Snow and Ice Map Posted for Winter Storm

Warm Air Intrusion Looks to Win Out 

Unfortunately the forecast models continue to track Sunday’s storm system inland during the evening hours which will allow for warmer air at 850mb (the mid-levels of the atmosphere) to be pulled westward off of the Atlantic on top of the cold air at the surface. This sets up a scenario where heavy snow will change over to sleet and freezing rain with ice accumulations causing extremely treacherous travel across the Mid-Atlantic as well as the potential for power outages.

Heavy Snow Develops Sunday Afternoon

Snow should develop areawide on Sunday between 4 and 6PM becoming heavy for several hours before a change over to sleet and freezing rain between 8 and 10pm. A snow thump of a few inches are likely before the change over to a wintry mix.  Confidence remains low on exactly when the transition will take place and how soon locations west of interstate 95 change over to rain (cold air at the surfaces may prove more stubborn causing an increased threat of an ice storm across the western and northern suburbs of DC).

 European Model Holds Steady

The heaviest precipitation should begin to taper off after midnight on Monday (Sunday night) with some wrap around snow showers likely on the back side of the storm system. Winds will become gusty during the storm with scattered power outages likely due to the ice accumulations on top of the snow.

Snowfall Accumulation Potential 

Below is how much snow I think will fall across the Greater Washington DC Region

Potential Ice Accretion from Freezing Rain

I remain concerned about locations along the interstate 81 corridor where a quarter of an inch of ice is possible before the system pulls away.  If sleet were to become the predominant precipitation type, then the risk of power outages would decline. Remember sleet is frozen rain drops that bounce when they fall, freezing rain is the liquid that falls as rain and then freezes as glare ice on all untreated surfaces.

Please refrain from traveling Sunday afternoon/evening across the Mid-Atlantic interstates as conditions will deteriorate rapidly.

Also please note this is an extremely tricky forecast as forecast models always try to scour out cold air at the surface too soon.  If freezing rain holds on long across the DC Metro, we may be looking at more of an Ice Storm with power outages due to the gusty winds.

Now is the time to prepare for possible power outages and stock up on items in case you were to lose your power. 


“Forecast Uncertainty” and “Three Scenarios” – Let’s Cut the Bull$hit and Get Right to the Truth

The Same Old Bull$hit

For those of you who have followed my weather blog you know the drill here in Washington. The “experts” clamor on about the various, “mind-numbing” solutions with the same three potential scenarios depending upon the outcome of the exact storm track.  There is a “50% chance of snow in DC changing to a wintry mix” and a “50% chance of all snow” — really? Why not just tune in 36 hours before the event for an accurate forecast?

Has anyone ever noticed that the same folks say the same thing with every winter storm 3 to 4 days out? There is always “three scenarios” to include:

  • The storm tracks from Cape Hatteras to Cape Cod dropping heavy snow from Washington to Boston
  • The storm tracks too far east and misses DC
  • The storm tracks too far inland wrapping in warmer air with snow changes over to rain

Why waste everyone’s time with potential scenarios?  Well for one, the media wants to get out ahead of the narrative for ratings (to pay their bills) and to ensure that they garner your interest — I mean nothing will get ratings like a potential snow storm that will shut the big cities down for a few days.

The Facts 

Forecast models utilize mathematical equations and the solutions 3 to 4 days ahead of a storm system are only as good as the input data.  How do we get input data? With weather stations and weather balloons of course.  A good sampling of the atmosphere is needed and that accurate input data will produce an accurate solution (where the storm will eventually track).  Until the upper-level energy that is responsible for the evolution of this storm tracks over a land mass (western Canada) on Friday, the forecast models will continue to fluctuate. In other words, don’t trust any potential outcome until Friday afternoon. 

Where is the upper level energy now? 

 

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Latest on Thursday Night Snowfall

The Setup

A cold front will slide southward and stall across the DC Area on Thursday, meanwhile a disturbance in the jet stream as well as a coastal low will interact to produce a 4 to 5 hour period of accumulating snow across our region between 10pm Thursday and 5am Friday. A period of heavy snow is likely during a one to two hour window likely between midnight and 2am, when snowfall rates may increase to 2″ per hour.

Snowfall Accumulations

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