March Out Like a Lion

The upcoming Easter weekend is looking stunning with mostly sunny skies and high temperatures ranging from the middle 60s to near 70 degrees.  But first we have to get through a rather rainy Wednesday and January-like temperatures on Thursday and Friday.

The latest high-resolution NAM model (image above, courtesy Pivotal Weather) shows widespread showers with some embedded thunder beginning around 1pm on Wednesday and continuing through the tail end of the evening rush hour.

An arctic front will then approach the DC Area on Wednesday night while a strong area of low pressure develops and rides northward along the front changing rain over to snow in our western zones. Some snow may even mix…

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Frost, Freeze and Snow …. Polar Vortex Arriving This Weekend

We started November 2019 bitterly cold, then winter 2019-2020 was mild and void of meaningful snow in D.C. Fast forward to Spring 2020 and temperatures in April were well below normal. We aren’t out of the woods yet as more record-shattering cold is coming for the upcoming Mother’s Day Weekend. Frost and Freeze Advisories may be issued this weekend and several storms will likely bring accumulating snows to the mountains from West Virginia to northern New England.

The image below (courtesy Pivotal Weather) shows the 500mb height anomalies.  500 mb height anomalies show where troughs and ridges are located in the atmosphere (a river of air). Red colors indicate ridging (blocking) and blue/purple colors indicate where the atmosphere is much thinner due to the presence of a very deep trough of low pressure. *Notice towards the end of the image below how the dark reds build across Greenland and northern Canada (indicative of blocking). Blocking allows the jet stream to buckle south and for the polar vortex to become dislodged southward into the lower 48. Bottom line – don’t put away your winter coats!

The dark blue and purple colors diving southeast across the Great Lakes, Mid-Atlantic and New England are indicative of a piece of the polar vortex breaking free from the arctic and a deep trough (dip in the jet stream) getting cut off below blocking over Greenland.  If this pattern had materialized during the Winter we would have been digging out from feet of snow. For the upcoming weekend this pattern will bring temperatures down to 30 degrees below average! Pretty impressive for early May! So how cold will it get?

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Big Changes Coming Next Week

The first arctic blast of the season may impact much of the eastern half of the nation behind a very strong cold front and complex storm system poised to impact the Mid-Atlantic Tuesday into Wednesday of next week.

The North Atlantic Oscillation (NAO), Arctic Oscillation (AO) are both trending toward their negative phases (cold signal in the east) and the Pacific North American (PNA) Oscillation is trending toward its positive phase (favors a ridge building over the western United States).

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