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Presidents Day storm Part 2


Ji

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The elitists of this forum can continue their contemptuous attitude about 'weenies', but the fact is that it's the Euro that is coming around to the NAM snow totals.  The globals are terrible at modeling CAD.  There was an LWX guy last night on this forum who basically said the NAM is a better model for this type of situation.

 

Anyway, back to your regularly scheduled Euro-hugging.

one primary issue is that you utilized past tense, "the NAM was right again", which is innaproriate as that would infer reanalysis of a completed event

perhaps wait til Tuesday for declarations of model skill

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Pretty sure no one has a clue which model is correct. Nor should anyone be thumping their chest over any one model. Unless I slept through the event and it's over, which is possible... I did drink a lot of wine last night.

 

the para HCM(Hug the Coldest Model) has been solid all week.  It has shown tons of QPF(Quantitative Posts of Failure) all week from some who just insist that cold always win

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It is simply amazing that some plastic, metal, and electricity can tell me that there will be a winter storm in 3 days and then it happens.

We like to be mean to the GFS and the CMC generally deserves it but today's NWP is one of the great scientific successes of our time I think.

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Advisories for the watch area, expanded the WWAs one zone east:

 

 

 

...WINTER WEATHER ADVISORY IN EFFECT FROM 1 AM MONDAY TO 10 AM
EST TUESDAY...

THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS
ISSUED A WINTER WEATHER ADVISORY FOR SNOW...SLEET AND FREEZING
RAIN... WHICH IS IN EFFECT FROM 1 AM MONDAY TO 10 AM EST TUESDAY.

* PRECIPITATION TYPE...SNOW...SLEET AND FREEZING RAIN.

* ACCUMULATION...3 TO 5 INCHES OF SNOW AND SLEET. AROUND ONE-TENTH
OF AN INCH OF ICE FROM FREEZING RAIN.

* TIMING...SNOW WILL BEGIN BETWEEN 1 AND 3 AM MONDAY MORNING. SNOW
WILL CHANGE TO SLEET AND FREEZING RAIN MONDAY AFTERNOON...AND
ALL FREEZING RAIN MONDAY EVENING. PRECIPITATION WILL GRADUALLY
CHANGE TO RAIN LATE MONDAY NIGHT INTO TUESDAY MORNING. 
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the para HCM(Hug the Coldest Model) has been solid all week.  It has shown tons of QPF(Quantitative Posts of Failure) all week from some who just insist that cold always win

 

it's not just "cold", though.  this is an arctic airmass, so i think it's been reasonable to have some doubts about how quickly the cold air gets scoured out.  it's 18 degrees and snowing in indianapolis right now.  generally, i think the idea hasn't changed the last 2 days.  how much precip can we score while temps are cold enough to snow?  that's the question.

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It's actually been quite steady on temps unless we're focused on a few hours as warmer air comes in.

 

Below is a snapshot for 6z Tue since that's when most of the area has just risen above freezing per the Euro. A little cooler with time but nothing huge. Arguably 0z temps (http://imgur.com/a/r9Toa) have been even steadier. Again, looking at a few hours difference here with any changes at most. The low warms things up at some point on approach regardless.  As noted by Wes and others the main difference here is more liquid early.

 

People forget the globals are getting pretty high resolution these days particularly the Euro. This might become the new need more sampling argument soon.

 

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But the precip start time is a hugely important detail that the NAM has been rock-solid on.  It's been bringing in the snow at around 03Z on Monday for at least the past 8 runs.  Meanwhile the GFS and Euro have been holding the precip back, which is why their snow totals have been lower.  In a situation like this where we know the cold is going to get scoured out, the precip start time is perhaps the most important variable in how much snow we get.  And on this, the Euro caved to the NAM - big time.

 

Yes, the Euro had the better model for the overall synoptic evolution, but weak on some details that are also very important in this particular situation.

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LWX map is pretty good though maybe high in spots? Not sure it's worth trying to pinpoint winners overall around here. Cold going in will level the field.

Yep. Some areas will go lower and some will be higher in the end with their forecast. ;)

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Comments like that are why I post less than I used to. 

Just wanted to say I think the vast, vast majority of posters here have nothing but the highest respect for you, Wes. I also think there is also a small army of folks such as myself who rarely post because we feel we don't have the in-depth knowledge to add to the discussion, but we search for your posts because we learn every time you weigh in. For us, you are invaluable. I know that the negative comments may sting, but please don't let them drive you away from sharing your knowledge and experience. Thanks!

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Just wanted to say I think the vast, vast majority of posters here have nothing but the highest respect for you, Wes. I also think there is also a small army of folks such as myself who rarely post because we feel we don't have the in-depth knowledge to add to the discussion, but we search for your posts because we learn every time you weigh in. For us, you are invaluable. I know that the negative comments may sting, but please don't let them drive you away from sharing your knowledge and experience. Thanks!

As a lurker I approve this message.

Sent from my SM-N920V using Tapatalk

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Forecast for DC Proper for Monday/Tuesday - Confidence Level - Medium

Midnight to 6am - Intermittent light snow becoming steadier toward dawn. Temps - low 20s.

6am - 2pm - Steady Light snow becoming moderate at times especially mid morning to early afternoon. Temps - mid to upper 20s

2pm - 6pm - Snow mixing with and changing to all sleet. Temps - upper 20s to low 30s.

6pm - Midnight - Sleet mixing with and tapering to light freezing rain/drizzle. Temps near 32.

Midnight - 5am - Light rain/drizzle with temps rising from near freezing to near 40.

5am - 3pm - Moderate to Heavy Rain, tapering to light rain/drizzle and ending. Temps rising into the mid to upper 40s.

Total accumulation - 2-3" with a healthy crust on top. However it will take a major beating on Tuesday.

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