Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 251411
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1011 AM EDT Sat Mar 25 2017

.SYNOPSIS...
A cold front over the southern tier of New York will sag south
across our area this afternoon and evening, becoming nearly
stationary just south of Delaware on Sunday. It then returns slowly
north as a warm front into our area Monday and Tuesday. Low pressure
crosses New Jersey Tuesday evening pulling the front out to sea.
Canadian high pressure follows into the northeast United States late
Wednesday and Thursday. Low pressure in the nations midsection on
Friday develops a warm front toward our area.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of mid-morning, broken mid and high-level clouds are moving
across the area, with more solid clouds noted north of a frontal
boundary roughly along the NY/PA border. Radar shows bands of
light precip falling but mostly not reaching the ground.

Temperatures range from around 40 in far northern NJ to around
60 in southern DE. This contrast will continue or even increase
a bit during today with somewhat greater daytime heating
expected over Delmava and southern NJ. The frontal boundary
noted above has started to push south into northern NJ and this
trend will continue through the afternoon. Increasing clouds and
NE winds will limit heating over northern NJ and adjacent PA
where afternoon highs are expected to be only in the 50s to low
60s. The chances for light rain or sprinkles will also increase
behind the front.

Previous discussion below:

Mild and dry weather early will be replaced by clouds and
higher chances for showers from north to south today. The
northern half of the area will have pops >= 50 % today and these
tail off to the south. A front will be moving N to S today and
cooler air will seep in behind it. Before the front moves thru
high temperatures will reach the 50s over the north and mid 70s
over Delmarva. Readings will trend downward once the front
passes. Models are offering somewhat different solutions with
regards to coverage and timing of showers. Confid in precip
timing is rather limited.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
The front continues to drop southward across the area and there
are better chances for overcast skies and scattered showers
along with it. Temperatures will slowly fall through the night
reaching the low/mid 30s across the higher elevations to the
north and mid 40s over Delmarva. The precipitation could become
a little ice at the highest elevations across the southern
Poconos late tonight. It appears the the chances will be low
enough as to not have to issue an advisory at this point.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
**Damp weather will be featured tonight - Tuesday**

500 MB: A strong ridge over the northeast USA Sunday weakens
considerably as a southern stream closed low in the Ohio Valley
opens up and moves into the northeast on Monday. It is followed
by a northern stream short wave in central Canada Tuesday,
which intensifies into Quebec Wednesday. The next southern
stream short wave should affect our area toward the end of the
week.

Temperatures: Calendar day averages  5 to 10 degrees above normal
Monday, 10 to 15 above normal Tuesday, 5 to 10 degrees above
normal Wednesday, near normal Thursday and Friday.


Forecast basis: 50 50 blended 00z/25 GFS/NAM MOS Sunday-Monday
blended downward with 2m NAM temps, then 00z/25 MEXMOS Monday
night-Tuesday and thereafter WPC guidance Tuesday night-Friday.


The dailies...

Sunday...there may need to be an icing hazard for the Poconos
and far northwest NJ (elevations north of I80). Despite warm
ground, if rain or drizzle develops as expected, it would glaze
on trees/wires, bridges and overpasses first. While qpf amounts
would not be heavy, the upslope and misty rain expected could
add up to a tenth of an inch of radial icing. Thats a worst case
scenario. Elsewhere...much much cooler Sunday afternoon compared
to this Saturday afternoon s of I-78 (20-25F cooler). Stratus
overcast and chance of a little light rain or drizzle but
confidence on rain/drizzle occurrence is average. East to
northeast wind may gust 15-20 mph.

Monday...East-west front south of Delaware attempts to edge
north as a warm front. Not convinced about how far north it can
move due to mostly west southwest flow aloft. The boundary layer
will be quite moist and there should patchy fog and measurable
drizzle/scattered showers in a cool inverted marine layer. Some
of the fog could be quite thick, especially elevations, near the
waters and along the warm front. I think the cooler NAM should
be more accurate, but since there is considerable uncertainty,
the forecast result was blended temps between the warmer and
cooler model solutions.


Tuesday...May be our best chance to warm up...and thin out the
murky low level cloudiness. Uncertainty. Also, a short wave
should organize low pressure development somewhere in the mid
Atlantic states with a batch of showers, especially near the
convergence associated with the low center Tuesday evening.


In terms of hydrology, given the above normal temperatures
through the long term, the snow pack north of I-78 will continue
to melt. The model consensus brings additional rainfall amounts
of three quarters of an inch to two inches across this area
through Tuesday evening. Unless there are significant changes,
we expect rises on area streams and rivers, but no flooding
concerns at this time.

Tides Sunday and Monday sunrise: At this time...expected to
remain below advisory threshold but will be monitored.

Wednesday...Clearing with north or northwesterly flow.

Thursday...Increasing clouds later on. Small chance pcpn arrives
Thu night?

Friday...Southern stream short wave crossing the lower Mississippi
Valley should spread precipitation into our area, mostly rain.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions in most areas early this morning with mostly CI/CS
clouds over the area. There could be a few patchy lower clouds or
some light fog before dawn, but mostly good weather early today
before a front moves thru and brings poorer conditions from N to S.
Cigs will decrease as the chcs for rains develop this afternoon and
persist into tonight. IFR conditions with rain and fog will arrive
over most areas. Timing of the decreases is somewhat uncertain.
Winds will shift to E or NE behind the front.  The IFR conditions
will persist into Sunday morning.

OUTLOOK...

Sunday and Sunday night...Cigs 500-1500 ft vsby ocnl below 3 mi in
patchy rain/drizzle/fog with icing on the ridges of ne PA and
nw NJ in layers below 3000 ft MSL. PATCHY LIFR in st/fog/drizzle
possible late at night. East northeast flow. Confidence: above
average.

Monday and Monday night...IFR conditions with periods of rain and
drizzle. Patchy LIFR possible. Easterly flow may turn southeast
to south Monday afternoon or night vcnty KMIV/KACY/KILG.
Confidence: average.

Tuesday...IFR conditions to start the day could improve to VFR
cigs in the afternoon with a light south to southwest flow?
Confidence: below average due to the position uncertainty of
the northward moving warm front.

Wednesday...Morning MVFR or VFR cigs becoming sct clouds near 4000
ft in the afternoon. Northwest wind gusty 20 kt. Confidence:
above average.

&&

.MARINE...
Seas continue to slowly decrease on the northern NJ coastal waters.
It looks like we will be able to drop the SCA flag for these waters
with the 330 issuance. Seas could linger close to 5 ft thru dawn
however. At 630 it looks like we will need another SCA flag for
tonight and into Sunday with a NE flow behind the front bringing
seas back up and gusts also should be around 25 kts. Looks like
just the nrn NJ waters will need the SCA for now the Sat night
period. Scat showers expected later this afternoon and tonight.

OUTLOOK...

Sunday-Sunday night...Small Craft Advisory in effect for the NJ
waters for combined seas increasing to 5 or 6 feet and
scattered gusts 25 kt.

Elsewhere, no SCA at this time for the DE waters though this is
being monitored. Confidence: average.

Monday-Tuesday...Winds may be below advisory levels, but seas could
remain elevated, possibly leading to Small Craft Advisory levels
for the NJ and De Atlantic waters. Confidence: average.

Wednesday...northwest wind...gusty 20 kt. Small chance gusty 25
kt. SCA possible but not likely. Confidence: average.

&&

.CLIMATE...
Record high temperatures today March 25 for reference...not
impossible to see one or 2 about 2F from record...closest
possibilities appear to be ACY GED

ACY-79 1963

PHL-82 1910

ILG-80-1939

ABE-77 1988, 1963

TTN-78 1963

GED-79 1959

RDG-81 1910

MPO-72 1939


March monthly average temp: While the negative departures will
diminish considerably the next few days...the month as a whole
for PHl is currently expected to end up about one half to 1
degree below normal.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 6 AM Sunday to 2 AM EDT Monday for
     ANZ452-453.
     Small Craft Advisory from 8 PM this evening to 2 AM EDT Monday
     for ANZ450-451.

&&

$$
Synopsis...Drag
Near Term...AMC/O`Hara
Short Term...O`Hara
Long Term...Drag
Aviation...Drag/O`Hara
Marine...Drag/Johnson/Klein/O`Hara
Climate...



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