Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 031132

Area Forecast Discussion
National Weather Service Mount Holly NJ
632 AM EST Sat Dec 3 2016

Strong low pressure near Newfoundland will move east today with high
pressure following into the northeast United States on Sunday. A weak
warm front approaches from the west Sunday night, followed by high
pressure Monday. Low pressure systems in south central Canada and the
lower Mississippi Valley on Tuesday will eventually consolidate into
a large storm over southeast Canada by early Friday. The coldest air
of the season so far, is likely to follow on blustery westerly winds.


The weather pattern for today features surface low pressure and a
trof aloft over the Canadian maritimes and surface high pressure
with ridging aloft over the Midwest. A fairly strong pressure
gradient between the two systems will result in continued gusty
northwest winds over the area today. Low level moisture off the
lower Great Lakes should maintain considerable cloudiness today,
especially north and west of PHL. We also extended a chance of
flurries or sprinkles through much of the day for higher elevations
in the Poconos. By late in the day the pressure gradient should
begin to relax as the whole pattern shifts east and the center of
high pressure approaches from the Ohio Valley. Max temps this
afternoon should be similar to today.


The surface high pressure will continue slowly eastward tonight
toward the mid-Atlantic region. Winds above the surface will
continue from the NW but should be diminishing. This plus the
usual nocturnal decoupling will result in lighter winds overnight.
Somewhat less low-level moisture and cloudiness is also expected
which combined with the lighter winds should result in overnight
min temps a few degrees cooler than early this morning.


500MB: A short wave in the Great Lakes weakens as it moves across
the northeast early Monday. A short wave in Texas Monday afternoon
weakens as it opens up northeastward toward the mid Atlantic
states Tuesday. A larger scale trough in the Plains states on
Wednesday strengthens as it crosses the northeast USA Friday.

Temperatures: Calendar day averages will run above normal, on a daily
basis Sunday through Thursday, and then cools below normal next

Forecast basis: Unless otherwise noted, a 50 50 blend of the 00z/3
GFS/NAM MOS guidance Sunday-Monday, thereafter the 00z/3 GFS MEXMOS
Monday night, and then the 04z/3 WPC guidance Tuesday-Friday, at
times blended with the 00z/3 GFS MEXMOS guidance.

The dailies...

This will be an active pattern for most of the week.

Sunday...Partly sunny,  Mixed sc and ci.  Confidence: well above

Sunday night and early Monday morning prior to 9 am...Cloudy with
a 2 to 7 hour period of pcpn (mainly midnight to 8 am). Light rain
Delmarva, and a mix of light r/s vcnty PHl-ACY and generally all
light snow near and N of I-78. A small snow accumulation is
anticipated in the north, since qpf should generally be under one
tenth inch. No matter, a slippery covering of half an inch to an
inch is expected on all untreated surfaces (nighttime) for ne PA
into nw NJ. Fcst temps may be two degrees too cool and that could
alter-lower any accum potential s of I-78. Light wind.
Confidence: Above average.

Monday late morning through Monday night...becoming mostly clear
with light wind. Confidence: Average, since we`re not sure how
much clearing there will be or how extensive the formation of fog-
stratus Monday night.

Tuesday...becoming cloudy with rain spreading northeastward and
maybe a little snow on the northern fringe as low pressure moves
northeast from the southern states. Most of the rain will be at
night. Confidence: average.

Wednesday...Probably cloudy and dreary with moist remains of the
eastward departing low pressure. Periods of rain/drizzle.
Confidence: below average on details.

Thursday...A strong CFP expected and it should clear out the moisture
but timing of this clean out is very uncertain due to model disparity.
There is a chance the EC will be correct in its expectation of a
frontal wave on Thursday. Confidence: average.

Thursday night...turning noticeably colder and blustery.
Confidence: average.

Friday...Blustery and cold with partly cloudy skies (flurries in
the Poconos?). Confidence: well above average.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

VFR conditions are expected through tonight across the area.
Ceilings BKN-OVC 040-050 are expected to continue much of the day
today for PHL vicinity and northwest owing to low-level moisture and
clouds from the lower Great Lakes. Surface winds have been somewhat
gusty through the night and gusts will increase after sunrise with
heating/mixing. Gusts should diminish around sunset with light NW
winds continuing through this evening.

Sunday...VFR sct-bkn aoa 4000 ft. NW winds 5-10 KT may gust 15 kt.

Sunday night and Monday...Sub-VFR possible, mainly Sunday night
(05z-11z/4) KABE/KRDG where a few hours of light snow are likely
and generally rain or snow mixed with rain elsewhere. Conditions
improve by midday Monday afternoon. light south wind turns to
northwest Monday afternoon and may gust 15 kt.

Monday night...VFR but with small potential IFR st/fog late. light
northwest wind turns north late.

Tuesday through Wednesday...Periods of MVFR/IFR conditions, mainly
late Tuesday into Wednesday. Generally rain/drizzle. northeast
winds...gusty to 20 or 25 kt coast late Tuesday becoming light
on Wednesday.


A gale warning remains in effect for coastal waters and the lower
Delaware Bay through this afternoon. NW winds will continue to gust
up to 35 kts for much of the day before diminishing late this
afternoon. The NW flow pattern leads to waves 4 to 5 feet in the
coastal waters well offshore (20 nm) and 2 to 4 feet over the lower
Delware Bay. Winds and seas will diminish tonight but a SCA will
likely be needed at least for a while this evening.

Sunday through Monday night. Generally tranquil conditions and no
marine headlines.

Tuesday through Wednesday...Low pressure off the mid Atlantic coast
could produce a short period of easterly gales. Seas build to 5-7 feet
on the ocean.


MARINE...Gale Warning until 6 PM EST this evening for ANZ431-450>455.
     Small Craft Advisory until 6 PM EST this evening for ANZ430.


Near Term...AMC
Short Term...AMC
Long Term...Drag 632
Marine...AMC/Drag is the U.S. government's official web portal to all federal, state and local government web resources and services.