Chantilly, VA 20153 Weather

What Has Changed

A Frost Advisory was issued for the piedmont from 1 to 9 AM Monday. A Coastal Flood Advisory was issued for Anne Arundel County through 7 PM this evening. Otherwise there have been minimal changes to the forecast through next weekend.

Key Messages

- 1) One more night of frost potential will give way to a warming trend early this week.

- 2) Dry conditions persist with increasing temperatures through the end of the week.

Discussion

KEY MESSAGE 1...One more night of frost potential will give way to a warming trend early this week.

High pressure remains centered along the Mid Atlantic coast this afternoon but will drift southwestward tonight. Low-level flow will turn westerly allowing for less of a marine influence. At the same time, temperatures aloft will begin rising. The surface gradient is weak enough that forecast soundings indicate sharp decoupling. This will send lows into the 30s again, particularly in outlying and low lying areas. A Frost Advisory has been issued for the piedmont where the growing season remains active, as these areas will likely decouple best. The advisory is based on the forecast lows, although there is some potential with dew points starting in the 40s and the moderating airmass, we may ultimately end up with just a heavy dew even if temperatures drop to the mid 30s. Ridgetops meanwhile will stay in the 40s. Expect river valley fog to develop again, although some guidance suggests the fog may affect more areas than in previous nights.

Expect temperatures to rise above normal (upper 60s to lower 70s) by Monday afternoon as the warming airmass mixes to the surface. Minimal cloud cover and light winds will remain persistent.

A backdoor front will drop into the area Tuesday, trailing low pressure moving into the Canadian Maritimes. Forcing and moisture with this front are limited, with the main effects being a few extra clouds and a wind shift to the north. Minimal low level cold advection will mean temperatures likely remain above normal for Tuesday.

KEY MESSAGE 2...Dry conditions persist with increasing temperatures through the end of the week.

Upper-level ridging builds over the Mid-Atlantic through the end of the week, resulting in continued high pressure and dry, stable conditions across the region. After a slight cool down Wednesday behind the backdoor front, temperatures should gradually warm some, with afternoon highs reaching the mid-70s by Friday with overnight lows in the 50s. As the front stalls and starts lifting back north, some extra clouds may form in the warm advection pattern Wednesday into early Thursday. Mostly sunny skies will return Thursday into Friday.

Aviation

Expect VFR conditions through this evening with only a few stratocu possible. NAM and related guidance continue to show more widespread fog development late tonight into early Monday morning, with at least some hint of this in other guidance and forecast soundings. Have put some minimal visibility reductions in the TAF, with fog most likely along river valleys. Any fog in Foggy Bottom will likely remain upstream of DCA given a westerly background flow.

Winds are shifting to the southerly quadrant this afternoon, likely becoming calm in many locations tonight. W/NW winds AOB 10 kts are expected Monday. A dry front will bring a wind shift to the north Tuesday, but VFR conditions will continue to prevail.

VFR conditions are anticipated to persist through the end of the week. Cloud cover may increase somewhat Wednesday as the front begins to lift north, but otherwise no precipitation is expected. Light northeast winds shift southerly Thursday before shifting westerly Friday.