Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
840 PM EDT Tue Oct 26 2021
 
Day 1
Valid 01Z Wed Oct 27 2021 - 12Z Wed Oct 27 2021 

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF 
THE NORTHEAST...

01Z Update...
The powerful storm that has developed southeast of New England 
this evening is forecast track to the west and then southwest 
overnight.  Upper level energy along with low-to-mid level 
frontogenesis will support some additional bands of moderate to 
heavy rain moving southwest across southern New England, 
southeastern New York, and northern New Jersey through the evening 
into the overnight.  A band of intense rainfall currently moving 
west across Cape Cod is expected to contribute to heavy rainfall 
amounts this evening across portions of eastern Massachusetts and 
Rhode Island.  It is unclear how far west this band will persist, 
however recent runs of the HRRR do show it producing another 
period of moderate rain overnight for Connecticut and the NYC 
metro.  Meanwhile, strong onshore flow north of the low is 
expected to support periods of at least moderate rain through the 
overnight across portions eastern Massachusetts, including the 
Boston metro, and Rhode Island.  Therefore, a Slight Risk was 
maintained for parts of eastern Massachusetts, Rhode Island, as 
well as western Long Island and the NYC metro.  A Marginal Risk 
was maintained for areas farther north and west, including 
portions of Upstate New York and western New England.  While 
widespread additional heavy amounts are not expected across these 
areas, recent runs of the HRRR have shown some signal for locally 
moderate to heavy amounts, which may result in additional runoff 
concerns given the heavy rains that have already occurred today.  
Latest 3-hr flash flood guidance values are an inch or less for 
most areas along and west of the Hudson Valley into the Catskills 
and northern New Jersey.

Pereira  
 
Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt