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WxUSAF

January 12-14, 2019 Storm Discussion STORM MODE

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LWX is thinking 3-6 across Eastern West Virginia and NOVA into Southern Maryland and 1-4 across Central and Northern Maryland but more uncertain there. Seems pretty reasonable, if not a bit bullish, all things considered.

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1 minute ago, wawarriors4 said:
From LWX: Forecast Discussion

An upper-level trough will eject out of the southwest overnight
Friday night into Saturday. An area of surface low pressure will
form over Texas in response to this upper-level feature, and
move into the southeastern U.S by Saturday night. Ahead of the
main surface low pressure system moving across the southeast,
another weak area of upper-level energy will be moving across
our area Saturday afternoon into Saturday night, which will
provide some extra lift ahead of the main system. At the same 
time, a strong surface high will funnel cold air in from the 
north, while southwesterly flow above the surface overruns the 
wedge of cold air. This combination of moisture and enhanced
lift will result in a period of snow starting late Saturday 
morning, continuing into Saturday night. Snow associated with
the main surface low looks to move in early Sunday morning and
continue throughout the day on Sunday. 

On Sunday, the primary surface low pressure system will slide 
by to our south through the Carolinas. The precipitation from 
this system will stretch northward and affect areas as far north
Pennsylvania. Temperatures will be plenty cold enough for snow
for the entire duration of this system, so precipitation types
will not be an issue. Latest runs of the operational Euro and NAM
are in fairly good agreement that the low will move off the 
coast around Cape Hatteras, while the operational GFS took a
slightly more southern track. However, GEFS and EPS ensembles
seem to be in fairly good agreement that more closely resembles
that of the operational Euro and NAM. While some uncertainty
remains in terms of the exact track, it seems as though most
guidance is in decent agreement. 

All of this being said, snow is likely across the entire area
Saturday afternoon through Sunday afternoon. Initial thinking is
for 3-6 inches of snow across eastern West Virginia, central 
and northern Virginia, and into southern Maryland. Amounts 
farther north are still a little more uncertain, and depend on 
how far north the system tracks, but looking at 1-4 inches 
across northern and Central Maryland. 

Pretty bullish.  3-6”?

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1 minute ago, wawarriors4 said:

LWX is thinking 3-6 across Eastern West Virginia and NOVA into Southern Maryland and 1-4 across Central and Northern Maryland but more uncertain there. Seems pretty reasonable all things considered.

agreed. its a good starting point. precip won't start falling for another two days, so there is time to work out those details. IMBY, my bar is 2". And that's mostly from the WAA thump. I'm not expecting much from the coastal portion. 

I think DC has a shot at seeing closer to 4" when all is said and done. 

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2 minutes ago, mappy said:

agreed. its a good starting point. precip won't start falling for another two days, so there is time to work out those details. IMBY, my bar is 2". And that's mostly from the WAA thump. I'm not expecting much from the coastal portion. 

I think DC has a shot at seeing closer to 4" when all is said and done. 

Yeah, it is a good starting point. I'm down neary Fredericksburg and my bar is still only o/u 3 inches, but I feel like we could do better than that. I agree DC could be near 4" when it is all over. Not sure what LWX will do in terms of headlines, maybe go watch then to advisory in certain areas and warnings in other areas or just hold off completely til late Friday. At least the winter feel will be around this weekend.

ETA: Seeing the map above, think LWX goes watch from maybe Prince William & Fauquier counties South after 0z runs tonight if all stays the pretty much the same

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2 minutes ago, wawarriors4 said:

Yeah, it is a good starting point. I'm down neary Fredericksburg and my bar is still only o/u 3 inches, but I feel like we could do better than that. I agree DC could be near 4" when it is all over. Not sure what LWX will do in terms of headlines, maybe go watch then to advisory in certain areas and warnings in other areas or just hold off completely til late Friday. At least the winter feel will be around this weekend.

i'm hopeful the waa thumb comes in better. but its been drier today on the models so that has me hedging my bets on accumulations, at least up my way. but with enough lift, and orthographic help, i can see higher elevations squeezing out more from the waa than lower elevations. 

ive given up on the coastal portion. it was never looking that great to begin with and models have is so so flat and strung out. i dont have a shot of seeing anything from that with it being so far south. 

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3 minutes ago, PivotPoint said:

Bob,

I know this questions gets kicked around a lot at leads like these but whats your opinion on the ensembles 60hrs out with this event and their usefulness. They seem jumpy with this event especially and one model seems to pick up on an idea then lose it, then another one picks up on the opposite idea. Do we just have to start choosing sides with one of the ops and make a reasonable assumption that it is the one handling the evolution the best? 

 

It's pretty easy honestly. Just blend the ops and it's a well agreed upon .1 - .4 from north to south. Southern zones look good for more. If i was making a forecast i would do exactly that. Something like 1-3" far northern zones, 2-4 in the meat of our area, and 5"+ across the bullseye area. Forecasters have another 24 hours before headlines need to be raised.  Should be more clear by then.

There is always boom/bust potential. Weak waa and no coastal enhancement amd its a bust. Boom can come from 2 different scenarios. Strong surge of waa precip and totals go up. Or coastal gets involved and enhances banding as it departs. The waa surge will be interesting to watch for another 24+ hours. Once the shield develops ops will have a better handle on how it progresses. Could break in our favor. Euro op and control just hinted at it.

The coastal enhancement is much more complicated. That has boom/bust potential at very short leads. Once the system is organzied in the plains and upper air features are mostly figured out we should probably see consensus on that piece but it's always tricky. 

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1 minute ago, mappy said:

i'm hopeful the waa thumb comes in better. but its been drier today on the models so that has me hedging my bets on accumulations, at least up my way. but with enough lift, and orthographic help, i can see higher elevations squeezing out more from the waa than lower elevations. 

ive given up on the coastal portion. it was never looking that great to begin with and models have is so so flat and strung out. i dont have a shot of seeing anything from that with it being so far south. 

100% agree, up your way, I think you'll maximize as much as you can in this storm the WAA and get your 2" (maybe even 3"). You'll probably do better up there than down my way in EZF during the WAA part of system, Fredericksburg scores on the developing coastal is my feeling at thats where we pick up maybe 3-5"+ after getting maybe 1" from WAA.

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Just now, wawarriors4 said:

100% agree, up your way, I think you'll maximize as much as you can in this storm the WAA and get your 2" (maybe even 3"). You'll probably do better up there than down my way in EZF during the WAA part of system, Fredericksburg scores on the developing coastal is my feeling at thats where we pick up maybe 3-5"+ after getting maybe 1" from WAA.

yup, i can see that happening. enjoy what you get! :) 

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5 minutes ago, Bob Chill said:

It's pretty easy honestly. Just blend the ops and it's a well agreed upon .1 - .4 from north to south. Southern zones look good for more. If i was making a forecast i would do exactly that. Something like 1-3" far northern zones, 2-4 in the meat of our area, and 5"+ across the bullseye area. Forecasters have another 24 hours before headlines need to be raised.  Should be more clear by then.

There is always boom/bust potential. Weak waa and no coastal enhancement amd its a bust. Boom can come from 2 different scenarios. Strong surge of waa precip and totals go up. Or coastal gets involved and enhances banding as it departs. The waa surge will be interesting to watch for another 24+ hours. Once the shield develops ops will have a better handle on how it progresses. Could break in our favor. Euro op and control just hinted at it.

The coastal enhancement is much more complicated. That has boom/bust potential at very short leads. Once the system is organzied in the plains and upper air features are mostly figured out we should probably see consensus on that piece but it's always tricky. 

Got it. Yea, good points.

I think the mins are pretty well set for 2" across dc metro, 1" Balt and NE MD, 3" from Richmond to EZF. Booms would probably be 6", 5", and 8" respectively.

Boom potential is probably best to wait and see when the precip shield develops and we can see where the best banding/growth settles in.

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54 minutes ago, SnowGolfBro said:

The Euro looks good for many of us South of DC. Significantly better than any model looked for my area on 12-9.  And i scored an inch and people just 25 miles to my South had 4-6 inches.  This is still being worked out by the models and even the Northern crew could get in on the good stuff this time.

Likewise. We ended up with anywhere between 3-5" in Central Calvert. Literally 15-20 min north and there was nothing. 

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3 minutes ago, wdavis5784 said:

Likewise. We ended up with anywhere between 3-5" in Central Calvert. Literally 15-20 min north and there was nothing. 

Right and the jackpot on the models is significantly farther North than the December storm, hence my optimism. Doesn’t mean we can’t get screwed but it’s worth noting that those of us South of DC have a decent shot at a warning event even based on current guidance

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3 minutes ago, SnowGolfBro said:

Right and the jackpot on the models is significantly farther North than the December storm, hence my optimism. Doesn’t mean we can’t get screwed but it’s worth noting that those of us South of DC have a decent shot at a warning event even based on current guidance

One thing I would say about the December storm...Jackpot was well into double digits so when the qpf did start shifting north there was an awful lot of juice to play with....but yes at this point my house was in the partly sunny portion of the event so already being in the moisture gives me hope

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4 minutes ago, SnowGolfBro said:

Right and the jackpot on the models is significantly farther North than the December storm, hence my optimism. Doesn’t mean we can’t get screwed but it’s worth noting that those of us South of DC have a decent shot at a warning event even based on current guidance

I'm really optimistic right now. I'd take the Euro/UK/CMC/FV3 over the GFS and NAM any day. Of course I'm always worried it could fall apart at short range but I think it's reasonably likely (~70%) that I at least meet my bar of 3". 

Edit: since the NAM looks like it's making a significant improvement it's just the GFS and GEFS vs everything else. B)

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1 minute ago, leesburg 04 said:

One thing I would say about the December storm...Jackpot was well into double digits so when the qpf did start shifting north there was an awful lot of juice to play with.

Yea, there's really nothing similar to 12/9 with the progression and type of event. They both share a tight northern cutoff but the reasons for potential boom scenarios are pretty different. The only thing Dec needed was less confluence. This one needs complicated coastal enhancement in a relatively hostile upper level setup 

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7 minutes ago, Woodbridge02 said:

I'm really optimistic right now. I'd take the Euro/UK/CMC/FV3 over the GFS and NAM any day. Of course I'm always worried it could fall apart at short range but I think it's reasonably likely (~70%) that I at least meet my bar of 3". 

Edit: since the NAM looks like it's making a significant improvement it's just the GFS and GEFS vs everything else. B)

not sure I agree with that.  h5 looks flatter to me than 12z.  slightly but I noticed it.  of course you can still have a better surface which what we mostly care about.  but it wont have the surface right just yet...not the NAM. 

 

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1 minute ago, Beachin said:

You start to see a trend on the NAM

namconus_apcpn_neus_fh69_trend.gif

The trend is that the nam is looking more like other more reliable guidance

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1 minute ago, Beachin said:

You start to see a trend on the NAM

namconus_apcpn_neus_fh69_trend.gif

It’s simply catching up to the rest of the modeling...the 12z run was horrendous 

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2 minutes ago, wawarriors4 said:

18z NAM definitely has more precip. The 0.5" qpf line is around EZF and DCA is ~0.3" at hour 69.

it is.  i'm a little concerned about having such a strong high beelining to the southeast like that, but if the front end stuff is as depicted, then it's game on.

also...just checked gfs for next weekend...intriguing.

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LWX also modified how they will do the Winter Weather Outlook for the week... interesting dividing lines.

The Shenandoah Valley in me also resents being named the "Piedmont."

D3_WinterThreat.png

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5 minutes ago, Chase said:

LWX also modified how they will do the Winter Weather Outlook for the week... interesting dividing lines.

The Shenandoah Valley in me also resents being named the "Piedmont."

D3_WinterThreat.png

That’s mostly for the WAA.  If the coastal were to ramp up close enough to the coast it would be after 7 am Sunday and could be more impactful with less confidence

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41 minutes ago, WVclimo said:

To add illustration to the AFD:

StormTotalSnowWeb.thumb.png.0cccd5ee5d7c16134ea2c5aa3c371b1c.png

Right along the lines of what I'm thinking for the northern tier. 1-2" sounds like a good call. If the coastal gets going then southern areas will do better than what they're currently saying.

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1 hour ago, Bob Chill said:

Probably doesn't mean much but there are quite a few more solutions that turn up the coast compared to 0z. If I lived in SNE I wouldn't totally give up after looking at the 12z eps. Most that make the turn are slower and lag trailing energy that is able to avoid the departing hammer and make a run towards the cape. Seems very unlikely to happen based on all op guidance. You never know though. 

What if that energy crashing southern cali that llinks up and totally crushes the lead wave ends up becoming a caboose.  Lol 

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10 minutes ago, nj2va said:

That is a great map in my opinion at least looking at NOVA/DC/etc

At this point in HoCo, my bar is set at flurries. :yikes:

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I'm confused as to why DC would experience any UHI effect in this scenario given temps in the mid-20s? Why would that limit our snow total?

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