Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 270525
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1225 AM EST Mon Feb 27 2017

.SYNOPSIS...
High pressure will move offshore during Monday. Low pressure
approaching from the west will lift a warm front through the
region on Tuesday. That low will track from the Great Lakes
region into eastern Canada on Wednesday. The associated cold
front will move across our area by Thursday morning, then an
upper level trough builds into the Northeast for the end of the
week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
High pressure centered just to our south overnight will slowly
shift eastward. A clear sky is over the area, however some high
level clouds are moving east-northeast from the upper Ohio
Valley. The combination of dry air, light to calm winds and a
clear sky has resulted in efficient radiational cooling
conditions. Temperatures dropped quite a bit through the
evening, however this drop has slowed or even leveled off for
most places. Adjustments were made based on the latest obs and
trends.

Some high level clouds will begin to increase toward daybreak.
Temperatures may rise a degree or two in some areas as we
approach daybreak as some high clouds arrive.

&&

.SHORT TERM /MONDAY/...
As the surface high moves farther east into the Atlantic,
southwest surface winds will become established across the area
on Monday. Substantial near-surface warm air advection will
contribute to a much warmer day Monday, with temperatures
returning to well above average values. A perturbation in the
west-southwesterly upper-level flow will approach the Mid-
Atlantic by 00Z Tuesday, with cloud cover continuing to
increase. However, residual dry air in the low levels and
generally weak large-scale ascent should prevent much if any
precipitation from occurring before sunset. Notably, model
guidance has been all over the place in the handling of this
system for days, rendering confidence much below average in the
details -- even for a 12-24 hour forecast.

There are at least some indications lift may become sufficient to
produce light precipitation to the west of the area (generally the
Appalachians westward in southern PA and adjacent MD/VA/WV) by late
morning or early afternoon. However, the aforementioned limiting
factors seem too much to overcome for generating precipitation in
the CWA by the end of the short term period. Thus, reduced PoPs on
Monday to non-mentionable levels.

Guidance has struggled mightily with temperatures in warm air
advection patterns this past month.  Went slightly above guidance
for highs based on the expected cloud cover present -- otherwise, I
would have gone well above guidance.  However, would not be at all
surprised to see highs several degrees warmer than forecast,
especially if the models are overdoing the moist air advection in
the 900-700 mb layer.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
A very active pattern continues through the long term.

Monday night through Tuesday night...warm front will lift north
through the region. Some weak lift is expected with the front
followed closely by a local vorticity maxima associated with the low
lifting into the Great Lakes Region. It isn`t exactly an
impressive set up for widespread precip, but models continue to
depict QPF across the region through this period. It looks like
the best chance through this period would be Tuesday afternoon
and evening, when we still have a slight onshore component to
the low level flow.

Wednesday and Wednesday night...This is the period of greatest focus
as it looks like our region will once again be solidly in the warm
sector as a pre-frontal trough slides offshore and the cold front
approaches from the west. With continued southwesterly flow, should
see temperatures once again well above normal, approaching record
highs (see climate section below). The combination of the very warm
boundary layer (resulting in a relatively unstable profile with
modest CAPE values) and a mid and upper level southwesterly jet
(resulting in bulk shear values above 50kt) means there is once
again a risk for strong or severe storms. The biggest source of
uncertainty right now is the timing, primarily of the cold front.
There are considerable differences with the GFS showing the most
progressive solution, bringing the cold front through Wednesday
evening, while most of the rest of the guidance shows a cold frontal
passage late Wednesday night. The GFS solution would be the highest
risk as the warmest conditions would be coincident with the best
lift. Even with the slower solutions, there remains some risk for
severe storms, it would just be a more limited period.

As for the hazards, it looks like the primary hazard would be strong
winds. Current model soundings show limited instability in the hail
growth region, limiting the threat of large hail. If there is
widespread rain on Tuesday leading in to the event, then the risk
for poor drainage flooding could increase for Wednesday.

Thursday and Friday...strong cold air advection with breezy
northwesterly winds. At this point, it looks like we will have at
least 2 consecutive days of below normal temperatures. A fast moving
low may dig across the region, though there remains considerable
uncertainty with the track.

Saturday and Sunday...High builds south, keeping us in the cold air
for a few more days, although there may be a modest warming trend by
Sunday as winds shift more westerly.

&&

.AVIATION /05Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

VFR through Monday afternoon. Clouds increase with ceilings of
8000-15000 feet expected after 12Z. Winds mostly light westerly
or even variable, then becoming southwest Monday and increasing
to around 10 knots (some local gusts to 15-18 knots possible in
the afternoon).

Outlook...
Tuesday...Should begin as VFR, but ceilings could lower to MVFR
later in the day as rain begins to move in.

Wednesday and Wednesday night...Thunderstorms are likely, primarily
Wednesday afternoon or Wednesday night. With any storms or showers,
MVFR or even IFR conditions are expected. There will be an abrupt
shift to breezy northwesterly winds with the cold front which should
arrive Wednesday night.

Thursday and Friday...Mostly VFR conditions. There is a small chance
of lower conditions with rain and snow showers Thursday night into
Friday. Very breezy northwesterly winds are possible both days.

&&

.MARINE...
Sub-advisory conditions are forecast through Monday afternoon,
as winds turn from westerly to southwest.

Outlook...
Tuesday through Wednesday...southwesterly winds at or above 25
kt likely, especially on the coastal waters. Periods of showers
and thunderstorms possible, especially on Wednesday.

Wednesday night...Thunderstorms and showers possible. An abrupt
shift to northwesterly winds is expected with a cold front either
late Wednesday night or Thursday morning.

Thursday and Friday...Northwesterly winds gusting above 25 kt are
likely through out the period. There is also a chance for gale force
gusts, primarily Friday afternoon and Friday night.

&&

.CLIMATE...
Record high temperatures for Wednesday, March 1st.

ACY 72-1972

PHL 76-1972

ILG 75-1972

ABE 67-1972

TTN 74-1972

GED 73-1976

RDG 74-1972

MPO 67-1972

The following monthly and seasonal average temperatures were
calculated with Sunday`s max/min and the 330 PM 2/26 Mount
Holly forecast.

**Record warm February** and a top 10 warmest winter,  again!

Records date back to the late 19th century. Details below.


February:

PHL 44.2. #1   Normal 35.7   Record 42.2-1925     POR 1874

ABE 39.4  #1   Normal 30.7   Record 38.6-1998     POR 1922

ACY 43.2  #1   Normal 35.3   Record 41.6-1890     POR 1874

ILG 43.0  #1   Normal 35.1   Record 42.3-1903     POR 1895



Winter (DJF)

PHL 40.4 #6 (last winter was 3#)  4 of top 10 since 2000.

ABE 36.0 #5 (last winter was #2)  4 of top 10 since 2000

ACY 39.9 #9 (last winter was #5)  4 of top 10 since 2000

ILG 39.4 #5 tie (ditto last winter) 4 of top 10 since 2000



Past two years of monthly average temperatures through February
2017, a summary of above normal months listed below:

For ABE: 23 consecutive months of above normal temps!

FOR PHL: 22 of the past 23 months have been above normal.

For ACY: 19 of the past 23 months have been above normal. For ILG:
17 of the past 23 months have been above normal.

(Jan-Feb-March 2015 was the last time we had significant and
persistent below normal monthly temps.)


RECORDS:
Allentown established a new record for February...three
consecutive record breaking days of 70+. Allentown did have 3
consecutive days of record breaking heat in 1991...but the
records were in the 60s (3rd-5th). Allentown has established 6
days of record high temperatures this month.


Snow: February least on record:

Atlantic City will be tied for 5th with 0.3".

&&

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

&&

$$
Synopsis...Johnson
Near Term...Gorse/Robertson
Short Term...CMS
Long Term...Johnson
Aviation...Gorse/Johnson/Robertson
Marine...CMS/Johnson/Robertson
Climate...



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