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Feb Long Range Discussion (Day 3 and beyond) - MERGED


WinterWxLuvr
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1 minute ago, high risk said:

       correct.     Still not great but a clear step forward.

Even with the old gfs known biases with cad, the 12z run shows impressive staying power if you ignore verbatim temps and focus on surface winds. I didnt realize how much it has shifted in just the last 5-8 runs. 

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19 minutes ago, Chris78 said:

I noticed the TPV hanging around longer in SE Canada. That should help some. Been a trend over the past several runs of the GFS

We need a combo of that PV hanging around longer/stronger/further southwest plus a less amplified trough to our west. The tpv trend has been going our way. The trough ehh. That’s why we see the start of the storm trending colder but still ending up warm. If we were to see the trough less amplified and shift east some also that’s how we could get a cold storm start to finish. Keep the wave under us. 

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2 minutes ago, Bob Chill said:

Even with the old gfs known biases with cad, the 12z run shows impressive staying power if you ignore verbatim temps and focus on surface winds. I didnt realize how much it has shifted in just the last 5-8 runs. 

         That's a good point.    When the ops GFS shows a decent cold air damming signal, you have to take notice, as it loves to mix things out quickly and switch the winds to a southerly component.    Both versions of the GFS (and other guidance) have a signal of a weak low trying to form along the coast - that setup with a dying low coming in from the west and a weak system forming to our east or southeast (has to be weak to not crank up the onshore flow) usually works very well for damming.

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Just now, psuhoffman said:

We need a combo of that PV hanging around longer/stronger/further southwest plus a less amplified trough to our west. The tpv trend has been going our way. The trough ehh. That’s why we see the start of the storm trending colder but still ending up warm. If we were to see the trough less amplified and shift east some also that’s how we could get a cold storm start to finish. Keep the wave under us. 

Midrange has been overdoing (sometimes substantially) precip/amping. If that's the case again, a weaker storm would be an even better outcome imo. We'll see how it goes.  My gut says thurs wont be the juicy deluge as depicted right now. Still going to be a mess but more of a good mess and less of a bad mess is discussion worthy at this time. 

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19 minutes ago, high risk said:

I'm going to focus on the GFS para entirely, because the original schedule would have made this the operational by now....  (The delay had nothing to do with model skill; some adjustments were needed to make it run a little faster to avoid delays for downstream systems).    While it still turns everyone over to ZR/IP/RA by the end of the day     1) it comes in with an impressive thump of snow for those north of I-66 (VA) and 50 (MD)  and outside the DC Beltway    2)   has over 1" of liquid for the northern half of the area      3)   keeps areas west and northwest of I-95 below freezing for most of the day                Verbatim, it's a winter storm for most, and the northern areas (and maybe as far south as Baltimore/Howard/Montgomery/Loudoun) are still in the game for 4-6" of snow before a transition.

Booooooooo, although I'm AM north of 66 and 50 .

But seriously, I wasn't even expecting any snow here, but even we could start out as a little snow, nothing super great like up north.   This one looks like the reverse trend we always have.

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6 minutes ago, stormtracker said:

Booooooooo, although I'm AM north of 66 and 50 .

But seriously, I wasn't even expecting any snow here, but even we could start out as a little snow, nothing super great like up north.   This one looks like the reverse trend we always have.

        Honestly, I just threw in that "outside the DC Beltway" disclaimer to match details of the GFS para output that are worthless at this range.     I can't figure out why it has snow on either side of DC at the start with sleet over DC, but I'd think that DC is still in the game for at least a minor initial thump, and with the trends you note, maybe we can aim even a bit higher.  

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25 minutes ago, Bob Chill said:

Midrange has been overdoing (sometimes substantially) precip/amping. If that's the case again, a weaker storm would be an even better outcome imo. We'll see how it goes.  My gut says thurs wont be the juicy deluge as depicted right now. Still going to be a mess but more of a good mess and less of a bad mess is discussion worthy at this time. 

It would. I see the possibility. I’m praying temps don’t surge too much during the rain Tuesday and destroy the snow pack up here. That does have some bearing on the outcome Thursday too!   

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24 minutes ago, CAPE said:

GEFS weaker and easter with LP in the Ohio Valley.

 

Holler at us in the southern md/lower eastern shore sub if there starts to be appreciable winter weather threat south of Baltimore Corner, otherwise hibernation mode starts until the @Lowershoresadness storm shows up on guidance again at the end of the month.

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@Ji UKMet keeps DC below freezing for the entire storm. Main sfc reflection is along the coast instead of the OH valley. First of the more reliable guidance (though UKmet does have some wacky solutions out in time it seems) to really do that, so I'm skeptical. Like you said probably more sleet than snow but 850s don't look too bad. Probably a warm layer above that.

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@Ji UKMet keeps DC below freezing for the entire storm. Main sfc reflection is along the coast instead of the OH valley. First of the more reliable guidance (though UKmet does have some wacky solutions out in time it seems) to really do that, so I'm skeptical. Like you said probably more sleet than snow but 850s don't look too bad. Probably a warm layer above that.
There was a cluster of eps that did that. Today euro run is most important of my life
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9 minutes ago, Ji said:

Even if half is sleet...ill take this and call it a February c09f04475e401434156635dc22d5ca06.jpg

Keep an eye on that sneaky wave around the 22/23. After that don’t assume everything cuts north the end of Feb into March if the NAO does go neg again. As wavelengths shorten it gets really hard for waves to cut with a -NAO regardless of the pac pattern.  It might not be a cold pattern but odds would favor some systems sliding east under the block.  For places like leesburg and Winchester and up here that works even in a not truly cold pattern.  Historically that has worked in the cities too. There were plenty of late season snowstorms where temps the day before were very mild in the past. But I honestly don’t know about 95 anymore. I need to see some “marginal” boundary temp setups break their way just once to believe they even still can anymore.  It’s been a long time since we saw a setup like that work for DC. 

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9 minutes ago, clskinsfan said:

The GFS is pumping up the SE ridge again in the long range. Just in time to ruin our chances in late February. 

Op run at range. Dont care. Remember what I said yesterday about details at range. Even with the SE ridge going about as ape as I think is possible (seasonal trend says it will be less) the op gfs snows on central PA 3 times from Feb 22 on!  At those ranges that’s the same as a hit. An op at those leads cannot pin down the boundary within that level of geographic detail.  So long as the NAO is negative again we will have a chance for waves to get suppressed.  Don’t take my word for it go back and look at the pacific in March 2018. It was PUTRID. Didn’t matter. Same in some other March cold snowy Nina’s. It’s really hard for waves to cut with a -NAO in March. 

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