Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
447 PM EDT Friday Oct 31 2014
a series of low pressure areas will organize off the middle Atlantic
coast tonight through Saturday night...and finally move northeast
into the Canadian Maritimes Sunday night. High pressure will move
in from the west on Sunday and crest over the region on Monday. A
warm front will cross the region on Tuesday followed by a cold front
Near term /until 6 am Saturday morning/...
through this afternoon...sprinkles may develop Monmouth/ocean
counties...and become heavier showers toward 6 PM. We see an ob of
sprinkles at kwri but unsure of it.
Tonight...strong 180 M hfc associated with closed low aloft moving
down into Georgia/SC early Saturday will permit considerable lift to
develop in our area late as vorticity aloft stretches northward.
Rain may be briefly heavy after midnight. Boundary layer appears
too warm for snow and sleet in the Poconos.
Gusty NE winds to 25 miles per hour develop Monmouth County coast after midnight.
50 50 blended 12z NCEP MOS guidance but trended with the slightly
warmer GFS mav dewpoints.
Short term /6 am Saturday morning through 6 PM Saturday/...
plenty of cyclonic moist inflow and rather unstable should wring
out pretty decent periods of rain through the midday hours. Chilly.
Noting large tt of nearly 55c and swi -1c and ki near 29c lower part
of Delaware-Maryland-Virginia Saturday morning. Could be isolated thunder but not in
Temps: lowered the 50 50 blended 12z NCEP MOS guidance per the
12z/31 European model (ecmwf) and the drier dewpoints filtering south during the
Gusty north winds 20-30 miles per hour...may gust 40 miles per hour nearest 2-5 miles of
the coast but no Wind Advisory at this time.
Long term /Saturday night through Friday/...
* windy with unseasonably cool temperatures on Sunday.
* Fair weather Monday through Wednesday with temperatures moderating each day.
* A cold front is projected to move through the region on Thursday.
The North Atlantic oscillation /nao/ is projected to enter a positive
phase beginning during the middle of the upcoming week. This favors a
progressive pattern with above normal heights over the eastern Continental U.S.. as
the ocean low impacting the region this weekend moves into the
Canadian Maritimes on Monday...heights begin to build over the eastern
Continental U.S. Signaling the return to a positive nao...but model differences
arise in the handling of shortwave energy entering the upper MS
valley by mid-week. Although the Euro and GFS have been in fairly
good agreement on this feature going back at least three days...
neither model has shown run-to-run consistency at this point.
The uncertainties in the model solutions increase between 12z/Tuesday and
12z/Thursday with regard to the amplitude and placement of the MS valley
trough and this will have a direct impact the timing of a cold front
centered around the Thursday timeframe. The gefs individual ensemble
members represent this uncertainty well with their placement of the
middle-level trough axis...one Camp clustering over the MS valley and
the other Camp clustering over the Appalachians. At this point...
will take the consensus approach...and use the ensemble mean
which is also in agreement with cips analog guidance.
Sunday...there is the potential of advisory level winds on Sunday as
low pressure rapidly deepens east of new eng and high pressure moves
into the Ohio Valley. Model soundings indicate northwest winds in
the 40 to 45 knot range at 850 hpa...and with steep low-level lapse
rates...will be able to realize some of that momentum at the surface
in gusts, especially over the higher terrain, coastline and offshore
waters. The flow aloft will be cyclonic and the column gradually dries
throughout the day...and with positive vorticity advection remaining to the northeast and a
strong downsloping flow...not expecting any precipitation. Temperatures
will be well below seasonable levels.
Monday...there will still be a tight pressure gradient early in the
day with lapse rates indicating momentum Transfer to about 950 hpa
where 25 knot winds reside. The winds will lighten as high pressure
crests over the region later in the day. Expecting a dry day with
temperatures below seasonable levels.
Tuesday...mid-level ridge crests over the area in concert with the
high pressure ridge shifting offshore. This may allow a warm front
to move through the region...bringing temperatures closer to
Wednesday through Friday...if the projected frontal passage timing
on Thursday holds...Wednesday could be unseasonably warm...followed
by a return to more seasonable weather on Friday.
Aviation /21z Friday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Rest of today...VFR ceilings overspreading at or above 3500 feet. Spotty MVFR
ceilings in New Jersey. North to northeast wind gusts increasing to 15 knots late
Tonight...ceilings lower to MVFR conds in periods of rain/drizzle.
Chance of IFR conds in New Jersey. North-NE wind gusts 15-20 knots. Chance of a
period of heavy rain after 05z/01.
Saturday...MVFR ceilings expected across the region. Localized
IFR conditions closer to the coast including kacy and kmiv and
possibly back to kphl and kilg during the morning-midday in
periods of heavier rain. Gusty north winds 20 to 30 knots.
Sunday...low level wind shear may be an issue at the terminals due to northwest
winds of 20 to 30 knots with gusts to 40 knots possible.
Otherwise...mainly VFR conditions expected.
Monday through Wednesday...mainly VFR conditions with MVFR possible
with the passage of a warm front on Tuesday.
tonight...Small Craft Advisory north-NE wind conditions develop but the headline is
superseded by tomorrows Gale Warning.
Saturday...gale conditions expected all waters by 6pm Saturday
with various starting times. At this time it looks like marginal
gale begins vicinity 44065 (nnj waters) near daybreak Saturday and
then spreads southward during the day with gusts increasing 5 knots
everywhere during the afternoon. We may see spotty gale gusts
during the late morning even in Delaware Bay.
Gale watch upper Delaware Bay changed to a warning at the 330 PM issuance.
Saturday night through Sunday night...gale conditions expected on
the Atlantic waters and Delaware Bay with peak gusts near 45 knots.
Seas as high as 10ft possible on the Atlantic waters.
Monday...Small Craft Advisory may be needed for both winds and seas.
Tuesday and Wednesday...a warm front may move over the waters on
Tuesday...expecting winds and seas to remain below Small Craft Advisory thresholds
during this timeframe.
a strong northeast flow associated with the strengthening low
pressure system off the East Coast will produce elevated water
levels down the shore through the weekend. Current guidance suggests
minor tidal flooding along both the New Jersey and Delaware coasts
for Saturday afternoon/S high tide...and perhaps again at the time
of high tide early Sunday morning. Total water levels (astronomical
tide plus the positive anomalies caused by the storm) from Atlantic
City south through Lewes Delaware have a good probability of being high
enough during Saturday afternoon/S high tide to warrant an advisory
statement...so one has been issued. Right now current guidance
suggests that while minor tidal flooding is expected in
Middlesex...Monmouth...and ocean counties...total water levels will
peak just short of advisory level criteria. This could be a close
call, so residents along the coast should keep abreast of updated
forecasts and advisories as this event unfolds.
Right now elevated water levels are also expected in the Delaware
Bay, with pockets of minor tidal flooding possible at the time of
high tide Saturday afternoon and evening up through Reedy Point. No
flooding is expected at this time in the tidal portions of the
Delaware River...including Philadelphia.
No problems are currently expected along the shores of the
Chesapeake Bay affecting the middle and upper portions of the
Maryland Eastern Shore.
New Jersey...coastal Flood Advisory from 1 PM to 7 PM EDT Saturday for
Delaware...coastal Flood Advisory from 1 PM to 7 PM EDT Saturday for
Marine...Gale Warning from 6 am EDT Saturday to 5 PM EST Sunday for
Gale Warning from noon EDT Saturday to 5 PM EST Sunday for