Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

000 
FXUS61 KPHI 180539
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1239 AM EST Sun Feb 18 2018

.SYNOPSIS...
Low pressure will continue to quickly move away from our area 
overnight. High pressure briefly builds across the area again 
on Sunday, then offshore Sunday night. A strong warm front lifts
northward across our area later Monday into early Tuesday, 
followed by a cold front late Wednesday. The cold front stalls 
to our south by next Thursday with a series of waves moving 
north and east along it late next week into early next weekend.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY/...
The remaining winter weather headlines have been cancelled. 
Watch for some slippery spots though on untreated surfaces.

Low pressure continues to rapidly move away from our area. As a
result, the precipitation has quickly ended across the northern
areas, although a few light snow showers will be possible for a
few more hours. Lots of low clouds remain with weak surface 
winds, however as drier air arrives later tonight the clouds are
expected to lift and start to thin. In addition, some fog around
is also expected to improve. Made some adjustments to the hourly
temperature, dew point and wind grids.

&&

.SHORT TERM /SUNDAY/...
High pressure is forecast to build into our region from the 
west for Sunday. We are anticipating a mostly sunny day with a 
northwest to west wind around 10 MPH.

Sunday afternoon is expected to become relatively mild. Highs 
are forecast to be in the lower and middle 40s in the Poconos, 
the Lehigh Valley and northern New Jersey. Readings should get 
into the upper 40s and lower 50s in northeastern Maryland, 
Delaware, southeastern Pennsylvania, and southern and central 
New Jersey. Much of the new snow cover should melt by day's end.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
**Record warmth possible Tue and expected Wed**

Sunday night through Wednesday....

To start the period Sunday evening, high pressure crests over 
the area in the evening before slowly moving east overnight. 
This will set up good conditions for radiational cooling due to 
light winds and mainly clear skies despite the airmass not being
all that cold. Lows by Monday morning should generally be in 
the 20s to low 30s. 

For Monday, the high continues to push off to the east through 
the day with a warm front approaching from the south and west 
ahead of the next system. This will bring increasing clouds with
some showers likely by afternoon...mainly over eastern PA. 
Highs will generally range from the mid 40s north to the 50s 
across the Delmarva and southern NJ. 

Some showers may continue into Monday evening before lifting 
out overnight as the front moves through. Temperatures will be 
quite mild with lows only dropping to the 40s to low 50s. This 
will be followed by near record warmth on Tuesday as a strong SW
flow takes hold. We continue to forecast temperatures above the
model consensus and are generally looking at highs ranging from
the 60s in the north to the low 70s across SE PA as well as 
much of the Delmarva and southern NJ. Areas right near the coast
will likely be cooler though. 

For Tuesday night into Wednesday, temperatures continue to warm
with record warmth forecast by Wednesday...highs currently 
forecast to reach the low to mid 70s over SE PA as well as much 
of the Delmarva and NJ. Conditions should be dry for the most 
part though by late Wednesday a cold front could bring some 
showers in from the west...mainly for eastern PA. 

Wednesday night through Saturday...

In the big picture, this period will be dominated by somewhat 
cooler, though still well above average temperatures as a long 
wave trough persists over the Rocky Mountains with the area in a
SW flow. Conditions will also trend more unsettled as a series 
of waves move north and east along a wavering front that will 
linger in the region.

For Wednesday night into Thursday, the aformentioned cold front
with some associated rain showers pushes south through the area
before stalling over the mid Atlantic. Forecast guidance then 
indicates a wave trying to move north along the front though 
there is uncertainty in how this all evolves as high pressure 
will also be building in to our north. The high could suppress 
precip mainly to our south into Thursday but again, these 
details are uncertain so we keep chances for showers in the 
forecast through Thursday. Beyond this time there may be a brief
break before a stronger low pressure system moves north along 
the front by later Friday into next Saturday. Highs Thursday and
Friday will generally be in the 40s and 50s with 60s possible 
again by next Saturday.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, 
KILG, KMIV, KACY and surrounding areas.

Overnight...MVFR/IFR conditions improving to VFR late. Light and
variable winds becoming northwest 5-10 knots late.

Sunday...VFR. Northwest wind around 10 knots.

OUTLOOK... 
Sunday night...VFR. Confidence: Well above average. 

Monday...VFR early, lowering to MVFR or IFR during the 
afternoon or evening with rain. South to southwest wind. 
Confidence: above average.

Monday night...MVFR/IFR conditions continue with rain possible 
in the evening, and low clouds/dense fog possible overnight. 
Confidence: Above average. 

Tuesday...MVFR/IFR conditions possible through midday in low 
clouds/fog. Conditions improving to VFR during the afternoon. 
Southwest winds may gust around 20-25 knots in the afternoon. 
Confidence: average.

Tuesday night...VFR early, then possibly lowering to MVFR/IFR 
as low clouds/fog may develop overnight. Confidence: average.

Wednesday...MVFR/IFR conditions possible early with low 
clouds/fog. Conditions improving to VFR during the day. chance 
of showers late in the day. Southwest winds may gust around 
20-25 knots. Confidence: Average.

Wednesday night through Thursday...Chance of showers with 
associated restrictions. Confidence: Below average.

&&

.MARINE...
Low pressure will continue to quickly move away from our area
overnight. A gusty northwest wind is expected to develop on the
coastal waters of New Jersey and Delaware in the wake of the 
low. As a result, we will issue a Small Craft Advisory for our 
ocean waters and for Delaware Bay. It will be in effect from 
4:00 AM until 11:00 AM Sunday. The wind is forecast to diminish 
gradually on Sunday afternoon. 

OUTLOOK...
Sunday night through Monday...Sub Small Craft Advisory south 
winds. Confidence: Well above average. 

Monday night...Sub Small Craft Advisory conditions expected, 
although southwest winds may gust around 20 knots. Confidence: 
Above average. 

Tuesday-Wednesday...Winds should stay below advisory levels, 
but seas may increase to near 5 feet. Confidence: Average.

Wednesday night - Thursday...Winds should stay below SCA levels
with seas persisting in the 3 to 5 foot range.

&&

.CLIMATE...
Record high temperatures could be challenged on Tuesday, 
February 20th and probably will be equaled or exceeded Wednesday
February 21st. These records are listed below.

February 20:

Atlantic City...70 in 1930

Philadelphia....70 in 1939

Wilmington......71 in 1930

Allentown.......68 in 1930

Trenton.........70 in 1930

Georgetown......68 in 2002

Mount Pocono....59 in 1930

Reading.........72 in 1930


February 21:

Atlantic City...74 in 1930

Philadelphia....72 in 1930

Wilmington......70 in 1953

Allentown.......67 in 1953

Trenton.........70 in 1930

Georgetown......71 in 2014

Mount Pocono....60 in 1930

Reading.........71 in 1930


We are not posting the monthly records at this time since our 
forecast is 3 to 7 degrees below the monthly record. We'll check
again Sunday and Monday to see if our forecast edges warmer. 

The following are the record warm mins for Wednesday Feb 21. 
Barring a sudden immediate cool down behind the cool front at 
1159PM Wednesday, there is a good chance of record warm daily 
minimum temperatures as well the previously referenced record 
highs. 

Record high mins for 2/21

ABE 46-1981
ACY 49-1954
PHL 49-2002
ILG 47-2002
RDG 48-1930
TTN 48-2002 

Atlantic City rainfall already ranks 11th wettest in February 
history with 6.50" in 2010 the wettest. By sunrise Sunday, 
Atlantic City should rank about 8th wettest in its historical 
database.

The February average temp for PHL projects 41.0 or 5.3F above 
normal or 8th warmest on record. This placement can change 
anywhere from 3rd to 12th depending on a 1 degree change in the 
eventual average. Bottom line...we're likely on our way to a top
10 warmest February on record. The warmest was last year with a
44.2F average. Years 2002 and 2012 flank our currently 
projected 8th warmest.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 4 AM to 11 AM EST this morning for 
     ANZ430-431-450>455.

&&

$$
Synopsis...Fitzsimmons
Near Term...AMC/Gorse

National Weather Service Glossary of Abbreviations