Forecast Discussion
Summary
SYNOPSIS
... High pressure builds into the region as low pressure meanders off the New England coast. A cold front will drop southward Tuesday, crossing the area Tuesday night. High pressure gradually builds in through the end of the week as another low spirals off the New England Coast.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Low pressure will remain off the coast of Maine while high pressure remains over the central CONUS. A northwest flow aloft will allow for more dry and cool conditions along with low humidity. The atmosphere will decouple in most areas, so winds will be light. Low temperatures will range from the 40s in the colder valleys and rural areas, to the 50s for most other locations with low 60s in downtown Washington and Baltimore.
SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... The upper low east of Maine drifts north Tuesday, then retrogrades west Wednesday, merging with an elongated shortwave trough moving south from northern Canada. These combine into a large upper low that spans from the Mid-Atlantic/eastern Great Lakes to Newfoundland. A blocking pattern over North America will keep the upper low in place over New England/Northeast through week's end.
Numerous shortwaves moving across the western periphery of the upper low could bring a low chance for showers each afternoon through Wednesday. However, given the dry air in place any shower activity is likely to be limited. The warmest temps this week are forecast Tuesday afternoon with highs reaching the low to mid 80s, then back to normal Wednesday with upper 70s to low 80s. Overnight lows in the upper 40s to low 50s west of the Blue Ridge, and 50s to the east.
LONG TERM /THURSDAY THROUGH MONDAY/... Looking through the latter portion of the week, expect a slight chance of pop up showers and thunderstorms mainly confined to the Chesapeake Bay in association with an upper-level low to the northeast providing some forcing. This system should lift up out of here by Friday with a continuation of NW flow and drier conditions. Temperatures in the Thursday-Friday period will remain below average with dry conditions expected for most of the area. Expect temperatures to warm up on Saturday with rising heights and flow returning more from the SW.
Into Sunday, surface temperatures continue to increase as the upper level flow becomes more zonal. Increasing dew point temperatures and a shortwave trough passing from the northwest may provide forcing for a few showers Sunday evening into Monday.