Slippery Friday Afternoon Rush Hour Possible

Snow showers will fall across the Washington Area on Friday afternoon continuing  off and on throughout the evening rush hour with lingering flurries possible overnight as bitterly cold air moves in and squeezes out any lingering moisture in the atmosphere. 

The following images are from the North American Model (NAM), images courtesy tropicaltidbits:

1PM Friday:

namconus_ref_frzn_neus_6    4PM Friday:

namconus_ref_frzn_neus_7

7PM Friday:

namconus_ref_frzn_neus_8

10 PM Friday:

namconus_ref_frzn_neus_9

1AM Saturday:

namconus_ref_frzn_neus_10

Regarding the Monday/Tuesday storm, I am reserving judgement until Friday night/Saturday morning’s model runs when the pieces of energy currently over the Pacific actually make landfall on the Pacific northwest coast which should give us better initialization and consensus on track.

Today’s models have all shifted west with a storm running up the spine of the Appalachians which would bring a brief period of snow before going over to heavy rain and washing away any hopes of a decent snowfall in the metro area.

Again, the track could shift back east (as the models may not be handling things well until the short waves reach the pacific northwest coast Friday night/Saturday). 


Thursday Update on Next Week’s Storm

The current models are still lacking a good deal of consensus involving the exact track  and temperature profile for the upcoming storm.  Current operational runs have become more bullish with some snow accumulating across the DC region on Monday afternoon and evening out ahead of any change over to ice or eventually rain on Tuesday afternoon.

Let’s look at the current operational (GFS, European, and Canadian) models (images courtesy weatherbell):  Bottom line is that the current GFS operational is further east with the heavy stripe of snow getting into the 95 corridor.  The Euro and Canadian are further west but do put down several inches of snow in the DC Metro before a change over to ice or rain. gfs_6hr_snow_acc_washdc_27 ecmwf_tsnow_washdc_28 cmc_snow_acc_washdc_32

Here is the latest surface depiction of the GFS (image courtesy tropicaltidbits.com):  Notice the rain/snow line pretty close to the interstate 95 corridor.  In this particular run of the GFS heavy snow gets right into the 95 corridor with a change over to rain across the northern neck of Virginia and southern Maryland.

gfs_mslp_pcpn_frzn_us_21 gfs_mslp_pcpn_frzn_us_22

Here’s the latest surface depiction of the Canadian (image courtesy tropicaltidbits.com): Accumulating snow to start on Monday afternoon/evening and then a change over to freezing rain and sleet with significant ice accumulation possible and a change over to heavy rain across the Bay.

gem_mslp_pcpn_frzn_us_20 gem_mslp_pcpn_frzn_us_21

Now lets look at the all important Ensembles for potential snowfall accumulation outcomes (images courtesy weatherbell):

First two images from the latest Euro Ensemble – verdict is out as to where the heavy snow band falls but generally speaking it looks as thought the current Euro favors a more inland track keeping the heaviest of snow between the western suburbs and mountains.

The last image is from the GFS Ensemble (GEFS)… also the verdict is out with several of the ensembles dropping heavy snow into the immediate Metro and others keeping it west across the higher elevations and western exurbs.

eps_snow_25_washdc_41 eps_snow_50_washdc_46 gefs_snow_ens_washdc_28

Bottom Line:  Snow and Ice accumulations will all come down to the exact track. The image below shows the GEFS (Global Ensemble Forecast System/GFS) storm track and precipitation type (still a lot of uncertainty in exact track):  The sooner the coastal storm takes over and strengthens, the better the likelihood of colder air remaining trapped longer east of the mountains.  Snow will likely fall out ahead of this system with several inches accumulating on Monday afternoon/evening.  If we do switch over to freezing rain and temperatures at the surface hold at 32 for most of Tuesday, parts of our area could be looking at a nasty ice storm.

The ground will be frozen due to the bitterly cold air coming late this week into the weekend.  This will help snow to accumulate rapidly and may help to hold in the CAD wedge (Cold Air Dam) east of the mountains making for the potential of a nasty ice storm in places before any possible change over to rain on Tuesday afternoon.

gefs_ptype_ens_ma_22

More updates to come…