Looking at the recent past, six of the past 7 days have had high temps below normal. This “chill down” was attributed to a southward push of the jet stream over the Northeast and Midwest. A notable change to the recent cool temperature regime will occur as developing breezes from the southwest ahead of a vigorous low pressure center moving from Iowa Sunday morning to Lake Huron Sunday night allows much warmer air to return.
Clouds will share the sky with patchy sunshine and it will be dry as temperatures rise into the low 70s later Sunday afternoon. Cloud cover and breezes from the south will keep conditions unusually mild as temperatures only fall to near 60. The aforementioned low pressure will move into Quebec during Monday.
A cold front attached to the low will move from central Pa. in the morning to the Northeast Seaboard by dusk. Moisture gathering along the front will support a corridor of showers that should reach the area by late morning and continue into the afternoon. A vigorous jet stream disturbance passing over the frontal zone may organize a new area of low pressure near New Jersey. If this should materialize the showers will linger for much of Monday. If this new low does not form, then the showers that occur on Monday should only last for about 3-5 hours. Regardless, there should be enough instability in the atmosphere to produce a few rumbles of thunder and some gusty winds across the region on Monday. In addition, despite plentiful cloud cover and expected showers, it will be unseasonably mild on Monday with temps peaking in the low 70s!