Area Forecast Discussion
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FXUS61 KPHI 240119
Area Forecast Discussion
National Weather Service Mount Holly NJ
919 PM EDT TUE AUG 23 2016
High pressure will shift offshore tomorrow. A cold front approaching
from the northwest will arrive Friday. Another area of high pressure
is anticipated to build east over New England, before shifting
offshore on Monday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
High pressure will continue to slowly drift to the east tonight.
Heights and thicknesses will slowly rise during the overnight,
resulting in slightly warmer temperatures compared to Monday
night. Surface dewpoints will slowly creep up as well, rising into
the upper 50s by daybreak. With clear skies, nearly calm winds,
and increasing low level moisture, patchy fog is possible well
after midnight tonight.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Another tranquil day on tap for Wednesday as high pressure continues
to drift off the Mid-Atlantic coast. With SW flow behind the
departing high, temperatures and surface dewpoints will be a bit
higher than today, with highs generally in the mid to upper 80s and
surface dewpoints climbing to near 60.
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Thursday through Friday...As the high slides further off shore, a
cold front will approach our region from the Great Lakes. Kept a
mention of slight chance of thunderstorms for Thursday night, as the
front gets closer, but removed mention of precipitation on Friday.
Even though the front will be crossing through the region on Friday,
think this period will remain dry as the large upper level high over
the southeastern U.S. will be building north through this time,
resulting in synoptic scale subsidence for our region.
Saturday and Sunday...Any post-frontal cooling trend will be
tempered by the building upper level ridge centered over the
southeastern U.S. Thus, have gone slightly above MOS guidance for
highs, but still kept it below raw model highs (for both the GFS and
ECMWF), until there is better run to run consistency on the position
of the ridge axis.
Monday and Tuesday...Next cold front is expected to approach our
region through this period. Some question as to how far south it
will get given the still persistent upper level ridge. Given the
uncertainty, kept 20 to 30 percent PoPs throughout this period.
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
VFR conditions will continue through the TAF period. With some low
level moisture increasing, patchy fog will be possible, mainly at
KRDG, overnight into early Wednesday.
Winds have lightened up and will remain light and variable across
the terminals. winds will start to pick up out of the west or
southwest around 14-16Z on Wednesday, remaining less than 10
knots. Winds are expected to shift more to the south or southeast,
especially at KACY and KMIV, during Wednesday afternoon.
Thursday...VFR conditions expected.
Thursday night...mostly VFR. MVFR conditions possible with isolated
to scattered thunderstorms.
Friday through Sunday...VFR conditions expected.
High pressure over the Delmarva will slowly drift offshore tonight
through Wednesday. S-SW winds at 5-10 KT will become W by Wednesday
morning before tuning S and increasing to 10-15 KT with occasional
gusts to 20 KT in the late afternoon. Seas will generally average 1-
Thursday through Friday...southerly flow increases especially
Thursday night with gusts above 20 kt expected. However, at this
time, winds and seas are expected to stay just below SCA conditions.
Winds will shift to northwesterly late in the day on Friday as a
cold front moves through.
Saturday through Sunday...winds and seas should remain below SCA
criteria through this time.
For Wednesday, the probable risk for the formation of dangerous rip
currents is presently low. However, conditions may approach
moderate should the waves increase closer to 2 feet and should the
southeasterly winds increase through the afternoon.
This coming Sun-Tue...model ensemble guidance on every successive
cycle continues to send 2-4 ft long period (15 to 17 second) east
southeast swell into our waters from the central Atlantic. If that
occurs, swimming and wading dangers will increase markedly.
A top 5 warmest August appears assured most of our forecast area
and a top 4 warmest June-July-August for Philadelphia, Allentown
and possibly Atlantic City.
Philadelphia appears on its way for warmest ever August.
Philadelphia August normal temp 76.6. Odds favor the nearly +4F
departure projected average of 80.4F could still be too low as
the ECMWF continues quite warm through the 29th (warmer than the
Philadelphia August ranking includes our 330 PM forecast temps (SFT
specific values) through the 30th and the FTPRHA GFS 2m PHL max/min
for the 31st. The 30 year normal is 76.6 and records date back to
1. 80.4 2016
2. 79.9 1980
3. 79.8 2001 and 1995
4. 79.6 2005
5. 79.5 2002
Regarding whether August can tie its record of 17 90F days. Its possible
but not probable. Can foresee 3 to 6 more 90 degree days to add onto
the 11 we have so far this month. The record of 17 was set in 1995.
The mean for the month is only 5.
Allentown will probably rank #2 or #3 warmest August. Records date
back to 1922. Normal 71.7 projecting a positive departure of nearly
1. 78.2 1980
2. 76.5 2016
3. 76.0 1937
4. 75.7 1955
Atlantic City represented records date back to 1874. The August
monthly normal is 74.4 and we`re projecting a positive departure
of more than 3.5 degrees. We`ll look at this again tomorrow but
ACY has a very good chance of ranking 1 or 2.
1. 78.1 2016
2. 77.9 2005
3. 77.1 2009
4. 77.0 1984
Seasonal: This summer 2016 for Philadelphia will probably be the
2nd or 3rd warmest June-July-August (JJA) in the period of record
dating back to 1874.
1. 79.6 2010
2. 78.7 2016
3. 78.6 1995
4. 78.3 1994
Allentown seasonal avg is projecting 74.9 or a ranking of around
#2 in the period of record that dates back to 1922.
1 75.3 1949
2 74.9 2016
3 74.6 2005 and 1980
4 74.3 1943 and 1937
Atlantic City seasonal average is projecting 75.8...4th warmest
in the period of record dating back to 1874.
1. 77.5 2010
2. 77.0 2011
3. 75.9 2005
4. 75.8 2016
5. 75.5 2008
90 degree days
season mean aug aug mean aug rer season rer
abe 30 17 9 4 16-1980 41-1966
acy 26 10 9 3 11-2010 46-2010
phl 35 21 11 5 17-1995 55-2010