What, When and Where:
A band of rain that moved through Virginia and eastern Maryland this morning was poised at noon to cause a rainy afternoon and a wet and splashy commute for Philadelphia, New York City and nearby places. After school sports will be affected in a number of localities.
This is more than a passing shower; some places will have at least two hours of rain. The rain will depart from Philadelphia after dark, and New York City by midnight. Some of the rain will affect eastern New England, including Boston, overnight. All places will see an increase in sunshine tomorrow.
Reasons for this prediction:
This midday radar display from the Dover, Del., radar shows where the rain was just before noon.
This computer model for the six hours ending at 8 p.m. EDT shows an area with substantial rain:
Short-range computer models usually have highest accuracy. The rain area behaved this morning as predicted by this model.
The radar does not show just one solid area of rain, so the rain can start and stop at your location. No lightning was observed in this rain area before noon, but that could change during the afternoon. In areas with little wind after the rain stops, fog could form.
As July draws to a close, a storm system swinging up from the Deep South will bring downpours that will break the back of the heat wave in much of the northeastern United States.
A renewed risk of severe weather will threaten portions of the north-central United States into midweek.
Heavy downpours will raise the concern for flash flooding along the Gulf Coast and lower Mississippi Valley through midweek.
A stifling heat wave will remain entrenched across the Northeast much of this week, despite a brief reprieve in humidity for some.
Dangerous heat will surge northward and send temperatures rising across the northwestern United States this week.
Severe thunderstorms rumbled through the Northeast on Monday, lashing the region with damaging winds while also unleashing heavy downpours that triggered flash flooding.
New York/MA (1819)
Two simultaneous cloudbursts, 45 miles apart; A bucket survey claimed 15" of rain fell at Catskill, NY. Highways were completely washed out. One washout started west of the old Albany Post Road and spread eastward across the road until it was 190 feet wide and 80 feet deep in a distance of 160 paces. At Westfield Valley, "suddenly the windows of heaven seemed to have been opened and the rain fell in such torrents that in less than 5 hours, Westfield River rose at least 20 feet above its usual height at low water. The river overflowed its banks with great rapidity and violence, sweeping away every bridge, fence and building which opposed its current."
Pittsburgh, PA (1872)
Cloudburst of 30 minutes followed by a flash flood. Over 133 people drowned on the north side of Butcher Run and Wood's Run.
New Jersey (1892)
Spectacular "double" waterspouts off Barneget Light at heights of 500-600 feet.