Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Mount Holly New Jersey
430 am EST Friday Jan 30 2015

Synopsis...
low pressure will move out over the New England waters today and a
cold front will cross the area this morning. Much colder and windy
conditions will arrive behind the front. High pressure will build
across the area for tonight through early Sunday. A low pressure
system will affect the area Sunday night through Monday. Another
high will move in for Tuesday and Wednesday. A coastal disturbance
may affect the area next Thursday.

&&

Near term /until 6 PM this evening/...
08z surface analysis shows an area of low pressure located just
northeast of Lake Ontario. A cold front extends southward from the
low down the Lee side of the Appalachians. A stronger Arctic cold
front was positioned over the Midwest.

Three areas of precipitation were noted on the regional mosaic radar at 430
am, each associated with separate middle-level shortwave troughs. There
was very light snow and flurries that has lingered along and north
of I-80 for much of the night. The second area to note was a band of
rain/snow showers that has started to develop over the past hour or
so to the east of I-95. Hires models have this area of precipitation shield
blossoming early this morning. Additionally there was an area of
snow back to the west over State College and Pittsburgh. Therefore,
expect periods of snow (mixing with rain toward the coast) through a
good part of the morning. Most locations will not pick up much more
than a half inch of snowfall (and not everyone will see measurable
snow). The Poconos and far northwest New Jersey may get an additional inch
with this activity where the snow will be the most persistent during
the morning.

The other story today will be the gusty northwest winds that develop
behind the first cold front this afternoon. Wind gusts up to 35 miles per hour
are expected through early this afternoon. A second cold front will
move through the area late in the day, marking the arrival of Arctic
air. Winds will strengthen further behind this front as lapse rates
become very steep and the pressure gradient tightens. A Wind
Advisory was issued for the entire forecast area starting at 4 PM
today. The higher elevations in eastern PA and northwest New Jersey are most
likely to get wind gusts near 45 miles per hour initially.

&&

Short term /6 PM this evening through 6 am Saturday/...
low pressure will rapidly deepens off the New England coast this
evening. Meanwhile, high pressure over the Midwest will build
eastward. A tightening pressure gradient between these two systems
will produce windy conditions across the middle Atlantic. As mentioned
in the near term, a windy advisory was issued for the entire area
and GOES through tonight. Momentum Transfer algorithms on GFS BUFKIT
soundings support mixing of 40 knots winds down to the surface while the
wind profile from the NAM are slightly weaker. Very steep lapse
rates will be present in the boundary layer under strong cold air advection as the
Arctic airmass moves in. The deeper mixing advertised by the GFS and
several sref members was favored in this setup, which supported a
Wind Advisory.

Low temperatures tonight range from near zero in the Poconos to middle teens
in the Delaware-Maryland-Virginia. Combined with the winds, wind chills are forecast
to be at or below zero across just about the entire area by early
Saturday morning. The Wind Chill Advisory that was already in effect
for the Poconos was expanded to Sussex County, New Jersey for wind chill
values of -10f to -20f.

&&

Long term /Saturday through Thursday/...
Saturday through Sunday afternoon...
high pressure to the west will continue to usher cold and windy
conditions Saturday with temperatures some 20 degrees below normal.
Wind advisories will be in effect for the County Warning Area for the morning
Saturday. Winds will subside by late in the day Sat as the high
crests over the area. Dry weather is forecast through Sunday
morning. Sky cover...partly to mostly sunny Sat and mostly cloudy
skies Sunday.

Sunday evening through Monday...
the next significant weather producer for our area will arrive from
the Ohio Valley Sunday and the center of the low will move across
the Delaware-Maryland-Virginia Monday morning. The most recent models are offering a
more northward trend with the system when compared to thu's model
runs. Clouds will thicken Sunday and snow will arrive over the
Delaware-Maryland-Virginia and southeast PA late in the afternoon. The precipitation will
overspread the whole area Sunday night and continue into Monday.
While snow will be the predominant p-type...some sleet will occur
over the Delaware-Maryland-Virginia and southern New Jersey later Sun night and into Monday.
Preliminary snowfall accums look to be 4 to 5 inches across the southeast
PA Berks County--Lehigh Valley--nrn New Jersey region with lighter amounts
both north and south. Sleet and rain (far south del) will reduce
the accums over the Delaware-Maryland-Virginia and southern New Jersey areas. If the track
continues a northward trend...then more rain will mix in over the
southern forecast area. The precipitation will end as snow once the low sweeps
by Monday afternoon bringing in colder air behind it. Severe weather potential statement product
will highlight the potential for a Sunday night/Monday wintry
weather event. Future forecasts will offer better snowfall forecast and
possible headlines...so check back later today and Sat/sun for
updates.

Monday night through Wednesday...
another high pressure system with cold air will affect the area.
High temperatures Tuesday will be in the teens and low 20s...so readings
again will be 15 to 20 degrees below normal. More wind chill
headlines possible across the far north. Moderating temperatures Wednesday with
highs in the upper 20s to middle 30s over the region.

Wednesday night through Thursday...
the 00z GFS and older 12z ec models both show another 500 mb trough
swinging across the Great Lakes with a surface low pressure developing
ahead of it. Both of these models also show the low pressure system
developing across the deep south and moving up the East Coast. The
latest 00z ec showed the low also...but pushed it offshore Thursday night
into Friday with higher quantitative precipitation forecast only near the coast. We have gone along
with the wpc and raised probability of precipitation up a bit for these periods. They are
still only in the chance range however.

&&

Aviation /09z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.

Majority of the terminals will have VFR for most of the day.
However, there are several areas of light snow that will move into
the area through about 15z. A brief period of reduced visibility to MVFR may
occur at just about any of the airports. There will also be a
stratocu deck that develops between 2500-4000 kft. The lower end of
that range would yield MVFR ceilings. Low clouds will start to scattered out
toward sunset.

Northwest winds will increase thruout the day. Expect winds sustained near
20 knots this afternoon and tonight. Gusts will generally be at or below 30 knots through
about middle afternoon but then increase to 35-40 knots late in the day and
tonight.

Outlook...
Saturday...VFR with windy conditions.
Saturday night through Sun afternoon...VFR. Increasing clouds Sunday.
Sun night through Monday...widespread IFR/LIFR. Snow and mixed precipitation.
Accumulating snow at phl.
Monday night through Tuesday...improving condition Monday evening. VFR Monday night
through Tuesday.

&&

Marine...
no changes to the marine headlines. Gale Warning GOES into effect at
9 am this morning. Gusts will generally be 25-30 knots this morning,
increasing to 35-40 knots late this afternoon into tonight. Seas will
also build to 5-8 feet by tonight. Went slightly above wavewatch
guidance for wave heights.

Outlook...
Sat and Sat night...gales diminish Sat. Small Craft Advisory conditions early Sat night.
Sun and Sun night...sub-sca conditions. Snow and sleet late Sun night.
Monday and Monday night...Small Craft Advisory conditions expected.
Tuesday...Small Craft Advisory seas on the ocean early then sub-Small Craft Advisory conditions.

&&

Phi watches/warnings/advisories...
PA...Wind Advisory from 4 PM this afternoon to 6 am EST Saturday
for paz054-055-060>062-070-071-101>106.
Wind Chill Advisory from midnight tonight to 11 am EST
Saturday for paz054-055.
New Jersey...Wind Advisory from 4 PM this afternoon to 6 am EST Saturday
for njz001-007>010-012>027.
Wind Chill Advisory from midnight tonight to 11 am EST
Saturday for njz001.
Delaware...Wind Advisory from 4 PM this afternoon to 6 am EST Saturday
for dez001>004.
Maryland...Wind Advisory from 4 PM this afternoon to 6 am EST Saturday
for mdz008-012-015-019-020.
Marine...freezing spray advisory from midnight tonight to 6 PM EST
Saturday for anz430-431-450>455.
Gale Warning from 9 am this morning to 6 PM EST Saturday for
anz430-431-450>455.

&&

$$
Synopsis...O'Hara
near term...Klein
short term...Klein
long term...O'Hara
aviation...Klein/O'Hara
marine...Klein/O'Hara

National Weather Service Glossary of Abbreviations