Congress Heights, DC Weather

What Has Changed

A Frost Advisory has been issued from 1 AM to 9 AM Sunday for portions of northern Virginia and central and northern Maryland. A Coastal Flood Advisory may be needed this evening for Alexandria. Sky cover was increased a bit into tonight across the southern half of the forecast area, but the forecast otherwise remains on track for the coming week.

Key Messages

- 1) Frost or freezing temperatures are possible in many areas tonight and Sunday night.

- 2) Dry weather continues through next week along with generally seasonable temperatures.

Discussion

KEY MESSAGE 1...Frost or freezing temperatures are possible in many areas tonight and Sunday night.

High pressure remains centered to our northeast this afternoon and will slowly drift southwestward through early Monday. Favorable conditions for radiational cooling will continue the next two nights, albeit with some caveats.

The growing season for 2026 has ended along and west of the Blue Ridge and Catoctin Mountains, but continues east of there. Any headlines for frost/freeze conditions will only be issued where the growing season remains active.

Other than some subtle differences, tonight into Sunday morning should reflect a lot of persistence from Saturday morning. This resulted in 31-36 degree low temperatures across northern Virginia and central and northern Maryland, particularly in rural, low-lying areas. Therefore, a Frost Advisory has been issued for these areas from 1 to 9 AM Sunday. Felt that subfreezing temperatures would be too localized for a warning. And while outlying areas along and east of I-95 could be chilly as well, the frost potential seemed too isolated for an advisory at this time. Meanwhile, confidence is lower for an advisory in central Virginia due to higher dew points and potential cloud cover, as this afternoon's stratocumulus field continues to drift westward and possibly bank along the Blue Ridge tonight if it doesn't break apart.

The high will be drifting southwest toward the central Appalachians by Monday morning, with several competing factors influencing temperatures. Low level flow will turn westerly, so areas along and east of I-95 may have a chance of being colder than Sunday without the modifying marine influence. Temperatures will also be rapidly warming aloft, so the ridges and any location that doesn't completely decouple will likely be warmer. There is also a sizable range of dew point temperatures forecast in models. However, the gradient will be negligible with decoupling likely, and the NAM has been particularly consistent in showing sharp surface inversions and the coldest temperatures of the weekend. All that to say, while coverage is a bit uncertain, the frost and freeze threat will persist through Monday morning.

Only minor changes have been made to the previous min temperature forecasts, which are near or below the coldest guidance which performs best in radiational cooling (MOS, NBM 10th percentile and Canadian Regional).

Aviation

VFR conditions are expected to prevail through early next week. There are some hints that a slight uptick in low-level moisture could lead to some patchy fog during the early morning hours tonight, and maybe more so Sunday night/Monday morning, though confidence in timing and extent of fog is low at this time. The NAM and related guidance is by far the most aggressive with this outcome (especially Monday morning), but is an outlier.

Light E to SE winds are expected today, with light to calm winds tonight. Wind direction may be a bit variable, ranging from SE to NE as high pressure passes directly overhead Sunday. Winds become northwesterly Monday but remain less than 10 kt.

VFR conditions are expected to continue through Thursday next week. Winds shift north to northwesterly Tuesday in the wake of a dry cold front, then shift east to southeasterly between Wednesday and Thursday. Cloud cover could begin to increase somewhat between Wednesday/Thursday as a frontal boundary approaches, but no precipitation is anticipated at this time.