Tuesday Update: Major Snow Storm for Some, Major Ice Storm for Others?

This is a very low confidence forecast as the latest forecast models continue to indicate a more inland track of the low pressure system which is increasing the threat of sleet and freezing rain and drastically cutting down on snowfall accumulations! My map below includes Snow, Sleet (frozen rain drops) and Freezing Rain.

Any deviation in track of the area of low pressure further to the west or back to the east will have a drastic impact on whether we are digging out from snow or sleet (or both), or losing power from ice accretion from freezing rain.

Here’s a look at the latest forecast models and what they are showing for potential snowfall accumulations:

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Remnants of Sally May Impact DC Area Late Week with Heavy Rain and Tornadoes

A cold front will cross the Washington region late tonight ushering in lower humidity and cooler temperatures for the early to middle portion of the upcoming work week. The latest European forecast models depict the potential for the remnants of Sally to impact our region during the later portion of the week. Should this threat materialize, the threat for heavy rain and tornadoes would increase Thursday night into Friday.

More Heavy Rain?

The latest European Forecast model (images below, courtesy Pivotal Weather) show heavy rain moving through the Washington Area Thursday night into the day on Friday. Depending upon how quickly the remnants move through, the threat of widespread flooding may not materialize.

Wind Shear & Tornado Threat

The next image shows bulk wind shear (wind shear is defined as winds that change speed and direction with height) increasing as the remnants of Sally potentially move through the Mid-Atlantic Thursday into Friday.  The threat from tornadoes would be relatively high for our area if wind shear values above 45 knots were to materialize as shown in the model image below. If the track of Sally’s remnants were to shift further south, the threat for tornadoes would decrease… stay tuned.

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High Impact Flooding Event for DC Metropolitan Area

Numerous strong to severe thunderstorms are expected to break out this afternoon and evening across the DC Region, well in advance of the approach of tropical storm Isaias.  Thunderstorms could produce strong, damaging winds with an isolated tornado possible. The image from the latest high resolution NAM model below (courtesy, tropicaltidbits.com) shows a nasty line of storms moving into our region between 4 and 8pm.

The latest ensemble models (spaghetti chart below) shows confidence in a storm track from just east of Richmond, VA to the mouth of the Potomac before crossing over the Bay into Delaware and New Jersey.

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