BOX into the winds
Saturday...
A deep positively tilted H5 trough stretching from Hudson Bay to
Alabama develops on Sat. Out ahead of this high amplitude trough,
strong SW flow will yield PWAT plume of 1.3 inches, or 99th
percentile according to NAEFS ensemble situational awareness table.
Strong jet dynamics (u and v wind component also at 99th percentile)
acting on the anomalous moisture plume will support periods of heavy
rain Saturday. Highs will be in the 40s but could be as warm as the
50s, depending on eventual track of surface low and associated warm
sector (most likely southeast MA). All model guidance has surface
wave rapidly intensifying as it tracks somewhere between the I-95
corridor to Cape Cod, then along or just off the Maine coast as a
sub 970 mb low. The low continues to deepen over the Maritimes
Sat night.
This rapid intensification, combined with strong cold air advection
on the backside and impressive pressure rise/fall couplet, will support
strong to perhaps damaging winds as the low exits southern New
England late Sat into Sat night. With 925mb temps rising to +10
to +13C across southeast MA and RI on Sat afternoon, the
potential of damaging pre-frontal winds mixing to the surface
would appear to hinge on the amount of insolation with best
chance of damaging winds across the MA coastal plains away from
the immediate south coast (SSTs are still in the lower 40s).
NAM/GFS Bufkit soundings show winds at the top of the mixed
layer at mid 40 to low 50 kts.
In addition, rain likely ends as a period of snow from west to east
late Sat/Sat evening, with some minor accumulations possible across
the interior higher elevation across the East Slopes and northern
Worcester Hills.