Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 280713
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
313 AM EDT SAT MAY 28 2016

.SYNOPSIS...
A ridge of high pressure across the mid-Atlantic region will maintain
generally fair and warm weather through most of the weekend. Moisture
from the remnants of a tropical system to our south may reach the
area Sunday night and interact with a weak frontal system to produce
showers and thunderstorms. More high pressure and dry but continued
warm weather are expected through the middle of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Prior to sunrise: patchy fog and haze near sunrise...thickest fog
probably nw NJ to the lehigh valley. otherwise patchy cu and
cirrus early this morning. of interest...dewpoints are several
degrees cooler all along the mid atlantic coast when compared to
24 hours ago! light south to southwest wind.

Today...Issuing an SPS for first heat wave and associated modest
heat related risk for early season warmth.

Expecting hottest day of this late May warm spell today and 1-3F
warmer than ydy in e PA and most of NJ...even a degree or so warmer
in De and MD E shore than ydy.

Early season heat wave (Day 3 of the minimum three consecutive
90f or greater required) is at hand for PHL/PNE/ABE/WRI while
other locations nearby in our CWA have been 89-90F the past two
days and today will be day 3, but cannot officially note them as
heat wave potential inclusive (GED/REG/TTN). So, after any early
morning low clouds/fog/haze...a sunny or mostly sunny day with
the forecast likely verifying above any of the warmest available
guidance be it bias corrected, or individual NCEP op MOS, super
and national blends (both blends 3-4F cooler than our official
fcst). Best of the automated guidance is the adjust MET but have
fcst warmer than that as well.

16c at 850mb with a south-southwest wind gusty to 20 mph this
afternoon should allow temps to rise to 1-3F above yesterdays
values (especially with slightly lower dewpoints), at least for e
PA and interior NJ. Heat index 90-95 for NJ and e PA and maybe
only near 90 DE/E MD. No advy but issuing an SPS. Synoptic Health
Warning Network has been highlighting early season concerns for
the I95 corridor the past several days. so while officially we
dont reach the HI early season criteria of 96 for the ILG-=PHL-TTN
metro corridor or 100 HI elsewhere, we think its the first heat
wave of the season for parts of this area and day3 and probably
a daily cumulative toll on health for those elderly or children
with respiratory ailments and no air conditioned relief.

Not anticipating convection this afternoon even in the pwat axis
of 1.5" near and north of I-78...northern portion of our CWA.
There is no known lift mechanism. Suppose something isolated can
develop but with suppressant ridging at mid levels (500mb) today
and lack of excessive moisture (PWAT of 1.5" for a 570 1000-500mb
thickness is not excessive), therefore it seems difficult to
develop afternoon convection. Have a small pop up north but
convection i do not think is weather story for today.

Max temps again 10-16F above normal with a general 50 50 blend of
the 00z/28 GFS/NAM MOS guidance except heavy reliance on the
warmer NAM BL and 2M temps, along with the overzealous RGEM and
HRRR warmth but corroborated by the GGEM and ECMWF 2m temps.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
Fair and not quite as warm as this morning because the PWAT lowers
northward from 1.5 to 1 inch tonight (also means lower dewpoints)
with minimum temps probably 6 to 12F above normal and a light
south to southwest wind. It may be hazy with patchy fog possible
after midnight?, primarily in the countryside. Lower dewpoints
reduce my concern for fog late tonight. In fact clouds from the
leading edge of nwwd moving tropical moisture may be arriving
over the Delmarva early Sunday morning.

Meanwhile, Any evening showers along and north of I-80 in NNJ/ne
PA quickly end during the evening.

This part of the fcst was a 50 50 blend of the 00z/28 GFS/NAM MOS
guidance.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
The current summer-like weather pattern over the mid-Atlantic
region is expected to continue through the extended forecast
period. Temperatures will be somewhat above normal and
precipitation will be mainly in the form of convective rain
showers and t-storms. Surface and upper-level features affecting
the area will remain relatively weak. One uncertainty at this time
is how much effect we will see from the tropical/sub-tropical
system now off the SE Atlantic coast.

Moisture from tropical depression 2 NE of the Bahamas is forecast
to move N into the mid-Atlantic on Sunday with an increasing
chance of showers and T-storms by afternoon. Showers and storms
are forecast to continue Sunday night into Monday as a weak
frontal system moves into the area from the NW. PWATS are forecast
to be near 2 inches over the area so some heavy downpours and
possible flooding can be expected. Clouds and precip will result
in milder daytime temps on Monday.

By Tuesday somewhat drier air is expected to push in from the W
and decrease the chances for precip as an upper-level trough moves
by to the N. Daytime temps will recover back into the 80s as there
is not much change in air mass with the with the associated surface
front. Wed and Thu should be mainly fair with high pressure
building in from the N/NE and low-level winds off the cool
Atlantic. Both the latest GFS and ECMWF suggest another frontal
system approaching from the W or NW by next Fri, with increased
chances for precip.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through 12z...VFR with MVFR vsby possible toward 10z in haze or
patchy fog. Small chc IFR stratus fog vcnty KRDG/KABE toward 10z.
Light south to southwest wind.

After 12z...any sub VFR vsby improves to VFR by 15z with only sct
clouds aoa 5000 ft and a south to southwest wind gusty to 18 kt
during mid afternoon. no convection expected at the TAF sites
though not impossible to see a brief mid afternoon shower vcnty
KABE/KRDG.

Tonight...VFR with possible patchy MVFR vsby in haze or patchy
fog toward 10z sunday. Light south to southwest wind.

OUTLOOK...

Mainly VFR conditions are expected through the period, except
MVFR possible Sunday night thru Monday night in showers and
T-storms.

&&

.MARINE...
No marine headlines anticipated through tonight.

Winds were gusty 20-30 kt for a time this past Friday evening
(44065 and Weather Flow sensors) along the coasts and this drove
seas upward to near 5 ft at 44065. That was stronger than we expected
24 hours ago. The southerly flow and associated wind wave have
subsided.

So in essence, a south to southwest wind occasionally gusty to
between 20-22 kt into tonight with Atlantic coastal waters seas
2-4ft and De Bay 1-2 Ft.

OUTLOOK...

Winds and seas are expected to remain below SCA criteria during the
Sunday thru Wednesday time frame. Poor visibility is possible
Sunday night through Monday night in showers and thunderstorms.

RIP CURRENTS: We will probably cautiously forecast a LOW risk
today but LOW does not mean NO risk!!! For safety swim in the
presence of lifeguards. there will be an incoming 2-3 foot mixed s
to se swell today of varying periodicity 4 to 9 seconds. A cooling
southerly wind will develop this afternoon with gustiness possibly
enhancing water buildup behind the sandbars which should mean an
enhanced low risk. Am concerned about early season heat and about
swimmers in unguarded areas. We do not want any news headlines
about rip current fatalities. These fatalities are all
preventable. They tend to occur in the younger male population,
after hours unguarded locations. Its not worth the risk.

&&

.CLIMATE...
We`ll be adding considerable information to this section between
4 and 5 am Saturday.

The KMPO temperature sensor was fixed yesterday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$
Synopsis...AMC/Drag/Johnson
Near Term...Drag  313am
Short Term...Drag 313 am
Long Term...AMC
Aviation...AMC/Drag 313am
Marine...AMC/Drag 313am
Climate...313 am


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