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Weather Headlines for the Washington Region

- The critical time for heavy wet snow today will be between 11AM and 4PM. Snowfall rates during this time frame could approach one inch per hour... marginal temperatures will prevent much of this from sticking except on grassy surfaces.

- A clipper will pass just south of the DC Area on Thanksgiving touching off a few snow flurries during the morning to early afternoon hours. High temperatures will hold in the middle to upper 30s.

- Black Friday will be breezy and continued cold with highs near 40.

Wednesday Morning Update

November 26, 2014
High Resolution Rapid Refresh (HRRR) shows temps dropping from lower 40s into the middle 30s by 11AM

High Resolution Rapid Refresh (HRRR) forecast model shows temps dropping from lower 40s into the middle to upper 30s by 11AM

High Resolution Rapid Refresh (HRRR) Model Total Snowfall

High Resolution Rapid Refresh (HRRR) Model Total Snowfall

GFS Model Total Snowfall

GFS Model Total Snowfall (image courtesy: weatherbell.com)

European Forecast Model Total Snowfall

European Forecast Model Total Snowfall (image courtesy: weatherbell.com)

The European Model this morning continues to be the most bullish on snowfall accumulations. Watch the temperatures between 11 and 1PM… if we do start to drop into the middle 30s then maybe the immediate northern and western suburbs of DC will be able to pick up several inches of snow.

Yesterday, the models were pushing this system through our area too quickly. On this morning’s model runs, the storm has slowed in its forecasted forward speed/movement. Once rain changes over to snow, it will stick around through at least the evening rush hour. Snow will probably taper off and end between 6PM and 9PM.

This storm has a lot of moisture to work with and there will likely be some banding showing up on the radar this afternoon as this system deepens off our coast. Simply put, it could be snowing very heavily in spots with rates of 1 inch per hour. If this occurs, temperatures should tumble a few degrees allowing for some accumulation.

Last Call (Snowfall Map) for Wednesday’s Storm

November 25, 2014

112614_DCstorms_Snowfall_Map

Track has shifted west:

  • The latest forecast models have tracked tomorrow’s coastal a bit further west, therefore I have had to adjust snowfall accumulations down, especially across the immediate Metropolitan Area including the interstate 95 corridor where colder air will now be a bit harder to move in from the northwest.

Marginal temperatures are complicating snowfall potential:

  • There will be several hours of heavy, wet snow likely between 11 AM and 4 PM.  If temperatures are able to drop into the lower to middle 30s, accumulations on grassy surfaces may be a bit higher. But given that some of the latest forecast models have held tomorrow’s temperatures in the middle to upper 30s during the heaviest snowfall, it would be very difficult for a lot of this falling snow to stick.  Still, many of the folks living in the northwestern suburbs will have a White Thanksgiving (all it takes in an inch of snow).

Model Errors Always Leave Room for Surprises:

  • The coastal storm hasn’t formed yet off of Hatteras, NC.  A shift in track of 25 to 50 miles back to the east would pull much higher snowfall totals into the interstate 95 corridor tomorrow.  It will be a nail biter between 11AM and 4PM as just how quickly temperatures fall will be key.

I hope everyone has a fantastic Thanksgiving!

 

 

Tuesday Update on our Pre-Thanksgiving Storm

November 25, 2014
Latest European Forecast Model Snowfall Potential (weatherbell.com)

Latest European Forecast Model Snowfall Potential (weatherbell.com)

The latest European Forecast Model is holding relatively steady with the idea of one to three inches falling inside the beltway on grassy surfaces with higher totals of 3 to 5″ occurring on grassy surfaces in our northern and western suburbs. The higher elevations will pick up between 6 and 8″ of snow with locations above 2,500 feet likely seeing totals of 8 to 10″.

Secondary roadways that are untreated will likely become slushy on Wednesday during the mid to late morning hours as temperatures being to cool to near or just slightly above freezing. Still the snow will come down at a good rate for several hours with large, wet flakes.

A potent clipper system will track just south of DC on Thanksgiving day likely touching off snow showers during the morning to early afternoon hours across the DC Metropolitan Area. Happy Thanksgiving!

DCstorms.com Snowfall Accumulation Map for our First Winter Storm of 2014-2015

November 24, 2014

112614_DCstorms_Snowfall_Map

A mix of rain and snow will begin to overspread the DC Region during the pre-dawn hours on Wednesday.  The mix of rain and snow will transition over to heavy, wet, snow from west to east during the morning to early afternoon hours on Wednesday.  Secondary, untreated, roads will become snow/slush covered making for slippery travel conditions.

Outer Northwestern suburbs:

  • Places like Frederick Maryland and Leesburg Virginia could see snowfall totals of 5 to 7″, mainly on grassy surfaces.  ** The highest elevations  (those above 2,500 feet) could pick upwards of 8 to 12″ of snow **  The Shenandoah Valley and foothills (below 500 feet) east and west of the Blue Ridge will likely see snowfall accumulation totals between 5 and 7″.

Northern & western Suburbs of DC and Baltimore (Fairfax, McLean, Reston, Gaithersburg, Rockville, Columbia):

  • The immediate northern and western suburbs of DC and Baltimore will likely see snowfall totals of 3 to 5″.

The Cities:

  • Downtown Washington and Baltimore will lose a lot of potential accumulation due to the relatively warmer waters of the Potomac and Chesapeake Bay as well as the urban heat island effect. Here I think accumulations will run between one and three inches on grassy surfaces.

Southern Maryland:

  • Southern Maryland and the Northern Neck of Virginia will be the last to change over to snow and these areas will probably remain just above freezing for a large portion of the storm.  In these areas I expect snowfall totals of one to three inches, although if temperatures cool faster than expected, there could be some locations picking up 4″.

Latest on the Pre-Thanksgiving Coastal Storm

November 24, 2014

Here are the latest European and GFS (Global Forecast System) model outputs for potential snowfall accumulations:

European Model showing potential snowfall accumulations on Wednesday.

Latest (Bullish) European Forecast Model showing potential snowfall accumulations on Wednesday. (Image courtesy: weatherbell.com)

GFS Model showing potential snowfall accumulations on Wednesday.

GFS Model showing potential snowfall accumulations on Wednesday. (Image courtesy: weatherbell.com)

My latest thoughts on Wednesdays Storm:

  • A mix of rain and snow will develop late Tuesday night from south to  north with most locations receiving a mix by Wednesday morning’s rush hour. The mix will change over to heavy, wet snow for most locations on Wednesday afternoon. Snow will continue through the evening, tapering off and ending before midnight.

 

  • The recent warm ground, mild temperatures and relatively higher November sun angle will likely cut down on some of the snowfall potential that the forecast models are depicting.

 

  • Heavy, wet snow will begin accumulating during the mid to late morning hours especially west of interstate 95 as temperatures should begin to drop from the middle 30s into the lower 30s.Temperatures should cool to near freezing Wednesday afternoon when snow will likely start to stick on untreated roadways.

 

  • Using a blend of the models, the northern and western suburbs could pick up 3 to 6″  with 2 to 4″ falling across the interstate 95 corridor.  Further east where the mix of rain and snow holds on longer, 1 to 3″ of snow is likely on grassy surfaces.  The higher elevations of Loudoun and Montgomery counties as well as the mountains could receive over 6″ of snow.  This could be one of those storms where National Airport gets 2″ of snow while Falls Church and Tyson’s Corner pick up 4″ or more.  Location will be key.

 

  • We are still 48 hours ahead of a coastal storm that hasn’t even developed yet.  Bottom line:  Track, intensity and eventual speed of this coastal storm can greatly increase or decrease accumulations across the immediate Washington Area. This system will have a high impact on travel on Wednesday. Stay tuned for updates.

 

 

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