wxmvpete

Yeah I'm at 2.7" 6 miles northeast of Westminster. A light but pretty snow falling. One of the negatives with such a good band to the south is the air has to sink somewhere. Looks like northern Carroll and most of Frederick county is dealing with that at the moment.

Got about 1.25" northeast of Westminster so far and sitting at 24F.

Latest 02Z HRRR at 6AM-- area averaged sounding including most of the DCA-BWI corridor shows a sufficient sounding for some great looking dendrites. We've had more saturated soundings, stronger omega, deeper DGZs in bigger events, but this will still produce some locally heavy snowfall rates and lead to some pretty tough travel conditions. Looks like snow lovers will want to enjoy this one. May not get another real good shot at this again for several weeks.

Absolutely. For just about everyone along and west of I-95 (including the metros), WPC 6-hr averaged SLRs are 10-12:1 generally between 06-12Z, but 12-18Z are 13-15:1 (Catoctins could approach 16:1), then 18-00Z tomorrow are 15-17:1. Question becomes how much moisture & lift can stick around the region that late.

Josh is on the grids today and I'm the afternoon winter shift, so I'll shoot him a message

Living on the edge of your Zone C and Zone D. I'd happily take another 3" as would my kids!

However, take a look at early this morning up near the Lower Susquehanna Valley- that sounding regains some of that moisture at mid-upper levels with increasing VVs through the depth of the column. That could be pretty impressive over eastern PA if that can materialize Tuesday AM.

Yep good catch, that is probably the primary reason this band isn't a bigger 1-2"/hr setup. The lowest layer of the DGZ on down to the boundary layer is sufficient to give folks an advisory level event (pockets of warning criteria still possible). You want that DGZ zone layer fully saturated with strong VVs. Still, this is enough to produce a nice event here.

Really starting to see returns filling in at higher radar tilts in western VA. What originally featured drier returns around 4,800ft out near the I-66/I-81 merger (around 850mb) is showing brighter returns. For those who have patiently waited in Northern MD, those heavier rates will be realized soon.

850mb warm air advection continues to increase with 850mb frontogenesis that will support a band of heavier snow N&W of DC in the coming hours. What becomes the wildcard is the approach of a 500mb jet streak over the OH Valley overnight. At the nose of the jet, divergent flow atop the atmosphere will support healthy vertical velocities 12Z Tuesday. This is driving the snowier solutions from northern MD into eastern PA. The new NAM seems to feature similar setup.

I also have a half inch northeast of Westminster. Quite a few cars spun out on the road going home.

As a heads up, these maps are resent to include our hemispheric fronts created from our Alaska desk. The fronts over the CONUS by our day shift medium range forecaster (Rausch, if you look at the Fronts tab on the homepage) is identical compared to this one. The new fronts and pressure from night shift likely won't make the web for a couple more hours, and the overnight forecaster would use the 12/18Z guidance as their foundation for this next set of fronts/pressures forecasts. Usually these fronts and pressures have to be sent out before the new suite of 00Z guidance comes in.

January 2014 event- the week before KIAD got 8.5". For those dates, cold with 0.3". January 2011 dates- KIAD 1.2" January 1992 dates-- cold and dry March 9-10, 1960 dates-- 5.8" at DCA (Bigger storm here to open that month) March 11-12, 1960-- cold and dry at DCA December 11-12, 1958-- cold and a Trace at KDCA March 24-25, 1940-- cold and a Trace in DC January 23-24, 1940-- big storm, 9.5" in DC and cold January 29-31, 1936-- Cold and 0.2" in DC December 28-29, 1935-- Cold and 6.3" of snow in that period. So we know it's cold, but it can give us a decent event based on the event.

May be pulling up xmACIS to check what they did.

Ahh it did start to try to hint at it on the 18Z ECMWF. Hadn't gotten a chance to look at it. Will be curious to see if it keeps making that adjustment at 00Z.