1:55 PM | *Major storm threat for early next week getting more and more interesting*

Deep upper-level trough of low pressure situated in the Southeast US early next week according to the latest (12Z) GFS model; map courtesy tropicaltidbits.com, NOAA/EMC

Overview
Any time a strong storm moves to a position off the Northeast US coastline in January it is time for concern – even in an overall mild weather pattern. Our “January thaw” will continue into next week with temperatures generally running at above-normal levels, but this period will be accompanied by more rainfall.  The next good shot at rain comes later tomorrow into tomorrow night from moisture pushing to the northeast from the Southeast US.  Following that, there continues to be signs for a major storm system to head into the Mid-Atlantic region early next week and it is likely to bring substantial rainfall to the I-95 corridor region from DC-to-Philly-to-NYC. In addition, colder is likely to wrap into this system and this could result in accumulating snow in the higher elevations of the interior Northeast US and it is not out of the question that the rain ends briefly as snow in the big cities along I-95.  Looking farther ahead, a colder weather pattern takes hold in the eastern US beginning late next week.

12Z GFS surface forecast map for late Monday night with strong low pressure situated off the Mid-Atlantic coastline.  Colder air is wrapping into the system at this time and rain changes to snow in higher elevation locations across the interior Northeast US (snow in blue, ice in purple, pink); courtesy tropicaltidbits.com, NOAA/EMC

Details
A deep upper-level trough will develop across the Southeast US by early next week (top) and this will set off the formation of a strong and slow-moving surface low pressure system. In fact, it appears there will actually be two parts to this overall storm system early next week with the first wave of low pressure producing rain in the I-95 corridor from Sunday into Monday and then a second and stronger system likely to produce more rain from late Monday into early Tuesday.  Colder air will wrap into this second system and a changeover to snow is looking more and more likely across interior higher elevation locations by Monday night.  In fact, there is an outside chance that the second system produces a changeover here from a cold rain to snow or sleet for a brief time late Monday night or early Tuesday before it finally pulls away to our northeast.  

5-day precipitation totals as predicted by NOAA from early today into early Tuesday  showing the continuation of the California onslaught and copious amounts of rainfall in the Northeast US from tomorrow's system and the early week "two-part" low pressure system.

The combination of strong upward motion associated with the deep upper-level trough, copious amounts of moisture streaming out of the Gulf of Mexico and western Atlantic, and slow movement will likely result in some significant rainfall around here during this event from later Sunday into early Tuesday.  The forecast of accumulated rainfall over the next 5 days includes tomorrow’s expected rainfall as well as the rainfall expected from the "two-part" early week major storm system.  Additionally, take a look on the rainfall map at the state of California where the onslaught continues.  The drought has "officially" ended across the northern half of the state and the southern half of California will get much relief over the next several days.  Looking ahead, the overall weather pattern looks to become colder for the eastern US late next week and this change is likely to bring about colder weather for us going well into the month of February.  

Meteorologist Paul Dorian
Vencore, Inc.
vencoreweather.com