Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 272234
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
634 PM EDT MON JUN 27 2016

.SYNOPSIS...
A cold front from the eastern Great Lakes through the Ohio Valley
will cross eastern sections of Pennsylvania and Maryland Tuesday
afternoon where low pressure will form. The front and area of low
pressure will drift east, off the mid Atlantic coast Wednesday
morning. Weak high pressure follows Thursday. Another cold front
will move through the region Friday night or Saturday and then
stall to our south later in the weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Showers were along and to the northwest of the Interstate 95
corridor in our region around 630 pm. The loss of daytime heating
and the lack of any significant instability should cause the
showers to continue weakening during the evening hours.

A weak surface trough will stall near the area overnight, and
another stronger short wave/vorticity impulse is expected to
approach the area toward daybreak Tuesday. This may help enhance
and increase the shower potential across southern areas overnight.
PW values should increase overnight, so if showers or
thunderstorms develop, they could produce some moderate to heavy
rainfall.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Showers could be ongoing at the start of the day Tuesday across
the eastern portions of the area as the initial short
wave/vorticity impulse moves across the area. By the late morning
into early afternoon, the first round of showers may begin to move
out and we could get a brief break in shower/thunderstorm
activity. However, showers and thunderstorms are expected to
develop to our west during the day as the cold front approaches
from the west. There is a moderate amount of instability and shear
to our west, so thunderstorms could become strong during the day.
The instability weakens some as does the shear moving into our
area, so the greatest threat for severe weather may be north and
west of our area. However, there will still be the possibility for
gusty winds and small hail across our northern areas, so we`ve
included this in the forecast. PW values drop some during the day,
but should still be near 1.5 inches, so there could still be the
possibility for some moderate to heavy rainfall with some
showers/thunderstorms.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
500 MB: A -1SD short wave nearing Buffalo NY Tuesday Night
weakens eastward Wednesday. A developing -2SD short wave trough
moves across Lake Huron Friday night.

Temperatures: The month of June through the first 26 days has
averaged 1 to 2 degrees above normal at PHL, RDG, ABE, TTN, within
.5 of normal at GED ACY and ILG and surprisingly -1F at MPO. the
final monthly departures should be within 3 tenths of degrees of
those listed above.

Calendar day averages over this coming long term period of
Wednesday- Sunday should average near normal, some days a bit
above, others a bit below.

Forecast basis: Unless otherwise noted, a 50 50 blend of the
12z/27 GFS/NAM MOS guidance Tuesday night - Wednesday night,
thereafter the 12z/27 GFS MEX MOS for Thursday and WPC Guidance
Thursday night-next Monday. Max temperature guidance was on some
days modified warmer by the previous 330 am PHI forecast as well
as the warmer 12z/27 ECMWF 18z 2m forecast temperatures. Nighttime
lows were lowered below guidance Wednesday morning and Friday
morning across e PA and nw NJ, where the radiating countryside
should get down close to the 12z/27GFS forecast 09z 2m temps.

Rainfall: not a bright outlook for alot of needed rainfall...it
certainly doesn`t look as if above normal rainfall can transpire
in this pattern. To me it looks like too strong a cyclonic flow at
mid levels.

The dailies...

Tuesday night...Any showers and scattered thunderstorms during
the evening, will tend to die out late at night. At most a
marginal risk of svr with 1000J of MLCape to start Delmarva area
and 0-6KM bulk shear increasing late evening but appears to arrive
too late for much impact in our CWA. Seems more like an SPS/MWS
evening...marginal. PWAT decreasing from 1.5". Confidence:
average.

Wednesday...Tending to dry out and looking like a very nice
summers afternoon after morning skycover clears. PWAT around 1
inch. Cooling afternoon sea breeze possible along the immediate
coast. Seasonable temps. Confidence: above average.

Thursday...Dry and nice with cooling coastal seabreezes. Small
chance of a shower or thunderstorm along the coasts Thursday night
in response to the western edge of an instability burst developing
northeastward near the mid Atlantic coast. PWAT overall near 0.85
inches. Seasonable temps. Confidence: above average.

Friday...much less confidence on the days outcome both temps and
rainfall. Chance of a shower. Very warm...a bit above normal in
some areas of the interior. Confidence: below average

Saturday...Hot. Could be strong thunderstorms on the Delmarva
late day or Saturday night where pretty good instability and
significant 0-6km bulk shear (40 kt) are modeled though MLCAPE is
so far, is modeled relatively low. Temps could reach the lower 90s
in the I-95 corridor. Confidence: average.

Sunday...Could have a lingering shower or thunderstorm threat in
association with the se Canada trough. Confidence: below average.

Monday (July 4)...For now it looks like a good day for outdoor
activity. Warm. Confidence: average or above average.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

VFR conditions continue across the area early this evening. An
area of showers will continue moving eastward this evening. It is
possible that some showers may be heavy enough to lower
visibilities to 4-6 miles, so we will continue our TEMPO group
with the potential. This line of showers will dissipate through
the evening, then we could be mostly dry for a good portion of the
overnight. More shower activity could develop and move into the
area around daybreak from the south and spread northward through
the morning. Additional showers and possible thunderstorms are
expected late in the day Tuesday as a cold front approaches from
the west.

Ceilings and visibilities are expected to begin to lower to MVFR
then IFR overnight as moisture gets trapped underneath a low level
inversion. This will likely continue through the day tomorrow
ahead of the approaching cold front, although the IFR may lift to
MVFR during the day.

South-southwest winds continue for most inland areas, while
closer to the coast winds are more south-southeast. Sustained
winds are around 10 knots. The winds will lighten some after
sunset, and become south-southeast everywhere 5-10 knots.

OUTLOOK...
Confidence for the periods discussed below is average or above
average,

Tuesday night...scattered leftover showers and isolated
thunderstorms should diminish and end. Patchy IFR stratus/fog
should develop late. Light winds.

Wednesday...becoming VFR after any early morning IFR stratus/fog
rapidly clears. Light west wind except possible afternoon sea
breezes coasts.

Thursday...VFR. Light west wind with coastal afternoon sea
breezes. Patchy IFR stratus/fog may develop late.

Friday...VFR. Chance for a shower. (least confidence of all the
days listed in this long term section)

Saturday...VFR. Chance of late day-or night time thunderstorms
Delmarva. Right now the northern fringe is in our area and some of
those storms could be strong.

&&

.MARINE...
Winds on the waters will continue to gust in the low 20s early
this evening. A few gusts around 25 knots may occur across the
far northern waters off the coast of Monmouth, but we believe they
will be infrequent and brief enough to preclude the need for a
Small Craft Advisory. Winds will diminish some overnight, but
should increase in gusts again Tuesday. Wind direction will
continue to be from the south to southeast tonight into Tuesday.

A few isolated thunderstorms are also possible late tonight into
Tuesday.

There is a moderate risk of rip currents today, and this may
continue into Tuesday.

OUTLOOK...
Tuesday night through Saturday... Winds and seas expected to remain
below SCA criteria. A chance for showers and scattered thunderstorms
with a slow-moving cold front Tuesday night and then again
Saturday. Small chance of a shower Thursday night or Friday.

RIP CURRENTS...low to possibly moderate at times this week, in
part dependent on the amount of onshore wind. In other words, not
much change from the somewhat active month of June. AWARENESS:
weak swimmers for their own safety should swim only in the
presence of lifeguards. It is not worth being a rip current victim
by swimming near jetties, or after the lifeguards go home, or with
untrained weak swimming bystanders who wont be capable of saving a
distressed swimmer, except to call 911, which then could be too
late.

&&

.CLIMATE...
Presuming less than one half of rain falls between now and the
end of June, Allentown could end up top 10 driest June on record
with the period of record back to 1922. Currently, as of 440 PM
(0.08 since 4P), Allentown`s 1.45" ranks #8 driest.

Elsewhere, with no additional rainfall, Atlantic City (1.32")
would rank 15th driest and Philadelphia (1.24") 14th driest.

For the month so far, deficits were generally 1.5 to 2.5 inches
except nil at KILG and near 1.5" KGED and KACY. That is generally
25 to 50 percent of normal (except near normal parts of DE).

Until we get any tropical rains, or the trough sharpens in the
Ohio Valley, the northeast states trough pattern is unfavorable
for persistent high humidity and associated widespread substantial
thunderstorm generated rainfall. Operational and ensembles so far
for at least the next 7 days, tend to keep paths of heavier rains
to the south and north of our forecast area. In other words no
significant change in we`ve been seeing the past month.

&&

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

&&

$$

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



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