Slick Travel on Untreated Roadways Possible Thursday Evening

The latest North American Model (NAM) is out and we are now 48 hours away from our possible first inch of snow across the Washington DC Metropolitan Area.

While any deviation in temperatures or a slight change in track can change the forecast, I wanted my readers to have an idea of what we are seeing in the short-range models.

First up let’s look at the future cast from the latest NAM model beginning Thursday at 4pm (21z) Thursday and ending at 1am (06z) Friday.

  • Blue colors indicate snow breaking out across the Metropolitan Area during the tail end of the evening rush hour.

 

  • This still looks like a quick hitting event as the system is forecast to really buzz out to sea rather quickly, still grassy surfaces in areas that receive a short period of some steady light snow could pick up a dusting to an inch.

6d39a713-0193-4040-8376-770e3dd70e03.gif

Same Model (NAM) showing Snowfall Accumulation potential (image courtesy WxBell) by 1am Friday:

hires_snow_washdc_61.png

Next up let’s look at the latest SREF (Short Range Ensemble Forecast) for DCA (National Airport)

  • The green line on the graph below shows the ensemble mean of 1/2″ of snow with the high end totals coming in at 1.5″

 

  • Generally speaking, one could deduce that locations that receieve several hours of steady snow with temperatures near the freezing mark could wind up with a solid inch of snow or possibly as much as 1.5″.

KDCA_2017010315_6snow.png

Temperatures right now look marginal (lower to middle 30s along the 95 corridor) but with temperature near freezing in the immediate western suburbs, any accumulation could cause slick travel conditions on untreated roadways.

hires_t2m_washdc_58.png

 


Round #2? Tuesday update on Possible Weekend Storm

The million dollar question right now is what happens with a piece of energy diving toward the Gulf coast on Friday? Does it phase with the northern branch and ride up the Mid-Atlantic and New England coastline providing a major snow storm? Or does phasing not occur (positively tilted trough) and it slides quickly out to sea after delivering several inches of snow to the Carolinas?

Latest GFS and GEM (Canadian):

The image below (courtesy TropicalTidbits) shows the latest Global Forecast System (GFS) model forecasting the time frame between 1AM Saturday and 1AM Sunday:

  • Future time-lapse below shows an un-phased system with two separate waves of low pressure sliding well off of the southeastern coastline with little fanfare in our region.

GFS_Weekend_Event.gif

The image below (courtesy TropicalTidbits) shows the latest Canadian (GEM) model forecasting the same time frame as the GFS above:

GEM_Weekend_Event.gif

  • Notice that the latest Canadian tracks the system further west and shows one main low pressure system instead of the two separarte areas of low pressure in the GFS model.

 

And for today’s Breaking News in the world of weather, the latest European model from overnight shifted the track much closer to the coast.  

We need to wait and see if this is a trend before we start getting excited. 

Here is yesterday’s (12z) run of the European modeling 7AM Saturday:

  • Notice the snow stays across eastern North Carolina with a track much further out to sea.

ecmwf_slp_precip_01021712z_Sat_7am.png

Here is the latest run of the Euro modeling 7AM Saturday:

ecmwf_slp_precip_00z_Sat_7AM.png

  • Notice the latest run of the Euro (image above) shows much heavier precipitation falling further north and west than it showed in the previous run.

 

Let’s compare the old run of the Euro for Snowfall Accumulation to the latest run:

Old Run (12z Monday):

ecmwf_tsnow_ma_27.png

Latest Run (00z Tuesday): 

ecmwf_tsnow_ma_25.png

Is the European forecast model on to something? Will future runs continue to shift the track further west and up the coast?

The biggest snow storms that bury the BOS-WASH (the Boston to Washington corridor, home to 55 million Americans) come from systems that track from Cape Hatteras to Cape Cod

While this storm may very well stay too far out to sea it is something that needs to be monitored closely

To be clear, I do not currently find the European Ensembles to be very promising as of now (meaning they are not *yet* showing consistency in producing heavy snow across the DC Area this weekend).  With that said, this is a fluid situation and as we get closer to Wednesday & Thursday the models will hopefully start to zero in on a solution.

For those of you that didn’t know, I have also been updating via Twitter, in other words, if you subscribe to receive my posts via email and do not visit my website, you might miss some of the updates that I am putting out on Twitter.  You can follow me on Twitter @DCstorms.  My Twitter feed is also located on the right hand side of my website as well. 

 

 

 


Round #1 …. Light Snow Likely Thursday Night & Friday Morning

The Washington Area may receive its first light accumulation of snow of the season Thursday afternoon into the first half of Friday according to the latest forecast models.

There is growing consistency among the GFS, GEM (Canadian) and European models that a coastal storm will develop just off of the Carolina coastline before zipping quickly off to the northeast, far enough away to spare us a significant snowfall but close enough to possibly bring the first inch of snow to parts of the region.

Let’s take a look at the latest information (note: subject to change and will need to be monitored)

Latest Global Forecast System (GFS) model:

The image below is from the 12z (this morning’s latest run at 7AM) GFS showing light snow rapidly developing across the Metro Area possibly during the Thursday evening rush hour but then quickly dissipating from north to south on Friday morning.

12zgfs_snow

Potential Snowfall Accumulation (latest GFS) if the above scenario is correct:

  • Dusting to 2″ with the higher totals being south and east of Washington

gfs_6hr_snow_acc_ma_15

Moving on to the Canadian (GEM) model:

The Canadian model (image below courtesy TropicalTidbits) shows a similar scenario as the GFS with light snow developing Thursday afternoon/evening and then tapering off rapidly on Friday morning.

00z_gem_snow

Potential Snowfall Accumulation (latest GEM) if the above scenario is correct:

cmc_snow_acc_nc_15

And now my favorite model (The European):

  • The next two images (courtesy WxBell) are taken from the European Ensembles which show a decent clustering of “red L’s” (indicative of the potential locations of the area of low pressure) on the maps (decent amount of consistency the closer they are to each other).

1am Friday morning (Thursday night): Notice the clustering of “Ls” on the map just off of the North Carolina coastline.

eps_slp_lows_ma_14

7am Friday morning: Notice the clustering of “Ls”  east of the VA/NC border, far enough out to sea to prevent heavy snow in our area but close enough for a dusting to maybe 2″ in spots.

eps_slp_lows_ma_15

Potential Snowfall Accumulation (latest European) if the above scenario is correct:

eps_snow_c_ma_17_fri

The latest European forecast model for snowfall accumulation (image above) currently predicts:

  • One-half to one inch of snow across the DC Metropolitan Area
  • One to two inches across lower southern Maryland, the northern neck of Virginia and the eastern shore of Maryland.
  • Two to three inches across the beaches of Maryland and Delaware

Disclaimer: 

Any future adjustments in track closer to the coast or a decrease in forward speed could increase accumulations across the DC Area

Any future adjustments in track further off the coast or an increase in forward speed could decrease accumulations across the DC Area.