Friday Night into Monday:
This period is more uncertain with below normal forecast confidence
given the differences in 500 mb evolution alluded to above. It does
look like rain develops later Fri night into Sat where PoPs were
increased into the likely to low categorical range for Sat. With
enough colder air in place at outside, precip may begin as brief wet
snow with perhaps some minor sub-Advisory accumulation in interior
Southern New England, but rain is likely to predominate. Rain may
continue or linger into the balance of the weekend, particularly
into southeast New England, and I opted to deviate from the dry NBM
to carry a lower Chance PoP mention for Sun into Mon. EPS and GEFS
show 24-hr rainfall probs Sat into early Sun that are in the
moderate to high range (50-80%) for a half inch or more of rain,
moderate (30-50%) for an inch or more of rain, and low (10-20%) for
24-hr rains over 2 inches. If higher rainfall materializes from a
stronger/slower solution, the potential would increase for areal
flooding; while astro tides are on the low side (~9.50 ft MLLW for
Boston Harbor) persistent onshore flow would also bring the risk for
splashover or minor coastal flooding. Potential for large forecast
changes in the coming days given the current model solution spread
for this period, so stay tuned!
Snow?