Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS61 KPHI 070224

Area Forecast Discussion
National Weather Service Mount Holly NJ
924 PM EST Fri Dec 6 2019

Low pressure across New England this evening will cause a cold front 
to cross the Middle Atlantic region. A large area of high pressure 
from the Great Lakes will build across the area this weekend. Once 
the high moves away early next week, a series of low pressure 
systems and fronts will affect the area into the middle of the week. 
More high pressure with cold air arrives for later next week.


930 pm update: Increased hourly temperatures a couple degrees
for the next few hours, as models are not accounting for mixing
from gusty post-frontal winds muting radiational cooling 
sufficiently. Otherwise, no changes were required.

630 pm update: Showers are moving steadily through New Jersey at
this hour, and have increased PoPs through 8 pm in advance of
these. Otherwise, forecast is in good shape.

Previous discussion...

Cold front is now progressing through PA as the mid and upper
level short wave trough digs closer to the region. A few 
showers continue to be possible late this afternoon into early 
this evening. Aside from the Poconos, where some snow may mix
with rain, for most of the region if we see any precipitation,
it should be all rain. 

As the cold front crosses our region this evening, expect an
abrupt shift to northwesterly winds and a brief period of breezy 
conditions behind the front. Much of the guidance shows winds 
staying relatively light even behind the front, but expect that the 
guidance is a bit too fast in showing the development of the 
nocturnal inversion in the higher elevations of NW NJ and the 
Poconos. Thus gusts of 20 to 25 mph will be possible in these 
locations through the evening. Additionally, this is a prime setup 
for gusty winds on the waters, so coastal locations, and especially 
locations near the mouth of the Delaware Bay could see wind gusts to 
30 mph through the evening.

Will likely see cold air advection for much of the night. Thus, 
expect lows to be slightly lower than this morning, with lows in the 
20s (with the exception of Philly and portions of Delmarva where 
lows could be right around 30).


High pressure begins to build in leading to decreasing, but still 
persistent northwest flow and cold air advection. With the large 
scale subsidence, should have dry weather and few clouds through the 
day. Temperatures are expected to be 5 to 10 degrees below normal, 
with highs in the 30s and lower 40s.


Saturday night and Sunday will feature nice weather as large
high pressure across the region Sunday morning will move
offshore Sunday night. Temperatures will be close to average
Sunday afternoon after a cold morning. Highs will reach the
low/mid 40s across the north and central areas while upper 40s
and low 50s will be across the metro areas and Delmarva. 

Low pressure will advance towards the area early next week. A
stream of moisture will develop over the area Sunday night and
persist through Monday and beyond. Frequent clouds and rains
will be found across the region. The rains and poor weather will
continue into Tuesday. It will become unseasonably mild,
especially Tuesday when highs will be in the 50s north/west and
low 60s for Delmarva and south NJ. QPF for the period could be
in the 1 to 2 inch range, so the possibility of some localized
poor drainage flooding can't be ruled out. Also, if temps do not
warm quick enough across the north/west areas Sunday night, a
little snow at the onset is possible. 

As the system moves away Tuesday night and Wednesday, colder air
will arrive from the N/W. P-type could become an issue again
with the rains possibly changing to snow before ending. We'll 
have to watch this with the possibility for some accums across 
the Poconos and north NJ. (other areas possible too). Temps 
will drop back through the 40s Wed and 30s Wed night. 

The end of next week will feature dry, but cold weather. Highs
Thu will be well below normal with 30s regionwide, some
moderation possible Fri. Another system may approach for next 
weekend with more rains/snows possible.


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

Tonight...VFR with CIGs dissipating by late evening. Southwest
winds will become abruptly northwest by 03z across the area,
with speeds of 5 to 15 kt. High confidence.

Saturday...VFR with northwest winds around or below 10 kt. High


Saturday night-Sunday...VFR expected. Increasing clouds Sunday. 

Sunday night thru Wednesday...Widespread IFR expected with LIFR
also possible at times. Rains, low clouds and fog much of the
time. Gusty winds expected, especially near the coast.


930 pm update: Converted the gale warning to a small craft
advisory for the northern New Jersey Atlantic waters, as
stronger gusts have not materialized this evening. Still
expecting a period of stronger gusts for the next few hours, but
no longer expecting gale conditions. No other changes were
necessary at this time.

Previous discussion...

Gale conditions are expected in the vicinity of Sandy Hook through 
late this evening, so have issued a gale warning for the coastal 
waters adjacent to Monmouth County. Otherwise, expect breezy 
southwesterly winds through early this evening, with SCA conditions 
expected on the rest of the Atlantic coastal waters. On the Delaware 
Bay, gusts near 20 kt are expected. 

Then this evening, a cold front will bring an abrupt shift to 
northwesterly winds resulting in SCA conditions on the lower 
Delaware Bay and most of the Atlantic coastal waters, with gales 
still possible for the Monmouth County coastal waters.

Winds should diminish quickly near sunrise, and during the day 
tomorrow, winds and seas should stay below SCA.


Saturday night-Sunday night...Sub-SCA. Fair thru Sunday than
rains developing Sun night. 

Monday-Wednesday...Small Craft Advisory conditions likely with Gales
possible. Rain and fog much of the time.


MARINE...Small Craft Advisory until 6 AM EST Saturday for ANZ431-


Near Term...CMS/Johnson

National Weather Service Glossary of Abbreviations