Area Forecast Discussion
Issued by NWS Mt. Holly, NJ-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KPHI 230147
Area Forecast Discussion
National Weather Service Mount Holly NJ
947 PM EDT SUN MAY 22 2016
A low is expected to develop off the coast of North Carolina and
then slowly drift northeast, lingering just offshore of our region
through Tuesday. A ridge will build over our region by mid week. The
ridge will slowly shift east through the remainder of the week.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --The mid/upper low affecting the area will continue to sink
southward tonight, but our area will remain on the northern side.
Cool an damp conditions will continue through the night. Showers
will dissipate from north to south overnight, and clouds may begin
to thin from north to south as well through the overnight hours.
Depending on how much thinning of the clouds occurs, some fog
could develop overnight light winds expected.
-- End Changed Discussion --
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
A low pressure system will start the day to our southeast and move
northeast toward Cape Cod by nighttime. While the system will be
offshore, daytime heating will result in some instability by the
afternoon hours. This will likely result in another round of
scattered showers forming and even some thunderstorms with CAPE
values of a few hundred J/KG. The highest chances look to be across
Eastern PA where the terrain may help out a little as well.
Temperatures should rise into the low and mid 70`s for the region
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Tuesday...the upper level low will linger over the northeastern
U.S. for one more day before lifting further northeast. As such,
should see any lingering showers across the region taper off by
the evening. A modest warming trend is expected going into Tuesday
resulting in temperatures once again near normal.
Wednesday and Thursday...Upper level ridge will shift east, with
the ridge axis over our region by Thursday morning. However,
unlike previous model runs, the 12z ECMWF and GFS now show the
center of the high much further south. As such, though there
should be a lull in rain chances on Wednesday, rain chances will
increase once again on Thursday, primarily for locations expected
to be west of the ridge axis (Generally E Central PA and NW NJ).
Of more certainty is that the region will have a very noticeable
warming trend, with 80s expected across much of the region both
Friday through Sunday...The GFS has poor run to run consistency
through this period, as it now shows a backdoor cold front
arriving in the region by Friday. If this scenario is correct,
persistent onshore flow could result in temperatures well below
normal especially Saturday and Sunday, and generally light and
steady precip through much of the period. For now though,
have not included this in the forecast, not only due to the poor
run to run consistency, but also because it seems an unlikely
pattern for late May that a cold front would be able to push this
far south under an upper level ridge. Even with models and
ensemble members that show the ridge lingering over the region,
should still see chances for showers and thunderstorms through the
weekend as the region could be on the periphery of the ridge.
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
VFR conditions are currently in place across all TAF sites this
evening, and scattered showers will dissipate from north to south
this evening and overnight. There is the potential for some fog
development overnight into Monday morning if clouds thin out
enough. We`ve introduced some light fog for all TAF sites, with
the thickest potential at RDG. Any fog should lift and dissipate
after sunrise Monday, and a return to VFR is expected. Scattered
showers could again develop during the day Monday.
Tuesday...Occasional MVFR conditions possible with showers and fog
especially Tuesday morning.
Wednesday and Thursday...VFR conditions likely. Small chance of MVFR
conditions with showers and thunderstorms Thursday afternoon and
Friday...Intermittent MVFR conditions with rain showers possible.
-- End Changed Discussion --
SCA tonight through late tomorrow afternoon on the ocean. While
winds will generally be northeasterly from 10-15 knots, seas will
remaining around five feet through tomorrow afternoon on the ocean
waters. Seas will likely be slower than wavewatch indicates coming
down because of an easterly, onshore flow component in the wind
direction. However, it is still expected that seas fall below five
feet by days end on Monday.
Tuesday through Friday...winds and seas should stay below SCA
We`ve recalculated the projected monthly temperature based on our
forecast and we`re still holding to a substantial warmup (summerlike
by Friday), lowering the average temperature departure by about 3
degrees from where we were through the 21st...still below normal
for the month at Philadelphia. A backdoor cold frontal intrusion
this weekend as proposed by the GFS would leaves us cooler for the
month, than now expected and projected.
Rainfall through 7 pm today (5.03) has raised Philadelphia`s
month of May ranking to 22nd wettest, dating back to 1872.
Atlantic City`s 4.61 total makes this so far, the 25th wettest
May dating back to 1874.
Corrected por PHl and 7 PM monthly amounts both locations.
MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ452>455.
Small Craft Advisory until 6 AM EDT Monday for ANZ450-451.