Had a late push to 95 imby
Day 1: 92
Day 2: 96
Day 3: 95
Day 4: 95
Cherry Hill, Sicklersville, Moorestown and some others were top dogs at 97
turning out to be a pretty solid moderate type heatwave.
Wednesday is likely to continue the heatwave for a 5th day.. It will be a dirtier sky but it will be much more humid than today causing oppressive conditions and the threat of thunderstorms exists from mid afternoon into the evening.
Thursday much of the area figure to continue the heatwave but for some locations the heatwave will end. Sunday may be the start of yet another heatwave with temps soaring back into the mid 90s next week. Will start a NEW thread on that over the weekend.
Hazard 1 -- The Heat
The temperature/
heat index forecast for Wednesday is quite
challenging, owing to several conflicting factors that will play
critical roles in
diurnal heating and mixing. First, a weak warm
front (mainly tracing a sharper change in surface
dew points) will
be lifting northward through the day. By late afternoon, the
front
will
likely have made progress through all of the
CWA. Generally,
dew points will exceed 70 degrees south of this boundary, though
this may not be entirely the case by afternoon, as stronger
south/southwest winds develop. This increased mixing will allow for
a fairly deep
boundary layer that may permit
dew points to drop to
near/below 70 by afternoon. If the higher
dew points win out, some
areas will flirt with
excessive heat warning criteria, but I suspect
mixing will be sufficiently strong to keep the environment mostly
within advisory levels.
The next issue involves residual effects from a passing
shortwave
during the overnight hours. Some passing showers may occur in the
northern
CWA into the early morning hours, and lingering cloud cover
will be a factor early on in the day. The question will be how long
this cloudiness remains (as it will have effects on the northward
progress of the
front and
insolation/
diabatic heating in general).
Some guidance is quite aggressive in eroding these clouds, but
confidence is not high (though this is the time of year where it
would happen). With such low confidence, have kept northern New
Jersey out of the
heat advisory for now (thanks to OKX for
coordination).
The final complicating factor is
convection (more on that below).
Should
convection develop or overspread the area earlier than
anticipated, maximum heat indices will be lower than forecast. Once
again, this is especially possible for the northern/western fringes
of the
CWA. However, the
downstream/preconvective environment will
be hot/humid and
likely early enough in the day to result in a few
hours of advisory criteria being
met (especially along/southeast of
the urban corridor).
Have hoisted a
heat advisory for areas roughly south of the I-78
corridor for Wednesday (except for the immediate coasts of NJ/DE),
where confidence is highest in warm-frontal passage, more limited
effects from morning cloud cover, and longer duration of
insolation
prior to
convection. In this region, highs generally in the lower to
mid 90s are expected (locally upper 90s in the urban corridor and
Delmarva), with maximum heat indices generally 100-105 north of I-76
and slightly higher to the south. Some fine-tuning of the advisory
may be required given what transpires overnight.