO NORTH AMERICA INTO
NEXT MIDWEEK. THIS PATTERN IS HIGHLIGHTED ALOFT BY AN AMPLIFIED
MID-UPPER LEVEL TROUGH OVER THE NERN PACIFIC...A MEAN RIDGE ALOFT
OVER WRN NOAM...AND AN AMPLIFIED/CLOSED MID-UPPER LEVEL TROUGH/LOW
OVER THE ERN US. DESPITE GUIDACE SIMILARITIES WITH THE OVERALL
FLOW THOUGH...FORECAST CONFIDENCE SHOULD BE TEMPERED SOME AS PER
LINGERING UNCERTAINY WITH WRN NOAM RIDGE AMPLITUDE...EMBEDDED
SYSTEM INTERATIONS...AND SUBSEQUENT EFFECT ON DOWNSTREAM ERN US
CLOSED LOW/TROUGH PROGRESSION.

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

Yep - fully describes an Omega pattern.

Therefore, it won't be easy to peg this down very well at this point as all blocks present variables that can't be accounted for at this far out, as alluded to by the HPC.

[albanyweather]

When could we start the first thread for "NE snow" !!!

surface too warm. Lets not get ahead of ourselves

[The Day After To...]

surface too warm. Lets not get ahead of ourselves

12z GFS hour 192 snow depth

Source

Attached thumbnail(s)

 

[hckyplayer8]

Lol at the 12z Euro. Has to be a off run as this is the first run it has shown increased ridging through Davis Strait area.

Just got to lol. Close to snowing back over the Western GL's during that run. At the very least, a very cold rain with temps in the mid 30's.

This post has been edited by hckyplayer8: Sep 23 2011, 03:59 PM

[jdrenken]

12z GFS hour 192 snow depth

Source

It's best to leave the snow maps alone until the climo supports it. The last cold shot that went thru the NE, there were post regarding the same thing. Did it snow? Of course not.

[hckyplayer8]

12z GFS hour 192 snow depth

Patience. If the current setup remains true, perhaps somebody in interior NE could see some dandruff. However as is, it is not a good setup for accumulating snow not much of anywhere in the lower 48.

It would build that snow cover in Eastern Canada though.

[TheMaineMan]

As jd pointed out, there is certainly no model consensus of a negative NAO during that time frame, at least not yet. Although there may be some potential during this time period, I'm not getting excited this far out. Thus far, I'd say maybe a few degrees below average but nothing particularly noteworthy. Northern regions might see some more frost, maybe even first freeze, but once you're in October that isn't too unusual.

[greenappleman7]

12z GFS hour 192 snow depth

Source

hahaha- GFS showed this a couple weeks ago [http://forums.accuweather.com/index.php?ac...t&id=141093]

This post has been edited by greenappleman7: Sep 23 2011, 06:22 PM

[Removed_Member_NYsnowlover_*]

surface too warm. Lets not get ahead of ourselves

I was joking around, i do not expect the first "decent" snowfall in the NE until mid- October, this is just too early, and it would require very special conditions.

[albanyweather]

I was joking around, i do not expect the first "decent" snowfall in the NE until mid- October, this is just too early, and it would require very special conditions.

Me too

[jdrenken]

Me too

You are correct in a way though...model hugging has commenced.

[Removed_Member_NYsnowlover_*]

You are correct in a way though...model hugging has commenced.

Another sign that the seasons are changing!!!!

[LoveNYCSnow]

I was joking around, i do not expect the first "decent" snowfall in the NE until mid- October, this is just too early, and it would require very special conditions.

even that sounds a little early although depends what you define as decent.

[Removed_Member_NYsnowlover_*]

even that sounds a little early although depends what you define as decent.

"decent" for October is over 5", it happened back in October of 2009.

[NorEaster07]

It's best to leave the snow maps alone until the climo supports it. The last cold shot that went thru the NE, there were post regarding the same thing. Did it snow? Of course not.

Do Mountains count? I was suprised seeing it on them as well but its not too rare for September up there.

Cannon mountain in New Hampshire...Elevation 4,080 feet, had a dusting of snow September 16, 2011 http://www.youtube.com/watch?v=R4mtDkTfDUQ
http://www.facebook.com/media/set/?set=a.2...mp;l=8b258e2810
http://www.cannonmt.com/

Mount Washington, NH 6288 Feet.. Snow on Sept. 16th
http://www.youtube.com/watch?v=OD5Tfx4NafI

This post has been edited by NorEaster07: Sep 23 2011, 10:45 PM