Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 221914
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
314 PM EDT FRI JUL 22 2016

.SYNOPSIS...
A frontal boundary is expected to move into the area late tonight
into Saturday, and thereafter slowly sag south of the area Sunday.
High pressure will briefly follow Sunday. Another frontal boundary
is expected late Monday into Tuesday and stall nearby or to our
south Wednesday and Thursday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
3 PM: We are in the process of issuing an advy/warning/watch to
cover the urban corridor and upcoming DNC multi concerns with advy
criteria Saturday. Larry-our extended forecaster will detail the
concerns Sunday and beyond in the long term section after 330PM.

Through 8 or 9 PM:

Around 1400J MLC at 21z vcnty TEB-ABE-RDG axis with KI 35+, TT49,
SWI -3. 0-6KM bulk shear poor-20-25kt. But the heat, waa and 30kt
at 500mb should allow 40-45 kt gusts, "IF" storms can get going.
That is the uncertainty. Also appears to be a weak mid lvl cap of
around 10C trying to develop late today that could impact the
life of any strong thunderstorm cells. pwat 1.75" would also mean
poor drainage flooding in a few locations. We are including HRRR
in the fcst . Not as confident south of I78 as north where
something should get going by 4 or 5 PM.

MAX HI today so far through 3PM TTN and WRI 100, 101 KPNE so could
have issued down here. This lends added value to our warning/advy
for Saturday.

Tonight...The wind shift from N38 to the Catskills should initiate
convection soon and we just dont know how long and how far
southeast. The pops may cover too large an area. Very late in the
night though, the wind shift should slide at least partially
through the region, possibly getting hung up along the MD border
to KACY which would impact tomorrow afternoons weather.

After midnight: Fair!

Fcst elements were produced using a 50 50 blend of 12z/22 GFS/NAM
MOS guidance. Unlikely for much if any fog/haze late at night.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Sunny, hot and humid Saturday with HI 100 or greater most areas
south and west of KBLM along the I95 corridor. Its also Day1 of
an excessive heat warning. While Saturdays values are less than
warning criteria, it is probably D2 of mid 90s actual max temps
that will likely last into the middle or end of next week.
Prolonged literal mid 90s heat will take a toll.

If the boundary hangs up near the Mason Dixon line to ACY, then
the potential would exist for late afternoon isolated severe
thunderstorms Delmarva. Still plenty of instability there with
better 0-6km bulk shear.  There is a subtle indication in the
convergent wind fields for a more sizable are of convection
Delmarva and s NJ late Sat.


Fcst elements were produced using a 50 50 blend of 12z/22 GFS/NAM
MOS guidance.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Hot and humid conditions are continued to be forecast for much of
the extended period, with Saturday, Monday and possibly Tuesday
expected to be the warmest days. It is possible that Sunday may be
slightly "cooler" and have lower dewpoints, leading to lower heat
index values, but it will still be quite hot. With 925 mb
temperatures forecast to be around 25/26 degrees, this would yield
highs into the mid/upper 90s Saturday, Monday and Tuesday. The
combination of the heat and humidity will lead to dangerously high
heat index values over the weekend into Monday, and possibly into
Tuesday. With several days of dangerously high heat index values
expected, we continue with the Excessive Heat Watch for all of our
forecast area except Carbon and Monroe counties in Pennsylvania
and Sussex county in New Jersey and have extended it into Monday.

There could be some isolated showers/thunderstorms late Sunday
into Sunday night across the far southern areas as a couple of
short wave/vorticity impulses move across the area. However, most
areas will remain dry.

On Monday, a pre-frontal trough will be in place across the east
coast, with a frontal boundary approaching the area late in the
day and overnight. As these features move eastward, along with the
associated short wave aloft, scattered showers/thunderstorms could
begin moving into the area late in the day Monday into Monday
night. There is a fair amount of instability forecast with the
heat and humidity, and there will be some weak shear present as
well. If any thunderstorms do develop, the could produce a brief
period of heavy rainfall and gusty winds.

There will be a chance of showers/thunderstorms each day from
Tuesday, Wednesday, and Thursday as several short wave/vorticity
impulses move across the area. The strongest of these short waves
may move across the area later on Thursday, leading to a greater
chance of showers/thunderstorms.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Remainder of this afternoon...VFR sct-bkn aoa 5000 ft with a sw
wind gusting 15-20 kt. Anticipating redevelopment of confection
nearand N of KRDG-KABE-KTTN later today. North-northwest wind
gusts to 40-45 kt possible in any tstms ne and e central PA and n
1/2 NJ...mainly near and n of KABE and KTTN.

Tonight...VFR with small chance MVFR haze/fog late at night, especially
wherever it rained after 21z/22 (today). There may still be some
leftover decaying sewd moving evening convection vcnty PHL-ACY as
it runs into the capped mid lvl thermal profile. Southwest wind
with gusts to 15 kt early shifting to light northwest late at
night.

Saturday...VFR sct-bkn aoa 5000 ft. Potential for convection may
still exist vcnty KILG/KACY/KMIV. Light west northwest wind in the
morning turning westerly in the afternoon with gusts 15 to 20 kt.
Winds may turn southwest at KMIV and KILG/KACY during the
afternoon.

OUTLOOK...

Saturday night-Sunday.  VFR.

Monday-Monday night...Generally VFR. A chance of showers and
thunderstorms which may briefly lead to lower conditions.
Gusty southwest winds 15-20 knots.

Tuesday-Tuesday night...VFR.

&&

.MARINE...
Today...Southwesterly winds will continue through the day today,
increasing this afternoon. For the New Jersey coastal waters,
expect gusts above 25 kt to develop by mid afternoon, with seas
expected to subsequently increase to 5 feet by this evening. For
the Delaware coastal waters and the Delaware Bay, wind gusts above
20 kts are possible, but should stay below SCA criteria.

Tonight...Winds and seas should subside before daybreak Saturday.

Saturday...Sub small craft advisory conditions anticipated. Max
gusts around 20 kt.

OUTLOOK...

Saturday night-Sunday...Sub-Small Craft Advisory conditions expected.

Monday-Monday night...Near Small Craft Advisory conditions possible
with increasing winds ahead of an approaching cold front.

Tuesday-Tuesday night...Sub-Small Craft Advisory conditions expected.

RIP CURRENTS...Added Cape May county to the moderate risk for the
formation of dangerous rip currents this afternoon so that all of
the NJ coast is now Moderate, while we`ve maintained low risk for
the Delaware Beaches. Confidence on how much southerly component
is a little below average so the moderate risk may end up low enhanced.
Essentially... a 3-4 ft chop driven by gusty southwest wind of
15-20 mph is near parallel to shore. This will create a decent
south to north long shore current and could result in some
surprisingly strong rip currents by mid afternoon along the NJ
shore, when also low tide occurs.

Saturday: The probability for the formation of dangerous rip
currents is Low.

Looking further ahead, with the Atlantic Basin still devoid of
tropical storms, the probable risk for the formation of dangerous
rip currents should be low this weekend, especially with lighter
winds and tendency more of an offshore component.

Next Monday the 25th, we might have enough wave height to around
4 feet late in the day and water buildup due to southerly winds,
to have a more widespread low enhanced or even moderate risk but
confidence on seas building that high is below average.

Water temperatures fell about 4 degrees between 6 am and 10 am,
implying upwelling. Values were variably down into the mid 60s to
lower 70s....colder along the NJ coast. Even colder upwelling may
develop Saturday when the wind turns more westerly.

&&

.CLIMATE...
Barring afternoon convective cloud debris, record breaking heat
is likely in our forecast area Monday. These records Monday are
vulnerably low. Our 330 am grids fcst record warm values of 97 at
Philadelphia and Wilmington Monday, 96 Allentown and a record equaling
96 at Reading.

Other near record (within 2F) or record warmth can occur on other
days, especially the 24th and 26th.

Based on 12z guidance we may extend the records to the 28th... if
we still are showing rather high modeled 2m temps. There may be a
slight warm bias on these modeled 2m temps at extended ranges...so
we are cautious about adding any additional information.

        23rd    24th    25th     26th     27th    28th
PHL 101-2011 98-2011 96-1899 101-1892 101-1940 100-1941

ABE  99-1955 95-1999 95-1999  98-1940  98-1955  97-1949

ACY 105-2011 100-2011 99-2010 96-2011&1963 99-2005  98-1999

ILG 100-2011 98-2011 96-1987 99-1894   100-1894 101-1894

TTN 104-2011 98-1910 97-1999 99-1892   100-1894 101-1894

GED  104-2011 99-2011 99-2010 97-2012  98-2005  99-1949

RDG  100-2011 96-2010 96-1999 99-1940  98-1955  99-1941

MPO   91-1955 91-1914 90-1999 89-1949  91-1955  93-1949

&&

.EQUIPMENT...
Lewes weather radio is intermittently off the air with an ac
replacement needed. We hope to have it going late today.

44009 data has stopped transmitting (batteries failed). It may
not be replaced til November.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Excessive Heat Watch from Monday morning through Monday
     afternoon for PAZ060>062-101-103-105.
     Excessive Heat Warning from 11 AM Saturday to 6 PM EDT Monday
     for PAZ070-071-102-104-106.
NJ...Excessive Heat Watch from Monday morning through Monday
     afternoon for NJZ007>010-012>014-016-020>027.
     Heat Advisory from 11 AM to 8 PM EDT Saturday for NJZ012>014-
     016-020>027.
     Excessive Heat Warning from 11 AM Saturday to 6 PM EDT Monday
     for NJZ015-017>019.
DE...Excessive Heat Watch from Monday morning through Monday
     afternoon for DEZ002>004.
     Heat Advisory from 11 AM to 8 PM EDT Saturday for DEZ002>004.
     Excessive Heat Warning from 11 AM Saturday to 6 PM EDT Monday
     for DEZ001.
MD...Excessive Heat Watch from Monday morning through Monday
     afternoon for MDZ008-012-015-019-020.
     Heat Advisory from 11 AM to 8 PM EDT Saturday for MDZ008-012-
     015-019-020.
MARINE...Small Craft Advisory until 5 AM EDT Saturday for ANZ450>453.

&&

$$
Synopsis...Drag/Robertson
Near Term...Drag
Short Term...Drag
Long Term...Robertson
Aviation...Drag/Robertson
Marine...Drag/Robertson
Climate...
Equipment...



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