Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
940 PM EDT Thursday may 28 2015
a cold front will move across the area overnight. High pressure
reestablishes itself off the East Coast Friday into Saturday.
Another cold front will then slowly move across the region
Saturday night or Sunday. High pressure will build over eastern
Canada early next week while the frontal boundary stalls to our
Near term /until 6 am Friday morning/...
showers and thunderstorms have dissipated within the past two
hours over most of the region. Some new showers have broken out
over northeast Maryland, but coverage is isolated. Additional
showers have developed west of the Chesapeake Bay. Recent hrrr
runs suggests this activity may continue into the early morning
Wind shift to the north (speeds very light) highlights the arrival
of drier air across the region. Dewpoint discontinuity provides
best identification of frontal boundary.
There may be some patchy fog/St overnight in the frontal boundary
area with confidence for fog/stratus formation below average. Patchy
fog is in the weather grids using the ups crossover tool.
Otherwise a fair night and a few degrees cooler up north late at
night due to drier air.
Forecast temperatures are based on the warmer 12z/28 NAM MOS and all other
guidance is derived off a 50 50 blend of the 12z/28 GFS/NAM MOS.
Short term /6 am Friday morning through 6 PM Friday/...
a nicer day with lower dewpoints...an ideal Summer day kphl
northeastward...warm but relatively comfortable with light east
winds turning southeast or S during the afternoon. Cooler coasts due to
the upwelled cooler ocean waters, especially nnj.
We have small probability of precipitation in during the morning Delaware-Maryland-Virginia and spreading
northward through east PA in the afternoon but confidence is below average. It should
be rainfree most of our forecast area on Friday. Only called it
showers per more stable environment and Chancey at worst in SW
portion of the forecast area
Forecast temperatures based on the warmer of the available 12z/28 NCEP guidance.
Remainder of the elements derived from the 12z/28 50 50 blended
Long term /Friday night through Thursday/...
high pressure will remain off the coast for the start of the period as
cold front advances from the west. With the low over Quebec, we will be
well in the warm sector and with out many triggers besides daytime
heating, expect Friday night to be dry and early Sat as well. By
later Sat, could see a few rain showers/thunderstorms mainly north and west.
By later Sat into sun, this is our best shot to see some decent
rain across the area, and we need it. The ECMWF, is still a bit
slower with the cfp, but overall timing diffs have decreased. Sat
night into sun appears to be the wet time pd, though it wont be
raining the whole time, and certainly not everyone will get rain
at the same times.
Behind the front, high pressure will move to the north and be anchored in
Quebec as the front stalls to our S. Northeasterly flow will set in the
forecast will be very dependent on where the front sets up. Expect Monday
to be cool and dreary whether or not it rains, but there will be
scattered showers at least, and possibly more in the way of precipitation. Guidance is
still having difficulty with determining of where the steadiest
rain might be and has had probs over the last few days with the
details of the forecast around Monday. Those still continue. It should be
noted that the CMC is much drier than either the GFS and European model (ecmwf) on
Monday. The GFS has a wet bias, but the ECMWF, except for one day
earlier this week has been consistent with some precipitation for Monday.
High pressure slides across to the north and east of the region
Monday night. With high pressure remaining entrenched over the
Atlantic Ocean, the cold front makes little headway through the
region and looks likely to remained stalled across or near our area
through Tuesday. As the northeastern high starts to push back into
our area, the front will push offshore, around Wednesday. The high
then remains over our area through the end of the week.
With the front remaining stalled in our area, a chance for some
showers will continue through Tuesday. As the front starts to push
offshore shower activity will exit from northwest to southeast and
as the high builds into our region, we should really start to dry
out, remaining dry through Thursday.
Temperatures start out quite warm, then take a nosedive Monday and Tuesday
before returning to more normal levels by the end of the period.
Aviation /02z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...cold front passage occurs with wind shifting to light north and then NE.
IFR St/fog may form in the frontal zone overnight otherwise predicting
generally VFR. Confidence: below average due to the uncertainty
regarding the formation of IFR St/fog overnight.
Friday...VFR with any leftover IFR dissipating by 14z and then
scattered-broken clouds at or above 4000 feet during the afternoon. Light east wind during
the morning becoming southeast to S during the afternoon. Isolated
showers possible for kilg and krdg during the afternoon. Thunder
unlikely in our area.
Friday night...VFR Erly, then lowering ceilings/visibilities with stratus/fog
possible. MDT confidence
Sat...lower conditions possible Erly, then becoming VFR during the
day. Scattered rain showers/thunderstorms and rain mainly north and west. MDT confidence.
Sat night-Mon...an extended period of MVFR/IFR conditions
possible. A chance of rain each day. Best potential for
thunderstorms and rain is sun with cold front passage Sat night into sun. Low confidence on exact
Monday night through Tuesday...improving conditions from northwest
to southeast. Lingering showers with MVFR ceilings/visibilities
Monday night improving to VFR by late morning/early afternoon on
do not anticipate Small Craft Advisory conditions through Friday. Southerly flow should
turn NE to east along the waters overnight and light onshore Friday.
Friday night-Sat...sub-sca conds expected, although winds may gust
around 20 knots at times and seas could approach 5 feet by the end
of the period.
Sat night-Mon...increasing seas especially later sun into Monday
with wind increasing above Small Craft Advisory criteria as well. An Small Craft Advisory will
likely be be needed for a portion of this time with the front to
our S and increasing northeasterly flow.
Monday night through Tuesday...easterly flow will continue across
the waters through Tuesday. Seas will remain elevated above 5 feet
on the ocean with winds gusting up around 25 knots.
new weblink, works best on firefox. Displays the forecast graphic et cetera.
Low risk continues through Friday.
Substantial upwelling occurred yesterday with the southerly flow,
especially nnj waters where 44065 water temperature dropped almost 9
degrees in 24 hours down into the upper 40s earlier this morning.
Chilly to swim most of central and nnj beaches despite well above
normal land temperatures.
may 2015...a top 5 warmest on record for large portions of our area.
Conservative values listed below from our 5 am sft and cooling the
near midnight Sunday night may 31 low temperature due to northerly flow cold air advection Sunday
Allentown will probably average very close to 65.9 or 6 degrees
above normal. Por back to 1922. At least 5th warmest on record.
Philadelphia will probably average close to 69.7 degrees or 5.8
degrees above normal. Second warmest on record.
Number 3 would be 69.2 in 2004.
Atlantic City may 2015 65.9 or 4.8 above normal and probable #3
por back to 1874
Wilmington Delaware solid por back to 1916 locked into #4 warmest
No available monthly historical data for kmpo kged kttn and krdg.