Scientific Forecaster Discussion
fxus61 kphi 220805
Area forecast discussion
National Weather Service Mount Holly New Jersey
405 am EDT sun Oct 22 2017
high pressure generally east of New England through Monday. A strong
cold front is forecast to move across our region Tuesday night. Low
pressure is expected to develop along the front and should be
located over or near New England and southeastern Canada on
Wednesday and Thursday. High pressure follows to our south for
Friday and Saturday.
Near term /until 6 PM this evening/...
there is varying amounts of CI clouds across the area early this
morning. Still enough cooling has occurred for some fog to develop
across (mostly) srn New Jersey attm. Vsbys have dropped to 1-2 mi at a few
of the metar sites. This fog will stick around through just after
dawn, before mixing out.
Another good weather day is expected with mostly sunny skies and
very warm temperatures again. Highs will be in the low/mid 70s in
most areas, easily 10 degrees above normal. Humidity levels will be a
little higher than Saturday, but still not too noticeable. Winds will
be light from the southeast or S.
Short term /6 PM this evening through 6 am Monday/...
low level moisture will continue to slowly increase over the area.
Low clouds and areas of fog should develop again Sunday night and
become more widespread (than Sat. Night). Low temperatures will drop
down only to the low 50s north and mid 50s to low 60s south/east.
These readings are well above the normal lows for this date.
Long term /Monday through Saturday/...
** hazards...possible dense fog Monday morning and then hslc severe
500mb: -2 to -3 South Dakota troughing develops in the Ohio Valley early and
midweek then weakens as it lifts newd negatively tilted through the
mid Atlantic states Thursday. Heights rise along the East Coast by
Saturday as a new -2sd trough develops in the Midwest and Great
Lakes region next weekend.
Temperatures: calendar day averages Monday and Tuesday 15 to 18
degrees above normal cooling to around 7 degrees above normal
Wednesday, and then near 3 degrees above normal Thursday and Friday
then warming to 5 to 10 degrees above normal next Saturday. These
departures are solidifying the high likelihood that October will be a
top 5 warmest on record, if not record warmest.
Forecast basis...unless otherwise note a 50 50 blend of the 00z/22
GFS/NAM MOS for Monday-Tuesday, then 00z/22 GFS mex MOS Tuesday
night and finally the 05z wpc d4-8 elements of 12 hour pop/Max/min
temps, and 6 hourly dewpoint, sky, sky and wind.
Monday...stratus lifts and thins in the afternoon. More humid.
Dewpoint near 60. South to southeast gust 15 to 20 miles per hour. Precipitable water 1.1
Monday night - Tuesday...humid with a south to southeast wind
increasingly gusty to 30 mph miles per hour on Tuesday as dewpoints rise into
the upper 60s. Showers should develop Monday night in E PA and
northern New Jersey, Chancey elsewhere. Then for Tuesday...bands
of showers and iso tstms with potential for a line or line segments
of marginally svr storms in the aftn/evening (40-45 kt). Mlc of
at least 300j appears most favorable in New Jersey. Sherb value just
under 1. Precipitable water builds to ~ 1.45 inches. Low temperatures Tuesday
morning 20-25 degrees above normal (60s) but the midnight lst
min temp may not allow a record high min except for phl/Acy/Abe.
Please see the climate section for our likely vulnerable
potential new record listing.
Tuesday night...cold front passage showers probably end from west to east but
there are model hints that low pressure forming on the front to
our east may keep the showers going across New Jersey. Precipitable water 1.5" in the
evening and still 1" or greater New Jersey/Delmarva 12z Wed. Might have
some patchy dense fog late, especially E PA.
Wed...do the showers linger in New Jersey as low pressure forms just to
our east and northeast. Lots of uncertainty. It should dry out
in E Maryland and se PA. West wind.
Thu...trough aloft passage. Coolest daytime high temps of the
week! Still lots of clouds and maybe a residual shower.
Fri...dry and milder with height rises. Southwest wind.
Sat...increasing clouds. Milder than Friday as a south wind
gusts possibly to 20-25 mph in the afternoon.
Aviation /08z Sunday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
High pressure is moving offshore this morning and the low level
moisture is beginning to return to the region. There is some very
shallow ground fog across Delmarva and srn New Jersey attm. This should burn
off rather quickly this morning. Another VFR day with only cirrus clouds
expected. Winds will be light and variable this morning and light
from the S or southeast this afternoon. Tonight...more added moisture will
result in more fog and also some St across the region. The 12z tafs
will have more details with regards to extent of the St and possible
vsby restrictions in fog.
Monday...IFR or MVFR conditions in stratus/fog Monday morning then
VFR sct-bkn near 4000 ft in the afternoon. South to southeast
gust 15-20 kt in the afternoon.
Monday night through Tuesday evening...conditions lowering to MVFR
and IFR in showers. Isolated thunderstorms and moderate to heavy
rain are possible on Tuesday, along with a south wind gusting around
30 knots. There is a small chance for a gust to 45 kt in a
thunderstorm Tuesday afternoon.
Tuesday night...after 04z/25 cigs generally between 2000-4000 ft in
a light west wind. Chance of IFR conds in St/fog.
Wednesday...conditions probably improving to VFR. West wind
gust 15 kt. Showers possible, especially coastal New Jersey.
Thursday...mainly VFR ceilings. West to northwest wind gusts to 20
high pressure across the waters early today will move further
offshore tonight. A fairly quiet day expected with mostly southeast winds
at 5 to 10 knots. Seas on the ocean 2-3 ft and 1-2 ft across del
Bay. Fair weather today and tonight.
Monday...no marine headline anticipated. Southeast flow slowly
Monday night...Small Craft Advisory Atlantic waters and Delaware Bay issued for the
period 04z/24 Onward through Tuesday afternoon. A short period
of 35-40 kt southerly gale gusts anticipated in the 19z/24-03z/25
time frame, possibly heavy shower or tstm enhanced. Best chc
for gale verification looks like lower Delaware Bay with a shorter
period gale gusts (smw) for the Atlc waters. For now have kept
this simple and the mww elaborates on the possible gale.
Seas on the Atlantic waters increase to between 7 and 10 feet
Late Tuesday night through Thursday...a Small Craft Advisory
will probably be needed on our ocean waters for wave heights of
5 to 6 feet, even as the wind becomes west to northwest around
10 to 20 knots. Also... low pressure developing nearby to our
east and northeast may increase the the west northwest gusts to
25 kt later Wed or Thu.
vulnerable record high minimums Tuesday the 24th are. As of this
forecast we are forecasting records here. However, if the cold
front speeds up and a little clearing ensues then the min temp
would probably fall just short. Right now the mid shift
forecaster has odds favoring record. Elsewhere for now...no
other records anticipated. We'll add locations if we forecast
warmer in future forecasts.
Allentown 58 1975
Atlantic City 63 2001
Philadelphia 63 1900
We will update the month of October data around 530am. Note we
are not looking at pcpn records due to expected 1-3" amts
44091 buoy drifted away from its mooring and has since been
recovered. Its return to service date is still unknown, though
we'll try to have an answer Monday afternoon.
Marine...Small Craft Advisory from midnight Monday night to 6 PM EDT
Tuesday for anz430-431-450>455.
near term...O'Hara 405
short term...O'Hara 405
long term...drag 405