Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 251249

Area Forecast Discussion
National Weather Service Mount Holly NJ
849 AM EDT Tue Oct 25 2016

High pressure near Hudson Bay Canada will build closer to our region
through mid week. A warm front on Thursday will be followed by a
cold front Thursday night as low pressure redevelops from near Lake
Erie Thursday to Long Island Friday morning. Weak high pressure
quickly follows Friday night before low pressure and its associated
frontal systems cross the mid Atlantic states Saturday. High
pressure will become dominant over our area by next Monday.


840 AM ESTF update: fcst sct light pcpn nw zones this morning and
increased pop 10 pct for more extensive wording and delayed drying
of pcpn til 17z (early afternoon). no change in the max temps from
our 330 am fcst. increased gusts 2-4 kts through this evening per
06z/25 gfs/nam transfer. Should be or become a mostly cloudybreezy

The continued northwesterly flow and cold air advection will result
in highs 5 to 10 degrees lower than what we saw yesterday. The
northwesterly flow will also result in dry air advection/decreasing
dew points through the day, which will set the stage for what is to
come tonight...


Surface high will move closer to the region overnight. This will
result in two things. First, skies are expected to clear quickly
through the evening hours, leading to clear skies overnight.
Secondly the decreasing pressure gradient will help winds decouple
quickly after sunset. In addition, the previously mentioned dry air
advection will mean that by this evening dew points will already be
in the mid 20s to lower 30s. All of this sets the stage for prime
radiational cooling conditions across the region.

As such, expect widespread frost and freeze across the region. The
freeze watch was converted to a warning, and includes all of the
region with the following exceptions: the Philly metro and
surrounding PA suburbs, Cape May County, and much of Delmarva, which
have a frost advisory; the NJ shore and DE beaches, where winds may
stay up through the evening hours enough to prevent frost formation;
and the southern Poconos and NW NJ where the growing season has
already ended.


Wednesday...Temps will rebound nicely from what is forecast to be
one of the coldest mornings thus far this fall, but still around
10 degrees below normal for highs. Some high and even mid-level
clouds later in the day in advance of an approaching warm front.

Wednesday night and Thursday...Still model disagreement at this
time with regard to precip amounts, thermal profile, and precip
type across northern NJ and the Poconos. The NAM continues its
trend of keeping the bulk of the precip northwest of the CWA,
while the GFS and ECMWF are in good agreement, indicating a band
of overrunning precip, focused north of the I-78 corridor. We
adjusted the precip starting time later, just after midnight on
Thursday morning. The column is below freezing to start, and with
the addition of wet bulb cooling, this will initially favor light
snow. Model soundings indicate the lack of a warm nose aloft, so a
gradual changeover to rain and even some spotty freezing rain is
likely by Thursday morning, although cannot rule out a period of
sleet. Any accumulation of snow and slippery travel will be more
confined to Sussex and Monroe counties, generally less than one
inch at this time. Otherwise, locally heavy rain showers for the
remainder of the area, with southerly winds gusty at times.

Thursday night and Friday...Precipitation ending from west to east
Thursday night with a blustery northwest flow to follow. Friday
will feature fair weather.

Saturday through Monday...Still considerable uncertainty, with
model timing differences, taking low pressure across the area
this weekend. Fair weather will return by Monday. Temperatures
are expected to rebound closer to normal during this time frame.


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

Today...VFR cigs aoa 5000 ft. nw wind with gusts increasing to
between 22 and 28 kt this aftn with steepening low level lapse
rates during midday.

Tonight...becoming VFR clear by 03z/26. NW winds may still be
gusting around 20 kt through 03z/26 vcnty KPHL/KACY but will
gradually decouple and decrease toward 09z/26.


Wednesday...VFR bands of variably thick cirrus aoa 20000 ft.
Northwest wind becoming north late in the day.

Wednesday night and Thursday...MVFR at times with a gusty
south wind on Thursday.

Friday and Saturday...VFR. Gusty northwest winds at times.


Winds will continue to gust near or just above 25 kt on all the
waters through the afternoon. On the ocean waters, SCA conditions,
primarily for winds could linger into late this evening, and even
after midnight we could continue to see winds gusting above 20 kt.

SCA likely Thursday into Friday, otherwise sub-SCA.


Minimum relative humidity values could be near or below 35
percent for portions of the region today and frequent
northwesterly wind gusts above 20 mph are expected from late
morning through late afternoon. However, at this time we are not
expecting red flag criteria to be met at this time.


This section will update by 11 am.

Our forecast indicates October should average at least 2 to 3 degrees
above normal for PHL and ABE. Some of the recent forecasts have
been colder and that may mean PHL and ABE slip to around 20th
warmest October on record, which is only noteworthy in that the
excessive monthly warmth of July, August, September eased in October.
Will reevaluate this afternoon and Tuesday. The colder scenario
than a week ago still has doubt and so we`ll try to be more definitive
late Tuesday regarding around 15th or around 20th warmest October.


PA...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
NJ...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
DE...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
MD...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
MARINE...Small Craft Advisory until 11 PM EDT this evening for
     Small Craft Advisory until 6 PM EDT this evening for ANZ430-


Near Term...Johnson/drag 849
Short Term...Johnson
Long Term...Franck
Aviation...Franck/Johnson/drag 849
Fire Weather...
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