Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS61 KPHI 240748

Area Forecast Discussion
National Weather Service Mount Holly NJ
348 AM EDT Mon Oct 24 2016

High pressure centered over central Canada will build closer to our
region through mid week. A warm front on Thursday will be followed
quickly by a cold front Thursday night. High pressure follows to our
south across the Carolinas next Saturday with another cold front
possible late in the weekend.


Low pressure and its associated cold front will move across the area
early this morning. Isentropic lift is leading to rain showers north
of I-78, with a couple tenths of an inch of precip over portions of
Sussex county NJ and the Poconos. This system will continue tracking
east, with precipitation moving out of the area around 12Z, followed
by a mostly sunny day. With cold air advection to follow, and steep
low-level lapse rates, northwest winds will gust up to around 30 mph,
especially late this afternoon. High temperatures will be close to
normal, generally in the 60s.


Winds will gradually diminish early tonight. The next short wave in
the northwest flow aloft skirts our area to the north later tonight.
Cloudiness will increase across portions of northern NJ and eastern
PA, but any precipitation in the form of rain showers or flurries
should remain to our northwest, given the lack of low level moisture
and down sloping flow. Low temps will be slightly below average, but
do not anticipate the need for any frost/freeze headlines, as temps
only get close to freezing over areas where the growing season has
already ended (Carbon, Monroe, Sussex-NJ, and Warren counties.


Tuesday...Cold air advection pattern continues with Tuesday night
likely being the coldest night of the season so far for many
locations. Highs on Tuesday are expected to be 5 to 15 degrees
below normal. For Tuesday night, current forecast lows in the
Lehigh Valley, Pine Barrens and the remainder NW NJ (areas that
have not yet had a freeze) are right around freezing (31 to 33).
At the very least, it looks likely that these areas will see frost
and could see a freeze. The Philly metro and Delmarva should be
a bit warmer, but could also see patchy frost.

Wedensday...Cold air advection continues for one more day, so
expect highs on Wednesday to be a few degrees lower than Tuesday.

Wednesday night through Thursday night...Most of the other
deterministic models have come into closer agreement with the more
progressive timing of the GFS. The good news with this solution is
that cloud cover should increase rather early on Wednesday night,
limiting radiational cooling (and also consequently making frost
unlikely). The bad news is that even so, precip arriving ahead of
the surface warm front due to warm air advection aloft and a mid
level short wave trough, could be a wintry mix across the southern
Poconos and NW NJ. Current model soundings of the GFS indicate a
warm layer from just above the surface through 7000 or 8000 ft
AGL. This would suggest more of a rain or freezing rain situation.
However, previous model runs depicted more of a rain/snow mix, so
for now will continue with that in the forecast, and continue to
mention potential for icy spots in these areas on Thursday

In addition to the earlier arrival of the precip, the dry slot and
surface cold front is also now expected to arrive earlier in our
region, leading to precip ending quickly on Thursday night if this
timing holds true.

Friday...a short wave ridge slides over the region through the
day, leading to quickly clearing skies and limiting the period of
cold air advection.

Saturday and Sunday...models are depicting another low pressure
system sliding over or just north of the region. As such, chances
for precip through this time period have increased from previous
forecasts. For now have stayed close to a blend of model guidance
until there is better run to run consistency.


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

Today...VFR conditions. Any lingering BKN070 to BKN090 ceilings clear
out around 12Z, followed by SCT050 ceilings during the day. The main
concern will be gusty west-northwest winds, 25 to 30 knots at times.

Tonight...VFR conditions. Northwest winds 10 to 15 knots with gusts
to around 20 knots early.


Tuesday and Wednesday...Mostly VFR conditions expected.

Wednesday night and Thursday...ceilings will lower to MVFR (with
localized IFR) by day break Thursday. Visibility restrictions
possible with rain showers Thursday into Thursday evening.

Friday...Ceilings should return to VFR early in the day.


Small Craft Advisory (SCA) extended for the near shore waters and
all of Delaware Bay thru 12Z Tuesday.

Today...Northwest winds around 20 knots with gusts 25 to around
30 knots, especially late this morning into this evening. Seas
generally 4 to 6 FT on the ocean and 2-4 FT in Delaware Bay.

Tonight...The SCA was extended thru 12Z Tue. A reinforcing shot
of cold air will lead to greater momentum transfer over the relatively
warmer waters, with high confidence of northwesterly wind gusts
around 25 knots through the overnight hours. Seas will remain
elevated on both the ocean and bay.

Tuesday...On the coastal waters could have gusts right around 25
kt, but confidence is low at this time.

Wednesday...winds and seas should stay below SCA criteria through
the day time hours.

Thursday and Friday...winds are expected to build through the day
on Thursday and could be near SCA criteria on the coastal waters.


Our forecast indicates October should average at least 2 degrees
above normal for PHl and ABE. Some of the recent forecasts have
been colder and that may mean PHL and ABE slip to around 20th
warmest October on record, which is only noteworthy in that the
excessive monthly warmth of July, August, September eased in
October. Will reevaluate tomorrow and Tuesday.


MARINE...Small Craft Advisory until 9 AM EDT Tuesday for ANZ430-431-


Near Term...Franck
Short Term...Franck
Long Term...Johnson
Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.