Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 291316
Area Forecast Discussion
National Weather Service Mount Holly NJ
916 AM EDT SUN MAY 29 2016
High pressure will continue to push further off the Middle Atlantic
coast through tonight. Tropical Storm Bonnie will move along the
southeastern United States coast over the next several days.
Moisture from this system will move northward and into our area
today and Monday. High pressure will build towards the region
Tuesday, remaining to our north through Thursday. A cold front
will move through the area over the weekend.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Still very warm but with lower dewpoints into midday, not quite
as uncomfortable...however, high dewpoints will be returning from
south to north during the mid and late afternoon hours with
morning southwest winds of 5 to 15 mph turning more southerly.
It will be a mostly sunny morning with increasing cirrus during
the afternoon. Then a wall of water via cloud cover (PWAT rising
from .5" now over the Delmarva to 2" by this evening) starts
advancing nwd through the Delmarva late afternoon with showers,
some heavy with possible FLS nuisance flooding, possibly also a
thunderstorm. Was conservative on the northward advance.
Do not have any showers near and N of I-80 midday-this afternoon
and we might need to add that in a late morning update. Whatever
risk of this...the risk shifts north out of our area by 3 pm.
Max temps...again well above normal...ranging from 7F above normal
south to as much as 16F above normal north where lower 90s expected
again in NNJ and ne PA. Otherwise mid to upper 80s Delmarva...PHL
88, to around 90-93F along and north of I-78 (Lehigh Valley ewd
through WRI-MMU). NAM BL temps have been increasing on recent
cycles. These max temps for the fourth consecutive day are significantly
above all other avbl MOS guidance/blends/bc adjusts (except some
ECMWF localized guidance).
The heat index will again rise to between 90-95F I-78 north. This
also should mean a 4th consec day of 90F at KABE and KWRI and a
possible official heat wave (see definition in CLI section) for
KRDG which is on the margin for 90F.
No major changes with erly mrng update. Still quiet wx wise. Just
made some minor adjustments to temps and clouds. Sky is relatively
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
Deep layer moisture, PWAT up to 2 inches, in part from Tropical
Storm Bonnie is forecast to move across the area with widespread
showers and isolated T-storms. General lift is aided and as
represented by the rrq of an upper level 80 kt 250MB jet core...over
southern Ontario. A sfc boundary will focus the heaviest rain, in
the light northerly flow immediately adjacent a forming sfc wind
shift. A 30 kt 700mb speed max may initially focus heaviest rain
near Chesapeake Bay-E Pa Sunday evening, then it appears the 850
southerly inflow will shift the axis of excessive rain potential
somewhere just to the east of I95 by Monday morning. Potential
exists for a couple of narrow swaths of 3-4" rains by 12z Monday...
more details possible late today. No flash flood watch attm but
am concerned about the I-95 corridor (ILG/PHL/PNE/PTW) in the
03z- 12z time frame.
Mild nighttime mins...10 to 15F above normal.
Light southerly wind with a shift to northerly near a developing
sfc convergence zone around or just east of I-95 late tonight.
.LONG TERM /MONDAY THROUGH SATURDAY/...
Moisture from Tropical Storm Bonnie will push northward and we will
continue to see showers and some thunderstorms on Monday. PWATS
remain high, around 2 inches in some areas, so expect some of the
showers to be fairly heavy, especially during Monday morning.
Memorial Day continues to look like a washout across the region. The
pops will start to drop from northwest to southeast but it looks
like we will continue to see some showers continuing into Monday
evening. Rain will linger longest over our southeastern areas,
likely ending by late Monday night.
With heavy rain possible, we will need to monitor the flash flooding
potential. As mentioned before, the PWATS are 1.5 to just over 2
inches across the region. Some heavy showers and thunderstorms could
drop one to two inches of rain with locally higher amounts possible.
We will continue to mention the flash flood threat in the HWO.
The guidance shows some pretty decent differences in how the
remnants of Bonnie are handled. The GFS is a bit dryer and keeps the
low to the south of the area and eventually dissipates it near the
Carolina coast. The ECMWF keeps the low spinning over the Carolina
coast with a gradual push to the northeast, moving it up the Mid-
Atlantic coast through the week. The ECMWF solution would keep us in
a cloudier set up and a wetter pattern with the chance for the
remnant moisture to make its way into the region for Tuesday through
Friday, with the best chances across our south and east zones.
With the uncertainty of where and when Bonnie will track
north/northeast, we have upped the cloud cover through the week and
introduced some slight chance/low chance pops. Again, the best
chances will remain across southern New Jersey and the Delmarva.
A low pressure system will arrive from the west and drag a cold
front through the region over the weekend.
.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Through 12z...Generally VFR. Light south wind.
Today after 12z...VFR with a south-southwest wind gusty to 15 kt
midday. Then MVFR or IFR conds in showers/iso tstms spread north
through the Delmarva into southern NJ and the Philadelphia late
this afternoon-evening. Please see the TAFS for more timing details.
No thunder in the TAF since uncertain where best chance of thunder
and whether much if any thunder occurs at night in tropical pwat.
Tonight...VFR to start, then MVFR to IFR conditions developing
later on in low clouds, fog, and heavy showers, maybe isolated
tstms. Sustained winds mostly under 10 kt with a convergence zone
of south wind along the coast while a light north wind should
develop near I-95 late at night.
Monday...MVFR to IFR conditions in rain, fog, and thunderstorms
affect the terminals. Conditions may drop below IFR at times due to
heavy rain. Light winds early will become south to southwest
around 10 knots or less. Higher gusts possible in showers and
Tuesday through Thursday...Mainly VFR conditions expected. Westerly
winds on Tuesday will become more easterly on Wednesday and
Thursday. Winds will generally be around 10 knots or less with gusts
up to 15 knots.
No marine headlines are anticipated through tonight although dense
fog may become a marine hazard toward dawn Monday on the nearshore
Atlantic waters where ssts are still 55-60F and the dewpoints
should be rising above the SST Monday morning.
Monday...Sub-SCA conditions are expected on the area waters. Fog is
possible in the early morning and again overnight. Waves may start
to build in response to Tropical Storm Bonnie but we expect them to
remain below 5 feet at this time. However, confidence is not high
that we will see much affect until Bonnie moves north of the
Tuesday through Thursday...Sub-SCA conditions are expected on the
RIP CURRENTS: Posted a low risk today. This may need an upgrade
this afternoon dependent on whether a stronger southerly wind
develops than now indicated. We are moving into the high tide
cycle this afternoon so that appears favorable for reducing the
frequency and coverage of rip current formation. Relatively cold
water temperatures along the north and central NJ coast probably
also minimizes risk taking. However, it will be quite warm by noon
with large beach crowds anticipated. Swimming within the watchful
eyes of life guards ensures a safe and fun beach experience.
This mornings LBI beach report is posted.
There is potential for heavy rain and localized flooding from tonight
through Monday. This is due to an influx of tropical moisture from
Tropical Storm Bonnie. PWATs are forecast to be near 2 inches,
well above normal, especially for late May. Depending on how the
heavier showers and t-storms set up, isolated locations could
easily receive 4 inches or more of rainfall. This may result in
localized flooding. The potential for heavy rain was added to the
For now please use a combination of the WPC and MARFC qpf fcsts.
As it stands now...general 1-2" is expected across the forecast
area with isolated 4+, mainly between 21z today and 21z Monday.
Daily record rainfalls that have a chance of exceedance, if heavy
showers can persist for 1 to 2 hours. Note, splitting amounts between
two days lowers the chance of a single day record event occurrence.
There is a good chance several long term climate sites will increase
to a top 10 ranking for the month of May in our CWA. PHL ACY AND ILG
only need an inch of rain these last 3 days of the month to rank
as a top 10 wettest month of May.
KGED 1.62 in 1990 por 1948
ACY 3.07 1984 por 1874
PHL 1.74 1908 por 1872
ILG 1.10 1983 por 1894
ABE 1.68 1968 por 1922
TTN 1.62 1912 por 1865
GED 2.04 1984 por 1948
RDG 2.92 1904 por 1869 (highly unlikely to approach a record
MPO 1.86 1990 POR 1901
Record max temps today appear less vulnerable today than yesterday
with only Mount Poconos 89F in 1911 being threatened. Right now we
KMPO projected for 87F.
You probably saw the near records yesterday at KMPO (-1), KABE
(-1), KRDG (-2). Daytime max temp guidance continues to be
significantly under forecast across PA/NJ for the past 3 days,
especially by Super and National blends. We are better off in
these sunny non-marine influenced summerlike regimes using the
latest operational guidance as a starting point and modifying
this upward by adding 4F to the 18z ECMWF 2m temps. The GFS 2m
temperature fcsts have also been biased low, in part because of
too much low lvl moisture.
Also a note about heat waves: here in the northeast USA, we tend
to stay close to the AMS glossary of Meteorology definition of a
heat wave and as follows: In 1900, A.T Burrows more rigidly defined
a `hot wave` as a spell of three or more days on each of which the
maximum shade temperature reaches or exceeds 90F.
May continues to project about 1 degree below normal, the warm
spell beginning the 24th having put a big dent in the well below
normal averages. In fact monthly average temp may be at or above
normal at KABE, KRDG and KTTN.