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January 2/3 Event - Disco., Nowcasting, and Obs.


wxmeddler

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If I only had access to h5 vort panels I would look at hr 30-36 and expect at least some snow. Comparing 36 from 12z to 48 from 0z it's better. Sharper and more dig. I guess we can totally blow it here but there are some obvious signs of potential. 

This storm, if I remember correctly was modeled 7-10 days ago to be a negatively-tilted large storm. I know it's not that now but where does one look for that negative tilt? 500 maps?

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Is the CWG forecast that post talking about a low/medium chance of scattered snow showers?

No,  Jason will be posting one later today with a map.  I think we have you in 2-4 and DC in 1-2 or something like that.  Out towards me we may be underdone but last time i had Jason nudge the lines down my way was a unmitigated disaster so I wasn't going to make such a suggestion.

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No,  Jason will be posting one later today with a map.  I think we have you in 2-4 and DC in 1-2 or something like that.  Out towards me we may be underdone but last time i had Jason nudge the lines down my way was a unmitigated disaster so I wasn't going to make such a suggestion.

 

yeah....if the euro is right, once the low transfers and amplfies, it is accumulating on the boardwalk in Ocean city...probably no reason to give you less snow than DC

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No,  Jason will be posting one later today with a map.  I think we have you in 2-4 and DC in 1-2 or something like that.  Out towards me we may be underdone but last time i had Jason nudge the lines down my way was a unmitigated disaster so I wasn't going to make such a suggestion.

That sounds pretty reasonable. Still the GFS hanging out there showing even 1-2 being a bit a stretch.

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from a nowcasting perspective we need to watch pressure falls.

 

http://weather.unisys.com/surface/sfc_con.php?image=3p&inv=0&t=cur

 

the longer we see less pressure falls north and east of OBX the better chance we have at a better outcome... the low out front is what kills us... the h5 is decent enough for us to get a fairly good event at this point without that low in front screwing us up and stealing moisture out from the best dynamics. Another benchmark to watch will be rain this evening/overnight. If we see rain developing across SE VA, this will surely overperform.

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If I only had access to h5 vort panels I would look at hr 30-36 and expect at least some snow. Comparing 36 from 12z to 48 from 0z it's better. Sharper and more dig. I guess we can totally blow it here but there are some obvious signs of potential. 

the trough digging further south was discussed earlier today and yesterday on another site.The analysis appears correct

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99% of us are snow freaks.  This system is interesting in other ways.  The looming cold has been discussed frequently here but let us give it a bit more thought.

 

The AFD from Mt. Holley is really interesting.  They seem fascinated with the potential energy associated with the counterclockwise large scale rotation from the developing storm to suck impressive cold into the region.   Here is their climate records discussion:

 

 

.CLIMATE...
FOR A PERSPECTIVE AT THIS FORECAST JUNCTURE...

THE COLD TEMPERATURES FORECAST SATURDAY MORNING WILL BE THE
COLDEST AT LEAST DATING BACK AS FOLLOWS:

OUR LATEST FORECAST FOR SATURDAY MORNING JANUARY 4, 2014:

KILG AROUND 7F. LAST TIME WAS 1/16-17/2009 AT 7 AND 5 RESPECTIVELY.
KPHL AROUND 7F. LAST TIME WAS JAN 17, 2009.
KABE AROUND 0F. LAST TIME THIS COLD WAS JAN 24, 2011.

FOR THOSE LOOKING AT RECORDS WITH A PROBABLE FRESH SNOW COVER TO
ASSIST MAGNIFYING THE INCOMING LATE WEEK COLD AIRMASS...

1/3 1/4
KACY...-2 1879 0 1918 POR 1874
KPHL...-3 1879 2 1918 POR 1872
KILG...+4 1918 -1 1918 POR 1894
KABE...+6 1945 -4 1981 POR 1922
KTTN...-4 1879 -1 1918 POR 1865
KGED...+8 1962 4 1979 POR 1948
KRDG...+1 1918 -5 1981 POR 1869
KMPO...-7 1904 -23 1981 POR 1901

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99% of us are snow freaks.  The looming cold has been discussed frequently here but let us give it a bit more thought.

 

The AFD from Mt. Holley is really interesting.  They seem fascinated with the counterclockwise large scale rotation from the developing storm to suck impressive cold into the region.   Here is their climate records discussion:

 

there is a thread for the cold

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Jason wrote it,  I just supplied the quote.  It's low confidence forecast. 

 

I don't see how anyone can have a high confidence forecast in our area yet. It's a complicated and evolving situation. I thought the boom and bust stuff was fine because as stated in the article, revision will likely be necessary later. 

 

Even tomorrow morning it might be tough to have a high confidence forecast. I hope to get 2" and DCA to break the streak. And I hope you do better than dca and me. I'd be happy with an inch so at least it can blow around and make Fri look and feel like the arctic tundra before it all gets washed down the sewer on sun-mon. 

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There is really no beating around the bush...It is a stellar run....biggest impediments are temps and how quickly we changeover/go below freezing...and the worry that it totally over amplifies

Nice run. Would make most of us around here happy. The Comeback comeback storm is alive. Who is buying for happy hour?

MDstorm

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there is a thread for the cold

Yeah but the looming cold will modify the impact of the snow that lingers.  I'm thinking that even with modest accumulations, the non-traveled portions of roads as well as sidewalks and driveways may have a nasty coating of dirt and road salt and cast iron icy snow/ice coating that lingers for days.  With even modest accumulations, traffic may be impacted Friday and well into the weekend as the road surfaces may be too cold for some of the melting chemicals to work. 

 

This has already been an over-performing winter for ground cover in N. MD.

In my area of N-central Maryland, we've already had about 10 days in December where the lawns were well covered with snow and now more to come in early January.  While the snow hasn't been deep, we've maintained above average ground cover for longer than most winters, already.

 

Anyhow, nice discussion everyone.

 

and on to the UKMET:

 

 

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At this point I think there are several things we need to watch on the radar. I have annotated two maps to illustrate this. Sorry for using WeatherBug maps... I work there now so feel somewhat obligated to do so, even though I admit we don't have the best radar in the world.

 

The first map below illustrates what I think most will agree is the model consensus. The key areas to note are the red circled area, being the impulse that is causing the pesky double low structure that is ruining what would otherwise be a MECS. The current model consensus is for the northern edge of that rain sheild to come off the east coast of NC... a very ENE orientation in precip. The two blue circled areas indicate our two impulses, the southern stream influence, currently over S TX, and the northern stream main vort, currently KS. Current model depictions forecast phasing to begin to occur when both impulses are over eastern TN. Because of this, precip begins breaking out across WV and MD and intensifies in to Eastern MD and S PA. There is also less influence from the gulf as the flow from the impulse over the southeast flattens the flow and does not allow the trough to sharpen and the PVA intensify. Eventually this impulse washes out east of Cape Cod, as the shortwave nears the coast and low pressure begins to take shape along the baroclinic zone. By then it is too late however for the DC region to capitalize and areas further north and east jackpot.

 

post-3403-0-81887500-1388603244_thumb.pn

 

However, lets consider this alternate possibility (which right now I'd say has about a 15 % chance of occuring). Lets assume the flow out in front is more NorthEast and precip tonight and tomorrow morning reaches SE VA. This would likely cause the initial low development to occur closer to the coast and further south. Lets also say the phasing occurs slightly earlier, over W TN instead of E TN because the NS vort takes a slightly further S path, and also, given the flow is more NE oriented, the SS vort takes a slightly northeast path. Then the situation changes for the DC area. Now we have a healthy precip shield we are not waiting to develop overhead. In addition, because of the difference in flow orientation, we pick up more moisture from the GOM (the yellow line) so we are dealing with better dynamics beginning to develop. The trough sharpens slightly more and we get more concentrated PVA. This naturally would cause the initial impulse to wash out, and while we would still have the double low strucutre, much more energy would be concentrated where the greatest PVA is... better lift, better dynamics and stronger low (this is very similar to the great euro solution we saw a few days ago, although with a slightly different evolution). This would move the jackpot area about 100 mi SW and BWI - DCA would be the jackpot.

 

The upper potential of this system is still limited though however due to the fast progressive flow and lack of blocking... by jackpot potential, I mean here 4-6 with lollis to 8 or 9, but still a healthy SECS for the area.

 

Something to think about, and not that far out of the realm of possibility. Radar tonight and early tomorrow morning will be telling. If the depiction is closer to that below, I'd begin to get interested in something nearing WSW criteria

 

 

post-3403-0-52876300-1388603256_thumb.pn

 

Of course, this is just one possible evolution. With so many factors at play, this is an incredibly complex system, and many other variables may factor in... those are just the ones I am seeing at the moment.

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