mattb65

Still 31.6 on the pws this morning. Impressive CAD almost always holds longer than predicted.

Mix of snow, pingers and rimed flaked for the last 30 mins. 3.75" and 28 degrees in Wheaton/Kemp Mill. There looks to be some heavies heading this way which will hopefully flip us back to more snow than ip.

A hair over 3" OTG in Kemp Mill/wheaton park region of silver spring, time to head out with the little guy and enjoy

Baltimore weenies can step off the ledge.

27 degrees, 2" OTG and moderate snow picking up in intensity. I was expecting 2-4" and think I may exceed the top end of expectations. Every storm has busted positive here this year, why not this one too.

These SWFE tend to come in hot with the thump, looks like this one is no exception. Herpaderp ftw.

Ferrier snow maps about to bust already, think it gave 1" for the event.

Here's the sounding at Hour 30 for the DC metro region - it painted this as snow on the 6z run and as mix on the current run, by this point approximatel 0.4" QPF has falling, prior runs had 0.5-0.75" QPF. It's a relatively minor difference and probably rate dependent. I think with a sounding like this it would be snow in heavy precip or snow/sleet mix in lighter precip. I personally don't see this GFS run as some huge step back, just another variation of the same with probably ~0.3-0.4" of QPF falling before we lose the column in the DC metro region - supports 2-4" of snow before we flip with some boom potential if big rates come in with the initial bands.

Well I think you need to adjust your previous posts - you seemed to indicate a transition Snow straight to Rain is what you expected. I think most agree with what you said in this post it'll be snow then pingers - duration TBD - NAM/Euro suggest only a few hours before going to ZR/Rn, other models suggest maybe a bit longer. With strong WAA like what is modeled and a retreating HP, I agree that a long duration pinger fest isn't all that likely.

Who is calling for 3 inches of sleet or 0.25 inches of FZRA in the metro regions??? This one is looking like a standard slop storm - 2-4" for most with some boom potential if rates come in hot and heavy followed by pingers for a while then a little ZR then rain overnight. Do you think this is going to snow for 3-5 hours then go straight to rain? Is that your call?

Guidance is pretty unanimous that this transitions to pingers before going over to rain. SWFE almost always go to pingers and often go earlier than models indidcate. Going straight from snow to rain is very unlikely.

Onset time 12z wed, more in line with other guidance on the 6z NAM (6 hrs slower than the 0z) still a big thump of snow to pingers, strong CAD wedge in place for this one.

Temps may cool enough overnight to flip Moco/Hoco back over to ZR based on 3K NAM, will have to wait and see how close to the beltway the freezing line sinks, 2M dews are below freezing as close as NW DC. Probably won't have a significant impact aside from some more icicles in the trees. Looks much more icy up near the MD/PA border though.

My wife had to drive up to PA and said the roads were a little dicey at times in baltimore Co and then snow covered once she got into PA with numerous people off the roads, pretty much bad roads where you'd expect them to be. I had no problems in MoCo at all, roads were fine.

Sleet line still racing north on radar but hints it maybe is starting to meet some temporary resistance around DC.

I don't have much hope for this event in my location besides brief frozen before the rain however, I wouldn't even look at the HRRR in this situation, it is going to push the boundary layer warming way too aggressively. It did it with the last event and will torch things too easily imo.

The 3k NAM is all wintry mix for areas just north of DC and has some cooling of the surface and midlevels in between wave 1 and wave 2 with sleet soundings shifting back to snow soundings for a time before the big push of warm air rolls in. Going to be a fine line between icy mess and 33 and rain for many.

Legit SN in Bethesda, Vis down to about 1/2 mile in this little band. Nice scene, not a bad week with 3 little snow events.

I saw a few rogue flurries on my walk in to work in Bethesda.

3k drops the temp from 31 to 17 when the snow squall rolls through at 1pm through the DC metro, hope it's onto something.

Dumping huge aggregates and 32.5 and dropping fast. Roads starting to slush up and traffic is a disaster as expected.

If rates improve to the point where it's heavy enough to form a slushy accumulation, this is the rare situation where there could be a flash freeze since temperatures are set to fall pretty sharply once precip shuts off.

One of the big risks for the metro areas is torching of the boundary layers - the most recent 11z HRRR gets BL wet bulb temps up into the mid-upper 30s in the DC/Balt metro before the onset of the more significant precipitation and thus we waste a significant amount of QPF to rain or non-accumulating snow. I've read on here that the HRRR has a bias of increasing BL temps during lulls but it's something to keep an eye on as a possible way that this event may fail in the metro regions. (11z even torches all the way to the MD/PA border so it would be a fail for everyone). 6z 3K NAM and HRDRPS keep wet bulbs down in the low 30s but RGEM is similar to the bad run of the HRRR.

6z NAM twins appear improved compared to their priors, same with the 6z hrrr. It's hard to have much confidence in their outputs when scrolling on TT through their last 5-6 runs. They fluctuate significantly from run to run. General there continues to be d-2" near 95 and immediate DC metro, 2-4" in favored NW zones

Assuming the timing on the NAM is correct, it seems there is a first wave favoring areas closer to the MD/pa line around 0900 with temps in the whole column supporting snow and supporting sleet mix closer to DC. Then the main chunk of snow comes in closer to 1300 which seems to be a speed up on terms of onset time and could cause pretty significant impacts on traffic assuming I'm reading the timing correctly. Boundary layer temps are 33 according to the 3k NAM in the DC metro so impact will depend on rates. Soundings clearly support snow as the ptype.