Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
902 PM EST Friday Mar 7 2014
low pressure located off Cape Hatteras, North Carolina this
evening will continue to move east northeastward and out to sea
overnight. A cold front will then cross the area from the
northwest late on Saturday into Sunday morning allowing for a
return of high pressure for the start of the new work week. The
high will depart to our south on Tuesday while a clipper like
system nears from the west-northwest. This is followed by the
potential for another coastal low pressure system to cross the
region late Wednesday and Thursday.
Near term /until 6 am Saturday morning/...
low pressure centered off Cape Hatteras around 900 PM will
continue to move to the east northeast and out to sea during the
The northwestern edge of the rainfall associated with the low
made its way into the far southeastern part of our forecast area
today. However, the precipitation shield was on The Retreat this
evening and it was entirely off the coast at 900 PM. As a result,
no additional rain is anticipated for the overnight hours.
The high clouds were continuing to clear from west to east.
However, stratocumulus covered much of our forecast area at 900
PM. The northwestern edge of the stratocumulus extended from
around Stroudsburg to Allentown to Morgantown in Pennsylvania. The
cloud bases were continuing to lower in the subsidence on the
outer edge of the departing coastal low. Also, the downward motion
was causing the cloud deck to spread northwestward. The trend may
continue until around midnight before the dry air to our west and
northwest puts a halt to the expansion of the clouds. The
stratocumulus should begin to erode from the west and northwest
after midnight with most locations becoming clear or partly cloudy
by daybreak. The clouds may linger until around or shortly after
daybreak along the southern New Jersey coast and at the Delaware
Temperatures should remain mostly in the 30s with the cloud cover
present. Readings are forecast to fall into the 20s at most
locations once the clearing takes place.
The wind should be light and variable from the fall line
northwestward and it will likely be from the north around 5 to 10
miles per hour on the coastal plain. Speeds may approach the 10 to 15 miles per hour
range right along the coast.
Short term /6 am Saturday through 6 am Saturday/...
Saturday looks like a pretty good day with temperatures close to normal
and considerable sunshine especially in the morning. Winds should
be relatively light west to northwest. Winds at 850mb are up to 40kt or so
but there appears to be an inversion above 950mb that will limit
downward mixing during the day. Clouds will increase during the
afternoon as a cold front moves southeastward into northern New Jersey and adjacent PA. There
is not much moisture with the front but we have put in just a
slight chance for -shra/-shsn over the Poconos for late in the afternoon.
Long term /Saturday through Friday/...
the 5-wave model guidance is showing weak troughing, pseudo-zonal
flow, across the region at the start of the period. By the middle
of next week we start to see a return to a rather familiar, and
frankly unable-welcome pattern, ridging in the west, troughing in the
east. The few blissful days of at or above average temperatures
comes to halt and winter once again takes grasp of the region. The
Silver-lining in all of this, at least we gain an extra hour of
daylight on the clocks in the evening...we actually only gain a
few minutes of actual daylight astronomically.
Generally speaking the latest 12z initialization looks pretty
good off the GFS/NAM/ggem though there are minor differences in
the thermal fields this morning...the 12z ec was slightly better
than the three above. For the most part the guidance seems to be
too cold across the Upper Middle-west and the northern plains and not
fast enough with the next cold front entering into the upper
plains. This will cause issues for the temperature forecasts
through the first half of the long term period as a parade of
clipper like systems should traverse close to our region before
the more established troughing takes over.
The first such system will track well to the north of the region
and push through a weakening cold front later on Saturday into
Sunday morning. Guidance is showing the low-level temperatures
crashing with the advancement of the front which would allow for
more of a rain/snow mixture. The issue with this system will be
the amount or no associated ice within the clouds. There is very
limited, nearly none, moisture being that the split flow in the
middle-levels continues and with the little forcing its not likely to
be a cold enough cloud producer. That being said decided to add in
some freezing drizzle across our northern most zones with a
rain/snow mix elsewhere.
Sunday will be a colder day with a stiff northwest wind as
temperatures falling below average behind the front. The good news
is there should be plenty of sunshine around to make it not feel
as bad. Did side more with the warmer mavmos in this case given
the above information, though it must be noted that the 2m
temperatures off the GFS have been under-performing the past couple
of weeks...at least.
Monday we will restart our warming trend with ridging slide to
our south and a nice return flow developing. Low-level
temperatures jump back up above freezing and will remain that way
through at least the later half of Tuesday, ahead of the next
northern stream system. Both Monday and Tuesday will feature dry
conditions and above average temperatures.
We then turn our attention to later on Tuesday as we watch how
fast/slow another frontal boundary will shift through the region.
Given the current speed of the northern stream would have to err
on the side of a faster movement of the cold front thus dropping
it through our region on Tuesday evening. The next big issue
becomes how the middle-level troughing progresses through the middle-
west and into the eastern U.S. By mid-week.
There is relatively good consensus from the Middle-Range model
package through about Tuesday, and then we start to see the
GFS/ggem/ec part ways with the speed and deepening of the trough.
To put it simply, we are will be in middle-March with split flow
still aloft and we need a deep thermal trough to change that with
phasing of northern and southern stream systems. We then need to
robust wave to develop along the frontal boundary that just moved
through to drag in enough cold air and then sling the southern
stream moisture overhead. Much like the last event, March 2-3,
there are a lot of moving parts that need to fall in-line for more
What does have somewhat higher confidence is the occurrence of a
low pressure moving by/through the region Wednesday into Thursday
producing precipitation. That being said went with a wpc approach
for probability of precipitation and rain/snow mixture for the time being.
Aviation /02z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Krdg and kabe...a period of MVFR ceilings through about 0500z or
0600z, the clearing with VFR through the rest of taf period. A
light and variable wind tonight should become west northwest
around 4 to 8 knots on Saturday.
Kphl/kpne/kttn/kilg...mainly MVFR ceilings until around 0700z to
0900z with a mainly clear sky thereafter. A north wind around 10
knots should become northwest overnight, then west northwest on
Kacy and kmiv...ceilings mainly in the IFR range until around
0900z to 1100z followed by VFR conditions through the balance of
the taf period. A north wind around 10 to 12 knots should become
northwest overnight then west northwest on Saturday.
Saturday night - Sunday...mostly VFR. Light rain/snow showers
possible early Sunday morning north of ridge...maybe some patchy
freezing drizzle late Saturday night.
Monday - Tuesday...VFR.
Tuesday night - Thursday...MVFR or lower in scattered showers.
Increasing chances for more rain/snow Wednesday into Thursday with
sub-VFR conditions likely.
a surface low off the NC coast is forecast to continue gradually
deepening as it moves northeastward and out to sea overnight. The surface pressure
gradient and associated winds will be strongest over the coastal
waters of southern New Jersey and Delaware...and so a Gale Warning remains in effect
for that area. The strongest gusts should occur this
evening...then winds will diminish overnight and will back from NE
to north to northwest by Sat morning. Elsewhere a Small Craft Advisory remains in effect except
for upper del Bay.
The sustained NE flow has caused seas to build to 12 feet at buoy
44009. Highest seas during the evening should begin to subside
overnight...but will remain elevated through the day on Saturday.
A Small Craft Advisory will likely need to continue for coastal waters...even after
Sunday - Tuesday...sub-sca conditions are expected at this time.
Winds become more northwesterly behind a cold front on Sunday.
Tuesday night - Thursday...increasing chances for a coastal low
pressure to near later on Wednesday. Seas and winds will increase
with this low. Small Craft Advisory conditions looks very possible.
Marine...Small Craft Advisory until 7 PM EST Saturday for anz450>452.
Gale Warning until midnight EST tonight for anz453>455.
Small Craft Advisory until 6 am EST Saturday for anz431.