10:50 AM (Tuesday) | *First significant precipitation event of the month in the Mid-Atlantic region to come Thursday into Friday…ending an unusual March dry spell*
Paul Dorian
The first decent precipitation event of the month of March comes to the Mid-Atlantic region from Thursday into Friday. Map courtesy NOAA
Overview
It has been an unusually dry month of March so far in the Mid-Atlantic region with zero precipitation reported in DC, Philly and NYC. The impact of the dry spell has actually been made worse with an extremely dry air mass in recent days featuring abnormally low dew point temperatures of below zero – indicative of very low moisture content in the atmosphere. Strong low pressure will bring this dry stretch to an abrupt end later in the week with significant precipitation from Thursday into Friday. The rain that falls on Thursday and Thursday night in the Mid-Atlantic region can be moderate-to-heavy at times and there is a chance that it changes briefly to snow on Friday as colder air wraps into the system.
A blocking pattern over southern Canada later this week will help to “force” low pressure to the southeast after it reaches the Ohio Valley. As such, colder air can filter into the system from the northwest-to-southeast potentially causing rain to change briefly to snow in some parts of the Mid-Atlantic/Northeast US. Map courtesy NOAA, tropicaltidbits.com
Details
There has not even been a trace of rain in the Mid-Atlantic’s I-95 corridor this month which is the longest stretch in almost six years in the Philly metro region and the longest March streak there since 1987. This dry weather is quite unusual for the month of March as, for example, it is the 2nd wettest month of the year in Philadelphia (PA) with about 3.8 inches of total monthly precipitation as an average. To exacerbate the impact of the dry spell, an extremely dry air mass in recent days has combined with strong winds to produce dangerous wildfire conditions and one such fire had to be put out quickly on Monday in New Jersey before it could spread too far from its origin. This extremely dry air mass of recent days had its origins way up in northern Canada. Fortunately, soil moisture is not in bad shape in areas north of the PA/MD border as the melting of the winter snows in recent weeks has helped the overall situation – more than 30 inches, for example, to the north and west of Philly. Weak low pressure can produce a light wintry mix today in the Mid-Atlantic region, but it will be certainly be far from anything significant and there is an equal chance that no precipitation actually reaches the ground given the still very dry lower atmospheric conditions in at least parts of the area.
Low pressure will reach the Ohio Valley on Thursday bringing rain to the Mid-Atlantic region…the first decent rainfall of the month. Map courtesy NOAA, tropicaltidbits.com
On Wednesday, strong low pressure system will push into the Rockies and then it’ll head into the Ohio Valley by Thursday. At the same time, strong blocking will be in place across south-central and southeastern Canada and this will impact the approaching low pressure system by not allowing it to push any farther north than the Ohio Valley. In fact, once this late week low pressure system reaches the Ohio Valley, it will be suppressed to the south and east and likely end up exiting off the Mid-Atlantic coastline.
Low pressure will shift from the Ohio Valley to the Mid-Atlantic coastline by early Friday as the result of a blocking high pressure system over southern Canada. With this path, colder air should wrap into the system from northwest-to-southeast potentially causing a brief changeover to snow (shown in blue) in parts of the Mid-Atlantic region and Northeast US with the greatest chance of a changeover in interior, higher elevation locations. Map courtesy NOAA, tropicaltidbits.com
As a result, rain will develop on Thursday and continue into Thursday night and some of it can be moderate-to-heavy at times. As the surface low shifts to a position off the Mid-Atlantic coastline late Thursday night into early Friday, colder air will tend to wrap into the system from the northwest and this can result in a brief changeover to snow; especially, across interior higher elevations of the Mid-Atlantic/Northeast US…something to monitor over the next couple of days. Strong high pressure will push into southeastern Canada by the end of the work week and it’ll act as the source for some cold air potentially causing a changeover to snow in some locations. This cold air mass will stick around into the early part of the weekend across the Mid-Atlantic/Northeast US.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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