Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Mount Holly New Jersey
732 PM EST Thursday Mar 5 2015

Synopsis...
a storm system will exit to our east this evening, then Arctic high
pressure builds in overnight and Friday. The high will then settle
to our south on Saturday. A weak low pressure system will track to
our north late Sunday into Monday, pulling a cold front across our
region on Monday. High pressure should then build into the area
Tuesday into Wednesday, with the next cold front scheduled to arrive
later Wednesday into Thursday.

&&

Near term /until 6 am Friday morning/...
650 PM headline adjustment: cancelled I-95 corridor; but extended
southeast New Jersey through central Delaware and a portion of Maryland east ashore through 01z;
and Sussex County Delaware had to extend through 02z, where too much
snow on radar. All products posted.

Continued modified call to action for more safety on snow removal.

Temperatures will tumble once skies clear. This should take place
fairly quickly after the snow ends given a steep drop in dew
points and considerable dry air advection. Record lows are
possible, please see climate section below. Low temperatures
tonight are composed of met/mav and the modeled two meter
temperatures from the GFS which has done well at night with snow
cover.

Wind chills are likely to fall below zero across most of the region,
with the Poconos seeing wind chills which may get close to advisory
threshold for a few hours. Given the limited window and marginal
values in terms of and advisory, will just continue mention in the
severe weather potential statement.

&&

Short term /6 am Friday morning through 6 PM Friday/...
sunny day with high pressure building in on Friday but still
cold. Did go a touch warmer than mav/met given the cool daytime
bias with snow cover. Other elements straight mav/met. Continued
northwesterly winds under 10 miles per hour or so.

&&

Long term /Friday night through Thursday/...
the overall synoptic setup is comprised of an upper-level trough
from the Midwest to the northeast and middle Atlantic. As short wave
energy moves through the flow, this feature should amplify a little
for a time or two. This should eventually weaken as energy ejects
across the Southern Plains late in the weekend and early next week,
with a ridge potentially building off the southeastern U.S. Coast.
This results in the upper-level flow turning more zonal next week.
We used a model blend for Friday night through Sunday, then went
with the 12z wpc guidance thereafter. We then made some adjustments
after additional collaboration with our neighboring offices.

For Friday night and Saturday...a short wave trough looks to slide
across the area, however a dry airmass results in no precipitation.
At the surface, high pressure builds over the area however its
center slides to our south through Saturday. This will result in a
gradual return flow being established and after a very cold start
Saturday, some moderation is expected in the afternoon.

For Sunday and Monday...a short wave is forecast to track near the
Midwest and Great Lakes Sunday, then well to our north Monday. This
will drive weak low pressure well to our north, however a cold front
is forecast to move through during Monday. It appears that the
moisture will be lacking with this feature as much of the lift
occurs well to our north. There could be a snow shower though Sunday
night into Monday across the far northwest. Otherwise, the airmass
is forecast to continue to modify as the flow comes more from the
west and not the north.

For Tuesday and Wednesday...high pressure should shift to our east
as a cold front moves across the Midwest and the Great Lakes. Low
pressure appears to track well to our north once again, with a warm
front lifting mostly to our northwest. While the flow looks fairly
weak, enough warm air advection is expected to occur to allow for further
moderation of the airmass with many areas getting into the lower 50s
Wednesday afternoon. The cold front should be arriving late
Wednesday, however given the track of the surface low and short wave
aloft it also looks to be moisture starved.

For Thursday...a weak surface high is anticipated to move across the
area, while a frontal boundary is draped from near Maine to the
Great Lakes then into the Central Plains. The airmass should be much
milder with afternoon highs getting into the 50s. The ocean and
Delaware Bay are cold and if there is light enough flow, then a
cooling affect can be expected closer to the coast.

&&

Aviation /01z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.

Tonight...MVFR snow at kmiv and kacy ends by 01z/6 followed by VFR
ceilings for a few hours then then VFR clear after 05z. North- northwest
wind gust 20 knots early then diminishes. For the remaining taf sites
VFR ceilings then becoming VFR clear 02z-04z.

Friday...VFR clear with scattered-broken cirrus at or above 20000 feet late in the
day. Light wind.

Outlook...
Friday night through Sunday...VFR overall. A weak system moving by
later Saturday should result in more clouds, however any
precipitation looks to stay to our north and west.

Monday and Tuesday...VFR overall. A weak cold front moving through
Monday should result in more clouds, however it appears that it
moves through dry.

&&

Marine...
added an Small Craft Advisory to lower Delaware Bay around 722 PM. Small Craft Advisory continues
along the altc coastal waters through the overnight hours.
Will review all the Small Craft Advisory material at 9 PM.

For Friday, winds and seas should remain below Small Craft Advisory criteria.

Outlook...
Friday night and Saturday...the conditions are expected to be
below Small Craft Advisory criteria, however the winds will
increase some from the west-southwest during Saturday. There is a
chance for some light freezing spray Friday night and Saturday
morning.

Sunday through Tuesday...we are anticipating sub Small Craft
Advisory conditions as a weak front moves through mainly during
Monday.

&&

Climate...
with a snow cover in place and another Arctic airmass settling
into the region and radiational cooling occurring we have another
chance for more record lows across the region.

Friday 3/6

Record lows

Acy 10 1888
phl 10 1978
ilg 11 1926
Abe 7 1960
ttn 7 1872
Ged 10 1978
ridge 7 1978
mpo -5 1909

The current forecast currently has most locations breaking there
record low on Friday morning. The one exception would be Mount
Pocono.

Saturday 3/7

Record lows

Acy 10 1890
phl 9 1960
ilg 11 1960
Abe 1 1960
ttn 7 1890
Ged 3 1960
ridge 10 1989
mpo -18 1911

It appears that reading and Atlantic City have the better chance
of getting to their record low Saturday morning.

Record daily snowfall for Thursday March 5

Another record event report will update around 745 PM. Kacy is
already posted. Kilg needs an update for 7 total.

Phl had 7.5 and Allentown 6.7.

Kacy 0.3 - 1960
kilg 3.7 - 1981
kabe 7.0 - 1917
kphl 8.8 - 1981

Fwiw...water equivalence of total snow depth in portions of eastern
PA is now well over 3 inches.

&&

Phi watches/warnings/advisories...
PA...none.
New Jersey...Winter Storm Warning until 8 PM EST this evening for
njz020>027.
Delaware...Winter Storm Warning until 8 PM EST this evening for dez002.
Winter Storm Warning until 9 PM EST this evening for dez003-
004.
Maryland...Winter Storm Warning until 8 PM EST this evening for mdz015-
019-020.
Marine...Small Craft Advisory until 6 am EST Friday for anz450>455.
Small Craft Advisory until midnight EST tonight for anz431.

&&

$$
Synopsis...gorse
near term...drag/Gaines 732
short term...Gaines
long term...gorse
aviation...drag/Gaines/gorse/O'Hara 732
marine...gorse/Johnson/O'Hara
climate...

National Weather Service Glossary of Abbreviations