Current temperatures range from 65-70 in the western regions, 70-75 in the rest of the area except for the coastal region which is currently around 60. The satellite image shows moisture beginning to push in both from the south and west as an area of low pressure pushes out into the Atlantic, and another area of low pressure moves in behind, but for the moment high pressure is in control over the region.
The upper air pattern is trough over the Great Plains with ridges over both the west and east coasts. The sounding data shows weak cold air advection over the region. No precipitation is currently over the region. The nearest area of precipitation is just off the Outer Banks of North Carolina. Mid-level dew points were from -25 to 0 degrees C, so with the dry conditions aloft, precipitation is not expected to be an issue for the rest of today.
The area of high pressure that is currently over head will begin to move into the Atlantic as a cold front and low pressure system push into the region. Saturday and Sunday will have positive forcing from vorticity adveciton as well as moisture transport from the gulf. Satuday has the potential for development of thunderstorms. There is a small chance that a few of the storms could be severe. The main threat would be strong damaging winds and a few isolated tornadoes. The shear over the region is expected to be high which will enhance the instability from the passing front and daytime heating. By Sunday, a deepening trough/low pressure system will begin to push up from the south and move along the Atlantic coast. The system will have frontogenesis as it pushes up the Atlantic seaboard. By the time it gets to the New York region, it will be nearly vertically stacked and very strong.
By Monday evening into Tuesday, the low begins to retrograde into eastern New York and parts of Canada. This could bring extensive rains to the area as the system pushes through. Current estimates are around 2 inches total with higher amounts in the east, but this could easily change with slight shifts in low track. Current track ensembles show high amounts of uncertainty as some runs had the system as far north as New Brunswick, or as far south as the gulf coast of Florida. All that ensembles seems to have a good handle on is that it will track up the coast, but the speed is uncertain at this point.
By Wednesday, the low retrogrades into northern Canada, and a shortwave begins to bring positive vorticity advection and some showers to the region. However, right now it looks like this system will bring a cold front through on Thursday and begin to quickly push into the Northeast. The precipitation potential looks to be minimal.
Point Forecast Sterling, VA-
Rest of Today-Temperatures will begin to fall into the 60's this evening as cloud cover begins to stream in.
Saturday- It will remain overcast for the day with high temperatures around 75. Precipitation will begin to move in, and heavy rains will be possible. Rain should be 1 inch or less. Some storms might be severe, the main threat being damaging winds. The low will fall to around 50.
Sunday- Much cooler temperatures with a high around 55. The rain will continue, with up to an inch possible. The low will be around 45.
Monday- More rain as the low continues to track up the Atlantic seaboard. High around 55 and a low around 45. Another half inch of rain is possible.
Tuesday- A chance of a few showers, but any totals should be less than a tenth of an inch. A high of 60 and a low of 40 is expected.
Wednesday- The rain finally moves out of the region, with mostly cloudy skies and a high around 65 with a low around 40.
Thursday- Another partly cloudy day with a high around 70 and a low around 50.