Presidents Day storm Part 2

[Deck Pic]

It has some similar features but that pattern was not amplified at all over CONUS. Was sort of just a moisture bomb running into cold air. Barely even a low pressure. Admittedly, this event is considerably weaker at the surface today than it was a few days ago which seemingly keeps the door open a bit. 

 

I think the door is open to something.  That something might not be that great.  We can't take advantage of an over performing air mass if it is dry

 

I think the euro probably won't be that great and probably won't clarify much.  Hope I'm wrong

[Ger]

He's probably talking about 2/21/15, and the situations are remarkably similar in a way, but we weren't sweating the front end thump as much.  It was a better precip delivery scenario.  But super cold fresh air mass, retreating high.  Low was to our west.  We ended up staying cold even here in the city longer than forecast, and it was probably the best icing scenario down here I'd seen in years. Treacherous to walk around.  I got 3.5" before the flip.

 

He's probably talking about 2/21/15, and the situations are remarkably similar in a way, but we weren't sweating the front end thump as much.  It was a better precip delivery scenario.  But super cold fresh air mass, retreating high.  Low was to our west.  We ended up staying cold even here in the city longer than forecast, and it was probably the best icing scenario down here I'd seen in years. Treacherous to walk around.  I got 3.5" before the flip.

Yes

[AnthonyDabbundo]

So the GFS and CMC, which were easily furthest east before, are now further west than the UKMET, which travels right up I95.... gotta love the model consistency

[Ian]

I think the door is open to something.  That something might not be that great.  We can't take advantage of an over performing air mass if it is dry

 

I think the euro probably won't be that great and probably won't clarify much.  Hope I'm wrong

This air mass is not nearly as good as last year. We set a sounding record (since 1948) for Feb on the 20th at 12z with -26.9C. Tonight was 21.9C and according to modeling we won't beat that in the morning. Pretty quick in and out with the "near extreme" cold. It could be enough, but that one peaked around here 24 hours out. This one peaked about 36-48 out and was considerably milder.

 

There's of course a reason for the conventional wisdom about CAD etc around here and it's certainly worth adding into a forecast.

[Deck Pic]

This air mass is not nearly as good as last year. We set a sounding record (since 1948) for Feb on the 20th at 12z with -26.9C. Tonight was 21.9C and according to modeling we won't beat that in the morning. Pretty quick in and out with the "near extreme" cold. It could be enough, but that one peaked around here 24 hours out. This one peaked about 36-48 out and was considerably milder.

 

There's of course a reason for the conventional wisdom about CAD etc around here and it's certainly worth adding into a forecast.

 

Yes.  That was an upper end event given the setup in terms of what happened after the flip. Temps not dissimilar, but that was colder to start and more entrenched which is probably why we pulled it off in DC.

[Ian]

Euro looks similar but a hair slower on transition.. like an hour or two prob.

[Deck Pic]

Euro is probably a 5pm flip for DC with an onset of precip around 5am.  Problem is only about 0.2" falls in that period.  So maybe 2" for the city then flip. Below freezing until 9pm, and then 45 degrees by 1am...lol

[Deck Pic]

Euro looks similar but a hair slower on transition.. like an hour or two prob.

 

It's a slight improvement on the front end but could be noise.

 

 

12z snow map

 

 

0z snow map

 

[Amped]

Euro nearly identical to the 18z gfs at 72hrs.

[ers-wxman1]

Pretty good consensus now for 2-4" of snow before the changeover...

[nflwxman]

Pretty good consensus now for 2-4" of snow before the changeover...

 

The bar was never really that high with this one outside of western VA.  2-4" would be a nice event.  I know we are in an age of big storms, but something about a medium sized messy event reminds me of the 90s.

[Inverted_Trough]

The bar was never really that high with this one outside of western VA.  2-4" would be a nice event.  I know we are in an age of big storms, but something about a small medium sides messy event reminds me of the 90s.

Also consider that recently we went about three years without having a snowfall event exceeding 2 inches.  We'd have killed for an event like this.

[Kevin Reilly]

Many of the ice events I've seen were too fast in retreating the cold air

It would be interesting to go back to past icing events and see the state of the Nao whether it was a neg neu or pos phase as compared to whats coming in

[BristowWx]

From this untrained and weary eye, 6z NAM seems to hold firm almost identical from 0z...in fact I think the CAD might be even a tad deeper and holds maybe another hour or two from fall line west...and precip is light for while until rain comes so ice seems on the table. But I could be wrong on all of this. Back to bed

[showmethesnow]

06Z 12 k NAM is a touch lighter on snowfall from west central VA up through central MD with total qpf somewhat lighter through that region as well. There was a slight shift north with the WAA strip of snow as well. Though initially colder the NAM comes in warmer then the 00Z as the main bulk of the storm arrives so ice looks minimal through the 95 corridor with very light precip while temps cooperate. By the time the heavier precip begins to move in we are already seeing 32 degrees which is the kiss of death for ground surfaces due to latent heat release (elevated surfaces can still see some icing though minimal). Per the NAM the areas favored for any significant icing will be the farther northern and western regions.

[Wonderdog]

6z GFS has light snow moving into DC Monday between 6-10am; looks to start to changeover late Monday afternoon and then to rain later Monday night. SLP goes from TN to Ohio to NY state, No where near I-95. I don't know if we get much of a front end dump.

[arlwx]

The latest from LWX:

 

.SHORT TERM /MONDAY THROUGH TUESDAY/

 

SNOW WILL MOVE NORTH AND EAST INTO MONDAY MORNING

AS WARM AIR ADVECTION CONTINUES AND SHOULD BE LIGHT TO MODERATE

ACROSS THE REGION. FCST SOUNDINGS SHOW WAA CAUSING TEMPS ALOFT TO

BECOME ABOVE FREEZING AS EARLY AS MONDAY AFTERNOON AND THEREFORE

SNOW IS EXPECTED TO CHANGE TO SLEET FROM SOUTHEAST TO NORTHWEST

INTO MONDAY EVENING. SFC TEMPS WILL ONLY RISE TO AROUND 30 DEGREES

MONDAY AFTERNOON BEFORE STAYING STEADY INTO MONDAY NIGHT. THE SFC

WARM FRONT WILL HAVE A HARD TIME MOVING NORTHWARD MONDAY NIGHT

INTO TUESDAY EVEN THOUGH GFS/ECMWF HAVE IT CROSSING THE REGION.

THE WEDGE OF HIGH PRESSURE IN PLACE AND LIGHT BOUNDARY LAYER WINDS

SEEM TO HANG ON TO THE COLD AIR MUCH LONGER THAN LOW RESOLUTION

MODELS PORTRAY. BASED ON CLIMATOLOGY KEPT TEMPS COOLER THAN

GUIDANCE.

 

ANY SNOW AND SLEET WILL TRANSITION TO FREEZING RAIN MONDAY NIGHT AS

WAA CONTINUES AND THE WARM NOSE ALOFT LOWERS TO THE SFC. LOW

PRESSURE WILL MOVE INTO THE OHIO VALLEY LATE MONDAY NIGHT AND WITH

IT...A SLUG OF MOISTURE IS EXPECTED TO MOVE FROM WEST TO EAST ACROSS

THE MID-ATLANTIC REGION INTO TUESDAY MORNING. THE WARM FRONT WILL

LIKELY MOVE SLOWLY INTO THE REGION FROM THE SOUTHEAST AND TEMPS WILL

BEGIN TO GO ABOVE FREEZING DURING THE DAY TUESDAY. TEMPS AT HIGHER

ELEVATIONS WILL ALSO BECOME ABOVE FREEZING BY TUESDAY MORNING. THE

WARM FRONT WILL LIKELY REACH NRN MD AND THE POTOMAC HIGHLANDS BY

LATE TUESDAY MORNING INTO THE AFTERNOON. THE COMBINATION OF SNOW AND

ICE WILL LEAD TO TREACHEROUS TRAVEL CONDITIONS FOR AREAS ALONG AND

WEST OF THE BLUE RIDGE MTNS AND THEREFORE A WINTER STORM WARNING WAS

ISSUED. ICE AND SNOW CONDITIONS FOR THIS AREA OF CONCERN INCLUDE

0.25 INCH OF ICE ACCUMULATION ON TOP OF MULTIPLE INCHES OF SNOW.

SNOWFALL ACCUMULATION WILL RANGE FROM 4-8 INCHES ACROSS THE SW CWA

TO 3-6 ALONG AND WEST OF THE BLUE RIDGE MTNS. FURTHER EAST...THE

POTENTIAL FOR 1-3 INCHES OF SNOW AND A TENTH OF AN INCH OF ICE IS

FORECAST.

LOW PRESSURE RAPIDLY MOVES INTO NYS TUESDAY AFTERNOON AND

PRECIPITATION SHOULD END WITH THE EXCEPTION OF A FEW RAIN OR SNOW

SHOWERS ALONG THE WESTERN SLOPES OF THE MTNS.

 

 

[showmethesnow]

4K NAM is noticeably lighter with snowfall totals through the 95 corridor with totals being almost cut in half. Very noticeable shift north and west with the precip field for the mid Atlantic region with somewhat heavier totals throughout. We also lose the 850 fairly quickly and yet hold on to the surface. Not going to look to hard into it but I think the 4k suggests the possibility of a somewhat moderate icing event. All in all there were some somewhat significant shifts in key features to its previous run as well as to the 12k NAM so it is hard to buy into this run wholeheartedly.

 

Looking at both NAM's over the last few runs it seems to be following what I expect to see. Picks up on the CAD before the globals but then holds onto it to long. Thus we see the globals come in line with the colder look of the NAM initially and yet then see the NAM move to the globals warmer look later.

[showmethesnow]

6z GFS has light snow moving into DC Monday between 6-10am; looks to start to changeover late Monday afternoon and then to rain later Monday night. SLP goes from TN to Ohio to NY state, No where near I-95. I don't know if we get much of a front end dump.

Somewhat interesting the large shift west with the track the last two op runs as well as the 00Z ensembles. Wonder if it is just a hiccup on the 00Z run and the 06Z is just tagging along. 

[snowfan]

Warnings have been hoisted for the far western burbs.

[snowfan]

4K NAM is noticeably lighter with snowfall totals through the 95 corridor with totals being almost cut in half. Very noticeable shift north and west with the precip field for the mid Atlantic region with somewhat heavier totals throughout. We also lose the 850 fairly quickly and yet hold on to the surface. Not going to look to hard into it but I think the 4k suggests the possibility of a somewhat moderate icing event. All in all there were some somewhat significant shifts in key features to its previous run as well as to the 12k NAM so it is hard to buy into this run wholeheartedly.

Looking at both NAM's over the last few runs it seems to be following what I expect to see. Picks up on the CAD before the globals but then holds onto it to long. Thus we see the globals come in line with the colder look of the NAM initially and yet then see the NAM move to the globals warmer look later.

925s and 850s are both gone by 7p monday on the 4k. Surface temps reach freezing in the cities at 1am tuesday with what looks like spotty precip around. After that we deluge.

[showmethesnow]

With the westward shift on the 00Z CMC it is now, for the most part, in line with my thoughts on how this plays out. Snowfall map looks reasonable. Loses the 850 quicker then previous runs and the NAM which I expect. Shows better CAD then the globals initially then has a more realistic erosion of it. The one thing I question though is it shows the possibility of fairly significant icing all the way to the bay. I am leaning more towards a minor icing event into the cities with the potential for moderate icing in the favored north and west suburbs.

[showmethesnow]

925s and 850s are both gone by 7p monday on the 4k. Surface temps reach freezing in the cities at 1am tuesday with what looks like spotty precip around. After that we delug

Thanks for letting me know. Didn't really feel like trying to time everything out with 6 hour panels after seeing some fairly significant shifts on key features suggesting this run was possibly a hiccup.

[nj2va]

6z RGEM is fairly dry tomorrow as most of the WAA is in central VA. For temps, the cities lose the surface around 00z Tuesday and at 6z Tuesday, areas west of Loudoun County and HGR are still below freezing.

Verbatim it's about 2" of snow for DC followed by <0.1" ice.

[Warm Nose]

We'll be lucky to squeeze an inch of SN out of this the way it looks now.

[Joshfsu123]

Think it is clear 2-4 inches is what to be expected; with a chance to bust low if moisture doesn't arrive on time.

That said, just a small shift of 50/75 miles north of the heavier precip in the AM tomorrow and the DC area could bust on the high end and get a little more snow than forecast.

I expect 1-2 personally for immediate DC area - good thing it is cold - won't waste a single flake until the changeover.

[aldie 22]

We'll be lucky to squeeze an inch of SN out of this the way it looks now.

I'd wager your area jackpots...as usual

[NinjaWarrior2]

NAM 2" for DC by 6:00am. Going to be a good thump it looks like, better than 6z. Probably lose snow around 3pm for DC. Might be a quicker change to rain. But after a good thump. 31 Sfc for DC at 4:00pm.

[WinterWxLuvr]

GEFS mean is a tad better for snow out here, still pretty weak and no idea if it has any merit. RGEM follows the others in being slower to get meaningful precip in here, my biggest concern. Perhaps the models start swinging more in our favor as we go through the day wrt the better precip getting in earlier.

[yoda]

12z NAM looks to be a bit colder and wetter with the first "wave"