Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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874
FXUS61 KPHI 291025
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
625 AM EDT Wed Mar 29 2017

.SYNOPSIS...
High pressure near Hudson`s Bay will build into our region
through Wednesday night. Low pressure moving through the Ohio
Valley on Friday will redevelop near the New Jersey coast
Friday night and move offshore on Saturday. High pressure
will move into the area for Sunday and Monday. Low pressure
over the Ohio Valley and its associated fronts will approach
our region on Tuesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Today...Becoming partly to mostly sunny with a gusty north to
northwest wind 20-25 mph. Max T in PHL today around 61-63F.
Slightly above normal max temps which may not occur until near
5 PM.


Forecast basis: 50 50 blended 00z/29 GFS/NAM MOS guidance and
the EC 2m temps which has 58 in PHL at 2 PM. I usually add 4-5F
on a p-m/s day with decently mixing n-w wind.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
Clear or mostly clear skies, a few fragments of sc in the early
eve and possibly a little cirrus. Some radiational cooling
expected. Light north wind. Normal or slightly below normal
mins.

Forecast basis: 50 50 blended 00z/29 GFS/NAM MOS guidance. Applied
minor 1-2F cooler than guidance adjustments in our 330 AM fcst
for tonight.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
The primary players during the long term will be two southern
stream systems that are expected to impact our region in the
Friday-Saturday and Tuesday time frames.

The first system may produce 1 to 1.5 inches of rain across
portions of the region, especially in the Delaware Valley. While
there could be some urban and poor drainage flooding, we do not
expect any major impacts on rivers and streams. There is also a
consistent signal in the models for mixed precip north of I-80,
with sleet and freezing rain the primary concerns, during the
Friday night and Saturday morning period. We have mentioned this
in the HWO.

Looking ahead to early next week, the next system is expected to
bring more precip to our region Monday night into Tuesday. This
setup looks warmer, given the absence of high latitude blocking,
and would favor predominantly rain.

&&

.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Today...early morning MVFR cigs will be drying out and lifting
to VFR sct-bkn near 3500 ft by 14z and become VFR clr by 21z.
North to northwest wind gusty 20-25 kt.

Tonight...VFR with fragments of sc in the evening and maybe some
thin cirrus at times. Light north wind.


OUTLOOK...

Predominantly VFR, except MVFR possible Friday into Saturday.

&&

.MARINE...
No headlines today. Northerly flow becomes northwest during the
daylight hours with gusts 20 kt.

Am thinking an SCA is needed for ANZ450-51 (NNJ tonight).
Elsewhere...gusty north wind through the night to around 20-22
kt.


OUTLOOK...

SCA likely Friday into Saturday, with the potential for gale
force southeasterly wind gusts Friday night, mainly across the
northern NJ waters. Otherwise, sub-SCA.

&&

.TIDES/COASTAL FLOODING...
Though astronomical tides will be gradually diminishing through the
week now that we are past the new moon, the threat of minor tidal
flooding along the NJ and DE Atlantic coasts increases late in the
week. This is a result of a low pressure system bringing a prolonged
period of onshore flow. The tide of most concern at this point
is the high tide on Friday evening/late Friday night. By this
tide cycle, it will take a surge of 0.8 to 1.0 feet to reach
minor flooding thresholds, which is possible but still uncertain
(it will be dependent on how quickly the on shore flow develops
and how strong it will be by then). At least one source of
guidance shows water levels reaching minor tidal flooding
thresholds with the Thursday evening/night high tide, but that
seems unlikely as the latest forecast depicts onshore flow
either developing right around or just after the time of that
high tide.

We have mentioned the potential of minor flooding along the
northern NJ coast in the HWO, where the threat is greatest
during the Friday evening/late Friday night high tide cycle.

&&

.CLIMATE...
Mo avg temps

    March Dep     Feb   DEP
ABE 38.0 -1.1     39.2 +8.5

ACY 41.6 -0.6     43.0 +7.7

ILG 41.7 -1.3     43.1 +8.0

PHL 42.2 -1.3     44.2 +8.5


This March will be a below normal month for temps.... One of
the VERY few the last two years.

We appreciate that this is possibly old news, but March temperatures
will average colder than the FEB average at all 4 long term climate
locations. The last time this occurred, 1984.

&&

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

&&

$$
Synopsis...Franck
Near Term...Drag 624
Short Term...Drag 624
Long Term...Franck
Aviation...Drag/Franck 624
Marine...Drag/Franck 624
Tides/Coastal Flooding...
Climate...



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