Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kphi 211337 
afdphi

Area forecast discussion
National Weather Service Mount Holly New Jersey
937 am EDT Sat Oct 21 2017

Synopsis...
high pressure centered over the area will move offshore later today
but continue to influence our weather into Monday. A cold front
approaching from the west is expected to approach the region on
Tuesday. Low pressure will move along the front Tuesday night
through Wednesday. Another low will affect the area Thursday before
more high pressure builds in for the end of the week.

&&

Near term /until 6 PM this evening/...

No significant changes with the mid-morning update.

Today...sunny. Light wind becoming southeast during the afternoon.
High temps a couple of degrees warmer than ydy. Used a 50 50 blend
of the 00z/21 GFS/NAM except straight warmer GFS 3 hourly and
Max T today, but trimmed a degree over I-95 to a Max of 78. Max
temps about 10 to 15f above normal with the greatest positive
departures i95 northwestward. Looks very good for 75-79 virtually
everywhere i95 corridor northwestward with support from the
00z/21 ec 2m temp fcst at 18z today. It will be slightly cooler
high terrain. The 72 we're fcstg at kmpo is 5f short of the
record of 77 - 1959. Effective sea breezing along the coast this
aftn with water temps in the 60s...which are still significantly
above normal for this time of year.

&&

Short term /6 PM this evening through 6 am Sunday/...
clear and nearly calm but patchy fog may form toward dawn Sunday,
especially se of I-95 where shallow moisture may increase enough
for fog. Certainly a dewy late night early morning. The fcst is
a 50 50 blend of the GFS/NAM MOS with Countryside temps lowered
2-3f below the blended guidance and not much above this mornings
mins...ranging from zero to +10 of normal depending on location.

&&

Long term /Sunday through Friday/...
high pressure will still be in control of the weather for Sunday and
Monday. Moisture will begin to arrive over the area however. This
will result in some cloudiness and areas of fog for Sunday morning
and increasing clouds for Monday. This will likely keep temperatures
a few degrees cooler than Saturday, but readings will still be above
normal for this part of October.

A slow moving front and a upper trough will arrive from the Ohio
Valley Tuesday-Wednesday. As it approaches, it slows, as low
pressure will be deepening across the tenn valley area. The low will
move along the front, just west of our region Tue-Tue night. This
should bring a period of showers and gusty winds to the area. Pops
are mostly in the likely/low categorical range at this time. Quantitative precipitation forecast
thru 12z Wed. Could reach 1/2 to 1 inch over much of the area.
The latest European model (ecmwf) model does have a few spots closer to 2 inches
of quantitative precipitation forecast however. Some of the guidance suggests that some tstms
are also possible. We will not have tstms in the grids at this
point, but will have to consider as we get closer to the event.
Temperatures will be above normal Tuesday, but then fall to
normal Wednesday as the front passes. Pops will decrease back to
chc or slgt chc levels after the front moves offshore.

There will still be a few sct showers around Thu as the upper low
crosses the area. After that, high pressure with drier air is
expected for Fri. Temperatures will be near normal for both of these
days.

&&

Aviation /14z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.

Through today...VFR with a few cirrus, especially this afternoon.
Light north to northeast wind trending southeast during this
afternoon.

Tonight...VFR with some cirrus. The IFR St/fog may develop,
especially southeast of I-95 toward dawn Sunday...also the river
valleys in NE PA and NW New Jersey.

Outlook...
Sunday...a little fog or stratus early...otherwise VFR,

Sunday night and Monday...low clouds and fog are possible from
late Sunday night into Monday morning. Otherwise...mainly VFR.

Monday night through Tuesday night...conditions lowering to
MVFR and IFR in showers. Isolated thunderstorms and moderate to
heavy rain are possible on Tuesday afternoon and Tuesday
evening, along with a south wind gusting around 25 to 30 miles per hour.

Wednesday...conditions improving to VFR.

&&

Marine...
winds and seas well below Small Craft Advisory criteria through tonight.

Light north winds 5-10 kt will veer over the next 24 hours,
becoming east around midday and then S-southeast late today and
tonight.

Seas in our coastal waters of around 2 ft through tonight.



Outlook...
Sunday thru Monday...sub-sca conditions with fair weather.
Monday night...Small Craft Advisory developing on the ocean. Chance of showers.
Tue-Tue night...Small Craft Advisory conditions on the ocean and del Bay. Showers.
Wed-Wed night...Small Craft Advisory on the ocean. Sub-Small Craft Advisory on del Bay. Chc showers.

&&

Fire weather...
relative humidity values are likely to drop to around 25% this afternoon but
light winds will limit the risk for a rapid rate of spread of
any wildfires.

&&

Climate...
**top 5 warmest October on record for phl and Abe and probably
for rest of our forecast area**

Our 330 am forecast for the next 7 days, then adding the
day8-11 from ftprha GFS 2meter Max/min temps yields the
following projections for average temperature in October.

Phl projects warmest October on record. The 64.7 degrees
projected average is more than 7 degrees above the October 30
year avg of 57.5. The projected positive departure is the same
as it is for the first 20 days of the month.

Previous top 3 average temps for October in phl

1. 64.5 2007

2. 63.5 1971

3. 62.7 1947

To drop out of the top 3 warmest the phl avg would have to
be 2 degrees lower than currently forecast.



Abe 60.3 or nearly 8 degrees above the 30 year avg of 52.5.
This is #2.

1. 60.8 2007

2. 60.3 2017 projected

3. 59.5 1984

4. 59.3 1947

5. 58.8 1971



The values below are the October departures from normal through
the 20th (yesterday).

Phl 7.2
ilg 7.1
Abe 8.5
mpo 6.9
ridge 7.7
ttn 7.8
Acy 7.0
55n 5.0
Ged 6.5



The last two years in phl ending 10/20/17 is the warmest in the
period of record dating back to 1872...averaging more than 3
degrees above normal.



Ditto Allentown, Wilmington being the warmest in their
respective periods of record.

&&

Equipment...
44091 buoy drifted away from its mooring and was recovered. Its
return to service date is unknown.

&&

Phi watches/warnings/advisories...
PA...none.
New Jersey...none.
Delaware...none.
Maryland...none.
Marine...none.

&&

$$
Synopsis...O'Hara
near term...drag/Gaines
short term...drag
long term...O'Hara

National Weather Service Glossary of Abbreviations