Adding The East for Heavy Rain Next Week?

Fig. 1-2: The 12Z GFS and ECM upper air forecast for the 8-14-day period.

Fig. 3: Accumulative rainfall in the Richmond, VA, area during the next 15 days according to all models.

Discussion: Signs of a possible shift of the heavy rainfall in the South-central U.S. entering May to the Mid-Atlantic (or Northeast) U.S. in the 8-14-day period are generating. The 12Z GFS unwinds a coastal low-pressure system in the 8-14-day period to soak New England (Fig. 1). However, the ECM is less progressive with the low-pressure area and keeps the storm center in the Eastern Tennessee Valley in the 8-14-day period encouraging a wet fetch of Atlantic moisture into the Mid-Atlantic region (Fig. 2). A precipitation amount forecast for 15 days highlights the differences between the models BUT does introduce the idea of potential heavy rain using Richmond as an example location. The 15-16-day forecasts indicate a range of 1.25 to 2.5 in. of rain utilizing the GFS/GFS ENS while the ECM OP indicates 5-6 in. or rain (Fig. 3). There are high spots of 10 in. of rain on the northern Mid-Atlantic Coast given the ECM forecast. Climate forecasts anticipate a shift in wet risk to the East Coast during MAY/JUN/JUL and the potential wet weather scenario later next week may be the beginning of that pattern.