Scientific Forecaster Discussion
fxus61 kphi 062001
Area forecast discussion
National Weather Service Mount Holly New Jersey
301 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.
Near term /through tonight/...
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 northwest New Jersey 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).
Short term /Saturday/...
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.
Long term /Saturday night through Friday/...
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 New Jersey. Quantitative precipitation forecast 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 New Jersey. (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.
Aviation /20z Friday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Tonight...mostly VFR conditions expected. Isolated showers are
possible through early evening, but the coverage will be very
limited and any impact will be brief, so have kept mention out of
the tafs for now. Southwesterly winds now will abruptly shift to
northwesterly between 00 and 05z. Moderate confidence.
Saturday...VFR conditions expected with few clouds. Northwesterly
winds mostly at or below 10 kt. High confidence.
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.
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 Small Craft Advisory 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 Small Craft Advisory 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 Small Craft Advisory.
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 anz451>455.
Gale Warning until midnight EST tonight for anz450.
Small Craft Advisory from 9 PM this evening to 6 am EST
Saturday for anz431.