Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 221625

Area Forecast Discussion
National Weather Service Mount Holly NJ
1225 PM EDT Sat Oct 22 2016

Low pressure along coastal New England will continue to track
northward this afternoon and intensify. This will result in windy
and much cooler conditions across our area through tonight.
Another cold front arrives Sunday night, then high pressure
gradually builds in through mid week. A warm front is expected to
lift north over our area at the end of the week.


For the 1230 PM Update, adjusted POPs to hang onto likely to
categorical for awhile longer as showers with the strong trough
axis aloft continues to pivot eastward. The trend is expected to
be less shower activity through the afternoon and ending from
south to north. Temperatures were adjusted to show a slower rise
overall for several areas.

The water vapor imagery shows a well defined upper-level trough that
is taking on a negative tilt across the Mid Atlantic and into the
Northeast (even closing off). This is driving an intensifying
surface low along the New England coast. This storm will continue
to lift northward through the day, with a tight pressure gradient
across our area. The cyclonic flow around this storm and with cold
air advection is resulting in much cooler conditions.

As this storm intensifies, windy conditions will be in place
across the area. The 12z Sterling, VA RAOB sampled winds to 40
knots up to 850 MB where an inversion is located. Some of this
will mix down to the surface, initially with the continued cold
air advection surge this morning, then through the afternoon as
the low-level lapse rates steepen a bit more. It appears that peak
wind gusts should be to around 40 mph, and therefore the thinking
is that much of the area remains below advisory criteria. The
wind on top of the much cooler temperatures will add a wind chill


Any lingering precip acrs nrn sections shud come to an end erly
tonight, then clouds will decrease as the upr flow becomes more
zonal, the sfc low moves away and high pres builds slowly in from
the s.  The wind will slowly begin to subside but will remain gusty.


Sunday...low will continue to lift NE away from the region.
As it does so, we should see the pressure gradient across the
region slowly decrease. However, low and mid level height
gradients will remain quite large through the day time hours, so
depending on how deep the mixing is, we could continue to see
windy conditions, though still not as windy as what we are
expecting today.

Sunday night...A secondary surface cold front slides through the
region late (after midnight). As mentioned by the previous shift,
a tight band of frontogenetic forcing along and just ahead of this
front could lead to some showers. However, limited synoptic scale
lift means that coverage should be quite limited across our

Monday and Tuesday...A robust northwest flow pattern sets up to
start the work week, resulting in continued cold air advection. In
fact, a few models even depict small QPF values across the NW
portions of the area in what looks like a lake effect pattern.
However, given that this is still a climatologically unlikely
time to see any lake effect precip, have kept the forecast dry.

Wednesday and Thursday...though the high associated with the
polar air mass builds closer to the region through this time, we
should actually see temperatures moderate a bit thanks to low
level flow shifting from northwesterly to westerly and possibly
southwesterly. Having said that, latest model runs backed off on
southerly return flow developing, so think that through the day
on Thursday we will continue to see slightly below normal

Friday and Saturday...there are big differences both between
models and run to run with how to handle the next upper level low
at the end of the week. The GFS depicts the upper level low
digging into the deep South with essentially no reflection of a
low in the surface pattern. The ECMWF on on the other hand, shows
a well defined extra tropical cyclone sliding across the Great
Lakes region resulting in first a warm front lifting over our
region and then a cold front sweeping through at the very end of
the forecast period. Given the uncertainty, have stayed close to
the previous forecast for now.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

This Afternoon...Ceilings are mostly VFR at Midday, with some
local MVFR lingering for a little while longer. Overall, the
ceilings are expected to be VFR. Showers will become less numerous
and shift north and east through the afternoon. Much of the shower
activity is on the light enough side, resulting in VFR
visibilities. Northwest winds 15-25 knots with gusts to about 35

Tonight...VFR. West-northwest winds 15-20 knots with gusts up to 35
knots should diminish some through the night. The wind gusts should
become less frequent through the night.

Sunday...VFR conditions expected. Breezy westerly winds continue.

Sunday night...Mostly VFR conditions expected but there is a small
chance of MVFR with showers after midnight primarily for TAF sites
north of KPHL.

Monday through Wednesday...Mostly VFR conditions expected.


The Gale Warning for the coastal waters and Delaware Bay will remain
in effect unchanged. Gale force gusts have already occurred across
the southern waters into Delaware Bay, and this will spread
northward through the day as low pressure in New England
intensifies. By late tonight, it is expected that the Gale Warning will
come down on the Bay but that will be reviewed later today.

Sunday...winds will diminish slightly on Sunday, and should drop
below gale conditions by late afternoon on the coastal waters.
However, SCA conditions will continue into Sunday night.

Monday and Tuesday...SCA conditions are expected to continue as
winds should continue gusting above 25 kt (though seas may drop
off below 5 ft.

Wednesday...winds are expected to subside below SCA criteria early
in the day.


MARINE...Gale Warning until noon EDT Sunday for ANZ452>455.
     Gale Warning until 6 PM EDT Sunday for ANZ450-451.
     Gale Warning until 2 AM EDT Sunday for ANZ430-431.


Near Term...Gorse
Short Term...Nierenberg
Long Term...Johnson
Marine...Johnson/Nierenberg is the U.S. government's official web portal to all federal, state and local government web resources and services.