Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Mount Holly New Jersey
735 PM EDT Friday Aug 22 2014

Synopsis...
weak low pressure will cross the area tonight and Saturday. High
pressure from southeast Canada will push southward for Saturday
night into early next week. The high will settle across the area
for the middle of next week before moving away Thursday. A cold
front may affect the area Thursday night into Friday.

&&

Near term /until 6 am Saturday morning/...
latest couple of mesoscale hourly model runs are shielding the eastern
part of our County Warning Area in the near near term from much precipitation. More breaks
are appearing in the clouds as the visible satellite imagery is showing
lower clouds advancing to the west while higher clouds are moving
toward the southeast. So evening adjustment are to lower probability of precipitation
east and keep them as is west. Temperatures are on/close to
schedule. Banking on clouds reforming east, or we may be a bit too
high during the evening.

Calling it scattered showers (numerous far west section of our cwa) through
tonight...most of it west New Jersey east PA and the Delaware-Maryland-Virginia.

Amounts may be a little more generous than what our gridded quantitative precipitation forecast
has and it could rain briefly heavy with isolated 0.75 inch amts
possible in east PA by morning due to precipitable water still 1.5 much of the
night. Slightly higher 1 inch amts possible Maryland East Shore and far S
Delaware where more instability and higher precipitable water.

No thunder in the forecast at this time since most of the instability has
receded westward just west of our County Warning Area with cooler Ely flow influx and
skycover.

Forecast temperatures/dewpoints and winds are the 12z/22 50 50 blend of the
GFS/NAM MOS guidance.

&&

Short term /6 am Saturday morning through 6 PM Saturday/...
deep moisture Saturday with weak vertical velocity due to trough axis aloft swinging
southward from New York state as well as weak low level upslope flow could result in
more widespread showers for a time during the morning and make it
a bleak Saturday morning.

Saturday afternoon should start drying out with brightening skies
toward 6 PM.

East-northeast wind maximum gust around 20 miles per hour.

50 50 blended 12z/22 GFS/NAM MOS guidance.

&&

Long term /Saturday night through Friday/...
the only unsettled weather for the long term part of the forecast
will be any lingering shower activity across the area...mostly
south...Saturday evening. The upper 500 mb trough will be crossing the
area and plenty of drier and subsiding air will arrive behind it.
We will just keep the slight chance probability of precipitation for southern New Jersey and the
Delaware-Maryland-Virginia...as was already in there. Temperatures Sat night middle/upper 50s
north/west and low 60s elsewhere.

An extended period of dry weather is slated from Sunday through the
middle of next week. An upper ridge will build up across the Great
Lakes sun and it will rotate across New England and the middle
Atlantic region next week. A strong surface high will crest over the
area Monday. This will bring pleasant weather with cool temperatures sun/Mon.
Temperatures will climb to near normal for Tuesday and then climb above normal
for Wed/Thu.

The next disturbance that will affect the area will arrive Thursday and
then move away Friday. It will probably bring a few showers to the
area. We have just painted some slight chance probability of precipitation for now. A tropical
system may move up from the Bahamas Tuesday north northeast Wed-Thu.
Since it will be staying well east of the area...it is not expected
to affect our weather...except for the possibility for some enhanced
seas. We will be watching any developments this weekend.

&&

Aviation /00z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.

The 00z tafs continued the idea of ceilings lowering to around IFR
threshold late tonight.

For this evening, expecting a MVFR ceiling to form if not already
present. Mention of showers late at krdg. Most of them have been
dissipating before reaching our area. Light east winds.

Overnight, greater confidence of a lower ceiling forming. Not as
confident about low MVFR vs IFR. IFR ceilings were kept at terminals
near the Delaware Bay and with some elevation, upslope flow. Another
shot of showers is expected to come through. Highest confid at
kabe. Some MVFR visibilities due to fog may also occur late. Winds should
remain light from the east.

On Saturday, conditions will improve to VFR as the morning
continues. Generally VFR conditions are expected during the
afternoon. Some widely scattered to scattered showers should be
around. But confidence too low to include. Best chance western
airports/terminals during the morning. Winds should back slightly
more toward the northeast, with speeds generally 10 knots or less.

Outlook...
Saturday night through Wednesday...mostly VFR.

&&

Marine...
sub-Small Craft Advisory conditions expected to continue through
tonight. However, seas may begin to approach 4 feet and winds may
begin to gust around 20 knots overnight as early flow increases as
high pressure approaches the area from the north.

Saturday...Small Craft Advisory issued for the snj and Delaware Atlantic waters and for now
none nnj waters. However...this forecast has trimmed sea state by 1
foot on Saturday and we may be too conservative. In which case may
need to expand the Small Craft Advisory into the nnj waters on one of our next forecast
shifts.



Outlook...
Saturday night...Small Craft Advisory flag continues Sat night and through 800 am sun for
the southern New Jersey and del coastal waters. Near Small Craft Advisory conditions further north.
Fair weather.

Sunday through Wednesday...winds and seas should stay below Small
Craft Advisory criteria.

&&

Rip currents...
low enhanced risk this afternoon.

The risk for the formation of dangerous rip currents probably increases
to moderate this weekend along the New Jersey coast with easterly swell of 4
feet at 7 seconds combining with the persistent onshore flow of 15
knots to build the water behind the sand bars...especially Saturday
afternoon.

&&

Phi watches/warnings/advisories...
PA...none.
New Jersey...none.
Delaware...none.
Maryland...none.
Marine...Small Craft Advisory from noon Saturday to 8 am EDT Sunday for
anz452>455.

&&

$$
Synopsis...O'Hara
near term...drag/gigi
short term...drag
long term...O'Hara
aviation...gigi/O'Hara
marine...drag/O'Hara
rip currents...drag

National Weather Service Glossary of Abbreviations