Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
357 am EST Sat Nov 22 2014
strong high pressure will remain over the Middle Atlantic States
today before moving offshore on Sunday. As the high moves
eastward, the southwesterly flow around it will bring a warming
trend to the area. Low pressure developing over the Southern
Plains will move northeastward on Sunday and bring a warm front
through the region Sunday night. The low will be near the Great
Lakes by Monday morning and as it moves into eastern Canada by
Tuesday, its associated cold front will cross the area. High
pressure will then build in from the south for Monday night and
Tuesday. Then, an area of low pressure may develop off the
Atlantic coast for Wednesday and Wednesday night.
Near term /until 6 PM this evening/...
the surface high will shift further southeast, leaving the region
with southerly return flow. As such, expect moist and warm air
advection through the day today. Thus, highs today should be around
5 degrees higher than yesterday.
Short term /6 PM this evening through 6 am Sunday/...
things get a bit more interesting tonight as middle level short wave
trough moves over the northeastern U.S.. both the GFS and NAM show
the best synoptic lift (as evidenced by 500 mb q vector convergence
and positive pressure advection on the 1.5 pv surface) staying just
north of our region. However, given how close the lift is, and given
that there could also be some orographic lift, have slightly
increased probability of precipitation in the Poconos, Lehigh Valley, and northwest New Jersey. But it
still seems like an unlikely event for our region, so most of the
region has probability of precipitation at or below 30 percent.
If there is any precipitation in our area, it will be either in the
form of rain or freezing rain (depending on surface temperature).
Model soundings show a robust and deep warm layer. While there could
be some seeder feeder cirrus clouds propagating overhead, with the
melting layer around 8000 feet msl, any ice crystals would melt
through the warm layer. Because of the continued warm air advection
even at the surface, see very few locations dropping below freezing
before the window of opportunity for precipitation closes. Since
too, the chance of precipitation is very small at this time, will
not issue a Freezing Rain Advisory, but will continue to mention the
potential in the severe weather potential statement.
Long term /Sunday through Friday/...
a nice warming trend is in store at the start of the extendd period as
high pressure moves offshore and strong southwesterly flow develops over the
Then, low pressure will take shape over the Southern Plains and begin to
move northeastward. The warm front associated with this low will move through the
region Sun night as the low really intensifies over the midsection
of the nation. Based on the latest guidance moving the precipitation in slower,
have removed probability of precipitation from the Sunday daytime hours. The best warm air advection is
Sun night and this is the wettest period with rain, some heavy at
times. We get dry slotted later Monday and in the warm sector, temperatures
will skyrocket and could reach record values in some locations,
then the cold front will cross the region Monday night, with
another chance of precipitation Monday evening before high pressure build back in for
later Monday night through Tuesday night.
Then, all eyes turn to the potential for a coastal low developing
around Wednesday. Model solutions are all over the place and confidence is
much below average at this time. The CMC is well offshore with virtually
no impact to our region. The GFS indicates the most impact for our
southern and eastern locations Wednesday into Wednesday night before the low pulls away
on Thanksgiving, bringing a dry Holiday. The European model (ecmwf) has the
strongest and most westward solution and would bring a mostly wet and windy
period from Wednesday into Wednesday night. It has some support from the
UKMET. Any wintry precipitation would be confined to northern aand western areas
at the onset and the end.
With the potential for significant impact due to Holiday travel
and one of the busiest air travel days of the year, this system will
continue to be watched and could end up being nothing or something
significant. The European model (ecmwf) made a decent westward shift from 21/12z to
22/00z, the GFS did not.
After this storms moves by whether far offshore or close to the
coast, another weak cold front may bring some precipitation Erly Friday.
Temperatures will start off fairly warm on Sunday, reach their zenith on
Mon, with near record warmth, then still be near normal on Tuesday before
taking a nose dive through the remainder of the week.
Aviation /08z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
VFR conditions are expected through the taf period. After 18z, middle
level clouds will increase, primarily west of the Delaware River valley,
including krdg and kabe, but ceilings are expected to be at or above
5000 feet above ground level. There is also a small chance of -ra or -fzra in this
area between 00 and 09z. However, at krdg and kabe, it is only a 20
percent chance, and any precipitation should be -ra.
sun...VFR, with increasing and lowering clouds by evening.
Sun night through early Monday...very poor flying conds with MVFR
expected and IFR possible if not probable in rain. Rain could be heavy
at times. East to southeast wind could gust in the 20 to 25 knots range. MDT to
Monday and Monday night...improving conds but still some MVFR possible in
lingering showers. Cold front passage/wsfht Monday evening. VFR by evening if not sooner. Low
to MDT confidence.
Wednesday...much uncertainty depending on the track of a coastal
low. Could be VFR if low is far enough east or MVFR/IFR in rain
and wind if low is far enough west. Best chance for VFR is western airports.
Best chance for degraded conds is eastern airports. Confidence very low.
winds and seas will increase by middle day today as the high shifts
further southeast. Wind gusts of 25 to 30 knots will be possible on the
Atlantic coastal waters this afternoon through very early Sunday
morning. Wave heights up to 5 feet are expected in the Atlantic, and
may be slower to decrease Sunday morning. For now have issued the
Small Craft Advisory from noon today through 6 am Sunday morning.
Sun...no marine headlines anticipated.
Sun night through Monday...Small Craft Advisory conds are expected and gales are possible
if not probable into Erly Monday as strong low pressure impacts the
Monday night into Tuesday....back end Small Craft Advisory conds as seas and wind subside
Wednesday...no marine headlines anticipated.
here are some record lows for overnight tonight for 11/22.
Atlantic City 12 set in 1879
Philadelphia 14 set in 1880
Wilmington 17 set in 1964
Allentown 17 set in 1969 and 1964 *has already been broken as
Allentown has had a low so far of 16*
Trenton 15 set in 1880
Georgetown 16 set in 1987
reading 16 set in 1969
Mount Pocono 5 set in 1969
Here are the forecasted lows for this morning.
Atlantic City 18
Although temperatures have generally been increasing, we will
continue to monitor the temperatures through the early morning hours
before sending out any record event reports.
Marine...Small Craft Advisory from noon today to 6 am EST Sunday for