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Thanksgiving Eve Coastal


Coach McGuirk

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Agreed. Perfwct track and about 1.1" for DC. Still Temp issues but very pretty. Xbox on board now too though not as wet. Canada only hold out

Low-level temps are a touch warmer on this run vs. 12z.  Very borderline below 925 between 12-18z.  After 18z it looks fine for everyone. 

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If we want a wet event there is probably no avoiding issues for Most of us.

 

Yep, all too true.  Especially for this time of year and coming off a couple or so very warm days.  I know that "prior warmth" may not be nearly as big a deal but it's not like temperatures will plummet into the 20s (or less) like they did this past January and March for those events that occurred after warm highs.  Still, getting a good coating in late November is quite the feat here.

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Going to have to watch the 500mb energy coming through on the backside of the trough behind the coastal.  It makes a nice pass through VA.  I could easily see the snow shutting off Wednesday evening and then another burst happening 6-12 hours later to provide another coating-1".  Did the Euro show anything with that?

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Going to have to watch the 500mb energy coming through on the backside of the trough behind the coastal.  It makes a nice pass through VA.  I could easily see the snow shutting off Wednesday evening and then another burst happening 6-12 hours later to provide another coating-1".  Did the Euro show anything with that?

 

That's an interesting scenario...in fact I was curious about that second vort coming through afterward, it's been showing up for awhile now.

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SFC at DCA and based on 18z GFS soundings

 

9z - 40 - def rain

12z - 37 - def rain

15z - 35 - probably rain

18z - 33-34 - probably snow

21z - 33 - def snow

0z - 33 - def snow

 

so about 0.4" would fall as snow...with some accumulation...I could see 2" for the city....maybe 3" for upper northwest...this is based on the model...not my forecast

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SFC at DCA and based on 18z GFS soundings

 

9z - 40 - def rain

12z - 37 - def rain

15z - 35 - probably rain

18z - 33-34 - probably snow

21z - 33 - def snow

0z - 33 - def snow

 

so about 0.4" would fall as snow...with some accumulation...I could see 2" for the city....maybe 3" for upper northwest...this is based on the model...not my forecast

 

Pretty reasonable taking the model verbatim.  Not anything crippling, but given the time of day and the travel, you know even that would be a potentially big problem (not Commutageddon levels...how about Gobble-gobble-geddon?).

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Pretty reasonable taking the model verbatim.  Not anything crippling, but given the time of day and the travel, you know even that would be a potentially big problem (not Commutageddon levels...how about Gobble-gobble-geddon?).

Surely this will lead the evening national news on both Tuesday and Wednesday and maybe Monday if it looks good then.

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The whole 12hrs of rain changing to snow doesn't make sense. The cold air is better on the front of this setup, and there is a weak 850mb crash well after the precip shuts off.  

 

My guess is we get a thump snow after maybe 20 minutes of evap cooling and then change back to rain towards the end as the precip lightens.

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LWX has updated its forecast maps...

StormTotalSnowRange.png

We took a good amount of feedback into account and improved these maps. We took out the wording of 10 and 90 percentile and left as min and max potential since that is the message we want to get across to our customers...a goal post of possibilities. Color scheme has been updated. Other change from WPC was to increase the number of ensemble members to 57 in contrast to 32 from last year. Extra 25 members are all random runs of the euro ensembles....better weighing vs a heavy sref base. We still use WPC 10 and 90 percentile as our starting point then tweak from there.
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We took a good amount of feedback into account and improved these maps. We took out the wording of 10 and 90 percentile and left as min and max potential since that is the message we want to get across to our customers...a goal post of possibilities. Color scheme has been updated. Other change from WPC was to increase the number of ensemble members to 57 in contrast to 32 from last year. Extra 25 members are all random runs of the euro ensembles....better weighing vs a heavy seed base. We still use WPC 10 and 90 percentile as our starting point then tweak from there.

 

Thanks for the explanation of changes...appreciate your insight into the products and the storm.  I like that you are including Euro members into the product.  

 

I think its a good first forecast given current guidance.

 

ETA:  Once the new GFS is formally put into production, will you eventually look to include members in the forecast?  Higher resolution should support better results.  

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We took a good amount of feedback into account and improved these maps. We took out the wording of 10 and 90 percentile and left as min and max potential since that is the message we want to get across to our customers...a goal post of possibilities. Color scheme has been updated. Other change from WPC was to increase the number of ensemble members to 57 in contrast to 32 from last year. Extra 25 members are all random runs of the euro ensembles....better weighing vs a heavy sref base. We still use WPC 10 and 90 percentile as our starting point then tweak from there.

Awesome, glad you're back!

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The whole 12hrs of rain changing to snow doesn't make sense. The cold air is better on the front of this setup, and there is a weak 850mb crash well after the precip shuts off.  

 

My guess is we get a thump snow after maybe 20 minutes of evap cooling and then change back to rain towards the end as the precip lightens.

 

I don't see that at all....at least here in DC...950mb to the surface is pretty bad until late morning..

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We took a good amount of feedback into account and improved these maps. We took out the wording of 10 and 90 percentile and left as min and max potential since that is the message we want to get across to our customers...a goal post of possibilities. Color scheme has been updated. Other change from WPC was to increase the number of ensemble members to 57 in contrast to 32 from last year. Extra 25 members are all random runs of the euro ensembles....better weighing vs a heavy sref base. We still use WPC 10 and 90 percentile as our starting point then tweak from there.

 

I presented to DC council with Steve Zubrick a week ago and he discussed it a bit

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