Area Forecast Discussion
Issued by NWS Mt. Holly, NJ-- Remove Highlighting --
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FXUS61 KPHI 201442
Area Forecast Discussion
National Weather Service Mount Holly NJ
1042 AM EDT Thu Oct 20 2016
A front which settled south of the region wednesday night will
push back across our area today. Low pressure will strengthen
across the Ohio Valley and move north of the area tonight and
Friday. A strong front associated with the low will cross the
region Friday evening. Eventually, strong low pressure will be
across New England this weekend and it will remain there into
early next week. High pressure will build across our area into the
middle of next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
High pressure remains centered over Maine as a broad area of low
pressure develops and strengthens over the OH/TN Valleys. A
stationary front remains along the Mid-Atlantic, and as the low
tracks to the north, that front will lift through the region as a
warm front. Due to the influence of the high, an E-NE flow remains
over the CWA. For coastal and southern portions, and onshore flow
is resulting in an airmass with surface dewpoints in the low to
mid 60s. For the rest of the CWA, however, that flow is ushering a
dry airmass from the north as surface dewpoints are in the upper
40s to mid 50s.
As a result of the dry air over much of the area, precip is
having a hard time developing. Current RADAR showing an area of
showers and thunderstorms over central and eastern PA, just west
of the PHI CWA boundary, lifting to the north. Only a few showers
have been able to develop over the Lehigh Valley and Pocono
Mountains this morning due to that dry air. It will take some time
for the dewpoints to increase enough to support more widespread
shower activity, probably not until this afternoon. Until then,
can continue to expect widely scattered, light showers. Will carry
low end chance PoPs, increasing to high end chance this afternoon
for the Lehigh Valley, Pocono Mountains, and northern NJ.
For the rest of the CWA, that warm front will continue to lift to
the north, but there is not much upper level support for showers.
In addition, surface moisture, with the exception of coastal and
extreme southern areas, is marginal, at best. Therefore, will
carry a dry forecast for most of the southern half of the CWA,
with slight chance PoPs for the central portions.
For temps, not making too many changes to the previous forecast.
Clouds, showers, and evaporative cooling, mainly this morning,
will keep temps from rising out of the low to mid 60s to the north
of I-80. For the rest of the region, temps will warm well into
the 70s, and into the low 80s across MD/DE. Record high
temperatures are likely across southern areas.
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Low pressure will continue to deepen as it moves northeastward from
the Ohio Valley to central PA tonight. Boundary layer winds are
forecast to strengthen sufficiently to progress the warm front
northward through eastern PA and NJ tonight. North of the front
across northeastern PA and northern NJ, pockets of drizzle and fog
are expected. Lows range from the mid 50s north of I-80 to the mid
60s south of the PA Turnpike/I-195.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Friday/Friday night...Low pressure and a strong front will cross the
region. Most of the models are not bringing too much precip to the
area, despite the strength of the systems moving through. The low
pressure system offshore will be bringing in more moisture from the
east, but much of it arrives too late to be acted upon by the cold
front. The system gets more organized north of the area, and the
higher rainfall totals will be there. The last of the rather mild
air will be swept away Fri evening with temps dropping back to
normal or slightly below normal values. Lows Fri night will be in
the low 40s north and mid/upper 40s south. Winds will increase
overnight with gusts 20-30 mph at times.
Sat thru Sun...Decreasing chc for showers Sat morning across the
area as the strong to the north moves away. Low chc pops will be
across the nrn and central areas Sat morning...decreasing back to
slgt chc by afternoon. It will be windy and cool Sat with highs only
the the upper 40s/low 50s north/west and mid/upper 50s over Delmarva
and srn NJ. Winds NW 15-25 mph with gusts near 40 mph possible. We
may to eventually consider wind related headlines if speeds trend
any higher. Winds diminish by Sunday.
Sun night/Mon...A weak upper system and sfc front may bring a few
sct showers across the far north. These system will also bring a
reinforcing shot of cooler air and gusty conditions Sun night and
Monday. The airmass looks rather dry attm, so we will hold on
mentioning any pops attm. This could be updated as the time gets
Mon night thru Wednesday...A mostly dry period with seasonable
temperatures. High pressure from the Midwest will build over the
area and reach the region Wed evening.
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Mainly a VFR forecast this morning with lower clouds around 4-5
kft AGL expanding from SW to NE across the area. An area of light
showers may develop in VC of RDG-ABE through 16Z, with CIGs
lowering to around 1500-2500 ft once precip falls. Model guidance
then shows an expansion of low clouds to the southeast toward the
I-95 terminals between 15-18Z. The onset of MVFR CIGs may be a bit
too quick as models have under-predicted the strength of the near-
surface dry air thus far. Eventually this afternoon, terminals
should experience at least temporary periods of MVFR.
Low clouds are likely to become more widespread after dark tonight.
CIGs may lower to below 1000 ft. The best chance for IFR CIGs
appears to be across the northern terminals. Stat guidance is also
indicating widespread fog with VSBYs less then 1 SM at many of the
terminals. This may be overdone with cloud cover already in place.
There could be a more localized region of fog maybe along and north
of a warm front but it is too uncertain to pinpoint which terminals
would be affected.
NE winds 5-10 kt early this morning will become E by this afternoon
and then S-SE late this evening and overnight after the warm front
Fri/Fri night...Showers likely with restrictions to MVFR expected.
IFR conditions possible. Gusty winds developing Fri night.
Sat through Sun...Some MVFR psbl erly Sat, especially n, then
mainly VFR. NW winds with 25-35 KT gusts psbl.
No marine headlines are expected for today. NE winds 5-15 kt this
morning will veer out of the east and then SE over the course of the
day and into tonight. Seas in our coastal waters will generally be
in the 2-3 ft range.
Fri...Mostly sub-sca, but winds and seas begin to increase late.
Fri night thru Sun...A Gale Watch has been issued. Strong gusts
and rough seas thru the period. Sct showers fri night and Sat
Sun night thru Tue...SCA conditions expected. Isolated showers
possible across the nrn NJ coastal waters Sun night.
-- Changed Discussion --Tide levels may come close to touching minor coastal flooding
thresholds at high tide late this morning and early this
afternoon. Latest guidance has Lewes, DE, and Sandy Hook, NJ just
touching minor coastal flooding benchmarks. Although a Coastal
Flood Advisory will not be issued, there may be some spotty minor
Guidance is also indicating the potential for minor tidal flooding
around high tide early Friday afternoon.
-- End Changed Discussion --
The following sites tied or set daily record high temperatures
yesterday (Wednesday, 10/19)
New RecordOld Record
Allentown, PA 84 82 (1963)
Trenton, NJ 86 83 (1963)
Philadelphia, PA 86 80 (1947)
Atlantic City, NJ 86 80 (1991)
Wilmington, DE 87 81 (1963)* record tied
Georgetown, DE8681 (1953)
Warmth of this magnitude seen the past few days is a rare
occurrence for this late in the year:
For Allentown, the only other year that recorded a high
temperature of at least 85 degrees this late in the calendar year
was 1947. In 1947, the high was 85 degrees on the 21st and 23rd of
October. Climate records at Allentown go back to 1922.
Here are the record high temperatures for today (10/20).
THU OCT 20
Mount Pocono, PA 75 in 1963
Reading, PA 80 in 1947/1953/1969
Allentown, PA 78 in 1936
Trenton, NJ 80 in 1969
Philadelphia, PA 80 in 1916/1938
Atlantic City, NJ 85 in 1987
Wilmington, DE 82 in 1969
Georgetown, DE 83 in 1953
Monthly average temperatures are projecting 3 degrees or so above
normal, which would rank in the top 15 warmest Octobers at
Philadelphia and Allentown. This is stated with the usual mid
month uncertainty. What we do know is that the warmth of this week
will virtually lock in an above normal month, especially since the
pattern for the last week of October does not indicate any lengthy
period of below normal temperatures.
MARINE...Gale Watch from Friday evening through Saturday afternoon for