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November 2011 Obs/Forecasting Discussion


WxUSAF

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GFS tomorrow night? Flurries?

:popcorn:

:P

This system's been looking like borderline changeover to snow (non-accumulating) as the second piece of energy swings through tomorrow... available moisture and low-level temps looking like the only potential hindrances at this point.

Beat you to it.

:)

The 6z GFS is getting our area close next Wed. :popcorn:

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LWX AFD hints at maybe a few isolated severe storms... (snipped from 930AM disco)

THIS WILL

HELP TO PROMOTE THE WARM FRONT LIFTING NORTH INTO THE SOUTHERN CWA

THIS AFTERNOON. AREAS NEAR/SOUTH OF THIS FRONT WILL ALSO HAVE A

CHANCE OF THUNDERSTORMS. WILL ALSO HAVE TO BE CONCERNED ABOUT A

SLIGHT RISK FOR SEVERE IN THIS AREA. THERE WILL BE PLENTY OF SHEAR

IN PLACE AND NEAR/SOUTH OF THE BOUNDARY THERE MAY ALSO BE SOME

INSTABILITY. IF INSTABILITY CAN TRANSLATE TO THE

SURFACE...ISOLATED DAMAGING WIND GUSTS WILL BE POSSIBLE. IN

ADDITION...CAN/T RULE OUT AN ISOLATED TORNADO GIVEN SHEAR AND

FORECAST HODOGRAPHS/SRH. THIS AREA WILL CONTINUE TO BE HIGHLIGHTED

IN THE HWO.

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You probably could get some flakes if there was some good VV's and dynamic cooling but your dealing with the leftovers and small hydrometeors. Meh.

I also don't see it, temps will be too warm at the surface. I'm not even considering writing anything for the CWG which shows how much I think of it.

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LWX AFD hints at maybe a few isolated severe storms... (snipped from 930AM disco)

I think the SPC's northern extent for severe is a bit too far north in our region... Fredericksburg, VA and points southwest and east could be in the game. If I wasn't busy this week I'd be half-tempted to head down to the VA/NC border for chasing, but even then with the sun going down so early it might not be worth it, anyway.

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I think the SPC's northern extent for severe is a bit too far north in our region... Fredericksburg, VA and points southwest and east could be in the game. If I wasn't busy this week I'd be half-tempted to head down to the VA/NC border for chasing, but even then with the sun going down so early it might not be worth it, anyway.

Could be. Updated HWO as of 3 mins ago mentions limited spotter activation may be necessary this afternoon for teh area i quoted below

SCATTERED THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND EARLY

EVENING...MAINLY ACROSS NORTHERN VIRGINIA ADJACENT TO THE TIDAL

POTOMAC RIVER AND INTO SOUTHERN MARYLAND. A FEW THUNDERSTORMS MAY

BECOME SEVERE WITH DAMAGING WINDS..

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12z GFS ensemble mean actually looks like it's going in a good direction late in the run. Yeah, it's still fantasy-land time, but weakens the Gulf of Alaska trough dramatically, keeps a -NAO, shows some weak troughing over us and hints of ridging out west.

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if the computer progs through the end of the month come close to being right with qpf, driest as in 01/02 and 07/08 look to be out, and that's a good sign

Are you suggesting that there is a correlation between a dry November and a lack of winter snow in DC? The driest November (1981) was followed by 22.5 inches of snow in 1981-1982, and the second driest (1965) was followed by 28.4 inches in 1965-1966.

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Are you suggesting that there is a correlation between a dry November and a lack of winter snow in DC? The driest November (1981) was followed by 22.5 inches of snow in 1981-1982, and the second driest (1965) was followed by 28.4 inches in 1965-1966.

I have not studied any relationships of patterns between seasons, but intuitively it would seem that a warm autumn would increase the odds of a cold winter, as a dry autumn would increase the odds of a wet winter. I know that in the large data set available there are probably analogs found to support any claim, but how about a statistical analysis of the odds of such occurring?

Personally, I'm relieved to see this warm weather in Nov, as I think it gives us a better chance of colder-than-normal conditions to follow in D/J. I know that we were quite cool in Oct (-2.2F) and that had me worried.

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Are you suggesting that there is a correlation between a dry November and a lack of winter snow in DC? The driest November (1981) was followed by 22.5 inches of snow in 1981-1982, and the second driest (1965) was followed by 28.4 inches in 1965-1966.

I believe the examples you gave are exceptions to a general rule that dry NOV do not bode well for the winter

I recall checking on it in the past, but I can't say there have been any studies

obviously, it does not always correlate, but it certainly did in 01/02 and 07/08

I would also note that our general winter weather (all things considered) has changed quite a bit since 1965 and 1981 and the recent years I mentioned likely carry more weight as being more in line with current patterns

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There is an incredibly weak negative correlation (R2 = 0.0037) between Fall DCA precip and Winter DCA precip (wetter Fall = drier Winter), but it is basically a shotgun blast graph that isn't even worth posting.

I don't dispute your numbers, but I'm just talking the month of NOV which I assume include other months of fall

plus, maybe I should have mentioned that I am talking snow and cold vs. precip in general

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12z GFS ensemble mean actually looks like it's going in a good direction late in the run. Yeah, it's still fantasy-land time, but weakens the Gulf of Alaska trough dramatically, keeps a -NAO, shows some weak troughing over us and hints of ridging out west.

I'm kinda glad you posted this because I was looking at the run and thinking the same thing. I know it's fantasy land but it does break down the -pna around day 9 or so and then moves things along in a semi decent pattern. It at least opens the door for the possibility of a decent pattern in early Dec. I hope future runs keep breaking down the disgusting epo / pna combo in the same general timeframe and not just pushing it later and later.

The one saving grace of the atrocious PAC is that it's stuck in a stable crappy pattern in Nov and not Dec. Losing 6 weeks of a 12 week window would keep the weenie suicide hotline ringing off the hook.

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I'm kinda glad you posted this because I was looking at the run and thinking the same thing. I know it's fantasy land but it does break down the -pna around day 9 or so and then moves things along in a semi decent pattern. It at least opens the door for the possibility of a decent pattern in early Dec. I hope future runs keep breaking down the disgusting epo / pna combo in the same general timeframe and not just pushing it later and later.

The one saving grace of the atrocious PAC is that it's stuck in a stable crappy pattern in Nov and not Dec. Losing 6 weeks of a 12 week window would keep the weenie suicide hotline ringing off the hook.

If support starts from run to run showing this then I will buy it but until then it is still, to me, doing the delayed but not denied right now. We need a flip point to fix itself more or less.

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12z NAM and GFS support some flakes (that won't accumulate) in the air for the DC region tomorrow... it'll be light rates, but freezing level is plenty low enough (around 950mb or lower) for flakes to reach the surface despite the warm-ish surface temps:

post-96-0-15936300-1321475797.png

post-96-0-77054800-1321475808.png

Keep in mind that the soundings are for 1pm tomorrow.

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