Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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841
FXUS61 KPHI 292214
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
614 PM EDT Thu Sep 29 2016

.SYNOPSIS...
Low pressure to the west will gradually move northeast toward the
Great Lakes and weaken through Sunday. It will continue to slowly
move eastward by Tuesday and bring a cold front through the
region. Several other waves of low pressure will move around the
larger low and unsettled weather will prevail.  High pressure
builds to our north for Tuesday into Wednesday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
**stormy**

Please do not estimate the power of this event for tonight and
Friday morning! A strong easterly gale together with a pwat axis
of almost 2 inches and max inflow almost coincidentally
aligned nw-se through De BAY this evening and crossing normal to the
coastal front or inverted trough developed by the cold air damming
of the past 24 hours, will result in considerable flooding, both
freshwater and tidal.

Along and north of I-78...periods of rain and drizzle

FCST basis: 50/50 blended 12z/gfs/nam mos. Thunder probably south
and east of PHL as per the modeled negative SWI.

FFA expanded into SNJ. EC is probably going to be correct with max
rainfall from this entire event in our area. We are thinking storm
totals widespread 3-6" delmarva with isolated 1 foot or even more
over Sussex County DE. For the new watch area...widespread 2-4
expected with at least isolated 6+ close to DE Bay and the
Atlantic coast. When i see EC synoptic scale qpf of 6"...my mind
thinks potential 9. I`m not saying 9 but if the EC pans out...highly
efficient rains with embedded convection can yield more than
model guidance. We realize this is the only model guidance with
this much qpf. We also realize that model guidance has been
focused west of our area and we`re realizing quite a bit more than
modeled.

Wind: NPW may not have large enough areal coverage into central DE and
will rereview by 6 PM.

Coastal flood: It appears a serious situation is developing for
Cape May and Sussex county DE where a moderate coastal flood event
appears locked in. The long duration of strong onshore winds (gale
gusts, now almost 24 hours) builds the waters in the back bays,
sometimes more than the ocean front. Follow the advice of local
officials.


RER`s already GED and will update this late today and again at 1
am.

Dual pol STA looks much better than the legacy STP at DOX and DIX
for the Delmarva (DOX returned to service early yesterday
afternoon, missing the morning heavy rain that occurred MD e
shore). That means adding 70 to 90% to LEGACY output on the
DELMARVA should be helpful/useful reality.

9.6 max so far...isolated in southern DE---HARBESON...more
general 4-5 inchers other parts of the Delmarva.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Heavy rains shift north during the day as the inflow and pwat axis
shift north. Heavy rains near and north of I-78 of shorter duration,
so no flood watch there. Cool and drizzly in the wake of diminishing
wind and rain.

50 50 blended 12z/29 GFS/NAM MOS guidance.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Unsettled weather continues to be forecast for much of the extended
period, especially the end of this week into the weekend.

The persistent upper low to the w will gradually will and move n
and ewd. Various different disturbances will move around this
low, and these individual features are difficult to time at best.
So unsettled wx is expected Sat and again on Sun, there shud be
more dry than wet periods and Sun will be drier than Sat, there
will still be lingering precip and clouds into the weekend. The
upr low finally crosses thru New Eng late Mon into Tue and any
last vestiges of precip shud go with it. There cud be some precip
on Mon, but again, small chcs.

Tue cud end up being a decent day then by midweek the global mdls
have divided themselves into 2 camps, a faster and slower camp. If
the faster camp is correct we could...repeat could (also could
not) have impacts from tropical storm Matthew by mid or late week.

If the slower camp is correct, then any potential impacts would
be much later. There are still a lot of differences in the mdls
wrt to both track and speed of the sys. Please see latest NHC
advisories.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Through tonight...MVFR cigs variable IFR conditions in showery
rains...some of that rain will be heavy. e-ne winds gust 20-30 kt
at times, except 35-40 kt vcnty ACY. Iso thunder possible but not
in the TAF attm due to low confidence.

Friday...MVFR CIGS variable IFR conditions in stratus/periods of
rain-drizzle. East to northeast winds are expected to gust 20-30
knots for much of the area Friday, with the strongest winds near
the coast. Winds diminish during the afternoon.

OUTLOOK...

Fri night-Sat night...A prolonged period of MVFR or IFR
conditions. Some SHRA expected to affect the TAF sites through the
period. Moderate confidence.

Sun-Mon...Some improvement, possibly to VFR. Low chc SHRA.
Moderate confidence.

&&

.MARINE...
GLW continued with verification of gales already most areas. Only
upper DE Bay waters have not yet verified and they may not til
late today.

Extended GLW a few hours and its all posted.

Waves heights 8 to 14 ft throughout through Friday morning slowly
subsiding late Friday.

Outlook...

Fri night-Sat...Gale warning has been extended into overnight
Friday night for the northern waters and could be extended
further. Elsewhere, conds will gradually decrease into Saturday,
but a backend SCA is likely before conds drop below.

Sat night-Mon...Wind and seas expected to drop below SCA criteria
Sat night or early Sun mrng and remain there thru Mon.

RIP CURRENTS...

There is a high risk for the formation of dangerous rip currents
along the NJ shore and the DE beaches today. Wave heights along
the coasts 5 to 9 feet.

Friday...Mount Holly`s last day of our daily 530am surf zone
forecast this year...probably high risk due to residual heavy
surf DE and ongoing easterly gale NJ.


We`ve had a complication in the HIGH RIP headline (double
headline), so we hope to clear this up at 630 PM.

&&

.HYDROLOGY...
Thinking that guidance is constantly modeling max rainfall far
too far west. The increasingly ely inflow at the sfc this evening
combined with being closer to the sbli subzero and constant instability
aloft through Friday and increasing 850 inflow to -4SD as well as
growing pwat axis to 2" by Friday morning as well as the 12z ECMWF
favoring the coastal front has resulted in an expansion of the

FFA expanded into SNJ. EC is probably going to be correct with max
rainfall from this entire event in our area. We are thinking storm
totals widespread 3-6" delmarva with isolated 1 foot or even more
over Sussex County DE. For the new watch area...widespread 2-4
expected with at least isolated 6+ close to DE Bay and the
Atlantic coast. When i see EC synoptic scale qpf of 6"...my mind
thinks potential 9. I`m not saying 9 but if the EC pans out...highly
efficient rains with embedded convection can yield more than
model guidance. We realize this is the only model guidance with
this much qpf. We also realize that model guidance has been
focused west of our area and we`re realizing quite a bit more than
modeled. FFA.

RER`s already GED and will update this RER later today and add
ACY PHL ILG records by 5PM in the climate section.

Dual pol STA looks much better than the legacy STP at DOX and DIX
for the Delmarva (recall DOX came back on line early yesterday
afternoon, missing the Wednesday morning heavy rain that occurred
on parts of MD`s eastern upper shore). that means add 70 to 90%
to LEGACY out put on the DELMARVA should be helpful.

9.5" max (isolated in s DE), mostly 4`s and 5`s, so far.

00z/29 ECMWF 48 hr max rainfall about 5" Md E shore.
12z/29 ECMWF 24 hr max rainfall through 12z Friday, 6" near Cape
May.

&&

.TIDES/COASTAL FLOODING...
It appears a serious situation is developing for Cape May and
Sussex county DE where a moderate coastal flood event appears
locked in. The long duration of strong onshore winds (gale gusts,
now almost 24 hours) builds the waters in the back bays, sometimes
more than the ocean front. Follow the advice of local officials.

Otherwise advisories continue as previously forecast today.

Last evening ACY was a touch into flood at 712PM (6.35 MLLW with
threshold 6.3). This morning Atlantic City NOS registered 6.6Ft
MLLW or .3 ft over the threshold.

This morning Lewes DE registered 6.6` MLLW (threshold 6.3), Cape
May 7.15 ft (threshold 7 feet MLLW)

Since tonight`s high tide cycle is higher than that of this morning,
and inflow should be stronger, flooding will be worse...probably
half a foot to a foot deeper, and expect reaching MDT threshold s
NJ and De Atlc shores.

The following two high tide cycles Friday will probably endure
minor tidal inundation flooding, especially NJ.

Additionally...waves this morning were at least 7 to 8 feet on
the coast (BTHD1) and may grow to 10 feet tonight. This could add
splashover wave runup problems to the lowlands.

&&

.CLIMATE...
Two successive days of records at GED with over 5.64" the past two
days.

Here are more daily records for consideration...possibly
vulnerable.

Today

ACY 1.57 1964
PHL 1.87 1963
ILG 1.97 1963
GED already daily record shattering

Sept 30

ACY 1,76 1964
PHL 2.41 2010
ILG 4.32 2010
TTN 1.50 1924
GED 3.15 1964


This section below will update on Friday.


September will be/is a top 10 warmest month through most of our
forecast area, for the 3rd consecutive month!

Also September will be/is enjoying a second consecutive top 5
warmest month in the period of record for PHL and ABE.

We`ve run the actual numbers through the 28th, then added the
forecast high/low for 29th and 30th.

Philadelphia: Expect a 73.8 degree average or about 5 degrees above
the monthly normal of 69.1. This will be a #4 or #5 warmest
September on record for Philadelphia.

Philadelphia September average temperature rankings

75.4 -1881
74.5 -2015
74.1 -1931 74.1 -1930
73.8 -2005 and 2016 #4

(small chance PHL avg will be 73.7 or #5 ranking)
72.9 -2010 72.9 - 1921

Philly ranked #7 warmest July followed by a warmest ever August in
the POR dating back to 1874.

Atlantic City: Expect a 71.2 degree monthly average temperature, or
4 degrees above the monthly normal of 67.2. This would equate to
an 8th warmest September in the period of record dating back to 1874.
Atlantic City recorded a #7 warmest July and then a warmest ever
August.

73.3 - 1961
72.8 - 1881
72.3 - 1931 and 1930
71.7 - 1921
71.6 - 2015
71.5 - 1933
71.3 - 2005

71.2 - 2016 #8
71.0 - 2010
70.6 - 2011 and 1906


Allentown: Expect a monthly average of 69.4 degrees, or 5.5
degrees above the monthly normal of 63.9 and a 4th warmest
September on record. Allentown ranked 8th warmest July and #2
warmest August in the period of record.

70.8 - 1961
70.3 - 1980
69.7 - 2015
69.4 - 1931 and 2016

(small chance Allentown will rank #5 at 69.3 degrees)

68.7 - 2005


&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flash Flood Watch through Friday afternoon for PAZ070-071.
NJ...Coastal Flood Warning until 1 AM EDT Friday for NJZ020>027.
     High Rip Current Risk through Friday afternoon for NJZ014-
     024>026.
     Flash Flood Watch through Friday afternoon for NJZ016>027.
     Wind Advisory until 6 AM EDT Friday for NJZ020-022>027.
     Coastal Flood Advisory until 2 AM EDT Friday for NJZ016.
     Wind Advisory from 11 PM this evening to noon EDT Friday for
     NJZ013-014.
     Coastal Flood Advisory until 1 AM EDT Friday for NJZ012>014.
DE...Coastal Flood Warning until 1 AM EDT Friday for DEZ002>004.
     High Rip Current Risk through Friday afternoon for DEZ004.
     Flash Flood Watch through Friday afternoon for DEZ001>004.
     Wind Advisory until 6 AM EDT Friday for DEZ003-004.
     Coastal Flood Advisory until 2 AM EDT Friday for DEZ001.
MD...Flash Flood Watch through Friday afternoon for MDZ008-012-015-
     019-020.
MARINE...Gale Warning until noon EDT Friday for ANZ452-453.
     Gale Warning until 2 AM EDT Saturday for ANZ450-451.
     Gale Warning until 8 AM EDT Friday for ANZ454-455.
     Gale Warning until 6 AM EDT Friday for ANZ430-431.

&&

$$
Synopsis...Nierenberg
Near Term...Drag
Short Term...Drag
Long Term...Nierenberg
Aviation...Drag/Nierenberg
Marine...Drag/Nierenberg
Hydrology...
Tides/Coastal Flooding...
Climate...614P



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