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February 12-13 Storm, Part III: Trilogy ends and then Obs thread soon!

stormtracker

By stormtracker,
in Mid Atlantic

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WxMan1

WxMan1

Posted
Posted

I was going to more or less say the same thing.  There's nothing "magical" about issuing one now, and the precip isn't due to get here until tomorrow evening.  Places to the southwest of LWX's area will be getting snow earlier, thus they've gone with a warning there now.  There has been a watch up for a day now, that's clearly given people a big heads-up.  Actually, I'm surprised they issued the watch yesterday afternoon, rather than waiting until this morning, but not a big deal.

 

Exactly.

 

I can say from my experience at WFOs that you do NOT want to box yourself (and surrounding offices) into a corner by coming out with a warning too early.  What would be the advantage?  The beauty about a WATCH is you as a forecaster only need to be 30-50% confident of meeting warning criteria (per the NWS Directives).  So, in essence, a watch can transition to a warning, advisory, or even on occasion, NOTHING as when the models shift considerably.

 

Also, the advantage of a watch is you can be VAGUE VAGUE VAGUE.  Lot's of "possible" or "potential" terms, and you can avoid specific snowfall accums and just focus on the warning criteria ("potential for 5 or more inches of snow").  

 

YES folks would love to have 24+ hours of lead time before an event.  But...isn't that what a WATCH is for?  From a verification standpoint, there is NO advantage being the "first with the worst" and coming out with winter storm warnings too early.  

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yoda

yoda

Posted
Posted

 

Its still snowing 7pm Thur there as well.. even close to 10pm

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usedtobe

usedtobe

Posted
Posted

wow...Canadian ensemble mean is a perfect track.....whoa....

 

and the OP is the best with the front thump...well over 1" by 12z thursday

Each piece of model output just confuses me.  If the rgem and nam are right, we'll be pummelled and have lots of snow on the ground by Thursday morning regardless of any possible mixing issues. 

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WxMan1

WxMan1

Posted
Posted

WXMAN1.....is this thundersnow sounding.  I can't tell whether it is unstable or neutral  above 600mb but think with strong frontogenesis you'd probably have CSI so it might not matter.  Other mets weigh in if you have an opinion.

 

attachicon.gifCWG_THUNDERSNO_FEB_2014.png

 

Yes indeed Wes...and look which layer that's in -- right within the max dendritic growth zone, i.e. between -10 and -20C. Not a bad lapse rate with the theta-e profile there.  All we need is the lift within that layer, and (then) we can "extract" that "potential" instability. 

 

AND...this is probably why there *has* to be a probability -- at least a 10-25% -- of at least 12" even east of I-95.  Convection with intense snowfall rates instead of a mix/rain/drizzle (dry slot) is a game changer obviously..

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BHweather

BHweather

Posted
Posted

 PSUBlizzicane2007: Read the other posters first before you post...then you will see that it would be unwise to make any real prediction right now given model inconsistency. 4" would be highly likely right now...more starts to become questionable.

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RickinBaltimore

RickinBaltimore

Posted
Posted

I think it's safe to say that even the models haven't given a consensus yet. There's still some indecision as to what's to come obviously. I'd like to see if the models move to a closer agreement at 0z. That Euro model (while usually pretty reliable) does seem an outlier this time. Either that or I got on weenie glasses.

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BTRWx

BTRWx

Posted
Posted

Exactly.

 

I can say from my experience at WFOs that you do NOT want to box yourself (and surrounding offices) into a corner by coming out with a warning too early.  What would be the advantage?  The beauty about a WATCH is you as a forecaster only need to be 30-50% confident of meeting warning criteria (per the NWS Directives).  So, in essence, a watch can transition to a warning, advisory, or even on occasion, NOTHING as when the models shift considerably.

 

Also, the advantage of a watch is you can be VAGUE VAGUE VAGUE.  Lot's of "possible" or "potential" terms, and you can avoid specific snowfall accums and just focus on the warning criteria ("potential for 5 or more inches of snow").  

 

YES folks would love to have 24+ hours of lead time before an event.  But...isn't that what a WATCH is for?  From a verification standpoint, there is NO advantage being the "first with the worst" and coming out with winter storm warnings too early.  

Even with all the improvements in forecast capabilities over the years, I feel like early issued Warnings defeats the purpose of its definition. Uncertainty should not be overlooked. "This product is issued by the National Weather Service when a winter storm is producing or is forecast to produce heavy snow or significant ice accumulations" http://w1.weather.gov/glossary/index.php?letter=w

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Deck Pic

Deck Pic

Posted
Posted

Each piece of model output just confuses me.  If the rgem and nam are right, we'll be pummelled and have lots of snow on the ground by Thursday morning regardless of any possible mixing issues. 

 

Wes...from what I can tell, the worst model (GFS) still gives us 3-4" on the front end, and every other model, 6"+....so I think we are good on the front end...lets see what the GFS says in 20

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