Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
1158 am EDT Tuesday Apr 28 2015
a large low pressure system over the western North Atlantic will
move slowly out to sea. A weak pressure gradient prevails over the
Middle Atlantic States Wednesday. Low pressure along the Carolina
coasts strengthens as it moves northeast Thursday night and
Friday. High pressure moves in from the west later this coming
Near term /until 6 PM this evening/...
the complex low off Nova Scotia will continue to lose its
influence over our weather gradually this afternoon. Meanwhile,
high pressure will work its way slowly into our region from the
We are anticipating a partly cloudy sky for this afternoon as
cumulus continues to develop.
High temperatures are forecast to be mainly in the 60s with a
northwest wind around 10 to 15 miles per hour gusting to about 20 miles per hour at
Short term /6 PM this evening through 6 am Wednesday/...
the high will continue to influence the weather tonight. Skies
will be mainly clear and winds will be light. Low temperatures
will drop into the low 40s north and middle or upper 40s elsewhere.
Long term /Wednesday through Monday/...
500 mb: below normal heights prevail in our area through Saturday
morning as one closed low in the western Atlantic weakens eastward
with a new closed low probably forming over the Middle Atlantic
States Thursday. It departs into the western Atlantic by Saturday.
Warmer ridging should develop in the eastern United States Sunday
and persist next week!
Temperatures: the month as a whole is now averaging within a
degree of normal through the 27th, ever so slightly on the warm
side of normal. Little change is foreseen in the April outcome.
Calendar day averages should be near normal Wednesday-Thursday and Saturday,
maybe 2 to 5 degrees below normal Friday. A warming trend with
above normal temperatures should begin Sunday and continue next
Forecast basis: unless otherwise noted, a 50 50 blend 00z/28
GFS/NAM MOS guidance Wednesday-Wednesday night. Then GFS mavmos
only for Thursday, 00z/28 mex MOS Thursday night and Friday, then
the 0521z/28 wpc gridded elements of maximum/min temp, 12 hour pop, 6
hour dew point- sky-wind from Friday night through Sunday.
Wednesday...partly cloudy. Northwest wind gusts near 15 miles per hour in
the afternoon. Seabreezes coasts? Confidence: above average. The European model (ecmwf)
tsection is drier than the GFS.
Thereafter: the 00z/28 NAM was pretty much disregarded after 12z
Thursday in lieu of gefs/ecefs guidance-pattern.
Regarding the new GFS implemented earlier this year. We are aware
of its wet bias but its not always so. Multi model choices
continue. Its appearing to ME the gefs is a more reliable
predictor than the GFS operational model (operational more
variable and maybe wetter bullseyes). This is similar to the ggem-
The 00z/28 gefs trended slightly further east but still rather
robust. Its so hard to believe when you check it against the
UK/ggem/ECMWF. Uncertainty in this forecast continues.
Thursday and Friday...mostly cloudy. Gusty NE wind 15-20 miles per hour late
Thursday afternoon and 20 to 30 miles per hour Friday. Have generally
maintained the 330 PM Monday Mount Holly weather forecast office forecast probability of precipitation and temperatures
for this period, due to the uncertainty. The 00z/28 gefs and naefs
still forecast 1/2 inch or greater southeast portion of the forecast area and 6 hour probs for
05 are very high on Friday. 850 east-northeast inflow looks to be -3sd but
if the gefs closed low verifies much weaker as per the ECMWF, the
surface low will be east and much weaker. Temperatures were continuity meshed
with the 00z/28 2m 18z Thursday and Friday forecast European model (ecmwf) temperatures.
Saturday...p/c. Northwest wind gusty 20 miles per hour. The ec has a chance of a
shower. So confidence: below average.
Sunday...p/c with a west wind 10-15 miles per hour. Milder. Confidence:
average (ec drier than gfs)
Monday...p/c and milder. The 00z/28 ec has a shower risk late.
Light wind. Confidence: below average.
Aviation /16z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
A large surface/upper air low well to the east and high pressure well
to the west will keep a northwesterly flow across the area today.
The pressure gradient will be modest...so some gusts over 20 knots
can be expected. Sky cover will be mostly scattered. Tonight...lighter
winds and mostly sky clear.
Wednesday...VFR. Northwest wind gust at or below 15kt. Late afternoon
seabreezes coasts? Nearly calm wind at night. Confidence: above
Thursday through Friday....VFR ceilings with possible MVFR/IFR conds
in rain or showers late Thursday into Friday, especially
kacy/kmiv/kilg. Sustained east to northeast wind around 10 to 15
knots Thursday and Friday is expected along with its potential
impact on operations at kphl. Northeast wind gusts 20 knots late Thursday
afternoon and possibly 20-30 knots at times Friday. Confidence: below
average. The GFS and its ensembles are alone on this bleaker
scenario whereas other typically reviewed models are not as
pessimistic about a significant western Atlantic low pressure
Friday night and Saturday...mainly VFR. Confidence below average
since the European model (ecmwf) has modeled a chance of showers Saturday.
the Small Craft Advisory will be allowed to expire at noon as
wind speeds continue to diminish over the water. Seas should
remain 2 to 3 feet this afternoon into tonight. Fair weather is
Wednesday through Thursday morning...no marine headlines are
Thursday afternoon through Friday...a Small Craft Advisory will
probably be needed for wind gusts of 25 to 30 knots and for waves
on our ocean waters in excess of 5 feet...possibly 7 to 10 feet
Friday. The wind direction is anticipated to back gradually from
the east to the north. There is still the potential for gale force
northeast to north gusts on Friday.
Friday night and Saturday...wind speeds are forecast to remain
below the Small Craft Advisory criterion. However, wave heights on
our ocean waters should remain around or above 5 feet...possibly 7
feet or more east of Delaware.
relative humidity values are forecast to drop into the 30 to 35
percent range in much of our region during the afternoon.
Meanwhile, occasional wind gusts around 20 miles per hour are anticipated.
Fine fuels will continue to dry. Due to the marginal fire weather
conditions, we will issue a Special Weather Statement for our
entire forecast area for the late morning and afternoon hours. The
product issuance has been coordinated with our partners at the