Temporary "Cool Down" Tomorrow

A back door cold front (BDCF) is currently stalled out in Eastern Massachusetts creating a sharp temperature divide in New England.  A BDCF moves from the east to west instead of the typical west to east motion.  These are notoriously difficult to forecast; my professor of meteorology at Umass-Lowell, Dr. Frank Colby, gave a great presentation on the topic my freshman year.  He showed the differences between what the computer models were forecasting to happen and what actually happened.  That is why some of our weather has been "unexpected" this week.  Take last night...severe thunderstorms ripped across Southern NH and Northern MA.  Click here to read storm reports.  Severe hail ( > 1 inch diameter) was reported for the first time in the month of March since at least 1950, when record keeping began (h/t to Climate Data Center).  Some asked me if that was really lightning that was occurring last night when there were clear skies.  The answer is yes and that is an indication of the strength of these thunderstorms.  In fact the storms exhibited a tornado signature for a time, although due to a temperature of 53 one did not form.  Thankfully I see none of that in the next 5 days or so.

NOAA-NCEP real time temperatures, click to enlarge (will not be blurry)

10 Meter Wind (~30 ft to eliminate friction effects)

Notice the way the contours sharply cut as one nears the coast in the temperature chart and notice the wind barbs are moving in two different directions in western and eastern MA.  That shows where the cold front is right now.  It will make its way into Central MA, RI and eastern CT tonight.  This will drop temperatures into the upper 40's for awhile before rebounding into the lower 50's tomorrow afternoon when the sky is less cloudy.  On Friday a typical cold front will push across the region and this will have two effects.  First temperatures will be raw and showers and even a thunderstorm or two will develop as the energy moves past.  Secondly, it will help move an area of high pressure offshore and flip winds back to the west and southwest.  That means warm temperatures will return this weekend and downright HOT temperatures early next week.  It hit 80 degrees today in Chicago and that will be moving east.

Quick Forecast...
Tonight-             Clouds Increasing lows upper 30's
Tomorrow-        Cloudy start gradually clearing, highs in low 50's
Thursday Night- Increasing Clounds, chance of shower, lows upper 30's
Friday-              Scattered showers, possible thunder, highs in low 50's inland, 40's coast
Friday Night-     Isolated showers, low around 40
Saturday-          Clearing skies, Highs upper 60's
Sunday-            Sunny, Highs lower 70's

Finally I do think we will approach 80 on either Tuesday or Wednesday next week (some towns both).  It also appears another back door cold front wants to develop at that time frame.  This is a long way out and subject to change however a repeat of last nights severe weather outbreak cannot be ruled out.  Despite the record warm winter and lack of snowfall in the United States snow cover in the Northern Hemisphere is still running above average.  With the cold air still locked to the north, any intrusion south into these warm temperatures is bound to fire more severe weather.  Thunderstorms ahead of regular cold fronts will need to be monitored as well. This is something to keep in mind as we enjoy the warm March.  Thanks for reading!