MN Transplant

1 hour ago, WxUSAF said:

I’m out of town. My wife says streets are good but lots of sidewalks are untouched.

The sidewalks are a disaster.  My neighborhood has always been good about clearing them, but this storm was a complete breakdown.  Kids walking to sledding locations have been walking in the streets.  No way was school ever opening.

mPING report of snow and weak radar returns around Chesapeake Beach

Sunday is going to be nasty with temps in the teens for much of the day and wind gusts at least into the 30s.

3 hours ago, pazzo83 said:

is there a good explanation for the big misses from the various model outputs?  Was there a model that was better on our actual realized temps?

The NAM 3km is doing pretty well IMBY, but isn't cold enough in the low-lying areas.  The HRRR is the inverse.  The globals are having all sorts of problems.  The fundamental answer is that the models just have so much trouble handling the very stable winter boundary layer and how much mixing there is.  

38 minutes ago, psuhoffman said:

@Terpeast @MN Transplant @WxUSAF

Question... something I've noticed anecdotally over the last 20 years, when 3-5 days out we have models projecting a favorable H5 feature for our area...it trends north a significant majority of the time.  However...when guidance has a cutoff h5 feature projected too far south of us...it does not tend to trend north as often.  

I can think of a logical reason, perhaps if a cutoff is far enough south its far enough removed from the NS flow and not impacted by minor variations the models typically get wrong...and which cause the north bleed in these features when they are around our latitude.  

Just wondering if you have also noticed this and if there is something to it, besides just random chance and us getting really unlucky lately.  

I'm just guessing here, but I would think that we are looking at two things:

1)  Confirmation bias. Unless there is an actual study showing that this is true, it may just be the snow weenie in all of us that remembers these types of changes.

2) But if the anecdotal theory is actually true, it might be that the patterns that result in an H5 feature going through the deep south may simply be more predictable due to the strength of the blocking required to make that pattern happen.

The fundamental problem with the lows is that the airmass is potentially historic in length, but not severity.  So, we are getting very cold in the favored spots, but overall it isn't just enough of a cold airmass to challenge some of the more fun numbers for many of us.

1 minute ago, WxUSAF said:

GGEM is like Boxing Day. But way worse!

Boxing Day was worse because it was hitting up north too. 

Just now, WxUSAF said:

@MN Transplant @Bob Chill @psuhoffman damn ULL keeps digging for gold! We might get a late north trend but this mid-range south trend may still put it out of reach.

I'm not giving this one a lot of my energy.  Glad I'm not forecasting for NC/Richmond/Norfolk!

Even though it is a whiff, you have to admire a 500 low track of Minneapolis to St Louis to Atlanta on the RDPS.  That's a unique one.

3 minutes ago, peribonca said:

Does anyone have the Z500 animation from January 25, 2000?

https://www.meteo.psu.edu/ewall/NARR/2000/us0125.php

9 minutes ago, WxUSAF said:

 

I’ve been saying this thing screams north trend late. Hasn’t happened yet, but still time for that…

I'd be more inclined to think there is a N shift late if we had already started a trend in that direction.  But we aren't seeing that.  GFS, GFSAI and AIFS are rock solid for a 500 pass through SC.  The Euro and GDPS dipped even further to Savannah.

3” QPF all snow around Salisbury.  Fantastic.

What a gorgeous 500 pass for Richmond

If you want a perfect representation of microclimate and cold-air drainage, check out Manassas this morning.  The airport sits at a low point, only 50-100' below the surroundings, but enough to perfectly bottom out in calm conditions.

Even though the HRRR was too low and the 3km NAM was too high, I'll give them both credit for correctly calling that temps would keep slightly falling after sunrise.  IAD is still sitting around their low of 3 or 4, BWI is still about 13.  I got down to 8.6 at 8am.

But our big local winner looks like it is Manassas at -1.  Colder than any of the MD Mesonet sites except for Garrett Co.

13 hours ago, WEATHER53 said:

I can’t answer for right there at their  thermometer because the problem is likely right there.  The parkway  runs close  by with lots of trees so nit heavily industrialized in any manner 8.5” more like it .  How much do you think they got and how do think they  do with temps  and snow? 
it also appears the 6.9 they reported is snow only when looking at the color coding accumulation maps you provided?

 

I think they got about 7" like what was reported.  I got 8.5" and they had less precipitation than I did, which was particularly important in the snow period before the sleet.

12 hours ago, WEATHER53 said:

So the bottom panel snow only?  Nothing additional including  sleet? 
some stations have two different colored values, is that snow first and sleet and snow second 

The colors don't mean anything other than more or less snow/sleet.

12 hours ago, Roger Smith said:

DCA reported 1.99" liquid and 6.9" snow. If I'm generous and say .09" of that was freezing drizzle (probably an overestimate) then their snow report equals real snow plus sleet at some possible-to-calculate ratio after an assumption is made on the snowfall to liquid conversion. I will assume 10:1 in my calculation that follows.

So let's say 5" real snow, then we have

5.0 + 1.40*(ratio/10) = 6.9

That reduces to 1.40*(ratio/10) = 1.9

and makes ratio/10 = .21, in other words a 2.1 :  1.0  ratio. Sleet ratios are often quoted at 3:1. 

For 3:1 to be correct, then snow at 10:1 is 2.7" .. that is clearly a low estimate based on regional reports.

So either this was very watery sleet or very underestimated sleet. I would guess what really happened is that 3" of sleet pounded 6" of snow down to 4 inches and sat on top giving 7 inches.  

Roger - my sleet was 2:1

1 hour ago, TSG said:

I noticed the GFS and Euro are considerably colder than the NAM3k. Are the mesoscale models going to be better at estimating this?

 

I think I'd go in-between.  Most of us will be single digits, with the favored spots (IAD, Manassas in VA) having a better chance at 0.

23 minutes ago, WEATHER53 said:

Comical to try and sell  that with 4” of snow everywhere and 15-25F with  heavy sleet and snow and 20+mph winds that theDCA station has a “warmth” element creeping into  it 

How much snow/sleet do you think DCA actually received?

Assume we are tracking the cold in this thread.  24.0 and the wind is picking up.

Models are all over the place on lows tonight, but the favored areas may make a run to 0.

• 12/5 - 1.9"
• 12/14 - 1.3"
• 1/26 - 8.5"

Total - 11.7"

Rooting for George now!

My pro-tip from this morning is to pull out the garden shovel.  The plastic snow shovels are no match for this mess.

3 minutes ago, mattie g said:

Gotta say...that seems kind of low for the amount of liquid equivalent since folks around us started off with 5" or so of snow (depending on where you are).

Funny thing is that it was kind of a calculated number.  At no point did I ever have more than ~7.7” on the ground.  A lot of compaction with the weight of the sleet on top.  But I also couldn’t find any place that would legitimately give me more than 3.5” of sleet.  So, yeah, a 2:1 ratio on the sleet.

I’m going to call it 8.5” total.  Insane precip at 2.33”.