Feb 21-22 Snow/Sleet Storm Obs/Nowcasting/Weenie/Panic/Hallucinations

[das]

So, my 10 year old daughter measured 3.1" for this storm for me in Clarksburg and said totals dropped very quickly as you head south towards Gaithersburg but looked the same as Clarksburg when you headed east towards Damascus. Anyone else get any obs in the area?

[gymengineer]

So others have mentioned it already--- but definitely beware of being near the southern edge of modeled-snowstorms in the Mid-Atlantic. Maybe it's different in other parts of the country, but in this region, the southern edge on the models has been tricky for at least the past decade. This past storm was a complete consensus across all models for 0.4+" liquid during the 12Z runs right before onset at DCA and IAD, near the southern extent of heavier precip. Even the later 0Z runs of the GFS and NAM as the event was underway, while reduced, were still in the 0.35-0.45" range. Verification was 0.2-0.3". That missing tenth would actually have verified most forecasts in the area. As has been analyzed on here, the most intense lift was north of modeling, hence we ended up with less dynamics and warmer mid-layers, and therefore more sleet in our already reduced precip amounts.

But that pattern has repeated itself in numerous storms in our recent past-- just go back to 1/26 and see how the Charlottesville area saw a bust worse than what DC saw this past storm. I remember how slowly they switched over to complete snow as the back edge headed NE-ward. Those of us in the DC area didn't pay much attention because we overperformed the model QPF. Maybe the most extreme short range bust was for Richmond during PDII on the southern edge. A foot of forecasted snow/sleet turned into pretty much all sleet. For our area, even within 24 hours on the models, you would want to be in the middle of the highest forecasted snow amounts, definitely not near the southern edge.

[BlizzardNole]

So, my 10 year old daughter measured 3.1" for this storm for me in Clarksburg and said totals dropped very quickly as you head south towards Gaithersburg but looked the same as Clarksburg when you headed east towards Damascus. Anyone else get any obs in the area?

We are in the Milestone area of Germantown -- we got 2.5". I ride the MARC to DC...each stop had less snow, and Silver Spring looked to have only an inch. Got to Union Station and there was only a half inch there.

I saw that some areas near and just east of Frederick (like Linganore) had around 5". So close!!

[EastCoast NPZ]

My observations over the years agree with this. I can't recall ever cashing in on an event in which we were on the forecasted southern fringe. I have not tracked and recorded these observations; it's all from memory, so it could be completely wrong - but it is my recollection. One doesn't have to look back far to find an instance of where being on the forecasted northern fringes paid off better for us, the end of Jan. storm last year. 24 hrs out we were forecasted to get maybe an inch, but eventually received 4 - 6 inches in these parts. Several times this year alone, 3 days ago most recently, we were on the forecasted southern fringe of an event, and each and every event underperformed. Granted, my examples are comparisons based on last years near-historic winter and this year's cursed winter.

I have a new motto:

If on the southern fringe; you'll have to try again.

So others have mentioned it already--- but definitely beware of being near the southern edge of modeled-snowstorms in the Mid-Atlantic. Maybe it's different in other parts of the country, but in this region, the southern edge on the models has been tricky for at least the past decade. This past storm was a complete consensus across all models for 0.4+" liquid during the 12Z runs right before onset at DCA and IAD, near the southern extent of heavier precip. Even the later 0Z runs of the GFS and NAM as the event was underway, while reduced, were still in the 0.35-0.45" range. Verification was 0.2-0.3". That missing tenth would actually have verified most forecasts in the area. As has been analyzed on here, the most intense lift was north of modeling, hence we ended up with less dynamics and warmer mid-layers, and therefore more sleet in our already reduced precip amounts.

But that pattern has repeated itself in numerous storms in our recent past-- just go back to 1/26 and see how the Charlottesville area saw a bust worse than what DC saw this past storm. I remember how slowly they switched over to complete snow as the back edge headed NE-ward. Those of us in the DC area didn't pay much attention because we overperformed the model QPF. Maybe the most extreme short range bust was for Richmond during PDII on the southern edge. A foot of forecasted snow/sleet turned into pretty much all sleet. For our area, even within 24 hours on the models, you would want to be in the middle of the highest forecasted snow amounts, definitely not near the southern edge.

[EastCoast NPZ]

Or....

If predicted on the southern fringe, be prepared to be screwed again.