CTP’s afternoon discussion talks about them being leery on double-digit totals in the LSV.
NEAR TERM /UNTIL 7 PM THIS EVENING/...
10AM/15Z: Initial shot of WAA snow (varying intensity) has
overspread the majority of the CWA as of 10AM. Only minor
adjustments needed to hourly T/Td with maxT still on track.
After seeing the 12Z extended HRRR run, we are growing a little
leary (somewhat less confident) in double-digit snowfall totals
across the Lower Susquehanna Valley. This would be the result of
a longer period wintry mix in the dry slot with the main
deformation band setting up farther to the north. We will
continue to monitor closely.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH MONDAY NIGHT/...
A long duration winter storm will continue to impact central Pa
in the form of lingering, light warm advection snow associated
with weakening primary low in the Ohio Valley, then potentially
more significant snow across the southeast half of the state
associated with a strengthening coastal low Monday.
The gradient between deepening coastal low and high pressure
over the Canadian Maritimes will result in an anomalous easterly
flow trained over eastern Pa, supportive of increasing snow
rates Monday. Model soundings indicate enough warm air will work
in aloft to result in a brief changeover to mixed precipitation
Monday roughly south of I-81. Otherwise, model consensus
supports a long duration, all snow event, lasting through Monday
night over eastern Pa.
Latest NBM snow probs and WPC guidance indicate most likely snow
totals by early Tuesday ranging from 10-14 inches across the
southeast half of the forecast area, to around 6 inches over
the northwest mountains. However, uncertainty remains with
regard to developing coastal low and placement of heaviest snow. Model
fgen fields and latest HREF snow rates currently indicate the
heaviest deformation band snow will fall northeast of the
forecast area Monday/Monday night. However, conceptual model of
a deepening mid level low over the northern Delmarva suggests
heavy snow rates are possible across the eastern part of Pa.
Thus, can`t rule out some of the upper end ensemble members,
which would result in higher than forecast totals across the
eastern counties. The other area of uncertainty is over the
extreme southeast part of the forecast area, which is on the
southern gradient of the heaviest precipitation. The arrival of
dry slot could potentially result in significantly lower than
forecast snow amounts over this region.
00Z GEFS indicates snow will taper off Monday night from west to
east, as surface low and associated easterly low level jet
lift into New England.