.NEAR TERM /THROUGH FRIDAY NIGHT/...
Expect an
active next 18 to 24 hours across the region as a
number of different impacts will felt across the region.
The first rounds of rain bands from the remnants of Debby have
moved over the region and we will continue to see periods of
rainfall throughout the next day. The bands have been moving
fast enough thus far to limit
flash flooding but the tropical
rainfall is starting to accumulation in portions of DelMarVa and
latest ACARS soundings are verifying that we are solidly in a
tropical environment, with high
precipitable water values and
very deep warm cloud layers, so localized
flash flooding cant be
ruled out this evening.
Into the overnight hours, low level
shear continues to
increase, though we will
likely keep a
stable boundary layer,
even as the remnant
front lifts northward.
On Friday, Debby will lift northward through central PA as it passes
to our west while merging with a frontal boundary. This will cause
it to start to take on more in the way of extra tropical
characteristics, though it will still have plenty of
moisture
with it (PWATs 2.5+ inches). With a track farther west, this
means that the very heaviest of the rain should stay to our
west and guidance has kept that trend. Even so widespread
showers will impact the region with a growing concern for
embedded tornados.
We are anticipating a buoyant airmass with a tremendous amount
of low level
shear (0-1 km
shear 30-40+ knots) and
helicity
along with lowering LCLs. This will create favorable conditions
for tornados to develop which is not uncommon for scenarios like
this where a tropical system passes to the west.
SPC has
upgraded the area to a
SLGT risk with a 5%
TOR for areas along
and west of the I95 corridor.
Forecast guidance continues to
indicate the potential for discrete cells in the warm section
across DelMarVA, southeastern PA and NJ with spin potential.
As a second round, then a
squall line of starts passing through
the area late in the afternoon into the evening from west to
east. There could be tornadic circulations that develop within
this line as well as in earlier cells and clusters that develop
and move through south to north ahead of the line.
The next threat, will be that a strong
low level jet between
40-55
kts develops at 850mb. With widespread rain that would be
convective at times, anticipate occasional gusts of 40 to 50 mph
to be possible mixing down. I dont anticipate frequent gusts or
prevailing strong winds, but those occasional gusts when
combined with saturated soils will have the potential to bring
down trees especially in the areas that received heavy
rainfall
earlier this week.
The heaviest of the rain is
likely to be north/west of the
urban corridor especially getting out into our western zones
from Berk`s County northward into the southern Poconos. Places
along and east of the I-95 corridor will still see some heavy
showers though and given how wet it`s been recently, this will
mean scattered instances of
flash flooding will still be
possible.
For Friday night, Debby lifts north of the area as it moves
into eastern Canada by Saturday. As mentioned above, the final
punch of heavy rain and wind should move through in the evening
with conditions actually starting to clear out overnight. Total
rain amounts for the Friday / Friday night period should
generally be around 2 to 3 inches over N/W area, 1 to 2 inches
near the I-95 corridor and up to around an inch near the coast.
Locally, amounts could be higher than these numbers. And in
addition to the threat of
flash flooding, there will be rises on
area creeks, rivers, and streams. This could result in at least
some points seeing
river flooding by later Friday night into
Saturday.
&&
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
Pleasant weather follows in the
wake of all the poor weather
from Thursday and Friday. High pressure ridges in from the west
and remains across the region.
Mostly sunny weather is expected
Saturday with some clouds for the far N/W. Much drier air will
be in place and temperatures will be comfortable. Highs will be
in the upper 70s to low 80s with perhaps some mid 80s close to
the shore. West to northwest winds around 10 mph are forecast.