Rain to spread into the Northeast; Warmer late in the week
1. A storm from the Carolinas will move northeastward to reach the Virginia coast late tomorrow, near New York City on Wednesday, then past Boston on Thursday. Stiff easterly winds precede the storm and its rain, but both diminish/end as the storm center goes by. This map shows what the pressure pattern looked like earlier this morning:
There is plenty of Atlantic moisture available.
Video:
Apr 24, 2017; 7:00 AM ET A storm moving slowly northeastward from South Carolina will spread rain through the Middle Atlantic states today and then into New England for tomorrow. Once the rain leaves, there will be a...
2. During the late morning, a band of very heavy rain with thunderstorms extended from eastern North Carolina southward over the ocean:
This feature will move northward, causing street and highway flooding as it goes.
3. The map below allows us to see how the eastern storm meshes with other features now affecting the United States.
We see that the eastern storm is well separated from any storminess affecting the middle and western parts of the nation. It appears that a new trough position aloft is becoming established over the Western states. When there is as trough in the West, we expect to see a ridge in the East, and that is likely become reality once the current storm exits the scene Thursday and Friday. This in turn will favor above-average temperatures in the East as we go from the end of April into early May. This does not mean there will be a simple pattern of warmth in the East. Rather, we should expect to see a series of cold fronts move across the Central states with violent thunderstorms, then weaken but not completely disappear as they run into the eastern ridge.
4. Back to the near term, the following three maps are GFS ensemble mean forecasts for 8 a.m. ET tomorrow and Wednesday. In each case, the precipitation is for the six hours preceding map time.
5. The East Coast storm and the cold frontal/low pressure system heading for the Upper Midwest can drop significant rainfall. The GFS ensemble mean rainfall totals from this morning until just after midday on Thursday are depicted on this map:
Note the sharp gradient between flood capable amounts of rain (the red to orange colors) and more moderate totals. Between the two primary weather drivers is a zone centered over Ohio that seems unlikely to have any important rain from either system through Thursday midday.
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