DarkSharkWX

From Dec 15(around time when we were expected to go into a favorable pattern) - Dec 24(latest date available) there doesn't seem to be any sign of a -PNA/SER at all. The PNA not being east enough(not over the Rockies) and the lack of 50/50 are one of the factors that contributed into the pattern not doing well.

tbf correlation doesn't equal causation - most of those years that had <1" for you before Jan 1st were bad for everyone because of a strong -PNA and SER which is different from what we've had so far and what is being shown on guidance the reason why we will go AN for the end of dec thru first week of jan is because of NPJ overextension - quite similar to a strong nino pattern

Based on NOHRSC, Manchester got only 0.1-1" during 2021 before 2022, and was a non-Nino year

and looks to be a legit +PNA over the rockies and a ridge bridge along with +SCAND in our peak climo

the +SCAND should eventually build into an -NAO and that along with the aleutian low will put pressure on the pv

All we need is a Canadian high, a ridge over the Rockies, and a 50/50 for a big snowstorm, high-latitude blocking/-EPO aren't necessary(though they obv help)

This certainly isn't a horrible look

10/-4 with -10 windchill in Gaithersburg now

12/-2 with -7 wind chill in Gaithersburg

28/25 gaithersburg

CAD over preforming rn

That would be putting stress on PV, with the Scandinavian ridging/high and low near the Aleutians. Good pattern for PV disruptions.

GEFS has the signal around 27th now

I wouldn't fully give up on this system yet, there is front-end thump potential as well as some potential for some backend snow. If this threat doesn't work out, we also have the 27th to look to

NPJ gets too extended which brings warmer period and pacific puke, however maybe the 27th threat could work out before we switch to a warmer period

New WPC forecast shows 10-50% of exceeding .25" of snow/sleet(liquid equivalent) for much of the mid-Atlantic/northeast, and even extending down into the southeast.

FCPS will most definitely close because of the widespread icing that is expected to continue(as well as the ISW), and MCPS might close as well.

Here's a wetbulb calculator if anyone needs it(<32 Tw freezing rain, >32 Tw rain): https://www.weather.gov/epz/wxcalc_rh

Looks quite icy outside here in northern MoCo. 32/30 with Tw in 30-32F range

Does anyone have FRAM on pivotal for the latest HRRR?

Wetbulb temperatures for DC and north are already 32 or lower. A study found out that the best wetbulb temperature for ZR is 27-30F, which isn't that off and will reach further south as temperatures drop.

Got to a low of 18 here in Gaitherburg, colder than I had expected. Right now 37/17

Think everyone in advisory will close/go virtual or at the very least delay

This is what a study found about precipitation rate, wind speed, wetbulb temperatures, and how they correlated to ILR. Freezing rain can occur even with temperatures above freezing, but if the wetbulb temperature is above freezing, freezing rain can't occur. The study generally found that wetbulb temperatures between 27-30F, greater windspeeds, and lighter precipitation rates all contribute to more efficient ice accretion. Here is the link if anyone is interested in it: https://training.weather.gov/wdtd/courses/woc/winter/fcst-hzds/ice-storm-accum/presentation_html5.html

The best conditions for optimal ice accretion are greater wind speeds(takes away hear from surfaces and advects cooler air), small droplets falling through a shallow melting layer, lower wetbulb temperatures, and lighter precipitation rates(heavier precipitation rates lead to more runoff and less efficient accretion).