We flood!
As far as timing for heavy rainfall goes, the latest suite of hi-res
model guidance suggests heavy downpours may begin to trickle into
western MA and CT a few hours before sunrise Saturday morning.
Expect showers and thunderstorms to continue east into eastern MA
and RI during the mid to late morning hours. Signals for excessive
rainfall are rather robust from the 00Z HREF with some 10 to 20
percent probabilities of 6 hour rainfall exceeding 100 year average
return intervals (ARIs). Furthermore, the HREF localized probability
matched mean QPF product is highlighting the potential for as much
as 5 inches of rain over localized areas. There is considerable
uncertainty with respect to which locations will experience the
heaviest rainfall, but generally all of southern New England will be
at risk, especially the urban areas. Given the strong signals for
heavy rainfall, we`ve raised a flood watch for all of southern New
England minus The Cape/Islands from 2AM Saturday to 8PM Saturday.
Activity should begin to wane by mid-afternoon on Saturday and
eventually clear our by Saturday evening. The atmosphere will remain
warm and muggy during this time, but with extensive cloud cover for
much of the day on Saturday, high temperatures should be confined to
the low to mid 80s.