12:00 PM | ***An amazing outbreak of cold air for the early part of the weekend with very strong winds…rain-changing-to-snow scenario on the table…much more bearable for Mother’s Day afternoon***

An extremely anomalous upper-level low will move on top of the Mid-Atlantic/NE US by the early part of the weekend representing the core location of an amazingly cold air mass for this time of year. Map courtesy NOAA, tropicaltidbits.com

Overview

Today is an unusually chilly day in the Mid-Atlantic region with temperatures far below-normal for the 6th of May aided by a low-level easterly flow of air and thick cloud cover. In fact, high temperatures today in much of the Mid-Atlantic region will be confined to levels rarely experienced for this time of year.  Believe it or not, this air mass may pale in comparison to what is on the way for the early part of the weekend. 

Quite an amazing outbreak of cold air will arrive in the Mid-Atlantic region and Northeast US on Friday night and the cold frontal passage may actually be accompanied by a rain-changing-to-snow event – even into higher elevation suburban locations just to the north and west of I-95. Saturday will turn out to be a very windy and unusually cold day in much of the northeastern quadrant of the nation with temperatures in the DC-to-Philly-to-NYC perhaps more than twenty degrees below normal.  While Sunday, Mother’s Day, will remain colder-than-normal, the afternoon will become much more bearable when compared to Saturday as there should be far less in the way of wind and plenty of sunshine.  Looking ahead, cold air outbreaks will likely continue into mid-May across the central and eastern US, but a pattern change to warmer looks like it’ll begin during the 3rd week of the month - and tropical season may not be far behind.

12Z NAM total snowfall forecast map by Saturday evening with quite an impressive display for this time of year. Map courtesy NOAA, tropicaltidbits.com

Details

Two ways to get chilly weather this time of year in the Mid-Atlantic region and Northeast US is to have thick cloud cover and an easterly flow of air in the lower part of the atmosphere as ocean temperatures in the western Atlantic are still quite chilly this time of year.  Indeed, both of these conditions are being met today and temperatures will do no better than the low-to-mid 50’s for highs in the big cities of DC, Philly and NYC.  These kinds of high temperatures could very well end up being some of the lowest maximums for the date of the 6th of May in many years.  Low pressure is intensifying off-shore at mid-day and an area of precipitation associated with this system is actually expanding and will result in additional showers for the I-95 corridor into the early evening hours in this very chilly air mass. It is so cool, in fact, that snow is being reported at mid-day across upstate Pennsylvania (e.g., DuBois, PA at 35 degrees with light snow) which is, of course, somewhat unusual for the early part of May.

Low pressure will form along an advancing cold frontal boundary zone and the result could be a rain-changing-to-snow event for a good part of the Mid-Atlantic region and Northeast US on Friday night/early Saturday. Map courtesy NOAA (12Z NAM), tropicaltidbits.com

After a chilly and breezy day on Thursday, the weather will become active again by later Friday as low pressure forms along a cold frontal boundary zone in the Tennessee Valley.  This system will push rain into the Mid-Atlantic region during the afternoon hours and, believe it or not, it could turn cold enough for a changeover to snow in parts of the region during Friday night; especially, in the higher elevation locations to the north and west of I-95. This system will intensify significantly by the time it reaches the northern New England coastline on Saturday morning and a very cold air mass for this time of year will flood the region riding in on strong NW winds. 

Quite an amazing outbreak of colder-than-normal air will encompass much of the northeastern quadrant of the US by the early part of the weekend. Map courtesy NOAA (12Z NAM), tropicaltidbits.com

Temperatures will be far below-normal throughout the northeastern quadrant of the nation on Saturday and it’ll be quite unstable in the Mid-Atlantic and NE US with an extremely anomalous upper-level low sitting on top of the region.  In addition to the very strong winds and unusual cold, there can be some rain and/or snow shower activity on Saturday given the unstable environment that is anticipated.  Mother’s Day (Sunday) will get off to a very cold start for this time of year and it’ll stay well below-normal; however, the afternoon will be much more bearable compared to Saturday as the winds should be far less noticeable and there should be some sunshine. One interesting note, the low temperatures on both Saturday morning and Sunday morning could very well be in the 30’s in Philadelphia and the last time they dropped below the 40 degree mark on May 9th or later was 1966.  There will very likely be a widespread area with near record or record lows on both weekend days in the Midwest/Great Lakes/Mid-Atlantic and NE US with this amazing cold air outbreak.

Cold air outbreaks have dominated the scene for weeks in the central and eastern US, but there is light at the end of the tunnel. It looks like the 3rd week of May will bring a transition to the overall weather pattern resulting in warmer-than-normal weather in much of the central and eastern US - and tropical season will not be too far behind. Map courtesy NOAA, tropicaltidbits.com

Looking ahead, the overall pattern that has resulted in cold air outbreaks for the central and eastern US finally looks like it may break down during the 3rd week of May.  It should remain generally colder-than-normal for much of next week in the Mid-Atlantic/NE US, but then a transition to warmer weather looks likely once we get by the middle of the month.  The temperature at Philadelphia has not reached the 80 degree mark yet this year and the latest that that has happened for the first time in a given year was May 20th (1984) – close call.  By the way, once we transition to warmer weather during the second half of May, the tropical season will not be far behind as often times it begins early following a chilly spring in the central and eastern US.   

Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com

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