From the WPC heavy rainfall discussion, flash flooding a concern again today:
PWs near 2 inches (2.5
standard deviations above normal) and modest deep-layer
instability should support organized convection along and ahead of
the boundary. Lift will be enhanced by a pre-frontal mid-level
shear axis and broadly diffluent flow between the retrograding
upper ridge and trough moving across east-central Canada.
Meanwhile, the uptick in sw-wsw low level flow ahead of the
surface front (25-30 kts) will foster backbuilding convection and
cell training, especially over the Slight risk region later this
afternoon and evening when the low-level inflow exceeds and
becomes more parallel to the 850-300 mb mean wind (Corfidi vectors
in opposite direction of the low-level inflow, thus bolstering
upwind propagation). In addition, much of the Slight risk area
(especially western PA and eastern OH) has lower FFG given the wet
antecedent soils. In fact, the latest (00Z) HREF 40 km
neighborhood probabilities of 3 hourly QPF exceeding the FFG peak
between 50-60% across far eastern OH and western PA between 21-00Z
this afternoon and evening.