Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 221501
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1001 AM EST Wed Feb 22 2017

.SYNOPSIS...
High pressure will remain anchored just off the east coast
through midweek. A backdoor cold front over New England may
approach the area, before moving northward as a warm front
Friday into Friday night. Low pressure moving through the Great
Lakes region will bring a strong cold front through the area on
Saturday. High pressure builds in from the west late in the
weekend, before moving offshore early next week, while another
warm front approaches the area.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Water vapor satellite imagery subtly captures a weak shortwave
trough moving thru the northern Mid Atlantic this morning. This
disturbance has resulted in a cloudy start to the day. Additionally,
regional radar mosaic showed multiple bands of light rain showers.
Kept PoPs below 20 percent with sprinkles across the I-195 corridor
and in far southern zones of DE/eastern MD for late this morning. A
more organized band of precipitation farther north (along and
north of I-80) warranted raising PoPs to introduce light rain
showers to the forecast thru the early afternoon. Otherwise, a
dry afternoon is in store. Hourly PoP/Weather grids were updated
earlier in the morning and sent to the web around 8 AM.

Temperatures have been slower to rise so far this morning than
previously forecast, likely owing to the overcast skies that have
tempered our ability to mix out the nocturnal inversion. Blending
our previous forecast with some of the latest rapid refresh guidance
resulted in max temperatures that are only a degree or two lower
than previous forecast. Therefore, we should be able to warm rather
quickly during the afternoon, especially once the cloud cover thins
out mid to late afternoon, despite the slow start.

The record highs for today are listed in the climate section below.
Most locations will fall several degrees short of their record based
on our latest projections. However, Mount Pocono may get close their
daily record...a forecast high of 56F would tie their daily record.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
The surface high is forecast to begin moving farther out to sea
tonight. However, it should keep a light southwest to south
surface flow in our region. The increase in low level moisture
may result in the development of low clouds and patchy fog late
tonight.

Temperatures are expected to remain mild for this time of the
year. Minimum readings should favor the 40s in northeastern
Maryland, Delaware, New Jersey and much of eastern Pennsylvania.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
A more active pattern is shaping up for the Thursday thru
Tuesday period, with the most impactful weather expected on
Saturday in association with a strong cold, preceded by the
potential record warmth Thursday into Saturday.

In terms of the mid-level pattern, a split flow regime will
begin to consolidate as phasing takes place over the upper
Mississippi Valley on Saturday. In spite of a couple fast moving
shortwave impulses near the area Thursday into Friday, 500 hPa
heights will continue to rise, reaching 570 Decameters by
Saturday. A more zonal pattern takes hold Sunday night into
Tuesday, as temperatures return to near normal for a change.
Several shortwave disturbances embedded within the zonal flow
will increase chances for generally light precipitation during
this time frame.

Thursday and Friday will feature a warm front just north of the
area, with diffuse shortwave energy moving along it. This will
promote the chance for scattered rain showers, mainly north of
an I-195 to PA Turnpike line. In fact, there could be a rumble
of thunder both days, especially on Thursday. Also, there is the
potential for record highs on both Thursday and Friday. Given
the proximity of a backdoor front, which may make it into
northern NJ on Friday, in addition to increased cloud cover,
record warmth potential is greater on Thursday. Finally, there
is the potential for some patchy fog both Thursday and Friday
mornings.

Saturday and Sunday...Saturday could be an active day as a
strong cold front moves through the region. We should be within
the warm sector, and the synoptic pattern is favorable for at
least a fine line of convection to move through much of the
area. Model soundings show a modest shear-low CAPE environment,
in addition to negative Showalter indices. While this is still a
ways out, there is at least a chance of thunder, and this
continues to be reflected in the forecast. In addition, some
heavier downpours are possible, with the potential for rainfall
amounts to approach one inch, especially closer to the Poconos.
Once again, record warmth is possible within the warm sector on
Saturday. If the timing of the system holds, fair weather is in
store for Sunday, with a return to near normal temperatures, and
gusty west-northwest winds.

Looking ahead to Monday and Tuesday, several shortwaves will
interact with a nearby frontal boundary, offering additional
chances of light precipitation. Details in timing and coverage
are low at this time, so the forecast reflects a general slight
chance of showers during this period. We expect temperatures to
continue near average as mentioned earlier.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Mainly VFR conditions expected through early tonight. However,
lower CIGs with stratus detected over Delmarva may spread
downstream and briefly result in MVFR CIGS at MIV thru about
17Z. Lower confidence that stratus reaches ACY. Otherwise, CIGs
should be above 7 kft today. Decreasing cloud cover is forecast
for the mid to late afternoon and into this evening.

Increasing low-level moisture late tonight may result in the
development of low clouds and some fog. There is the potential
for MVFR and IFR conditions at that time. Confidence in the
onset and extent of the stratus/fog is low at this time.

A light southwest to south wind is anticipated to develop for
today at speeds around 4 to 8 knots. The wind should become
light and variable at most locations for tonight.

OUTLOOK...

Thursday...Potential for MVFR/IFR in early morning clouds and
fog, otherwise, VFR. Southwest wind gusts to 20 knots possible
in the afternoon.

Thursday night through Saturday...There is the potential for
MVFR/IFR at times, especially Thursday night through Friday
night with a warm front nearby, and again on Saturday with
showers and potential thunderstorms ahead of a cold front. Winds
out of the south on Saturday could gust to at least 20 knots.

Saturday night and Sunday...Becoming VFR Saturday night with
gusty west-northwest winds anticipated into Sunday.

&&

.MARINE...
High pressure located off the Middle Atlantic Coast today
should maintain a southwest to south flow over the coastal
waters of New Jersey and Delaware for today and tonight. Wind
speeds and gusts should remain mostly less than 15 knots. Wave
heights on our ocean waters are forecast to range from 2 to 3
feet. Waves on Delaware Bay are anticipated to be 2 feet or
less.

OUTLOOK...

Sub-SCA conditions are forecast Thursday into Friday. SCA
possible Friday night into Saturday, with gales possible
Saturday night into Sunday.

&&

.CLIMATE...
High temperature records for Wednesday-Saturday. Although most
of these records will probably remain intact, the greatest
potential to break a few of these records will be on Thursday.

Wednesday 2/22    Thursday 2/23   Friday 2/24   Saturday 2/25

ACY 68-1991       72-1985         75-1985       77-1930

PHL 68-1997/1974  75-1874         74-1985       79-1930

ILG 69-1997/1974  72-1985         78-1985       78-1930

ABE 68-1974       71-1985         76-1985       74-1930

TTN 66-1997       74-1874         74-1985       76-1930

GED 72-1997       67-1985/1990    72-1961       76-1975

RDG 70-1974       72/1932/1922    77-1985       77-1930

MPO 56-1997       60-1977         60-1984       70-1930

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$
Synopsis...Franck
Near Term...Klein
Short Term...Iovino
Long Term...Franck
Aviation...Franck/Iovino/Klein
Marine...Franck/Iovino
Climate...



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